21st Conference on Climate Variability and Change


Observed Responses of Global Precipitation and Surface Temperature to ENSO


Guojun Gu, NASA/GSFC and Univ. of Maryland Baltimore County, Greenbelt, MD; and R. F. Adler, G. J. Huffman, J. J. Wang, and D. T. Bolvin

The global features of the ENSO impact on precipitation and surface temperature are documented and examined for the period of 1979-2006 using two model-independent data sets: the GPCP monthly precipitation and the NASA-GISS surface temperature anomaly products. In the tropics, following the El Niņo in the tropical central-eastern Pacific, surface warming spreads rapidly across the entire tropical region, except in the tropical western Pacific where intense cold anomalies appear due to the eastward shift of warm water, and in the equatorial Atlantic where negative temperature anomalies occur likely caused by the anomalous Walker circulation. Rainfall anomalies tend to show similar asymmetrical patterns. In the tropical oceans, positive (negative) rainfall anomalies are generally seen lying over the regions with warm (cold) temperature anomalies. However, quite different features occur over the tropical lands, particularly in tropical South America where negative rainfall anomalies are dominant accompanying the peak El Niņo, concurrent with surface warming extending from the tropical Pacific.

The effects of ENSO extend deeply into the mid-high latitudes, particularly in the north and south Pacific. Lag-correlation analyses of zonal mean anomalies with Nino 3.4 indicate that this extending is roughly symmetrical about the equator for both rainfall and temperature, though the asymmetrical geometry and a zonal mean north hemisphere ITCZ. The strongest positive correlation between precipitation anomalies and Nino 3.4 is focused within a narrow band (10S-10N) sandwiched by two negative correlation ones. In contrast, a much wider positive correlation zone for surface temperature roughly covers the entire tropical region (25S-25N). The correlations between Nino 3.4, and the global and tropical total precipitation anomalies are weak for any time lags (0-12 months). This weak correlation confirms that ENSO may only shift the major rainy zones by inducing the large-scale circulation anomalies, but could not effectively contribute to the total precipitation changes, if any. On the other hand, high correlations are seen between Nino 3.4, and both the global and tropical mean temperature anomalies, showing the widespread impact of the ENSO events across the global surface.

Session 12A, Seasonal-interannual variability II
Thursday, 15 January 2009, 8:45 AM-9:45 AM, Room 129A

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