Air Pollution, Aerosols and Clouds in the Climate System

The Cloud Makers - A video about effect of aerosols on cloud

2009-02-10T22:42:00.016-05:00

I found a very interesting video about effects of aerosols on clouds and how the GLORY mission of NASA going to address this problem. Click on the image or the link below to view the video.

Play video "The Cloud Makers"

Image courtesy: NASA Goddard Space Flight Center

Long Range Transport of Dust Aerosols

2008-10-04T10:41:00.009-04:00

Continuing from our last blog post on the issue of aerosol radiative forcing (ARF) and the importance of its vertical distribution, l would like to bring to attention another important aspect associated with aerosols that affect global ARF. This aspect is the transport of aerosols which is very closely related to its vertical distribution. One of the largest sources of aerosols is desert. These desert dust aerosols have gained much attention due to the long range transport associated with them. The dust from these deserts is lifted higher in the atmosphere and ‘because of the fast large-scale transport in the upper troposphere, aerosols such as dust and black carbon, once they enter the upper troposphere (above ~8 km), can be transported around the earth in a latitudinal belt in a week or two’. ‘The impact of long range transport of dust and air pollution from their continental sources over oceanic regions is one of the outstanding problems in understanding regional and global climate change’ and in also determining the air quality of regions to which dust is advected to. Using Calipso and surface micropulse lidar, Huang et al., [2008] observe the long-range transport and vertical distribution of Asian dust aerosols during the PACific Dust EXperiment (PACDEX). ‘The MPL measurements were made at the Loess Plateau (35.95°N, 104.1°E) near the major dust source regions of the Taklamakan and Gobi Deserts’ in China during March-May 2007. They find that ‘Dust events were more frequent in the Taklamakan, where floating dust dominates, while more intensive, less frequent dust storms were more common in the Gobi region. The vertical distribution of the CALIPSO backscattering/depolarization ratios indicate that non-spherically shaped dust aerosols floated from near the ground to an altitude of approximately 9 km around the source regions. This suggests the possible long-range transport of entrained dust aerosols via upper tropospheric westerly jets. A very distinct large depolarization layer was also identified between 8 and 10 km over eastern China and the western Pacific Ocean corresponding to dust aerosols transported from the Taklamakan and Gobi areas, as confirmed by back trajectory analyses. The combination of these dust sources results in a two-layer or multilayered dust structure over eastern China and the western Pacific Ocean.’ We have seen in our last blog spot that ‘the vertical distribution of dust aerosols is another critical factor impacting the effects of dust on radiative forcing and climate [Claquin et al., 1998; Zhu et al., 2007; Forster et al., 2007].

References:

Huang, J., P. Minnis, B. Chen, Z. Huang, Z. Liu, Q. Zhao, Y. Yi, and J. Ayers (2008), Long-range Transport and Vertical Structure of Asian Dust from CALIPSO and Surface Measurements during PACDEX, J. Geophys. Res., doi:10.1029/2008JD010620, in press.

Claquin, T., M. Schulz, Y. J. Balkanski, and O. Boucher (1998), Uncertainties in assessing radiative forcing by mineral dust, Tellus, Ser. B, 50, 491–505.

Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. Lowe, G. Myhre, J. Nganga, R. Prinn,G. Raga, M. Schulz and R. Van Dorland (2007), Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change 2007: The Physical Science Basis. contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Zhu, A., V. Ramanathan, F. Li, and D. Kim (2007), Dust plumes over the Pacific, Indian, and Atlantic oceans: Climatology and radiative impact, J. Geophys. Res., 112, D16208, doi:10.1029/2007JD008427

Impact of Aerosol Vertical Distribution on their Radiative Effects

2008-09-20T17:26:00.015-04:00

From over a decade of aerosol research, it is now a well established fact that atmospheric aerosols play a crucial role in altering the earth's radiation budget [IPCC 2007]. Toa large extent, the effect on aerosols on the top-of-atmosphere radiation balance has been addressed using both observations and global models. A close review of literature suggests the imperative need to address the vertical distribution of aerosols in the atmosphere [Gadhavi et al., 2006] and that is exactly what aerosol science is gearing towards. Recently, there have been many research studies that have begun to address this question. One interesting paper by Johnson et al., appeared in JGR last week that talks about this very issue.

This paper provides very good insights into this topic by using ground and aircraft based lidar observations during DABEX field campaign. 'In general, mineral dust was observed at low altitudes (up to 2 km), and a mixture of biomass burning aerosol and dust was observed at altitudes of 2–5 km.'

For clear sky conditions, when the observed low-level dust layer was included in a radiative transfer model, the absorption of solar radiation by the biomass burning aerosols increased by 10%.' This enhancement in absorption is due to reflection of solar radiation by dust aerosols in background up into the biomass burning aerosol layer above. This situation is analogous to presence absorbing aerosols over a bright background. Thus, depending on the distribution of aerosols and the type of aerosols present at different heights in the atmosphere, their radiative effects can be altered. This in-turn changes the differential heating of the atmosphere and hence the atmospheric stability that influences convective and turbulent motions and clouds [Ackerman et al., 2000]. This can be important for both TOA and surface radiation budget. The scenario is a little more complex when aerosols are above clouds. 'For example, the elevation of biomass burning aerosols above marine stratocumulus clouds during the Southern African Regional Science Initiative (SAFARI-2000) greatly enhanced their absorption of shortwave radiation. This led to a positive direct aerosol shortwave radiative effect over the Southern Atlantic, whereas the effect was negative in clear sky conditions [Keil and Haywood, 2003; Abel et al., 2005; Myhre et al., 2003a]'. Thus, the need to consider the treatment and appropriate representation of vertical distribution of aerosol species in the global models when estimating the impact of anthropogenic absorbing aerosols is crucial.

Please refer to the paper by Johnson et al (below) for all references in this blog-post:

Johnson, B. T., B. Heese, S. A. McFarlane, P. Chazette, A. Jones, and N. Bellouin (2008), Vertical distribution and radiative effects of mineral dust and biomass burning aerosol over West Africa during DABEX, J. Geophys. Res., 113, D00C12, doi:10.1029/2008JD009848

Principal components analysis (PCA) for source identification

2008-06-23T03:10:00.014-04:00

Source identification for atmospheric aerosol is important for developing effective strategy to reduce their emissions. One of the methods for source identification is principal components analysis (PCA). My attention was drawn to this method recently first through a review article about methods and results for aerosol source apportionment over European region and then through the article “Identification of PM sources by principal component analysis (PCA) coupled with wind direction ”. Dr. Viana Rodríguez, Mª del Mar is the lead author on both the articles . She is a researcher at the Institute of Earth Sciences Jaume Almera, Spain.

