Indian summer monsoon rainfall variability in response to differences in the decay phase of El Niño

Self Cite

The present study examined the ability of Coupled Model Intercomparison Project phase 5 (CMIP5) models in representing the differences in decaying phases of El Niño and their impact on south Asia and east Asia monsoon during June and July (JJ), the early summer monsoon months. El Niño decay is classified into three categories, based on the timing of decay with respect to the summer season after the peak phase of El Niño. Analysis suggests that many CMIP5 models are able to capture the differences in the decaying phase of El Niño. Observed rainfall anomalies are positive over most parts of south and east Asia regions during the early decay (ED) years mainly due to anomalous Tropical Indian Ocean (TIO) Sea Surface Temperature (SST) warming and La Niña like forcing from the eastern Pacific. Most models show significant skill in capturing the positive rainfall anomalies over south Asia and TIO SST warming in ED years. However, many models have failed to represent east Asian rainfall anomalies due to weak Western North Pacific (WNP) anticyclone and its association with El Niño‐Southern Oscillation. In case of mid‐decay (MD) years, observed rainfall anomalies over south Asia is negative especially in the monsoon trough region and positive over east Asian region. Low‐level divergence induced by anomalous WNP anticyclone extending to head Bay of Bengal and Gangetic Plain region in MD years caused low rainfall over south Asia. These features are however not well organized in many CMIP5 models. In no decay (ND) years, the rainfall anomalies over south and east Asia regions are negative in almost all the CMIP5 models, which is consistent with the observations. This study highlights the importance of proper representation of differences in the decaying phase of El Niño and associated teleconnections in CMIP5 models.

Section: Data Models and Methodsmentioning

confidence: 92%

Section: Data Models and Methodsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Impact of differences in the decaying phase of El Niño on South and East Asia summer monsoon in CMIP5 models

Srinivas

Chowdary

Gnanaseelan

et al. 2019

Self Cite

“…Previous studies have revealed that circulation anomalies located near the NWP are sensitive to the tropical ocean status. Local SST anomalies (Wang et al ., ; Wang and Zhang, ), or the remote ocean status, as the tropical Indian Ocean SST anomalies (Yang et al ., , ; Wu et al ., ; Xie et al ., , ; Xie and Zhou, ), equatorial central and eastern Pacific (CEP) SST anomalies (Wang et al ., ; Xiang et al ., ; Chen et al ., ; Chowdary et al ., , ; Tao et al ., ), all contribute to the development and maintenance of anomalous circulation.…”

Section: Possible Mechanismmentioning

confidence: 99%

Interannual variation of precipitation over the Hengduan Mountains during rainy season

Dong

Huang

et al. 2017

The present study investigates the interannual variability of precipitation over the Hengduan Mountains (HMs) during rainy season based on daily precipitation dataset of 151 meteorological stations. More HMs precipitation is associated with an anomalous lower level cyclonic circulation over the northern South China Sea (SCS) and the upper level Silk Road pattern (SRP)‐like geopotential height anomalies. Along the north flank of the anomalous cyclonic circulation, easterly wind anomalies weaken climatology winds and prevent further movement of southwest moisture transport, leading to the enhancement of moisture convergence over HMs. Diagnosis shows that anomalous vertical motions are owing to the advection of anomalous temperature by basic zonal winds. The anomalous lower level cyclonic circulation over the northern SCS is related to La Niña‐like sea surface cooling in the equatorial central and eastern Pacific. This cooling adjusts the Walker Circulation, causing positive precipitation anomalies near the SCS, which trigger the anomalous cyclonic circulation as a warm Rossby wave response. The distribution of upper level geopotential height anomalies over the mid‐latitude Asian land resembles the SRP. Due to its barotropic structure, the SRP leads to warm and cold anomalies over the central Asia and the central China, respectively. The advection of anomalous temperature gradient by mean westerlies leads to anomalous ascending motions and more precipitation over HMs.

“…Since the SSTA evolution during El Niño decay is also of diversity, Chen and He () identified that different distributions of summer rainfall anomalies are closely associated with different SSTA patterns in the decaying phase of El Niño. These diversities in El Niño's properties and their climatic impacts are robust (Chowdary et al, ).…”

Section: Introductionmentioning

confidence: 99%

The diversity of La Niña decay and the corresponding spring and summer precipitation anomalies over eastern China

Chen

Zhu

et al. 2019

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.