Global Precipitation and ENSO

Scientists associated with the Mesoscale Atmospheric Processes Branch not only produce global precipitation data sets, but also use these data to monitor global climate anomalies. One major component of this activity is to characterize the ENSO phenomenon. We begin by monitoring the precipitation anomalies in the Indian Ocean / Maritime Continent / Pacific Ocean:
Link to image showing precipitation anomalies 
in the Indian Ocean /Maritime Continent / Pacific Ocean
Figure 1 (click to enlarge)

Taking the largest precipitation anomalies within the Maritime Continent and Pacific Boxes in Figure 1 , indices of the strength of the Walker Circulation are computed (Curtis and Adler 2000). A detailed summary of the methodology can be found here. A table of the these values can be found here The time series of ENSO in terms of gradient of precipitation anomalies is shown in Figure 2.

Link to graph showing time series of ENSO
Figure 2 (click to enlarge)

Recently precipitation anomalies in the eastern Indian Ocean have been linked to MJO propagation and the initiation of El Ninos. An empirical scheme has been developed to determine when precipitation anomalies in the eastern Indian Ocean may be important for the development of El Nino. Detailed information about this technique is in press at Geophysical Research Letters (Curtis et al. 2001).

Link to prediction index graph
Figure 3 (click to enlarge)

From this work a prediction index was developed and is shown with ESPI (Figure 3). Note that for the five strongest El Ninos the index is high about 12-16 months before the middle of the events. The index has recently shot up leading to a forecast of El Nino conditions.

Precipitation anomalies over the globe are quantified during El Nino and La Nina events. Figure 4 gives the average El Nino minus La Nina conditions for the 31 year period from 1979 through 2010.

Link to Image showing El Nino minus La Nina Composites of Global Normalized Precipitation Anomalies

Figure 4 (click to enlarge)

Figure 5 is a reproduction of Plate 4 in Curtis et al. (2001) showing the rainfall anomalies for the 1997-98 El Nino in relation to the canonical El Nino-related weather patterns from Ropelewski and Halpert (1987).

Link to image Showing rainfall anomalies and weather patterns from Ropelewski and Halpert (1987)
Figure 5 (click to enlarge)

Link to image Showing Global Precipitation Scenario for 2002-2003
Figure 6 (click to enlarge)

Combining our prediction and monitoring efforts we present the global precipitation scenario for the 2002-03 El Nino. Fig. 6 represents the average response to El Nino in time and space.

REFERENCES

  • Curtis, S., and R. Adler, 2000: ENSO indices based on patterns of satellite-derived precipitation. J. Climate, 13, 2786-2793.

  • Curtis, S., G. J. Huffman, and R. F. Adler, 2002: Precipitation anomalies in the tropical Indian Ocean and their relation to the initiation of El Niņo. Geophys. Res. Letters, 29(10), 1441, doi:10.1029/2001GL013399.

  • Curtis, S., R.F. Adler, G.J. Huffman, E. Nelkin, and D. Bolvin, 2001: Evolution of tropical and extratropical precipitation anomalies during the 1997 to 1999 ENSO cycle. Int. J. Climatol., 21, 961-971.

  • Ropelewski, C.F., and M.S. Halpert, 1987. Global and regional scale precipitation patterns associated with the El Nino / Southern Oscialltion. Mon. Wea. Rev., 115:1606-1626.

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