Application of the principal components analysis method for aerosol is based on the foundation that each source has unique blending of various aerosol components. Variability of the components is strongly correlated among themselves when they are coming from same source when compared to a case where they are coming from heterogeneous sources. Mathematically, PCA seeks to determine matrices A and S in the equation C=A∙S, where column matrix C represents concentration of various particulate matter (PM) components, S is the source contribution and A is the source profiles.

The article Viana et al. (2006) is more about results obtained using PCA analysis rather than the method itself. I liked the article for its clear conclusions and bold figures. I think figure 1 will be useful for those who are interested in knowing typical combination of various aerosol sources for given total mass. Figure 4 will be very useful for the people of the town Llodio, for knowing where to look for reducing pollution. I have recreated images for quick look using data from the manuscript.

References:

Viana, M., et al., (In Press), Source apportionment of particulate matter in europe: A review of methods and results, Journal of Aerosol Science, Accepted Manuscript.

Viana, M., X. Querol, A. Alastuey, J. I. Gil, and M. Menéndez (2006, December),Identification of pm sources by principal component analysis (pca) coupled with wind direction data, Chemosphere 65 (11), 2411-2418.

Aerosol Radiative Effects over Global Land: A Satellite based Study

2008-02-24T13:49:00.003-05:00

GRL published an article on estimation of aerosol radiative effects over global land using purely observations from Terra satellite on February 22, 2008. Although, I am one of the co-author in the paper but I would like to congrats Falguni Patadia, first author of the paper for her research, which is first attempt in certain ways. This paper presents the estimation of top of the atmosphere (TOA) short wave aerosol radiative effects over global land areas for each half degree by half degree grid point. The uniqueness of the study comes from the fact that it is purely observation based study, which does not involve any complex radiative transfer and/or climate model runs. Results of the study are encouraging and matches very well with other purely model or hybrid (model and observations) type of studies. This research used one year worth of satellite observations of TOA fluxes derived from CERES broadband instrument, MODIS high resolution cloud masks and MISR derived aerosol optical thickness data sets to perform the analysis. As we all know that, aerosol impacts in climate change studies in one of the most uncertain component and level of scientific understanding about this component is very low. This study is certainly a good start and will help to understand aerosol effects on earth-atmosphere radiation budget. For more details on the results and methodology, please refer the publication and if you do not have access to the article, we will be happy to share reprints with you.

Complete Reference:

Patadia, F., P. Gupta, and S. A. Christopher (2008), First observational estimates of global clear sky shortwave aerosol direct radiative effect over land, Geophys. Res. Lett., 35, L04810, doi:10.1029/2007GL032314

Is atmospheric aerosol an aerosol? comments on the article by Jaenicke

2008-02-17T22:50:00.003-05:00

The title of a recent article "Is atmospheric aerosol an aerosol?" by Jaenicke caught my attention. This took me back in time, when I was just beginning my career in this field. The first definition I came across or rather assumed was: "anything solid or liquid suspended in the air is aerosol". According to this definition birds and aeroplanes were also aerosols! Thinking of birds and aeroplanes as aerosols wasn't intuitive hence I had to search for a more refined definition. A better one that I came across (well I don't remember from where) was: "any thing suspended in the air and doesn't have self-propelling mechanism is aerosol". This definition implied that mosquitoes are not aerosols but bacteria and virus are. However, this new definition didn't help me win an argument with my friend Neeraj (one of the authors of this blog) who held an opinion that water and ice clouds are aerosols as well, whereas I held the opinion that they are not. We concluded arguments by accepting that clouds are special cases of aerosols and if not explicitly mentioned, atmospheric aerosols mean liquid and solid particles suspended in the air and have aerodynamic diameter between 1e-3 and 1 µm.

Technically aerosols are defined as colloid of air and solid/liquid particles, where air is the dispersion medium and particles are in dispersed phase. The word aerosols brings-in naturally the interaction between particles and air. When particles are not in the air, for example particles collected on filter papers, they are no more aerosols. Hence aerosol is a state of particles rather than the particle itself. This is the reason why most pollution and chemistry related studies report them as particulate matter (PM) because these studies require collecting them on filter papers, while most climate related studies report particles as aerosols since particles are climate modulator as long they are in the air.

Coming back to Jaenicke's article, he starts with questioning the very definition of atmospheric aerosol as colloid. Schmauss and Wigand were probably the first to define atmosphere as colloid of air and particles. The word colloid itself was coined in the year 1875 by Gerber to describe a pseudosolution prepared by Selmi (reference in Jaenicke, 2008) . Jaenicke sees a reason to question this definition because colloid implies a stable state, homogeneity and monodispersed size distribution. Hardly any of these is true for atmospheric aerosols. On the other hand there are properties such as surface-to-volume ratio, interactions between nearby particles, multiple scattering, etc that support their definition as colloid. Jaenicke concludes that atmospheric aerosols can be considered colloid in dynamic equilibrium.

The crux of the paper is not the discussion on the definition of aerosol but modeling aerosol concentration in the atmosphere under the framework of dynamic equilibrium. Dynamic equilibrium by its nature results in highly variable aerosol concentration. Which in turn requires better temporal resolution for measuring them. In this discussion, Jaenicke highlights quite a few gaps in our knowledge about atmospheric aerosols.

References

Jaenicke, R. (2008). Is atmospheric aerosol an aerosol?-a look at sources and variability. Faraday Discuss 137, 235-243.

Art work: courtesy Malkaush

Satellite remote sensing of active fires: Impact of clouds

2008-02-03T13:49:00.000-05:00

It has been long time since passive satellite observations in visible and thermal part of the spectrum have been used to monitor and quantify the biomass burning over global areas. Space sensors such as AVHRR, MODIS, and GOES are some of the examples, which continuously monitor vegetation fires under clear sky conditions. But, these sensors are limited to cloud free conditions and there could be large errors in estimation of fire activities due to lack of sampling under cloudy conditions. Remote Sensing of Environment published a research article entitled “Quantifying the impact of cloud obscuration on remote sensing of active fires in the Brazilian Amazon” by Wilfrid Schroeder and coauthors discuss the bias in remote sensing fire data due to possible cloud cover during fire activities over Brazilian Amazon.

