Seminar coordinator: Prof. Greg McFarquhar (mcfarq at illinois.edu)
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Collectively the sensors in the A-Train provide an unprecedented dataset for assessing the impact of aerosols in the climate system. Co-located CloudSat and CALIPSO observations, for example, are essential for quantifying the magnitude of aerosol direct radiative forcing that depends critically on the relative locations of clouds and aerosols in the atmosphere. This presentation will document the results of recent efforts to quantify aerosol direct effects both globally and regionally using CloudSat’s new multi-sensor radiative flux and heating rates product. The globally and annually averaged direct radiative effect of aerosols is found to be more consistent with estimates from global models than those derived from passive satellite observations. On regional scales, however, large discrepancies exist between modeled and observed aerosol forcing that are found to be closely related to biases in model cloud cover, particularly in subsidence regions.
Analysis of the latest global cloud, precipitation, radiation, and aerosol datasets from sensors in the A-Train constellation also reveals strong evidence that aerosols influence the capacity of clouds to produce rainfall. These observations offer the potential to evaluate and provide new observational constraints on the representation of aerosol indirect effects in numerical models. It will be shown, for example, that the precipitation frequency susceptibility of marine clouds to changes in aerosol concentration is consistently overestimated in global climate models suggesting that current climate predictions may over-estimate the increase in shortwave cloud radiative forcing owing to precipitation suppression in warm clouds.
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