Improvement of Multimodel Ensemble Seasonal Prediction Skills over East Asian Summer Monsoon Region Using a Climate Filter Concept

2013 ◽  
Vol 52 (5) ◽  
pp. 1127-1138 ◽  
Author(s):  
Doo Young Lee ◽  
Joong-Bae Ahn ◽  
Karumuri Ashok
Keyword(s):  
Summer Monsoon ◽  
North Atlantic ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Seasonal Prediction ◽  
Multimodel Ensemble ◽  
Suitable Climate ◽  
Asian Summer ◽  
Summer Monsoon Region

AbstractThe authors propose the use of a “climate filter” concept to enhance prediction skill of a multimodel ensemble (MME) suite for the East Asian summer monsoon (EASM) precipitation and temperature at 850 hPa. The method envisages grading models on the basis of the degree of reproducibility of the association of EASM variability with a few relevant climate drivers with the respective model hindcasts for the period 1981–2003. The analysis identifies the previous winter Niño-3.4 and spring North Atlantic Oscillation indices as the most suitable climate drivers in designing a climate filter for evaluating models that replicate the observed teleconnections to EASM well. The results show that the hindcast skills of a new MME with the better-performing models are significantly higher than those from the nonperforming models or from an all-inclusive operational MME.

scholarly journals Projections of East Asian summer monsoon change at global warming of 1.5 and 2 °C

2018 ◽  
Vol 9 (2) ◽  
pp. 427-439 ◽  
Author(s):  
Jiawei Liu ◽  
Haiming Xu ◽  
Jiechun Deng
Keyword(s):  
East Asia ◽  
Summer Monsoon ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Precipitation Change ◽  
High Latitudes ◽  
Multimodel Ensemble ◽  
Epr Method ◽  
Asian Summer

Abstract. Much research is needed regarding the two long-term warming targets of the 2015 Paris Agreement, i.e., 1.5 and 2 ∘C above pre-industrial levels, especially from a regional perspective. The East Asian summer monsoon (EASM) intensity change and associated precipitation change under both warming targets are explored in this study. The multimodel ensemble mean projections by 19 CMIP5 models show small increases in EASM intensity and general increases in summer precipitation at 1.5 and 2 ∘C warming, but with large multimodel standard deviations. Thus, a novel multimodel ensemble pattern regression (EPR) method is applied to give more reliable projections based on the concept of emergent constraints, which is effective at tightening the range of multimodel diversity and harmonize the changes of different variables over the EASM region. Future changes projected by using the EPR method suggest decreased precipitation over the Meiyu belt and increased precipitation over the high latitudes of East Asia and Central China, together with a considerable weakening of EASM intensity. Furthermore, reduced precipitation appears over 30–40∘ N of East Asia in June and over the Meiyu belt in July, with enhanced precipitation at their north and south sides. These changes in early summer are attributed to a southeastward retreat of the western North Pacific subtropical high (WNPSH) and a southward shift of the East Asian subtropical jet (EASJ), which weaken the moisture transport via southerly wind at low levels and alter vertical motions over the EASM region. In August, precipitation would increase over the high latitudes of East Asia with more moisture from the wetter area over the ocean in the east and decrease over Japan with westward extension of WNPSH. These monthly precipitation changes would finally contribute to a tripolar pattern of EASM precipitation change at 1.5 and 2 ∘C warming. Corrected EASM intensity exhibits a slight difference between 1.5 and 2 ∘C, but a pronounced moisture increase during extra 0.5 ∘C leads to enhanced EASM precipitation over large areas in East Asia at 2 ∘C warming.

scholarly journals Variations in the East Asian summer monsoon over the past millennium and their links to the Tropic Pacific and North Atlantic oceans

2019 ◽  
Author(s):  
Fucai Duan ◽  
Zhenqiu Zhang ◽  
Yi Wang ◽  
Jianshun Chen ◽  
Zebo Liao ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
North Atlantic ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Meridional Overturning Circulation ◽  
Central China ◽  
Ice Age ◽  
Future Global Warming ◽  
Asian Summer