The abstract read as “Vegetation fires remain as one of the most important processes governing land use and land cover change in tropical areas. The large area extent of fire prone areas associated with human activities makes satellite remote sensing of active fires a valuable tool to help monitor biomass burning in those regions. However, identification of active fire fronts under optically thick clouds is not possible through passive remote sensing, often resulting in omission errors. Previous analyses of fire activity either ignored the cloud obscuration problem or applied corrections based on the assumption that fire occurrence is not impacted by the presence of clouds. In this study we addressed the cloud obscuration problem in the Brazilian Amazon region using a pixel based probabilistic approach, using information on previous fire occurrence, precipitation and land use. We implemented the methodology using data from the geostationary GOES imager, covering the entire diurnal cycle of fire activity and cloud occurrence. Our assessment of the method indicated that the cloud adjustment reproduced the number of potential fires missed within 1.5% and 5% of the true fire counts on annual and monthly bases respectively. Spatially explicit comparison with high resolution burn scar maps in Acre state showed a reduction of omission error (from 58.3% to 43.7%) and only slight increase of commission error (from 6.4% to 8.8%) compared to uncorrected fire counts. A basin-wide analysis of corrected GOES fire counts during 2005 showed a mean cloud adjustment factor of approximately 11%, ranging from negligible adjustment in the central and western part of the Brazilian Amazon to as high as 50% in parts of Roraima, Para and Mato Grosso.”

For more details refer the original publication:

Wilfrid Schroeder, Ivan Csiszar and Jeffrey Morisette, Quantifying the impact of cloud obscuration on remote sensing of active fires in the Brazilian Amazon, Remote Sensing of Environment, Volume 112, Issue 2, 15 February 2008, Pages 456-470.

Air pollution in mega cities in China: A Review

2008-01-26T13:07:00.000-05:00

Air pollution (both gas and particle) in Chinese mega cities is one of the biggest growing problems due to rapid increase in industrial activities in the area. A review article on air pollution in China entitled “Air pollution in mega cities in China” by Chan and Yao is published in January 2008 issue of Atmospheric Environment. This article provides through review of available literature on air pollution research in China and focused areas are Beijing, Shanghai, and the Pearl River Delta region.

Here, I am providing some highlights of the article. Please refer original article for more details.

"Air pollution has become one of the top environmental concerns in China. Currently, Beijing, Shanghai, and the Pearl River Delta region including Guangzhou, Shenzhen and Hong Kong, and their immediate vicinities are the most economically vibrant regions in China.”

“Air quality in most Chinese cities has improved despite the rapid growth of the economy…, however… He et al. (2001) and Ye et al. (2003) reported that PM2.5 concentrations in Beijing and Shanghai, the two largest cities in China, were about 10 times and six times the WHO guideline values, respectively.”

“From 1980 to 2005, the urban population in China increased from 19.6 to 40.5%. The number of cities increased to over 660, and more than 170 cities had over 1 million permanent residents (not including the migrant population) in 2004.”

“Much attention has been paid to reducing emissions, particularly vehicle emissions. Although the number of vehicles has increased by about 10% per year in these cities, NO2 and CO concentrations have not increased due to effective control measures… Particulate pollution is still severe, and it is the major air pollution problem in the mega cities.”

Complete Reference:

Chan, C. K. and X. Yao (2008, January), Air pollution in mega cities in china, Atmospheric Environment 42 (1), 1-42, doi:10.1016/j.atmosenv.2007.09.003

One Year of Aerosol Blog (about us)

2008-01-08T15:57:00.002-05:00

Hello all Readers,

Today, aerosol blog completed successful one year. So we thought to write a blog about our blog. The blog was started last year in first week of January. Initially there were only two authors (Harish and Pawan) but soon Falguni, Neeraj and Dilip joined team, making it possible to post 42 posts in one year, almost one post per week. Here we take a look on what make us to start this blog, what content is dear to us and what is the future of this blog.

"Hey listen to this!"

It is common tendency of human being when we see something interesting we want to share it with others. Who is not aware of such a friendly shout "hey listen to this" with family members at home, with friends in hostel, when someone found interesting paragraph in news-paper or book. We five members of current team once upon a time where in Physical Research Laboratory and use to enjoy such a sharing. Later on we moved to different places but still use to shout through e-mail "Hey see this is interesting". Every year more than 7500 peer reviewed articles are published in the field of atmospheric science, quite a big fraction of it are published in the field quite close to our research work. We realized that it would be very useful if there would have been a guide to help short-list relevant articles. With these two intention we started blog, later on we realized that blog is quite promising medium for publication and can work as e-magazine.

Objectives

Our current objective is to provide pointer to information relevant to the research in the field of aerosols, clouds and climate change, be it journal article, book, web-site, biography, patent, database, conference or job. It is also part of objective to provide perspective why that piece of information is interesting. However as far as possible we want to focus on technical aspects of the research in this field rather than popular aspects. In future we want to transform our blog in e-magazine with its own articles, commentaries, digest and announcements.

Is this blog free?

This blog is free for viewing, but free is very deceptive word. We believe truly free viewing should be free of advertisements. What is the point in shortlisting articles if again one has to search them through jungle of ad links. We are able to provide it free because we are using resources available free of charge. As stated in earlier paragraph that we intend to make our blog an e-magazine. This may require some kind of investment such as server, software, domain name etc. But it will be our highest priority to run this blog free of charge and free of advertisement.

Who are the authors?

We are currently five authors who are responsible to update blog on regular basis. We have established credentials in this field and have articles published in peer reviewed journals. More information about authors can be found at their home-page listed below

Harish Gadhavi- http://www.atmos.umd.edu/~harish/
Post doctoral research fellow at University of Maryland, College Park

Pawan Gupta - http://www.nsstc.uah.edu/~gupta/
Graduate student at University of Alabama, Huntsville

Neeraj Rastogi - http://www.prl.res.in/~nrastogi
Post doctoral research fellow at University of Georgia, Atlanta

Falguni Gupta - http://www.nsstc.uah.edu/~falguni/
Graduate student at Universtiy of Alabama, Huntsville

Dilip Ganguly - http://www.prl.res.in/~dganguly/
Post doctoral research fellow at Princeton University, Princeton, NJ

We welcome contributions from anyone who wants to contribute or share a piece of information consistent with the theme of blog. Announcement regarding conferences, job are most welcome. Contact information can be found in the end of the blog

Copyright

We have unspecified status of copyright for our blog. Authors own the copyright individually as allows the law. If not specifically mentioned about restriction, feel free to use our blog for non-commercial purpose. We sometime use figures and texts from others as fair use policy allows, but copyright to those figures and texts belongs to originating source. We try our best to cite full reference for such a source. If we have adversely used copyrighted material, please bring to our notice and we will immediately remove it. Contact information can be found in the end of the blog

Please see the home-pages of authors to contact authors individually.

