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A collocated SSM/I and radiosonde measurement data set provided by the NASDA(Japan)was used to retrieve the total precipitable water(PW)over oceans.The retrieval results obtainedwith several regression algorithms were compared against the radiosonde measurements.It isshown that:(a)the routinely operational algorithm of Alishouse et al.(1990)yields significantunderestimation in high PW regime and overestimation in low PW regime;(b)a cubic correctionby Colton and Poe(1994)is not sufficient and globally improves slightly the retrieval results;and(c)the regression algorithm with the form of brightness temperature(T_b)function In (280-T_b)gives a little largely scattered retrievals in whole PW range but without considerable over-andunderestimates in low and high PW regimes.To improve the estimation of the oceanic precipitablewater from the SSM/I measurements,a composite algorithm with different forms of T_b function inlow.medium and high PW regimes is proposed and tested.
A collocated SSM / I and radiosonde measurement data set provided by the NASDA (Japan) was used to retrieve the total precipitable water (PW) over oceans. The retrieval results obtained with several regression algorithms were compared against the radiosonde measurements. It is isshown that :( a) the routinely operational algorithm of Alishouse et al. (1990) yields significant underestimation in high PW regime and overestimation in low PW regime; (b) a cubic correction by Colton and Poe (1994) is not sufficient and globally improves slightly the retrieval results; and (c) the regression algorithm with the form of brightness temperature (T_b) function In (280-T_b) gives a little greater scattered retrievals in whole PW range but without considerable over-and underestimates in low and high PW regimes.To improve the estimation of the oceanic precipitable water from the SSM / I measurements, a composite algorithm with different forms of T_b function inlow .medium and high PW regimes is proposed and tested.