The NCEP–NCAR, NCEP–DOE, and TRMM Tropical Atmosphere Hydrologic Cycles

Abstract

Estimates for the tropical atmospheric hydrologic cycle from the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis I (RI), the NCEP–Department of Energy (NCEP–DOE) reanalysis II (RII), and the Tropical Rainfall Measuring Mission (TRMM) precipitation are provided herein for the period 1998–99. From 40°N to 40°S, the TRMM-based evaporation, precipitation, and reanalyses moisture convergence have values of (2.9, 2.5, −0.44) mm day⁻¹. Corresponding evaporation, precipitation, precipitation minus evaporation, and analysis errors from the RI and RII, respectively, are (3.4, 3.0, −0.42, 0.021) mm day⁻¹ and (3.7, 3.4, −0.31, 0.13) mm day⁻¹. These large differences among the analyses as well as their differences with TRMM indicate the uncertainty in estimating the tropical hydrologic cycle with reanalyses, which can have errors in precipitation and evaporation as well as moisture convergence. In addition, the RI and RII precipitation, evaporation, and precipitation minus evaporation correlate with the “estimated” monthly values at (0.49, 0.29, 0.83) and (0.48, 0.34, 0.79). The smallest correlations occur over the tropical landmasses, although there are tropical oceanic regions where the correlation is also small. The correlations also tend to be higher during the Northern Hemisphere winter and spring.