Thanks to Harish for preparing these notes!

The Story of Stuff

2007-12-08T15:19:00.001-05:00

Couple of days back, a professor in my department forwarded me the link of this movie, saying it is 20 min long but worth seeing. After seeing I realized that this was the best animation I have ever seen.

Click on the image or here to see movie. I don't want to spoil surprise by writing more about movie but if you trust my words, you are guaranteed your time will not be wasted.

Inter-relationship between the chemistry of aerosols and precipitation and their implications

2007-11-29T18:40:00.000-05:00

The large-scale anthropogenic emissions have been increasingly affecting the air quality as well as regional and global climate by altering Earth’s surface temperature and precipitation patterns. These pollutants are removed from the atmosphere via wet and dry deposition, which in turn may adversely affect the terrestrial and aquatic environments, ranging from acidification of soils and inland waters to the damage of buildings and monuments. The regional precipitation chemistry provides the simplest way to assess the influence of human activities on the composition of the atmosphere, and to improve knowledge of physico-chemical processes related to the atmospheric transport and deposition of pollutants. The chemical composition of an individual precipitation event is dictated by ‘in-cloud’ and ‘below-cloud’ scavenging of atmospheric aerosols and gaseous species derived from natural and anthropogenic sources. Wet and dry deposition also provides information on the exchange of chemical components between the atmosphere and the land/ocean and hence it is an important link in understanding the biogeochemical cycles of important chemical elements such as N, P and S.

Rastogi and Sarin (2007) have discussed the inter-relationship between aerosol and rain composition collected over a period of three years at Ahmedabad, an urban city located in a semi-arid region of India. They have proposed a simple way (comparison of ionic ratios in aerosol and rain) to understand the dominant scavenging processes (in-cloud/below-cloud) of chemical species and the phase (gaseous vis-à-vis particulate) from which it is scavenged by rain. By first direct measurement of alkalinity in rainwater over India, they have discussed the reason of alkaline rain over their study region, in spite of high concentrations of acidic pollutants like SO4 and NO3.

For more details, please read the following article and references therein:

Rastogi, N. and Sarin, M.M., 2007. Chemistry of precipitation events and inter-relationship with ambient aerosols over a semi-arid region in western India. Journal of Atmospheric Chemistry 56, 149-163. (DOI 10.1007/s10874-006-9047-5).

Dust Aerosol: Spherical Vs Non-Spherical

2007-11-04T19:19:00.000-05:00

In most climate and radiative transfer models, optical properties of aerosols are modeled using spherical shape assumptions. This assumption is based on sound scientific reasoning. All liquid aerosols have spherical shape because of surface tension. Solid aerosols, which are water soluble also eventually absorbs water vapor from atmosphere and transform themselves into spherical shape.

However, dust aerosols are neither liquid nor water soluble. Soot aerosols also fall in this category. Hence, they may not necessarily have spherical shape. This requires that we should examine the validity of spherical shape assumption, particularly for these two types of aerosols. There are two aspects to look at for importance of spherical shape assumption. One is relative magnitude of non-spherical aerosol number concentration. If there are not quite large number of non-spherical particles in the atmosphere, then we need not worry about it. Li and Osada (2007) have shown using model study that dust particles are essentially spherical when away from source regions, this is due to preferential settling of non-spherical dust particles. (See our earlier blog). This kind of studies are relatively few and recent. We can expect to see in future their modeling results being compared with observations of Saharan dust transport over Atlantic ocean.

Second aspect is effect of non-sphericity on optical properties. It is believed that when non-spherical particle are randomly oriented, their overall impact can be modeled by assuming them spherical with some kind of equivalent effective radius. Though this assumption appears correct intuitively, not extensively validated. Recently, I come across an article by Yang et al. (2007), who have compared optical properties of aerosols for spherical and non-spherical (spheroid) shape assumptions. They have shown that the non-sphericity has negligible impact on optical properties in long-wave (terrestrial) spectrum. However quite a large effect can be seen in short wave (solar) spectrum.

Figure (12) of Yang et al. (2007) show the effect of spherical and spheroidal shape assumption on estimates of brightness temperature and top of the atmosphere reflectivity. The black curves represent clear sky condition, blue curves dust particle with spherical shape and red curves represent dust particle of spheroid shape (aspect ratio 1.7). When used spheroidal shape assumption to calculate top of the atmosphere reflectance, quite a large difference can be seen in shortwave (~30% difference at 500 nm)

References

Li, J. and K. Osada (2007, September). Preferential settling of elongated mineral dust particles in the atmosphere. Geophysical Research Letters 34, L17807+.
Yang, P., Q. Feng, G. Hong, G. W. Kattawar, W. J. Wiscombe, M. I. Mishchenko, O. Dubovik, I. Laszlo, and I. N. Sokolik (2007, October). Modeling of the scattering and radiative properties of nonspherical dust-like aerosols . Journal of Aerosol Science 38 (10), 995-1014.

Conferences in the field of aerosol, cloud and climate

2007-11-04T09:45:00.001-05:00

Recently I received quite a good number of conference related notifications. Many of reader of this blog may be participating it and they shouldn't miss the dead-line so I am listing them below. If you know conference that is not listed below but related to theme of this blog please let us know.

15th National Space Science Symposium, India (NSSS-2008)

National Space Science Symposium is one the largest gathering of space scientist in India. It covers wide variety of subjects including remote sensing of atmosphere and climate change study. The next NSSS is going to be held at Radio Astronomy Centre (NCRA-TIFR) in Ooty between 26 and 29 February 2008. Ooty is one of the famous hill-station in India.

Last date to submit abstract Dec 7, 2007.

