The documentation of the zonal pattern of global wind system can be traced back to centuries ago. The prevailing descriptions in most oceanography books, however, have been of little change during the past decades. The present work represents a new effort to update our knowledge on this issue using the newly available multi-year TOPEX altimeter data. As a result, the positions and intensities of major zonal features of the marine wind system are reexamined and more precisely defined. The seasonal, annual, and interannual variabilities of these features in terms of both amplitude and phase are analyzed in detail. Uncertainties associated with the estimated intensity and the peak/trough positions of the zonal wind belts are discussed. Meanwhile, a possible connection between the meridional shift of the Pacific doldrums and the occurrence of an El Nino event is observed.

The availability of muhiple sateilite missions with wind measuring capacity has made it more desirable than ever before to integrule wind data from various sources in order to achieve an improved accuracy, resolution. and duration. A clear understanding of the error charaeterlsties associated with each type of data is needed for a meaningful merging or combination. The two kinds of errors-namely, random error and systematic error-ate expected to evolve differently with increasing volume of available data In this study, a collocated ocean Topography Experiment (TOPEX)-NASA Seatterometer (NSCAT)-ECMWF dataset, which covers 66S-66N and spans the entire 10-month lifetime of NSCAT. is compiled to investigate the systematic discrepancies among the three kinds of wind estimates, yielding a number of interesting results, First, the satellite derived wind speeds are found to have a larger overall bias but a much smaller ovemli foot-mean-square (rms) error compared to ECMWF winds, implying thai they are highly converging but are systemalically biased. Second. the TOPEX and NSCAT wind speed biases are characterized by a significant "'phase opposition" with latitude, seasnn, and wind intensity, respectively. Third. the TOPEX (NSCAT) bias exhibits a low-high-low <high-low-high) pattern as a function of wind speed, whose turning poim at 14.2ms-1 coincides well with the transitional wind speed flora swell dominance to wind sea dominance in wave condition, suggesting that the degreee of wave development plays a key role in shaping wind speed bias.

Using the newly available TOPEX Microwave Radiometer (TMR) data spanning 1993 through 2002. a 10 yr climatology of oceanic water vapor [OWVI is constructed, of which the distribution and variation at various spatial-temporal scales we investigated The new dataaet confirms most of the well-known OWV features, and yields a number of interesting findings, due to its high quality, long duration, and unique orbit. I) The TMR-derived climatology compares well in both overall pattern and general statistics, with similar results based on radiosondes and other satellites. Climatological comparisons with sea surface temperature and oceanic precip itation suggest thai the western Pacific warm pool is "mirrored" in the atmosphere as a "'wet pool," whereas the meteorological equator is refleclcd in OWV as a Iransocean equatorial wet belt. 21 It is lound that El Nifio (La Nifia) events are accompanied by a significant increase (decease) in the amount of OWV between 10s and 10N with a somewhat unexpected Southern Hemisphere dominance. This is parieularly evidem during the 1997198 El Nino when the interannual variability of OWV reaches a record high. Composite maps of annual OWV anomalies disclose a dipnlelike pattern in the western equatorial Pacific with a phase opposition between El Nino and La Nina years. 3) The annual amplitude of OWV is characterized by six cross-continent wet belts located largely in the subtropics of both hemispheres. The phase patterns of the annual and semiannual variations are hemispherically divided, and climatologically co.elated, respectively. North (south) of the intertropical convergence zone (ITCZ), a majorily of the oceanic areas have their water vapor maximum in August (February). Early peaks in July are found over a few continental shelf regions of the Northern t-lemisphere (NH), while late peaks in March are fouiid in the tropical oceans of the Southern Hemisphere (SHh Moreover. two delayed maximums in September are visible in the interior North Pacific and North Adandtic, respectively. 4) The daily cycle of OWV is strongly eoupled with its seasonal cycle, and is therefore unstable in nature But a double peak streture with a general hemispheric phase reversal can still be identified. 5) The ratio of the NH versus SH OWV is roughly 1.17:1, and tile relative importance of the interannuah annual, semiannuah diurnal, and semidlurnal variations in terms of mean amplitude is approximately I.fi:5:1.2:1:1. [n view of these encouraging results, further exploration of present and future "attlmele-borne" radiomeler data will no, doubt lead to an improved and complementary understanding of the OWV system in many aspecls.

