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?

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 pr...

Last Thursday Warren Wiscombe was in my department ( AOSC, Univ of Maryland ) to give a talk. Many of us have greatly benefited from radiative transfer code DISORT. He is a co-author to that code. He has written few other excellent algorithms and code for atmospheric remote sensing. His code for the Mie scattering can be downloaded here . His talk was about deriving cloud properties using ground based zenith radiance measurements. Focus of the talk was cloud optical depth. Cloud optical depth is very important parameter for climate modeling as can be understood from the fact that at any time more than 60% of the earth’s sky is covered with cloud. Cloud optical depth (COD) can range anywhere between 1 and 80+. In spite of such high importance, not only it is poorly understood parameter but also a challenging task to measure it. Turner et al. (2007) highlight this problem by showing five different techniques resulting in five different values for same cloud (see figure). Warren descri...

Multi-angle Imaging SpectroRadiometer (MISR) is an instrument flown aboard terra satellite by NASA on August 1999. As its official web-site truly claims; no instrument like MISR flown before in the space. The unique feature of MISR is its nine cameras looking in nine different directions simultaneously. This affords us to view a given place on the earth from different angles and made it possible to estimate many physical parameters from space. Concept of the MISR is based on a fact that if directional dependence of the scattered light is studied carefully it can reveal many features about target. Sunlight falling on the earth is not scattered equally in all directions. Halos around the moon in the presence of cirrus clouds is one of such phenomena. Ability to view a given location from multiple angle has made it possible to observe many physical quantities for atmospheric aerosols and clouds which otherwise were not possible or difficult to observe from space such as single scattering...