A technique for mapping downward longwave radiation using satellite and ground-based data in the tropics


A new technique for mapping downward longwave radiation using ground and satellite based data has been developed.

Downward longwave radiation from this technique agrees well with that obtained from measurements.

Comparisons of the developed model and other models have been done.

Downward longwave radiation over Thailand has been generated.


This paper presents a technique for mapping monthly average hourly downward longwave (LW) irradiance using ground- and satellite-based data. A model relating LW irradiance to a satellite derived-brightness temperature of the earth-atmospheric system, relative humidity and ambient air temperature was formulated. This model was validated against LW irradiance obtained from measurements at 4 sites in the tropics and discrepancy in terms of root mean square errors and mean bias errors was found to be 1.89% and −0.69%, respectively. After the validation, the model was used to calculate monthly average hourly LW irradiance over Thailand and the results were displayed as LW maps. These maps reveal the influence of various factors on LW irradiance.


  • Downward longwave radiation;
  • Satellite data;
  • Tropics

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