scholarly journals Summer High Temperature Extremes in Southeast China: Bonding with the El Niño–Southern Oscillation and East Asian Summer Monsoon Coupled System

2014 ◽  
Vol 27 (11) ◽  
pp. 4122-4138 ◽  
Author(s):  
Weiwen Wang ◽  
Wen Zhou ◽  
Deliang Chen
Keyword(s):  
High Temperature ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Coupled System ◽  
Temperature Extremes ◽  
Southeast China ◽  
Interdecadal Shift ◽  
Asian Summer ◽  
High Temperature Extremes

Abstract This study investigates summer high temperature extremes (HTEs) in southeast China and their linkage with the El Niño–Southern Oscillation (ENSO) and atmospheric circulations in the East Asian summer monsoon (EASM). An interdecadal change in HTEs associated with the abrupt shift of the ENSO–monsoon climate in the late 1980s is demonstrated. Before this interdecadal shift, the interannual variability of HTEs was linked mainly to temperature adjustments associated with the meridional displacement of the East Asian jet stream (EAJS), whereas after the shift HTEs were found to follow an ENSO cycle, which may be due to intensified and persistent ENSO activities, tropical Indian Ocean (TIO) warming, and changes in atmospheric teleconnections. Impacts of the EAJS, the South Asian high (SAH), and the western North Pacific subtropical high (WNPSH) on HTEs are further investigated based on empirical orthogonal function (EOF) analysis. It is found that mainly the first leading EOF mode with a homogeneous spatial pattern shows dominance before the interdecadal shift, whereas both of the first two leading EOF modes show dominance after the interdecadal shift. A possible mechanism of how HTEs in southeast China are linked to the EAJS, the SAH, and the WNPSH in the ENSO–monsoon coupled system is proposed.

scholarly journals Interannual Seesaw between the Somali and the Australian Cross-Equatorial Flows and its Connection to the East Asian Summer Monsoon

2014 ◽  
Vol 27 (11) ◽  
pp. 3966-3981 ◽  
Author(s):  
Chen Li ◽  
Shuanglin Li
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Yellow River ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Significant Negative Correlation ◽  
Subtropical High ◽  
Yellow River Valley ◽  
Asian Summer

Abstract The correlations among the summer, low-level, cross-equatorial flows (CEFs) over the Indian–west Pacific Ocean region on the interannual time scale are investigated by using both the NCEP–NCAR reanalysis and 40-yr ECMWF Re-Analysis (ERA-40) datasets. A significant negative correlation (seesaw) has been illustrated between the Somali CEF and the three CEFs north of Australia (the South China Sea, Celebes Sea, and New Guinea; they are referred to in combination as the Australian CEF). A seesaw index is thus defined with a higher (lower) value representing an intensified (weakened) Somali CEF but a weakened (intensified) Australian CEF. The connection of the seesaw with the East Asian summer monsoon (EASM) is then investigated. The results suggest that an enhanced seesaw corresponds to an intensified EASM with more rainfall in north China, the Yellow River valley, and the upper reach of the Yangtze River. The seesaw reflects the opposite covariability between the two atmospheric action centers in the Southern Hemisphere, Mascarene subtropical high, and Australian subtropical high. Whether the seesaw–EASM connection is influenced by El Niño–Southern Oscillation (ENSO) or the Indian Ocean SST dipole mode (IOD) is analyzed. The results remain unchanged when the ENSO- or IOD-related signals are excluded, although ENSO exerts a significant influence. This implies an additional predictability for the EASM from the CEF seesaw.

scholarly journals Improving the Prediction of the East Asian Summer Monsoon: New Approaches

2012 ◽  
Vol 27 (4) ◽  
pp. 1017-1030 ◽  
Author(s):  
Ke Fan ◽  
Ying Liu ◽  
HuoPo Chen
Keyword(s):  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Statistical Prediction ◽  
Multimodel Ensemble ◽  
Prediction Ability ◽  
Asian Summer ◽  
Prediction Approach

Abstract East Asian summer monsoon (EASM) prediction is difficult because of the summer monsoon’s weak and unstable linkage with El Niño–Southern Oscillation (ENSO) interdecadal variability and its complicated association with high-latitude processes. Two statistical prediction schemes were developed to include the interannual increment approach to improve the seasonal prediction of the EASM’s strength. The schemes were applied to three models [i.e., the Centre National de Recherches Météorologiques (CNRM), the Met Office (UKMO), and the European Centre for Medium-Range Weather Forecasts (ECMWF)] and the Multimodel Ensemble (MME) from the Development of a European Multimodel Ensemble System for Seasonal-to-Interannual Prediction (DEMETER) results for 1961–2001. The inability of the three dynamical models to reproduce the weakened East Asian monsoon at the end of the 1970s leads to low prediction ability for the interannual variability of the EASM. Therefore, the interannual increment prediction approach was applied to overcome this issue. Scheme I contained the EASM in the form of year-to-year increments as a predictor that is derived from the direct outputs of the models. Scheme II contained two predictors: both the EASM and also the western North Pacific circulation in the form of year-to-year increments. Both the cross-validation test and the independent hindcast experiments showed that the two prediction schemes have a much better prediction ability for the EASM than does the original scheme. This study provides an efficient approach for predicting the EASM.

A New Upper-Level Circulation Index for the East Asian Summer Monsoon Variability

2015 ◽  
Vol 28 (24) ◽  
pp. 9977-9996 ◽  
Author(s):  
Guijie Zhao ◽  
Gang Huang ◽  
Renguang Wu ◽  
Weichen Tao ◽  
Hainan Gong ◽  
...  
Keyword(s):  
East Asia ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Late Summer ◽  
Good Choice ◽  
Circulation Index ◽  
Asian Summer

Abstract The East Asian summer monsoon (EASM) and its variability involve circulation systems in both the tropics and midlatitudes as well as in both the lower and upper troposphere. Considering this fact, a new EASM index (NEWI) is proposed based on 200-hPa zonal wind, which takes into account wind anomalies in the southern (about 5°N), middle (about 20°N), and northern areas (about 35°N) of East Asia. The NEWI can capture the interannual EASM-related climate anomalies and the interdecadal variability well. Compared to previous indices, the NEWI shows a better performance in describing precipitation and air temperature variations over East Asia. It can also show distinct climate anomalous features in early and late summer. The NEWI is tightly associated with the East Asian–Pacific or the Pacific–Japan teleconnection, suggesting a possible role of internal dynamics in the EASM variability. Meanwhile, the NEWI is significantly linked to El Niño–Southern Oscillation and tropical Indian Ocean sea surface temperature anomalies. Furthermore, the NEWI is highly predictable in the ENSEMBLES models, indicating its advantage for operational prediction of the EASM. The physical mechanism of the EASM variability as represented by the NEWI is also explicit. Both warm advection anomalies of temperature by anomalous westerly winds and the advection of anomalous positive relative vorticity by northerly basic winds cause anomalous ascending motion over the mei-yu–changma–baiu rainfall area, and vice versa over the South China Sea area. Hence, this NEWI would be a good choice to study, monitor, and predict the EASM.

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