A new method for estimation of near surface specific humidity over global oceans |
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| Authors: | R Singh P C Joshi C M Kishtawal P K Pal |
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| Institution: | (1) Atmospheric Sciences Division, Meteorology and Oceanography Group, Space Applications Centre (ISRO), Ahmedabad, India |
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| Abstract: | Summary A new methodology for deriving daily averages of near surface specific humidity (Q
a
) is developed. Remotely sensed parameters, total water vapor (W), boundary-layer water vapor (W
b
), and sea-surface temperature (SST) are used to derive Q
a
. Genetic algorithm (GA) is used to find the empirical function relating the input (W, W
b
, and SST) and output (Q
a
) parameters. The input data consist of 2 years (1999–2000) of daily W, W
b
, from SSM/I (Special Sensor Microwave Imager), and SST data from AVHRR (Advanced Very High Resolution Radiometer). COADS
(Comprehensive Ocean Atmospheric Data Set) observations of Q
a
are used to develop and evaluate the new methodology.
The performance of the algorithm is measured with COADS observations, which are not used in the development phase. The global
mean rms error for daily averages Q
a
is 1.5 ± 0.40 g/kg. Slightly higher discrepancies between Q
a
derived from the new method and COADS observations are found over the Northwestern Pacific, North Atlantic oceans and Arabian
Sea. This method improves upon the humidity retrieval of Liu (1986), Schulz et al (1993), and Chou et al (1997). |
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| Keywords: | |
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