The TOPEXgPOSE1DON mission offers the first opportunity to observe rain cells over the ocean by a dual-frequency radar altimeter (TOPEX) and simuhaneously observe their natural radiative properties by a three-frequency radiometer (TOPEX microwave radiometer (TMR)). This work is a feasibility study aimed at understanding the capability and potential of the active/passive TOPEX/TMR system for oceanic rainfall detection. On the basis of past experiences in rain flagging, a joint TOPEX/MR rain probability index is proposed. This index integrates several advantages of the two sensors and provides a more reliable rain estimate than the radiometer alone. One year's TOPEX/TMR data are used to test the performance of the index. The resulting rain frequency statistics show quantitative agreement with those obtained from the Comprehensive Ocean-Atmosphere Data Set (COADS) in the Intertropical Convergence Zone (ITCZ), while qualitative agreement is found for other regions of the world ocean. A recent finding that the latitudinal frequency of precipitation over the Southern Ocean increases steadily toward the Antarctic continent is confirnled by our result. Annual and seasonal precipitation maps are derived from the index. Notable leatures revealed include an overall similarity in rainfall pattern from the Pacific, the Atlantic, and the Indian Oceans and a general phase reversal between the two hemispheres, as well as a number of regional anomalies in terms of rain intensity. Comparisons with simultaneous Global Precipitation Climatology Project (GPCP) multisatellite precipitation rate and COADS rain climatology suggest that systematic differences also exist. One example is that the maximum rainfall in the ITCZ of the Indian Ocean appears to be more intensive and concentrated in our result compared to that of the GPCP. Another example is that the annual precipitation produced by TOPEXffMR is constantly higher than those from GPCP and COADS in the extratropical regions of the northern hemisphere, especially in the northwest Pacific Ocean. Analyses of the seasonal variations of prominent rainy and dry zones in the tropics and subtropics show various behaviors such as systematic migration, expansion and contraction, merging and breakup, and pure intensity variations. The seasonality of regional features is largely influenced by local atmospheric events such as monsoon, storm, or snow activities. The results of this study suggest that TOPEX and its follow-on may serve as a complementary sensor to the special sensor microwave/imager in observing global oceanic precipitation.

A detailed study on global oceanic precipitation is carried out using the simultaneous TOPEX and TMR (TOPEX Microwave Radiometer) data. It is motivated by he success of a series of feasibility studies based on a few years of TOPEX TMR data, and the availability of a decade-long new dataset thai spans I992-2002. In this context, a previously proposed rain probability index is improved by taking into account the dirfference of the dynamic range of the TOPEX-measured backscatter coefficients at the Ku and C hands and the lalitudinally compiementary sensitivities of the TOPEX and TMR rain detections, leading to a refined joint precipitation index, which is generaIly consistent and quantitatively compable with existing precipitation climatologies from the Global Preelpitafion Climatology Project (GPCP) and the Comprehensive Ocean-Atmosphere Data Set (COADS). The new TOPEX-TMR precipitation climatology, on the one hand. confirms the fundamental features of global oceanic rainfaIt with additional details, and, on the other hand, reveals a number of interesting characteristics that are previously unknown or poorly defined. 1) The spatial variability of the western Pacific "rain pool" (the atmospheric counterpart of the oceanic wan pool) is chacterized by an interannual zonal migration, an annual cycle of meridional seesaw. and a semiannual cycle of expansion and shrinking. 2) The Pacific, Atlantic, and Indian Ocean inter-pical convergence zones (ITCZs) all have RU annual cycle of cross-basin oscillation with east and west stops in JJA and DJE respectively. 31 A well-defined prominent rainy zone is observed in the southeast China Seas sound Taiwan Island, connecting with the Pacific rain pool in the south. 4) Between El Nifio and La Nifia years, there is a systematic sign reversal of the geographical distribution of precipitation anomaly, which exists globally rather than in the tropicaI oceans only. 5) On a global basis, interannual and annual precipitation variabilities are of the same magnitude, bul the interannual (annual) component is more important for the Southern (Northern) Hemisphere. 6) For the Tropical oceans, "season" defined by rainfall usually has a one quarter delay with respect to the corresponding meteorological season. For the "marine deserts" in the subtropical oceans, however, the raln-based season is found to be anticorelated with the meteorological season. In addition, the annual cycle of the Atlantic precipitation is nearly 180 out of phase with respeet to thm of the Pacific and Indian Ocean for the same hemisphere.