NASA Technical Reports Server (NTRS) : The pdf

NASA Technical Reports Server (NTRS) : The

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In our most advanced modeling tools for climate change prediction, namely General Circulation Models (GCMs), the schemes used to calculate the budget of solar and thermal radiation commonly assume that clouds are horizontally homogeneous at scales as large as a few hundred kilometers. However, this assumption, used for convenience, computational speed, and lack of knowledge on cloud small scale variability, leads to erroneous estimates of the radiation budget. This paper provides a global picture of the solar radiation errors at scales of approximately 100 km due to warm (liquid phase) clouds only. To achieve this, we use cloud retrievals from the instrument MODIS on the Terra and Aqua satellites, along with atmospheric and surface information, as input into a GCM-style radiative transfer algorithm. Since the MODIS product contains information on cloud variability below 100 km we can run the radiation algorithm both for the variable and the (assumed) homogeneous clouds.

The difference between these calculations for reflected or transmitted solar radiation constitutes the bias that GCMs would commit if they were able to perfectly predict the properties of warm clouds, but then assumed they were homogeneous for radiation calculations. We find that the global average of this bias is approx.2-3 times larger in terms of energy than the additional amount of thermal energy that would be trapped if we were to double carbon dioxide from current concentrations. We should therefore make a greater effort to predict horizontal cloud variability in GCMs and account for its effects in radiation calculations

• Creator/s: NASA Technical Reports Server (NTRS
• Date: 1/1/2007
• Year: 2007
• Book Topics/Themes: NASA Technical Reports Server (NTRS), CLIMATE CHANGE, ATMOSPHERIC GENERAL CIRCULATION MODELS, RADIATIVE TRANSFER, THERMAL ENERGY, ATMOSPHERIC RADIATION, ENERGY BUDGETS, VARIABILITY, REFLECTED WAVES, MATHEMATICAL MODELS, LIQUID PHASES, Oreopoulos, Lazaros, Cahalan, Robert F., Platnick, Steven

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