Broad subject areas covered in this conference

Space- and ground-based astronomy and astrophysics, planetary science / exploration
Solar radiation and its interaction with earth's near and distant environment
Magnetosphere, ionosphere, thermosphere, and middle atmosphere phenomena
Space based oceanography, meteorology, and tropospheric studies
Climate changes and geosphere-biosphere interaction processes

EGU General Assembly 2008
European Geophysical Union's general assembly will be held in Vienna, Austria between 13 and 18 April 2008.
Last date to submit abstract: January 14, 2008
Last date to submit financial support application: December, 7, 2007
Last date for registration: March 31, 2008
Subject area covered are
It covers all disciplines of Earth, Planetary and Space Sciences

AOGS 2008
Asia Oceania Geosciences Society's (AOGS) 5th annual meeting will be convened between 16 and 20 June, 2008 in Busan, Korea.
Abstract submission dead-line: Jan 24, 2008
Author registration dead-line: Apr 22, 2008
This also covers all the subjects in Geoscience area.

International Conference on "Terrestrial Planets: Evolution through Time"

This conference will be held between 22 and 25 Jan 2008 in Physical Research Laboratory, Ahmedabad, India. Last date for abstract submission is November 15, 2007.

Following are the main theme of conference

Early solar system and Planetary processes
Evolution of the Indian Plate: Precambrian to Recent
Paleoclimate and Paleoenvironment
Tectonics-Erosion-Climate and Carbon cycle

Acknowledgment
Images used here are taken from the web-pages of those conferences.

BIOAEROSOLS

2007-10-23T17:48:00.000-04:00

Indoor or outdoor air may contain thousands or even millions of microorganisms and biological particles in just one cubic meter of air. These airborne particles are collectively referred to as bioaerosols. Examples of bioaerosols include viruses, bacteria, fungi, pollen, fragmented particles from microbial cells or insects, and by-products of living organisms (e.g. animal dander, insect excrement). The size of these particles generally varies between a fraction of a micrometer (µm) to approximately 30 µm. Bioaerosols may originate from numerous natural or man-made sources such as agriculture (harvesting, storage, composting etc) and industrial activities (manufacturing, food processing etc), indoor surfaces (ceiling, wall, carpets, house plants) and water treatment plants etc.
Particle size is an important factor in determining risks associated with microbial contamination. In general, particles > 20 µm (fungi, algae, pollen etc) affect Region 1, Particles < 20 µm (mostly bacteria and some fungi, algae) affect Region 2 and particles < 1or 2 µm (mostly viruses and some bacteria) affect Region 3.

Modern airborne sampling of bioaerosols employs one of three protocols: 1) impactor sampling, 2) liquid impinger sampling, or 3) filtration sampling. Each of these methods pulls a measured volume of air with the aid of an electric or battery-powered pump. The air is then directed through a chamber (or a series of chambers), guiding the spores (particles) on a specific trajectory to a solid agar disc or adhesive medium (impactor samplers), a liquid buffer (impinger samplers), or a filter (filtration samplers). With the impactor method, cells or spores are usually cultured on a suitable nutrient medium. Each organism is then identified and reported as colony forming units m-3 (CFUs per cubic meter).
Since state and federal standards for most of the bioaerosols do not exist, the most common practice compares indoor cell concentrations to concentrations measured outdoors during the same sampling event. This unofficial benchmark implies that indoor counts should not be significantly greater than outdoor counts. When indoor concentrations are significantly greater, it is generally assumed that an indoor amplification source exists. In other words, there is likely microbial contamination present on indoor building materials. Such basic approaches do not apply to all microorganisms. Relatively high levels of one airborne microbe may represent very low risks, while extremely low levels of more dangerous contaminants should trigger immediate action. Other important factors must also be considered, including the location of air samples, frequency of detection, frequency of sampling, type of air sampler, and the environmental conditions while assessing the effects of bioaerosols.
For more information and understanding, please refer the following book and other literature

Macher, Janet (Ed.), Bioaerosols: Assessment and Control, American Conference of Governmental Industrial Hygienists, Cincinnati, Ohio, 1999.
ISBN: 978-1-882417-29-2

Conference & Symposiums on Environment Science: AGU and AMS 2007-2008

2007-10-15T11:56:00.000-04:00

Annual fall meeting of American Geophysical Union (AGU) and annual meeting of American Meteorological Society (AMS) is approaching close in December 2007 and January 2008 respectively. These are two biggest events in USA where more than 20 thousands scientist from around the world get together to discuss, show and present their research in various areas of Earth Sciences. Environment science is one of the main focus area in both meetings and several thousands research studies on the same will be presented.

The next AMS (88th Annual Meeting) will be held in, New Orleans, LA, USA during 20-24 January 2008.

Please click on the link to see various topics covered by AMS-2008

http://www.ametsoc.org/meet/annual/programsandevents.html

and

This year AGU Fall meeting will be held in San Francisco, CA, USA during 10–14 December 2007.

For more details click here

http://www.agu.org/meetings/fm07/

IPCC gets Nobel Peace Prize

2007-10-12T18:56:00.001-04:00

The Norwegian Nobel Committee has decided that the Nobel Peace Prize for 2007 is to be shared, in two equal parts, between the Intergovernmental Panel on Climate Change (IPCC) and Albert Arnold (Al) Gore Jr. for their efforts to build up and disseminate greater knowledge about man-made climate change, and to lay the foundations for the measures that are needed to counteract such change.

Indications of changes in the earth’s future climate must be treated with the utmost seriousness, and with the precautionary principle uppermost in our minds. Extensive climate changes may alter and threaten the living conditions of much of mankind. They may induce large-scale migration and lead to greater competition for the earth’s resources. Such changes will place particularly heavy burdens on the world’s most vulnerable countries. There may be increased danger of violent conflicts and wars, within and between states.

Through the scientific reports it has issued over the past two decades, the IPCC has created an ever-broader informed consensus about the connection between human activities and global warming. Thousands of scientists and officials from over one hundred countries have collaborated to achieve greater certainty as to the scale of the warming. Whereas in the 1980s global warming seemed to be merely an interesting hypothesis, the 1990s produced firmer evidence in its support. In the last few years, the connections have become even clearer and the consequences still more apparent.

Al Gore has for a long time been one of the world’s leading environmentalist politicians. He became aware at an early stage of the climatic challenges the world is facing. His strong commitment, reflected in political activity, lectures, films and books, has strengthened the struggle against climate change. He is probably the single individual who has done most to create greater worldwide understanding of the measures that need to be adopted.

