Vairamani Ramanathan

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[1] A global estimate of the direct effects of anthropogenic aerosols on solar radiation in cloudy skies is obtained by integrating satellite and ground-based observations with models of aerosol chemistry, transport, and radiative transfer. The models adopt global distribution of aerosol optical depths (from MODIS), clouds, water vapor, ozone, and surface(More)
Sea surface temperatures (SSTs) in the equatorial Indian Ocean have warmed by about 0.6–0.8 K since the 1950s, accompanied by very little warming or even a slight cooling trend over the northern Indian Ocean (NIO). It is reported that this differential trend has resulted in a substantial weakening of the meridional SST gradient from the equatorial region to(More)
Every year, from December to April, anthropogenic haze spreads over most of the North Indian Ocean, and South and Southeast Asia. The Indian Ocean Experiment (INDOEX) documented this Indo-Asian haze at scales ranging from individual particles to its contribution to the regional climate forcing. This study integrates the multiplatform observations(More)
Boreal spring climate is uniquely susceptible to solar warming mechanisms because it has expansive snow cover and receives relatively strong insolation. Carbonaceous particles can influence snow coverage by warming the atmosphere, reducing surface-incident solar energy (dimming), and reducing snow reflectance after deposition (darkening). We apply a range(More)
Greenhouse gases (GHGs) warm the surface and the atmosphere with significant implications for rainfall, retreat of glaciers and sea ice, sea level, among other factors. About 30 years ago, it was recognized that the increase in tropospheric ozone fromair pollution (NOx, CO andothers) is an important greenhouse forcing term. In addition, the recognition of(More)
Black carbon is generated by fossil-fuel combustion and biomass burning. Black-carbon aerosols absorb solar radiation, and are probably a major source of global warming1,2. However, the extent of black-carbon-induced warming is dependent on the concentration of sulphate and organic aerosols—which reflect solar radiation and cool the surface—and the origin(More)
[1] Black carbon (BC) and organic carbon (OC) are the largest contributors to the aerosol absorption in the atmosphere, yet the absorption cross sections of BC and OC per unit mass are subject to a large uncertainty due to morphology, physicochemical properties, and the mixing state of carbonaceous particles. Theoretical studies suggest the possibility of(More)
The microphysical, chemical, optical, and lidar data collected during the Indian Ocean Experiment (INDOEX) resulted in a self-consistent aerosol formulation for a multiple-scattering Monte Carlo radiation model. The model was used to simulate the direct aerosol radiative forcing, cloud radiative forcing, and heating rates for typical winter monsoon(More)
[1] This study integrates global data sets for aerosols, cloud physical properties, and shortwave radiation fluxes with a Monte Carlo Aerosol-Cloud-Radiation (MACR) model to estimate both the surface and the top-of-atmosphere (TOA) solar radiation budget as well as atmospheric column solar absorption. The study also quantifies the radiative forcing of(More)