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This article describes a variational framework for assimilating the SSM/I-derived surface rain rate and total precipitable water (TPW) and examines their impact on the analysis produced by the Goddard Earth Observing System (GEOS) Data Assimilation System (DAS). The SSM/I observations consist of tropical rain rates retrieved using the Goddard Profiling Algorithm and tropical TPW estimates produced by Wentz.In a series of assimilation experiments for December 1992, results show that the SSM/I-derived rain rate, despite current uncertainty in its intensity, is better than the model-generated precipitation. Assimilating rainfall data improves cloud distributions and the cloudy-sky radiation, while assimilating TPW data reduces a moisture bias in the lower troposphere to improve the clear-sky radiation. Together, the two data types reduce the monthly mean spatial bias by 46% and the error standard deviation by 26% in the outgoing longwave radiation (OLR) averaged over the Tropics, as compared with the NOAA OLR observation product. The improved cloud distribution, in turn, improves the solar radiation at the surface. There is also evidence that the latent heating change associated with the improved precipitation improves the large-scale circulation in the Tropics. This is inferred from a comparison of the clear-sky brightness temperatures for TIROS Operational Vertical Sounder channel 12 computed from the GEOS analyses with the observed values, suggesting that rainfall assimilation reduces a prevailing moist bias in the upper-tropospheric humidity in the GEOS system through enhanced subsidence between the major convective centers.This work shows that assimilation of satellite-derived precipitation and TPW can reduce state-dependent systematic errors in the OLR, clouds, surface radiation, and the large-scale circulation in the assimilated dataset. The improved analysis also leads to better short-range forecasts, but the impact is modest compared with improvements in the time-averaged signals in the analysis. The study shows that, in the presence of biases and other errors of the forecast model, it is possible to improve the time-averaged ''climate content'' in the data without comparable improvements in forecast. The full impact of these data types on the analysis cannot be measured solely in terms of forecast skills.

The magnitudes of bulk air-sea surface flux estimates calculat•;d using three temporal averaging methods were compared. The reference method is a simple average of P axes computed from hourly values of bulk meteorological parameters termed the sampling method (SM). In • ontrast, the scaler averaging method (SAM) computes the average flux from the average of the bulk data; th•:s it ignores correlations between variables. The vector averaging method (VAM) is similar to the SAM but us,:s the magnitude of the average wind vector rather than the average magnitude of the hourly wind vectors. 'Fhe data used in this study were collected during the Tropical Ocean and Global Atmospheric pilot cruise of the R/V Wecoma in the equatorial Pacific Ocean near 0øN, 145øE from February 17 to March 10, 1990. The ratios of the SAM and VAM values relative to the SM values were studied as.a function of averaging periods from 2-72 hours. The ratios vary little for times exceeding 36 hours. For averaging periods of 72 hours, the SAM estimates of Q•r, QJ•, %, and xy were 102%, 61%, 21%, and 69% of the SM estimates, respectively; the VAM ratios were even lower. These results suggest that air-sea surface scaler fluxes and stress components ,:omputed from monthly, weekly, and even daily averaged bulk meteorological parameters can be seriously in ,mor in equatorial, temporally variable wind regimes. 20,211 Weather Rev., 106, 223-232, 1978. Analysis of the convectively modified GATE boundary layer using in situ and acoustic sounder data, Mon. Weather Rev., 107, 985-993, 1979. LEDVINA ET AL.: AVERAOINO OF BULK FLUX ESTIMATES FOR THE TROPICAL PACIFIC 20,217 Hanawa, K., Accuracy of air-sea heat and momentum fluxes in the sea south of Japan, J. Oceanog•. Soc. Jpn, 65, 767-774, 1987. Hanawa, K., and Y. Toba, Critical examination of estimation methods of long-term mean air-sea heat and momentum transfers, Ocean Air Interactions, 1, 79-93, 1997. Hellerman, S., An updated estimate of the wind stress on the world ocean, Mon. Weather Rev., 95, 607-626, 1967. Hellerman, S., and M. Rosenstein, Normal monthly wind stress over the world ocean with error estimates, J. Phys. Oceanogr., 13, 1093-1104, 1983. R.H., and G.Y. Young, Heat and moisture budgets of tropical mesoscale anvil clouds, J. Atmos. Sci., 40, 2138-2147, 1983. Kondo, J., Air-sea bulk transfer coefficients in diabatic conditions, Boundary Layer Meteorol., 9, 91-112, 1975. Liu, W.T., K.B. Katsaros, and J.A. Businger, Bulk parameterization of the air-sea exchanges of heat and water vapor including the molecular constraints at the interface, J. Atmos. Sci., 36, 1722-1735, 1979. Marsden, R.F., and S. Pond, Synoptic estimates of air-sea fluxes, J. Mar. Res., 41,349-373, 1983. Smith, S.D., Coefficients for sea surface wind stress, and wind profiles as a function of wind speed and temperature, J. Geophys. Res., 93, 15,467-15,472, 1988. Weare, B.C., Uncertainties in estimates of surface heat fluxes derived from marine reports over the tropical and subtropical oceans, Tellus, Set. A, 41A, 357-37...

A short‐term observational study of the surface energy budget of the equatorial western Pacific Ocean was conducted in preparation for the Tropical Ocean and Global Atmosphere program Coupled Ocean‐Atmosphere Response Experiment (TOGA COARE). Data were obtained between February 17 and March 10, 1990, during the TOGA pilot cruise of the R/V Wecoma near the equator and 147°E longitude. Analysis of the 443 hours of turbulent and radiative fluxes collected was focused on the influence of deep precipitating convection on the day‐to‐day variability of the surface energy budget. Partitioning the data series according to the degree of local convective activity allowed comparison of the surface energy budgets for various convective regimes. As was observed in the tropical Atlantic during the GARP Atlantic Tropical Experiment (GATE), the surface fluxes of sensible and latent heat were larger during periods influenced by deep precipitating convection. Moreover, the mechanisms by which convection affected these fluxes were similar to those described in the tropical Atlantic. Variations in the shortwave radiation caused by convective clouds and their by‐products were found to contribute even more than the surface fluxes to the day‐to‐day variability of the surface energy budget. It is concluded that the existence of convectively disturbed days had a significant impact on the surface energy budget for the entire cruise period as well as on the day‐to‐day variability within that period.

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