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| The Formation of Precipitation Anomaly Patterns during the Developing and Decaying Phases of ENSO |
| HU Kai-Ming,HUANG Gang |
| State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029,State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029 |
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Abstract This study proposes a new explanation for the formation of precipitation anomaly patterns in the boreal summer during the El Nino-Southern Oscillation (ENSO) developing and decaying phases. During the boreal summer June-July-August (JJA) (0) of the El Nino (La Nina) developing phase, the upper level (300-100 hPa) positive potential temperature anomalies resemble a Matsuno-Gill-type response to central Pacific heating (cooling), and the lower level (1000-850 hPa) potential temperature anomalies are consistent with local SST anomalies. During the boreal summer JJA(1) of the El Niño (La Nina) decaying phase, the upper level potential temperature warms over the entire tropical zone and resembles a Matsuno-Gill-type response to Indian Ocean heating (cooling), and the lower level potential temperature anomalies follow local SST anomalies. The vertical heterogeneity of potential temperature anomalies influences the atmospheric stability, which in turn influences the precipitation anomaly pattern. The results of numerical experiments confirm our observations.
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Received: 20 September 2009
Revised: 17 December 2009
Accepted: 22 December 2009
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