Abstract. Variations of East Asian summer monsoon (EASM) during the last millennium could help enlighten the monsoonal response to future global warming. Here we present a precisely dated and highly resolved stalagmite δ18O record from the Yongxing Cave, central China. Our new record, combined with a previously published one from the same cave, indicates that the EASM has changed dramatically in association with the global temperature rising. In particular, our record shows that the EASM has intensified during the Medieval Climate Anomaly (MCA) and the Current Warm Period (CWP) but weakened during the Little Ice Age (LIA). We find that the EASM intensity is similar during the MCA and CWP periods in both northern and central China, but relatively stronger during the CWP in southern China. This discrepancy indicates a complicated regional response of the EASM to the anthropogenic forcing. The intensified and weakened EASM during the MCA and LIA matches well with the warm and cold phases of Northern Hemisphere surface air temperature, respectively. This EASM pattern also corresponds well with the rainfall over the tropical Indo-Pacific warm pool. Surprisingly, our record shows a strong association with the North Atlantic climate as well. The intensified (weakened) EASM correlates well with positive (negative) phases of North Atlantic Oscillation. In addition, our record links well with the strong (weak) Atlantic meridional overturning circulation during the MCA (LIA) period. All above-mentioned correlations indicate that the EASM tightly couples with oceanic processes in the tropical Pacific and North Atlantic oceans during the MCA and LIA.

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.

scholarly journals Influence of the Summer NAO on the Spring-NAO-Based Predictability of the East Asian Summer Monsoon

2016 ◽  
Vol 55 (7) ◽  
pp. 1459-1476 ◽  
Author(s):  
Fei Zheng ◽  
Jianping Li ◽  
Yanjie Li ◽  
Sen Zhao ◽  
Difei Deng
Keyword(s):  
Summer Monsoon ◽  
North Atlantic ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Dominant Mode ◽  
The North ◽  
Secondary Role ◽  
Asian Summer ◽  
The North Atlantic

AbstractThe dominant mode of atmospheric circulation over the North Atlantic region is the North Atlantic Oscillation (NAO). The boreal spring NAO may imprint its signal on contemporaneous sea surface temperature (SST), leading to a North Atlantic SST tripolar pattern (NAST). This pattern persists into the following summer and modulates the East Asian summer monsoon (EASM). Previous studies have shown that the summer NAST is caused mainly by the preceding spring NAO, whereas the contemporaneous summer NAO plays a secondary role. The results of this study illustrate that, even if the summer NAO plays a secondary role, it may also perturb summer SST anomalies caused by the spring NAO. There are two types of perturbation caused by the summer NAO. If the spring and summer NAO patterns have the same (opposite) polarities, the summer NAST tends to be enhanced (reduced) by the summer NAO, and the correlation between the spring NAO and EASM is usually stronger (weaker). In the former (latter) case, the spring-NAO-based prediction of the EASM tends to have better (limited) skill. These results indicate that it is important to consider the evolution of the NAO when forecasting the EASM, particular when there is a clear reversal in the polarity of the NAO, because it may impair the spring-NAO-based EASM prediction.

scholarly journals The 4.2 ka BP event: multi-proxy records from a closed lake in the northern margin of the East Asian summer monsoon

2018 ◽  
Vol 14 (10) ◽  
pp. 1417-1425 ◽  
Author(s):  
Jule Xiao ◽  
Shengrui Zhang ◽  
Jiawei Fan ◽  
Ruilin Wen ◽  
Dayou Zhai ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
North Atlantic ◽  
Surface Waters ◽  
East Asian Summer Monsoon ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
Mean Annual Precipitation ◽  
Northern Margin ◽  
Proxy Records ◽  
Asian Summer

Abstract. The 4.2 ka BP event has been widely investigated since it was suggested to be a possible cause for the collapse of ancient civilizations. With the growth of proxy records for decades, however, both its nature and its spatial pattern have become controversial. Here we examined multi-proxy data of the grain-size distribution, ostracode assemblage, pollen assemblage, and the pollen-reconstructed mean annual precipitation from a sediment core at Hulun Lake in northeastern Inner Mongolia spanning the period between 5000 and 3000 cal. yr BP to identify the nature and the associated mechanism of the 4.2 ka BP event occurring in the monsoonal region of eastern Asia. Higher sand fraction contents, littoral ostracode abundances, and Chenopodiaceae pollen percentages together with lower mean annual precipitation reveal a significant dry event at the interval of 4210–3840 cal. yr BP that could be a regional manifestation of the 4.2 ka BP event in the northern margin of the East Asian summer monsoon (EASM). We suggest that the drought would be caused by a decline in the intensity of the EASM on millennial-to-centennial scales that could be physically related to persistent cooling of surface waters in the western tropical Pacific and the North Atlantic. The cooling of western tropical Pacific surface waters could reduce moisture production over the source area of the EASM, while the cooling of North Atlantic surface waters could suppress northward migrations of the EASM rain belt, both leading to a weakened EASM and thus decreased rainfall in the northern margin of the EASM.

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