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Investigating the Role of Aerosols and Clouds on the Radiation Budget in Niamey, Niger
Allison Marquardt Collow and Mark Miller
Department of Environmental Sciences, Rutgers University, New Brunswick, NJ
Goals
-Simulate the radiative impact of measured aerosols and clouds on the radiation budget in the atmospheric column over the West African Sahel (Niamey, Niger)
-Investigate the role clouds and aerosols on the heating rate profile individually and when combined
Data and Methods
-Aerosol properties derived from observations made by a Multifilter Rotating Shadowband Radiometer (MFRSR)
-Cloud properties measured using a 95 GHz vertically pointing cloud radar, micropulse lidar, and laser cielometer
-The radiation budget was modeled every 5 seconds using the shortwave (SW) version of the Rapid Radiative Transfer Model (RRTM) for the entire month of August 2006
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Aerosol Heating Effect
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Cloud Heating Effect
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Figure 1: Diurnal cycle of aerosol optical depth at 500, 615, 674, and 870 nm for the 2006 wet season in Niamey, Niger
Figure 4: Individual heating components(a) Diurnal heating rate profile with clouds and aerosols minus clouds, (b) Diurnal heating rate profile with clouds and aerosols minus aerosols
Conclusions
-Aerosols are present in the wet season and must be included in radiation transfer calculations.
-Clouds and aerosols can result in an increase in radiative heating of ~5°K per day in the lower and upper troposphere.
-The combined heating from clouds and aerosols is larger than the heating from the individual components, but smaller than when the components are added separately.
-The radiative heating rates in this region are a result of an inseparable radiative feedback between clouds and aerosols.
Acknowledgements
Allison Marquardt Collow and Mark Miller are supported by DOE Award DE-FG02-08ER64531.
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Figure 3: RRTM calculations for August 2006 with clouds and aerosols present (a) Diurnal profile of downward SW radiation in Wm-2, (b) diurnal profile of upward SW radiation in Wm-2, (c) diurnal profile of downward direct SW radiation in Wm-2, (d) diurnal profile of downward diffuse SW radiation in Wm-2, (e) diurnal profile of net SW radiation in Wm-2, (f) diurnal profile of heating rate in °K per day
Figure 2: Monthly average RRTM calculated and observed radiative flux divergences for August 2006 (a) clear sky, (b) Cloudy sky (c) Aerosols present, (d) Clouds and aerosols present