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Daily precipitation distributions over the intra-Americas sea and their interannual variability

Author(s): S. CURTIS

Journal: Atmósfera
ISSN 0187-6236

Volume: 26;
Issue: 2;
Start page: 243;
Date: 2013;
Original page

Keywords: Daily precipitation | climate variability | western hemisphere warm pool | satellites

The seasonal (March to October) and interannual variability of the cumulative distribution function (CDF) of precipitation is examined for Meso-America, the eastern Pacific and western Atlantic, commonly referred to as the intra-Americas sea (IAS). Large-area precipitation CDFs were constructed over land and temperature pools greater than 28.5º C and between 26.5º and 28.5º C. The cooler waters tend to have their precipitation distributions shifted to lower values as compared to land and the western hemisphere warm pool (WHWP). The land and the WHWP have similar precipitation distributions from March to May. From June to October the land histogram of precipitation is narrower (less light and heavy rainfall) relative to theWHWP histogram. The highest probability of finding heavy to extreme precipitation over the WHWP is in June. From 1997 to 2008, in the summer months, the El Niño/Southern Oscillation (ENSO) is related to the CDFs of precipitation over land, where during El Niño there is a shift toward lower daily rain totals. There is not a strong relationship between ENSO and the CDFs of precipitation over the ocean pools. Finally, a large WHWP in May-June-July is related to the CDF of precipitation over the WHWP in October, namely a shift towards higher daily rain totals and more extreme events. The size of the July WHWP explains 75%of the variability in the frequency of rainfall greater than 50 mm within the WHWP in October, and theroot mean square error between the observed points and the linear models is about 0.005. However, thereason for this apparent predictability is not simply due to a warm seasonal anomaly leading to local thermodynamiceffects. The concurrent correlation between the size of the WHWP in October and the CDF ofprecipitation therein is small, indicating a lack of a contemporaneous response. Here it is shown throughatmospheric-oceanic reanalysis that rainfall extremes in October are dependent upon the development ofthe Atlantic portion of the WHWP in May-June-July. Large WHWPs in these months are consistent with anearly onset of the Atlantic warm pool and atmospheric instability over Central America leading to extremeprecipitation events in the fall.
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