J. Vanderlei Martins

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Urban air pollution and smoke from fires have been modeled to reduce cloud formation by absorbing sunlight, thereby cooling the surface and heating the atmosphere. Satellite data over the Amazon region during the biomass burning season showed that scattered cumulus cloud cover was reduced from 38%in clean conditions to 0%for heavy smoke (optical depth of(More)
The effect of anthropogenic aerosols on clouds is one of the most important and least understood aspects of human-induced climate change. Small changes in the amount of cloud coverage can produce a climate forcing equivalent in magnitude and opposite in sign to that caused by anthropogenic greenhouse gases, and changes in cloud height can shift the effect(More)
[1] A cloud masking algorithm based on the spatial variability of reflectances at the top of the atmosphere in visible wavelengths was developed for the retrieval of aerosol properties by MODIS. It is shown that the spatial pattern of cloud reflectance as observed from space, is very different from that of aerosols. Clouds show a very high spatial(More)
Observations of the aerosol optical thickness (AOT) by the MODIS instruments aboard Terra and Aqua satellites are being used extensively for applications to climate and air quality studies, as indicated from 28 publications in 2004 alone. Data quality is essential for these studies. Here we add to the published MODIS validations by investigating the effects(More)
[1] Aerosol absorption of sunlight, in particular by black carbon soot and dark organic material produced from incomplete combustion of fossil fuel and from vegetation fires, is emerging as a key component of climate forcing. However, global characterization of black carbon emissions, distribution and absorption of sunlight cannot be determined within a(More)
[1] As a part of the EAST-AIRE study, Nuclepore filters were collected in two size ranges (coarse, 2.5 mm < d < 10 mm, and fine, d < 2.5 mm) from January to May 2005 in Xianghe, about 70 km southeast of Beijing, and analyzed for aerosol mass concentration, spectral absorption efficiency and absorption coefficient. Twelve-hour aerosol mass concentration(More)
[1] Fuel biomass samples from southern Africa and the United States were burned in a laboratory combustion chamber while measuring the biomass consumption rate, the fire radiative energy (FRE) release rate (Rfre), and the smoke concentrations of carbon monoxide (CO), carbon dioxide (CO2), and particulate matter (PM). The PM mass emission rate (RPM) was(More)
1 Department of Physics, and Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, MD, USA 2 Climate and Radiation Branch, NASA – Goddard Space Flight Center, Greenbelt, MD, USA 3 Institute of Earth Sciences, The Hebrew University of Jerusalem, Israel 4 Catholic University, Washington DC, USA 5 Department of(More)
[1] The retrieval of aerosol optical depth (ta) over land by satellite remote sensing is still a challenge when a high spatial resolution is required. This study presents a tool that uses satellite measurements to dynamically identify the aerosol optical model that best represents the optical properties of the aerosol present in the atmosphere. We use(More)