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.