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A New Radiative Time-stepping SchemeA short description of the time-stepping scheme testPeter Hill, 19 Feb 2008

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Motivation

• Transmissivity =

• Regions with low transmissivity

• Absorption predominantly due to a strong gaseous absorber

• Absorption by clouds, aerosols and weak absorbers has little effect.

• Regions with high transmissivity

• Absorption predominantly due to clouds

• Gaseous absorbers are all weak.

• Treatment of main gaseous absorber is computationally more expensive.

• Clouds change on much shorter time-scales than the concentration of gases.

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Idea

Replace existing spectral file with two new files

• A slow file for treating strong gaseous absorption, called less frequently.

• A fast file for treating clouds and minor gases, called more frequently.

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NAE Diagnostics

SW Heating Rates,1 August 09.00

In experiment, fast is called every 3 time-steps, while slow is called every 18, the operational calls radiation every 12 time-steps.

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NAE Diagnostics

LW Heating Rates,1 August 09.00

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Questions and answers