A 10-yr climatology of Amazonian rainfall derived from passive microwave satellite observations

In this study, a satellite-derived precipitation "climatology" (climate des cription) over northern South America using a passive microwave technique, the Goddard Profiling algorithm, is presented. The results are statisticall y adjusted to have the same probability distribution as a rain gauge datase t. The climatologies take the form of the mean estimated rainfall for a 10- yr+ period with subdivisions by month and meteorological season. For the 6- yr period 1992-97, when two satellites were in operation, diurnal variabili ty (to the extent it is discerned by four unequally spaced observations) is presented. In the mean, dramatic patterns of alternating morning and eveni ng maxima are seen stretching from the northeast (Atlantic coast) across th e continent to the Pacific. The effects of local circulations caused by top ography, coastlines, and geography (river valleys) on the rainfall patterns are evident, particularly in the region around Manaus, Brazil, where the N egro and Solimoes Rivers merge. The interannual variability of the IO-yr ra infall estimate is examined by computing the deviations of yearly and warm- season (December-February) rainfall from their respective long-term means. Rainfall anomalies associated with Fl Nino and La Nina events then become a pparent. This gauge-adjusted satellite climatology enhances existing (gauge based) climatologies by increasing the spatial resolution and providing a common, spaceborne platform for assessing interannual variability. It maint ains the same first- and second-order statistics as does the gauge dataset, and allows a first attempt at examining the diurnal cycles by utilizing pa ssive microwave observations (up to) four times per day.