The present study investigates the diversity of the La Niña decaying phase and the corresponding spring and summer precipitation anomalies over the eastern China. Based on the differences in sea surface temperature anomaly (SSTA) evolution during the La Niña decaying phase, 18 La Niña events in the period 1961–2016 are classified into three types—namely, the “persistent type” (P‐type), the “re‐intensified type” (R‐type), and the “fast‐decay type” (F‐type). Precipitation responses over eastern China during the decaying spring and summer of the three types of La Niña present significant differences. For the R‐type La Niña decaying spring, the enhanced precipitation appears over northeastern China but significant suppressed precipitation anomalies are observed elsewhere, particularly in Yellow River basin, the Yangtze River basin, and southeastern China. Significant negative precipitation anomaly appears over northeastern China in both P‐type and F‐type La Niña decaying spring. In the decaying summer, for P‐type La Niña, dry anomalies are apparent in southern and northern China. For R‐type La Niña, negative rainfall anomalies are notable in northeastern China, the Hetao region, and the middle reaches of the Yangtze River basin. For F‐type La Niña, significant negative rainfall anomalies are found over the Yangtze River basin and parts of northern China. The responses of the large‐scale circulation anomalies to the distinct SSTA patterns of the different types of La Niña are responsible for the diversity of rainfall anomalies over eastern China. The precipitation anomaly pattern in eastern China is closely associated with the different types of La Niña decay, and it is seasonal‐dependent. These two aspects should be taken into account when conducting seasonal predictions of spring and summer rainfall anomalies over eastern China using El Niño–Southern Oscillation as a predictor.
The simulated sea surface temperature anomaly (SSTA) over the tropical Pacific during El Niño-Southern Oscillation (ENSO) is investigated in three representative coupled models: CESM1-CAM5, FGOALS-s2, and FGOALS-g2. It is found that there is a significant westward shift bias in reproducing the zonal distribution (ZD) of the ENSO-related SSTA in CESM1-CAM5 and FGOALS-s2, whereas the SSTA-ZD simulated by FGOALS-g2 is relatively realistic. Through examining the SSTA-ZD during both warm and cold phases of ENSO separately, the authors reveal that the SSTA-ZD simulation bias during the ENSO cycle mainly lies in the bias during the warm phase. It is noted that both the simulated zonal wind stress anomaly (τ 0 x) and shortwave heat flux (SW) anomaly exhibit westward shift biases in CESM1-CAM5 and FGOALS-s2, while the counterparts in FGOALS-g2 are relatively reasonable. The westward shift biases in representing τ 0 ENSO海温异常纬向分布的模拟偏差及偏差成因:基于三个CMIP5耦合模式的 初步分析 摘要 本文分析了三个典型的 CMIP5 耦合模式 (CESM1-CAM5, FGOALS-s2 和 FGOALS-g2
Eastern China (EC) suffered an extreme drought with long-lasting duration and record breaking intensity in late summer-autumn 2019. Our diagnosed results show that the central Pacific (CP) El Niño, in tandem with warm sea surface temperature anomalies (SSTAs) over the Kuroshio extension (KE) region, induces the meridionally elongated cyclonic circulation anomalies stretching from the western North Pacific (WNP) to the Yellow Sea. Its western flank corresponds to overwhelming low-level northerly wind anomalies over EC, which result in deficient moisture and anomalous descent over EC and hence cause the extreme drought in 2019. To investigate the relative contributions of SSTAs over different regions, we performed sensitivity experiments, and analyzed the relationship between the extreme drought like 2019 (2019Drought-like event) and the SSTAs in CMIP6 historical simulations. Modelling evidences reveal that both warm SSTAs over the central-equatorial Pacific and the KE region are indispensable for shaping the meridionally elongated cyclone anomaly. Specifically, the cyclone anomaly over the WNP induced by CP El Niño aligns with the cyclone anomaly over the Yellow Sea induced by the warm SSTAs over the KE region, merging into a meridionally stretched cyclone anomaly to the east of EC. Consequently, the northerly anomalies stretch across EC, leading to unfavorable atmospheric conditions and the rainfall deficit there. Projection results show the occurrence probability of 2019Drought-like event will increase by 20% (decrease by 40∼50%) under high (medium-low) emission scenario compared to present day climate, indicating the nonlinear response of extreme drought to different emission scenarios and the urgency of carbon emission reduction.
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