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| Regime Behavior in the Sea Surface Temperature-Cloud Radiative Forcing Relationships over the Pacific Cold Tongue Region |
| WU Chun-Qiang,ZHOU Tian-Jun,De-Zheng SUN |
| LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029;Graduate University of Chinese Academy of Sciences, Beijing 100049;National Satellite Meteorological Center, China Meteorological Administration, Beijing 100081, China,LASG, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China,Cooperative Institute for Environmental Studies/University of Colorado & NOAA/Earth System Research Laboratory, Boulder, Colorado, USA |
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Abstract Previous analyses on the estimates of water vapor and cloud-related feedbacks in the tropics usually use observations over the Earth Radiation Budget Experiment (ERBE) period (1985–89). To examine the sample dependence of previous estimates, the authors extend the analysis to two additional periods: 1990–94 and 1995–99. The results confirm our hypothesis, i.e., the values of the feedbacks depend on the period of data coverage. The differences in the feedbacks from cloud radiative forcings (CRFs) estimated from the three periods are particularly significant. Two possible causes for these differences are proposed. First, a regime behavior in the CRFs-Sea Surface Temperature Anomaly (SSTA) relationship over the cold tongue region is revealed: when SSTA is below –0.5oC, the CRFs anomalies are insensitive to the SSTA; when the SSTA is between –0.5oC and 2.0oC, the CRF anomalies are positively correlated with the SSTA; however, when the SSTA exceeds 2.0oC, the CRF anomalies decrease with the SSTA. This regime behavior is due to the regime behavior of cirrostratus and deep convective clouds. Second, the CRFs-SSTA relationship is regulated by remote forcings. Warming of the far eastern equatorial Pacific would reduce the water vapor convergence over the central Pacific by weakening the trade wind over the southeastern Pacific, thereby reducing the feeding of moisture to the convective flow. The results suggest that CRFs-SSTA relationships during ENSO events are nonlinear and strongly depend on the magnitude and the spatial distribution of the SSTA.
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Received: 13 August 2010
Revised: 01 September 2010
Accepted: 01 September 2010
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