By awarding the Nobel Peace Prize for 2007 to the IPCC and Al Gore, the Nobel Committee is seeking to contribute to a sharper focus on the processes and decisions that appear to be necessary to protect the world’s future climate, and thereby to reduce the threat to the security of mankind. Action is necessary now, before climate change moves beyond man’s control.

Causes of the reduction in uncertainty in the anthropogenic radiative forcing of climate betweeen IPCC (2001) and IPCC (2007)

2007-09-30T16:42:00.000-04:00

The Inter-governmental Panel on Climate Change reviews the best available scientific information on climate change and publishes a report every 5-6 years. The fourth assesment report was released this year and is the IPCC 2007 report. In contrast to the IPCC 2001 report, this report emphasizes with greater confidence that global warming is due to human/anthropogenic activities. Until recently, the sign of the anthropogenic radiative forcing was uncertain largely due to the uncertainty associated with radiative effects (direct and indirect) of atmospheric aerosols. Haywood and Schulz in their recent paper (titled above) inter-compare the probability distribution function of anthropogenic radiative forcing from IPCC 2001 and IPCC 2007 and show that a significant progress has been made in reducing the uncertainty in anthropogenic radiative forcing since IPCC 2001. They conclude that " the single most contributor to this conclusion appears to be the reduction in the uncertainty associated with the aerosol direct effect, followed by the provision of a best estimate for the aerosol cloud albedo indirect effect ".

References :

Haywood, J. M., and M. Schulz (2007), Causes of the reduction in uncertainty in the anthropogenic radiative forcing of climate between IPCC (2001) and IPCC (2007), Geophys. Res. Lett., doi:10.1029/2007GL030749, in press.

http://www.ipcc.ch/

UN/Austria/ESA Symposium on “Space Tools and Solutions for Monitoring the Atmosphere in Support of Sustainable Development”: My Experience

2007-09-23T23:15:00.000-04:00

The United Nations (UN) office for outer space affairs, the government of Austria and the European Space Agency (ESA) jointly organized a symposia on “space tools and solution for monitoring the atmosphere in support of sustainable development”. The United Nations invites participants from several nations to attend the symposium every year. There were more than 70 scientists representing more than 41 countries who gathered in Graz, Austria during September 11-14 to discuss various available space tools for monitoring the atmosphere in support of sustainable development. This year’s symposium included a hands-on tutorial and interactive training session on “Satellite Tools and Applications for Air Quality”. I was part of the team, which developed material and conducted the training session. I would really like to take this opportunity to thank my supervisor Dr. Sundar Christopher for providing me this wonderful opportunity and NASA’s applied science program manager Lawrence Friedl for financial support and organizers of the symposium for giving me this amazing opportunity to attend the symposium. It was indeed a great experience to meet and listen to many scientists from different parts of the world on many different aspects of air quality and monitoring atmospheric composition using satellite measurements.

The symposium was a good combination of invited talks, participant presentations and hands-on training workshop. Invited talks covered several important areas including overview of earth observations, satellite applications for atmospheric monitoring, global and regional initiatives, air quality (ozone and particulate matter), climate change and weather.

Hands-on training on satellite tools for air quality monitoring was informative and every single participant experienced handing of satellite data and I am very sure they enjoyed it immensely. The training used four different case studies of heavy aerosol events when particulate matter air quality on the surface was very poor in the region. Case studies covered two recent biomass burning events, one dust storm and one with a mixture of urban pollution and smoke from fires. The participants from the symposium were divided into groups of 3-4 people and each group was provided with a laptop computer. After initial introduction on monitoring air pollution from satellite observations, each group analyzed one case study. Air quality analysis includes identifying different features such as aerosols, clouds, water, land etc in the satellite images, quantifying aerosol loading using aerosol optical thickness, observations on local meteorological conditions and back trajectory analysis to track air mass in and out from the regions of interest. One of the most important parts of this exercise was to obtain different data sets and images from freely available online resources. Every group liked this part and learnt simple solutions to address specific air quality events using satellite imagery. Finally, participants used the tools that they learnt in the workshop to identify air quality color codes in their city or region of interest.

I really enjoyed the entire training session and discussed many different issued related to air quality in different parts of the world. The last day of the symposium was used to identify different problem associated with air quality research and monitoring of air pollution in the participant's country or region. There were several recommendations made by two working groups on air quality monitoring network, data sharing, and policy related issues to the United Nations.

Evening receptions and tours within Graz city were wonderful and served as a time of relaxation after the busy working days for all participants.

Finally, I would like to congratulate and thank all the people who were directly or indirectly involved in organizing such a great successful symposium.

More details about the symposium can be found out on following web link
http://www.unoosa.org/oosa/SAP/act2007/graz/index.html

(Pawan Gupta)
The University of Alabama in Huntsville
Huntsville, AL, USA

P.S: The participants were eager to know the various resources that are available to them on the internet for various data sources. Here are a list if some websites that will be useful.

GIOVANNI: MODIS, MISR, TOMS, OMI aerosol daily and monthly data can be obtained and visualize online using various options available.

MODIS Atmosphere: Details description on MODIS atmospheric products such as aerosols, clouds, water vapor and atmospheric profiles. This is very good site to learn about data, algorithms and updates on publications.

MODIS Rapid Response System: True-color, photo-like imagery and false-color imagery are available within a few hours of being collected by MODIS.

NASA Visible Earth: This is good catalog for different Earth’s images from NASA.

International Air Quality: This site is hosted on USEPA webpage, which provides link to available online resources for international air quality monitoring.

IDEA: This site provides surface and satellite assessment of particulate matter air quality over United States.

NRL Aerosol Page: This site provides model forecasts of various aerosol fields for global regions. This site also maintain very good list of links related to atmospheric aerosol research.

History of Aerosol Science

2007-09-17T13:25:00.000-04:00

The first time my interest in aerosol science picked up was when I learnt about nuclear winter -- a phenomena which refers to possible climatic impact of all-out nuclear war. What really fascinated me was the idea that if one wants to control climate or weather in predictive manner, aerosols are going to be the best tool; for a reason that they have relatively short life-time giving control over their introduction and removal in the atmosphere. Well! this is not the subject of today's post. Thinking of my own interests in this field led me to think about history of aerosol science. Couple of years before I read Spencer Weart's "The Discovery of Global Warming". I am fascinated by its content and writing style. Experience was not less than reading suspense thriller. Later on, I come across a comment that book is weighted toward contributions of American scientists than European scientists. I do not know the truth as my knowledge in the history of climate science is limited. But if asked Weart's book is my first recommendation.

