Wann-Jin Chen

Modified Bowen ratio method in near-sea-surface air temperature estimation by using satellite data

The near-sea-surface air temperature can be derived through Special Sensor Microwave/Imager (SSM/I) microwave and Geostationary Meteorological Satellite (GMS-5) infrared data by using a so-called modified Bowen ratio method (MBRM). A specified value (/spl kappa/) that was defined to be a ratio between bulk coefficients c/sub e/ and c/sub h/ was viewed as a constant and was input into this retrieval model for the derivation of near-sea-surface air temperature. However, there is insufficient evidence to prove the hypothesis why the specified value can be viewed as a constant and used in this model. This study strives in providing an answer. By using the iterative technique, the fact that the optimal /spl kappa/ value oscillated merely within a small range for present experimental area covering the area from 10/spl deg/N to 30/spl deg/N and 105/spl deg/E to 135/spl deg/E is shown clearly. The small oscillation does not strongly affect the value of the derived near-sea-surface air temperature. Therefore, the optimal /spl kappa/ value could be considered as a constant both temporally and spatially. Moreover, the results show that the rmse of the estimated near-sea-surface air temperature from SSM/I and GMS-5 data are 1.46 and 1.69 K, respectively. Therefore, the MBRM may be a good approach to estimate this parameter. However, the optimal /spl kappa/ proposed in this study may be suitable only to present experimental area. Generally speaking, this is due to the fact that the /spl kappa/ values are usually larger further to the north (in higher latitudes) than to the south (in lower latitudes) and also during the cold season than in the warm season.