Air Pollution, Aerosols and Clouds in the Climate System

 When it comes to explaining role of aerosols in Earth's climate and in particular their effects on clouds, we can't ask for better than this Meinrat Andreae's video article.  Meinrat Andreae, Latest Thinking, What is the Impact of Aerosol Particles on Cloud Formation?, https://doi.org/10.21036/LTPUB10396 , 2004   What is the impact of aerosol particles on cloud formation?

Sometime I wonder are there any questions left which Google can not answer? Today I stumble upon one such question, when I was just curious to know which station is oldest running station for aerosol related observations? I know in Barrow,Alaska and South Pole, CMDL is monitoring AOD since 1977. But don't know whether these are the oldest stations. And what about black carbon, surface size distribution, PM10, scattering coefficient. I guess one can expect to get long-time series for PM10 at least. Let us compile the list. Leave the name of station and time period in comment, you know for aerosol related obs. are being made from the station.

India Oil Depot caught fire on October 29, 2009 at around 7:30 pm local time. This depot is located about 10 miles south of the Indian pink city Jaipur in the state of Rajasthan. Fire is so massive that the entire area is covered by black smoke clouds. Smoke and haze are visible up to 16 miles away from the fire location. This image is taken by NASA’s MODIS onboard EOS Aqua satellite on October 30, 2009 during its pass over India . Original data for the image is taken from NASA’s MODIS Rapid Fire System and processed at University of Alabama in Huntsville , AL . For more news on fire http://news.bbc.co.uk/2/hi/south_asia/8333211.stm

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. Mathemat...

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 n...

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 Y...

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 ...

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 Modern airborne sampling o...

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 associ...

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 l...

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 trans...

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 i...

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 opera...

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...

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, stand...

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 atm...

Ultraviolet (UV) radiation plays very important role in bio-geo-chemical cycle. Their harmful effects include skin cancer, cataract, immune suppression, reduction in crop yield, etc. Beneficial effects are synthesis of vitamin D in human body, treatment of psoriasis, etc ( Lucas et al., 2006 ). My interest in UV radiation is how it interacts with atmospheric aerosols. Aerosols are one of the many factors which determines amount of surface reaching UV radiation. While scattering type of aerosols may reduce surface reaching UV radiation, they increase the actinic flux which in turn increases the photolysis rate for smog formation ( Dickerson et al., 1997 ). Relation of aerosol and UV radiation is not one-way; while aerosols affect surface reaching UV radiation, they are affected by surface reaching UV radiation. This is particularly true for naturally produced sulfate aerosol. Recently scientific community has shown a lot of interest to study UV induced sulfate aerosol production to bet...

Its time for aerosol scientists to gear up for the upcoming Glory Mission that has a fantastic passive sensor for monitoring aerosols from space with unmatched retrieval accuracies of 0.02 over ocean and 0.04 over land! This article on the Glory Mission appeared in BAMS in the May 2007 edition, volume 88, number 5. It has a very detailed description of the science objectives, the instruments on Glory, measurement objectives, the data products from these instruments, associated uncertainties and validation plans. Glory is basically a part of the A-Train constellation of satellites. It is scheduled to be launched in 2008 and will carry two independent instruments : 1) The Total Irradiance Monitor (TIM) 2) The Aerosol Polarimetry Sensor (APS) The main purpose of the Glory mission is to help address the challenge of reducing uncertainty in adequately contraining climate sensitivity. Glory is intented to specifically meet the following four scientific objectives : " • improve the quant...

7Be and 210Pb are the natural radionuclides present in the atmosphere. Several studies have shown that useful information about transport, removal and residence time of aerosols in the atmosphere can be obtained from the measurements of 7Be and 210Pb. 7Be (half-life = 53.3 days) is produced by cosmic ray spallation of nitrogen and oxygen primarily in lower stratosphere and upper troposphere. Therefore, 7Be is used as a tracer of stratospheric or high tropospheric sources such as ozone, stratospheric bomb fallout debris, stratospherically injected volcanic components. In contrast, 210Pb (half-life = 22.3 years) is a progeny of 238U. The source of 210Pb is radioactive decay of 222Rn (half-life = 3.8 days), a noble gas, continuously emitting from soils to the atmosphere. Thus, 210Pb is a tracer of continental air as more than 99% 222Rn is emanating from the surface of continents. Half-life of both the radionuclides are long enough with respect to their residence time in the lower atmosphe...

NASA in collaboration with CNES, BALL, IPSL and Hampton University launched state-of-art dual channel space LIDAR on April 28, 2006. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) is flying in constellation of satellites called A-Train along with Aura, PARASOL, CloudSat, Aqua, taking Earth observations within 7-8 minutes and OCO will soon join them to complete the A-Train. CALIPSO took its first observation (image on right) on July 24, 2006 and last December its level 1 radiance, lidar level 2 vertical feature masks, cloud and aerosol layer products are released to the public. These data sets are unique in various ways and will provide new dimension (vertical) to the aerosol research. CALIPSO provides long awaited global vertical profiles of aerosols in the atmosphere, which will be very useful for air quality, earth radiation budget and climate change studies. An example is shown below: Read More About Image Here This graphic shows a flight comparison betw...