Estimation of cloud liquid water over oceans from dual oxygen absorption band to support the assimilation of second generation of microwave observation on board the Chinese FY-3 satellite
2017
Dong, Peiming | Weng, Fuzhong | Huang, Qunbo | Han, Yang | Han, Wei
To make up for the absence of observation-based information of cloud liquid water (CLW) in assimilation of second generation of microwave observation on board the Chinese FengYun-3 satellite, two algorithms using double oxygen-absorption band microwave sounding observation at 52.80 and 118.75 ± 2.5 GHz, one using brightness temperatures directly and the other utilizing a cloud emission and scattering index derived from the brightness temperature, are proposed to estimate CLW over oceans. Their performance was evaluated by verifying the estimations from FY-3C double oxygen absorption band microwave observations and that from the traditional Grody scheme applied to microwave measurements at 23.8 and 31.4 GHz from the MetOp-B satellite. An additional experiment was conducted to investigate the impact of regression analysis on the actual brightness temperature and reanalysis data, or the simulated measurements. It is demonstrated that CLW can be retrieved from double oxygen absorption band microwave sounding measurements. The estimations are comparable to the results obtained using the traditional scheme applied to Advanced Microwave Sounding Unit measurements. While total precipitable water was not well obtained as the traditional scheme did, it is feasible to perform regression analysis on actual brightness temperature and reanalysis data; however, for all estimations that the regression was conducted on, the results obtained using actual brightness temperature and reanalysis data were weaker than those obtained using regression coefficients from the simulated data set. The results could be improved by better matching the satellite observations and CLW data used in the regression analysis.
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