The climate scientist J. Murray Mitchell, Jr. took up the question, with the help of improved data on how minuscule particles (aerosols) moved through the upper atmosphere. Studies of fallout from nuclear bomb tests had shown that fine dust injected into the stratosphere would linger for a few years, but would not cross from one hemisphere to the other. With that in mind, Mitchell pored over global temperature statistics and put them alongside the record of volcanic eruptions. In 1961, he announced that large eruptions caused a significant part of the irregular variations in average annual temperature in a given hemisphere. On the other hand, average temperatures had fallen since 1940, a period in which the world had seen few major eruptions. Mitchell concluded that the recent cooling was an "enigma." He thought it might signal a new phase of a decades-long "rhythm," the sort of cycle that generations of climatologists had tried to winkle out of their data

While thinking of Weart's book, I started searching what resources are available on Internet about history of aerosol science and to my delight I found that Weart has created web-pages to supplement his book. On his web-page you can read history of aerosol science and global warming with full references, illustrations and pictures of scientists. A link is available to download whole web-site in zip file so one can burn his/her own CD, or one can download PDF file and print it and of cause one can read it online. Following is the link to table of content.

Climate Change: Discovery of Global Warming
http://aip.org/history/climate/

Treating Dust As A Spherical Particle: Good/Bad Assumption?

2007-09-06T10:11:00.000-04:00

It is widely know that dust is essentially non-spherical and hence radiative transfer calculations treating dust as a spherical particle are not adequate. A recent laboratory based study on dust particles by Jingmin Li and Kazuo Osada is very interesting. This article appeared in GRL this month. They study the preferential setting of elongated mineral dust collected from snow in a high mountain in Japan. The positions of particles' centers of gravity and folding centers are analyzed using a scanning electron microscopy and optical microscopy. Their results suggest that a preferential orientation exists for particles settling heavy side down (as expected) but what is interesting is the analysis of results from Ginoux's model wherein they apply this preferential orientation information and show that : " away from the source regions, dust particles are essentially spherical, which considerably simplify the calculation of settling velocity in transport and of radiative transfer models."

Figure above shows the relative difference of calculated settling velocity between ellipsoidal and spherical particles {Δu∞ = 100% × [u∞ (λ) − u∞ (λ = 1)]/u∞ (λ = 1)}. For example, the settling velocity of particles of 2 μm diameter increases respectively around 50%, 100%, and 165% for aspect ratios of 2, 4, and 10. The relative difference decreases with increasing particle size. For particles of 10 μm, the settling velocity increase for ellipsoids is around 30–40%, with little difference shown for aspect ratios of 1–10. On the other hand, a 40% decrease of settling velocity for ellipsoids is apparent at around 40–50 μm for the aspect ratio of 10.

Reference :

Li, J., and K. Osada (2007), Preferential settling of elongated mineral dust particles in the atmosphere, Geophys. Res. Lett., 34, L17807, doi:10.1029/2007GL030262.

Aerosols heat up

2007-08-28T17:09:00.000-04:00

Aerosols are thought to have a cooling effect on the atmosphere, and therefore to have mitigated some of the expected global warming over this period. This is, however, a highly uncertain conclusion, in part because the total amount and vertical distribution of solar radiation that is absorbed by aerosol particles is imperfectly known. There was an interesting article in Nature (Vol-448, 2 August 2007) under “News and Views” by Prof. Peter Pilewskie. In the same issue, Ramanathan et al. (on page 575) report that the aerosol clouds above large regions of Asia actually cause as much warming as greenhouse gases — in contradiction, at first glance, to the notion of aerosol particles as a cooling agent.

Figure 1. Smog drifts down India's populous Ganges valley and out into the Bay of Bengal. This is the source of 'atmospheric brown clouds' over the Indian Ocean, and the climatic effect of its constituent aerosol particles is investigated by Ramanathan and colleagues

For more information and understanding, please refer following two articles and references therein:

Pilewskie, P., 2007, Aerosols heat up, Nature 448, 541-542.

Ramanathan et al. 2007, Warming trends in Asia amplified by brown cloud solar absorption, Nature 448, 575-578.

Aerosol Optical Thickness: MODIS Improved Product over Land

2007-08-12T12:20:00.000-04:00

MODIS aerosol optical thickness (AOT) retrieval algorithm over land is continuously improving and now operational to produce collection 5 aerosol data products. Both Terra and Aqua data has been reprocessed using new retrieval algorithm. Click here to view current data processing status. New algorithm replaced the surface reflectance assumptions, the set of aerosol model optical properties, and the aerosol lookup table to reduce uncertainty in the product. In collection 5 retrievals of small-magnitude negative AOT values (down to −0.05) are considered valid, thus balancing the long term statistics of τ in near zero AOT conditions. Initial validation exercise conducted on this algorithm shows much improved retrievals of AOT. As consequence, global mean AOT for the test bed is reduced from ∼0.28 to ∼0.21.

Last month two research articles published in JGR-Atmosphere discussing new algorithm:

Levy R. C., L. A. Remer, S. Mattoo, E. F. Vermote, Y. J. Kaufman (2007), Second-generation operational algorithm: Retrieval of aerosol properties over land from inversion of Moderate Resolution Imaging Spectroradiometer spectral reflectance, J. Geophys. Res., 112, D13211, doi:10.1029/2006JD007811.

Levy R. C., L. A. Remer, O. Dubovik (2007), Global aerosol optical properties and application to Moderate Resolution Imaging Spectroradiometer aerosol retrieval over land, J. Geophys. Res., 112, D13210, doi:10.1029/2006JD007815.

International Symposium on Aerosol Chemistry Climate Interactions

2007-08-06T14:02:00.000-04:00

My alma mater Physical Research Laboratory, Ahmedabad, India is holding an International Symposium on Aerosol-Chemistry-Climate Interactions

Symposium will be from 20-22 November 2007. Last date to send abstract is 31 August 2007.

