4 Matching Results

Search Results

Advanced search parameters have been applied.

Observations and simulations of climate forcings and feedbacks. Final report

Description: The research conducted under this agreement sought to use available satellite data sets to document a variety of climate feedback processes by understanding the mechanisms of current climate variability (seasonal, interannual, temperature dependence). Comparisons with feedback processes operating in the GCM were performed to determine which aspects of the variability serve as the most reliable proxies for decadal climate change. This report focuses on three general areas of progress: upper troposphere water vapor, low cloud optical thickness, and tropical cumulus anvil clouds.
Date: February 1, 1996
Creator: Del Genio, A.D.
Partner: UNT Libraries Government Documents Department

Measurements and modeling of the effect of convective clouds on the upper tropospheric moisture budget

Description: The goal of this study is to determine the upper tropospheric moisture budget associated with convective events, and in particular to extend process models to higher altitudes than have been achieved previously. Although upper tropospheric moisture concentrations are several orders of magnitude lower than those near the surface, upper tropospheric moisture exerts an important influence on climate. On a per-molecule basis, greenhouse absorption due to water vapor is about one hundred times more effective at high altitudes than at low altitudes. Several one-dimensional radiative convective models have been used to demonstrate the importance of upper tropospheric moisture on climate. These models show that for a given fractional increase in water vapor at a given altitude the response or change in surface temperature is qualitatively the same. At present, considerable controversy exists over the nature of the vertical redistribution of water vapor in a changing climate, and particularly the distribution of water vapor in the upper troposphere. Lacking suitable data, this controversy is also reflected in the cumulus parameterization schemes that are currently used in models. Understanding upper tropospheric moistening processes are therefore of prime importance in addressing the water vapor feedback question.
Date: June 1, 1994
Creator: Bisson, S. E.; Goldsmith, J. E. M. & Del Genio, A. D.
Partner: UNT Libraries Government Documents Department

Analyzing signatures of aerosol-cloud interactions from satelliteretrievals and the GISS GCM to constrain the aerosol indirecteffect

Description: Evidence of aerosol-cloud interactions are evaluated using satellite data from MODIS, CERES, AMSR-E, reanalysis data from NCEP and data from the NASA Goddard Institute for Space Studies climate model. We evaluate a series of model simulations: (1) Exp N- aerosol direct radiative effects; (2) Exp C- Like Exp N but with aerosol effects on liquid-phase cumulus and stratus clouds; (3) Exp CN- Like Exp C but with model wind fields nudged to reanalysis data. Comparison between satellite-retrieved data and model simulations for June to August 2002, over the Atlantic Ocean indicate the following: a negative correlation between aerosol optical thickness (AOT) and cloud droplet effective radius (R{sub eff}) for all cases and satellite data, except for Exp N; a weak but negative correlation between liquid water path (LWP) and AOT for MODIS and CERES; and a robust increase in cloud cover with AOT for both MODIS and CERES. In all simulations, there is a positive correlation between AOT and both cloud cover and LWP (except in the case of LWP-AOT for Exp CN). The largest slopes are obtained for Exp N, implying that meteorological variability may be an important factor. The main fields associated with AOT variability in NCEP/MODIS data are warmer temperatures and increased subsidence for less clean cases, not well captured by the model. Simulated cloud fields compared with an enhanced data product from MODIS and AMSR-E indicate that model cloud thickness is over-predicted and cloud droplet number is within retrieval uncertainties. Since LWP fields are comparable this implies an under-prediction of R{sub eff} and thus an over-prediction of the indirect effect.
Date: October 1, 2007
Creator: Menon, S.; Del Genio, A.D.; Kaufman, Y.; Bennartz, R.; Koch, D.; Loeb, N. et al.
Partner: UNT Libraries Government Documents Department

Midlatitude Continental Convective Clouds Experiment (MC3E)

Description: The Midlatitude Continental Convective Clouds Experiment (MC3E) will take place in central Oklahoma during the April–May 2011 period. The experiment is a collaborative effort between the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility and the National Aeronautics and Space Administration’s (NASA) Global Precipitation Measurement (GPM) mission Ground Validation (GV) program. The field campaign leverages the unprecedented observing infrastructure currently available in the central United States, combined with an extensive sounding array, remote sensing and in situ aircraft observations, NASA GPM ground validation remote sensors, and new ARM instrumentation purchased with American Recovery and Reinvestment Act funding. The overarching goal is to provide the most complete characterization of convective cloud systems, precipitation, and the environment that has ever been obtained, providing constraints for model cumulus parameterizations and space-based rainfall retrieval algorithms over land that have never before been available.
Date: April 10, 2010
Creator: Jensen, M. P.; Petersen, W. A.; Del Genio, A. D.; Giangrande, S. E.; Heymsfield, A.; Heymsfield, G. et al.
Partner: UNT Libraries Government Documents Department