Comparison between ground measured and satellite estimates of downward longwave radiation at Ilorin, Nigeria
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One of the useful factors for appraising the total energy budget of the earth’s surface is downward longwave radiation (DLR). Though satellite-derived data are plenteous and are often used in atmospheric studies, however, its conformity with the rare ground measurements is essential. In this work, ground measured and satellite-derived DLR data for about five years from September 1992 to August 1994 and June 1995 to April 1998 in Ilorin (8.50° N, 4.55° E), Nigeria were compared, using two main statistical measures of correlation coefficient and the t-test. Furthermore, the mean relative percentage deviation (E%) was also used to determine the monthly parity between both data sets. The seasonal patterns of both sets of data were similar but had inherent slight differences and E% produced good monthly fits expect once in 57 months, which was in June 1996. That enormous deviation was also detected graphically. Correlation coefficient values were high during the dry seasons but low during the rainy seasons and the t-test sometimes showed statistical significance between both data sets. Most times, the seasonal patterns of satellite-derived data match ground truth except in an extreme case of remarkable deviation from normal in the ground measured data. Using satellite-derived data is recommended unless precision is required and short duration of data is not an issue.
Downward longwave radiation (DLR), Ground measured data, Satellite-derived data, Parity
Obot N.I. (2019). Comparison between ground measured and satellite estimates of downward longwave radiation at Ilorin, Nigeria. MAUSAM 70, (3), 533–540.