The topics covered are

1. Observations of Atmospheric Parameters
Measurements of trace gases, aerosols, using in situ and remote sensing techniques

2. Transport and Transformation of Trace Gases and Aerosols
Long range and inter-continental transport, and stratosphere-troposphere exchange

3. Modeling of Atmospheric Processes
Emission inventories, sinks, model development and evaluation

4. Radiative Forcing and Climate Change
Aerosol-cloud interactions, impact on environment and climate

5. Space Instrumentation for Probing the Lower Atmosphere
Advances and developments in space techniques, sensor characterization and retrieval algorithms

Limited traveling and registration fee support will be provided to young scientists (below 35 years). For more information refer to conference web-page at http://www.prl.res.in/~acclint2007

Remote Sensing of Spectral Aerosol Properties: A Classroom Experience

2007-07-30T10:01:00.000-04:00

From my graduate school experience I find that the best way to learn and understand science is by getting your hands dirty with the relavant data when it comes to understanding remote sensing. Like remote sensing courses at many other universities in the United States, the University of Alabama in Huntsville offers two courses in Satellite Remote Sensing, ATS670 and ATS770. These courses are tailored in a manner to that allows students to get hands on experience with state-of-the art remote sensing datasets such as the MODIS . In ATS670, students select a MODIS image of their interest and perform a supervised and unsupervisd classification of the image to identify different features in the image such as land, water, clouds, aerosols, vegetation etc. The beauty of doing all this is that the student doesn't get to use any classification software! They write their own routines to perform all the required tasks including trivial tasks such as calculating minimum, maximum, mean, standard deviation to more sophisticated tasks such as histogram equalization, contrast streching, gray flipping, edge detection, fire detection, cloud detection in images to name a few. The journey begins with learning the basic principles of remote sensing and understanding the fundamentals behind seperating features in a remotely sensed image based on spectral signatures. Once the basics unfold, students write their own programs to read the MODIS image, perform a true color three band overlay, pick samples, perform image classification using several techniques such as the parellelopiped method, migrating means method, minimum distance, maximum likelihood methods and the mahalonobis classifier. The ingredients of this course a perfect blend of theoritical and practical classroom learning. ATS770 is more advanced and students use several radiative transfer models and other remote sensing tools to perform retrievals such as for cloud and aerosol properties.

Having taken these courses I have a great appreciation of hands-on experience in learning remote sensing and this is what attracted my attention to a paper by Robert Levy that appeared in the BAMS, 2007 (reference below). This paper talks about the challenge instructors face in bridging the gap between current research and the classroom and how the University of Maryland and NASA Goddard Space Flight Center teamed up to "design a graduate class project intended to provide a hands-on introduction to the physical basis for the retrieval of aerosol properties from state-of-the-art Moderate Resolution Imaging Spectroradiometer (MODIS) observations". "This paper reviews the basic physics of the remote sensing of aerosols and describes selected findings and lessons learned by the students." Students use both hand calculations based on given look-up tables of aerosol properties and the operational MODIS aerosol retrieval algorithm to carry out the class project. Aerosol retrievals are done over selected AERONET sites (shown in figure below) that aid validation of retrieved products.

Students investigated the reflectance v/s wavelength relations over these sites and they find a surface dependence. Figure alongside shows retrievals obtained by hand calculations by using selected fine and coarse mode geometries of aerosols and the fitting error was estimated to find the best fit. Overlaid is the MODIS retrieval in black. Best fit spectral AOT retrievals were then compared with AERONET AOTs . Details on the codes used and the instructions to perform the exercises is given at :

www.atmos.umd.edu/~levy/MODIS_Aerosol_Project/

This paper illustrates how " Projects such as this provide an opportunity for students and young scientists to become familiar with (and less apprehensive of) datasets of this magnitude". This paper is a must read for all those interested in learning aerosol retrieval techniques.

References :

Levy, R.C., and R.T. Pinker, 2007: Remote Sensing of Spectral Aerosol Properties: A Classroom Experience, Bull. Amer. Meteor. Soc., 88, 25–30

http://www.nsstc.uah.edu/~sundar/ats670.html

http://www.nsstc.uah.edu/~sundar/ats770.html

Levoglucosan: a unique tracer of biomass burning aerosols

2007-07-20T16:44:00.000-04:00

Atmospheric aerosols in general and biomass burning aerosols in particular have recently attracted extensive interest owing to their ability to affect the climate on local to global scales. These climatic effects include a direct radiative effect due to the aerosols’ ability to scatter and absorb incoming sunlight, an indirect effect due to the aerosols’ ability to serve as cloud condensation nuclei (CCN), increasing the cloud’s reflectivity and lifetime, a semidirect effect which leads to reduction in cloud cover, owing to aerosols’ ability to absorb sunlight, changes in precipitation patterns, and export of pollutants and water vapor to the stratosphere. Therefore, it is important to assess human contribution to aerosol emissions, and to assign a source to both anthropogenic and natural aerosols, for understanding the respective contribution of different aerosol types to climate change.

Levoglucosan (1,6-anhydro-β-D-glucopyranose) is a unique tracer for biomass burning sources in atmospheric aerosol particles. It is a product of cellulose combustion, which has been recognized as a biomass burning tracer. When cellulose is heated to over 300°C, it undergoes various pyrolytic processes, yielding a highly combustible tar, a major constituent of which is levoglucosan, a dehydrated glucose containing a ketal functional group. Some of the levoglucosan is consumed in various reactions during combustion but it is nonetheless emitted in large quantities in the resulting smoke aerosol. Therefore, it can be utilize as a specific tracer for the presence of emissions from a biomass burning source in atmospheric particulate matter. Unlike other indicators used for the same purpose, levoglucosan is source-specific to burning of any fuel containing cellulose. Combustion of other materials (e.g., fossil fuels) or biodegradation and hydrolysis of cellulose do not produce levoglucosan. Levoglucosan is relatively stable in the atmosphere, showing no decay over 10 days in acidic conditions, similar to those of atmospheric liquid droplets. Levoglucosan is also used in other fields of chemistry and engineering, such as pyrolysis and fire-retardants research, biofuel research, biology, organic synthesis and as a biomass burning tracer in sediment analysis for the paleorecord.
For more information, please see the following paper and references therein.

Schkolnik G. and Rudich Y. (2006), Detection and quantification of levoglucosan in atmospheric aerosols: A review, Analytical and Bioanalytical Chemistry, 385, 26-33.