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Based on the 1983∼2011 CMAP data, the precipitation anomaly in East Asia and its nearby sea regions (hereafter called East Asia for short) demonstrates the '+−+' pattern before 1999 and the '−+−' pattern afterwards; this decadal change is contained principally in the corresponding EOF3 component. However, the NCC_CGCM forecast results are quite different, which reveal the '+−+−' pattern before 1999 and the '−+−+' pattern afterwards. Meanwhile, the probability of improving NCC_CGCM's forecast accuracy based on these key SST areas is discussed, and the dynamic-statistics combined forecast scheme is constructed for increasing the information of decadal change contained in the summer precipitation in East Asia. The independent sample forecast results indicate that this forecasting scheme can effectively modify the NCC_CGCM's decadal change information contained in the summer precipitation in East Asia (especially in the area of 30°N-55°N). The ACC is 0.25 and ACR is 61% for the forecasting result based on the V SST area, and the mean ACC is 0.03 and ACR is 51% for the seven key areas, which are better than NCC_CGCM's system error correction results (ACC is −0.01 and ACR is 49%). Besides, the modified forecast results also provide the information that the precipitation anomaly in East Asia mainly shows the '+−+' pattern before 1999 and the '−+−' pattern afterwards. [ABSTRACT FROM AUTHOR]

With the influence of global warming, the global climate has undergone significant inter-decadal variation since the late 1970s. Although El Niño-Southern Oscillation (ENSO) has been the strongest signal for predicting global climate inter-annual variability, its relation with the summer rainfall in China has significantly changed, and its indicative function on the summer rainfall in China has weakened. This has led to a significant decrease in the accuracy rate of early conceptual prediction models for the Three Rainfall Patterns in the summer of eastern China. On the basis of the difference analysis of atmospheric circulation system configuration in summer, as well as the interaction of ocean and atmospheric in previous winter between two phases, i.e. before and after the significant global warming (1951 to 1978 and 1979 to 2012, respectively), we concluded that (1) Under different inter-decadal backgrounds, the atmospheric circulations that impacted the Three Rainfall Patterns in the summer of eastern China showed consistency, but in the latter phase of the global warming, the Western Pacific Subtropical High (WPSH) was on the strong side, the position of which was in the south, and the blocking high in the Eurasia mid-high latitudes was active, while the polar vortex extended to the south, and meridional circulation intensified. This circulation background may have been conducive to the increase of the circulation frequency of Patterns II and III, and the decrease of the circulation frequency of Pattern I, thus leading to more Patterns II and III and fewer Pattern I in the summer rainfall of eastern China. (2) In the former phase, the corresponding previous winter SST fields of different rainfall patterns showed visible differences. The impact of ENSO on North Pacific Oscillation (NPO) was great, and the identification ability of which on Patterns I and II of summer rainfall was effective. In the latter phase, this identification ability decreased, while the impact of ENSO on the Pacific/North American (PNA) teleconnection pattern increased, and the identification ability of the PNA on Patterns II and III also increased. Based on the new inter-decadal climate background, this study reconstructs the conceptual prediction model for the Three Rainfall Patterns in summer of eastern China by using the previous winter PNA and the Eurasian (EU) teleconnection indexes. The fitting effect was satisfying, though it is necessary to be further tested. [ABSTRACT FROM AUTHOR]

A continuous overcast-rainy weather (CORW) process occurred over the mid-lower reaches of the Yangtze River (MLRYR) in China from February 14 to March 9 in 2009, with a large stretch and long duration that was rarely seen in historical records. Using the empirical orthogonal function (EOF), we analyzed the geopotential height anomaly field of the NCEP-DOE Reanalysis II in the same period, and defined the stable components of extended-range (10-30 days) weather forecast (ERWF). Furthermore, we defined anomalous and climatic stable components based on the variation characteristics of the variance contribution ratio of EOF components. The climatic stable components were able to explain the impact of climatically averaged information on the ERWF, and the anomalous stable components revealed the abnormal characteristics of the continuous overcast-rainy days. Our results show that the stable components, especially the anomalous stable components, can maintain the stability for a longer time (more than 10 days) and manifest as monthly scale low-frequency variation and ultra-long-wave activities. They also behave as ultra-long waves of planetary scale with a stable and vertically coherent structure, reflect the variation of general circulation in mid-high latitudes, display the cycle of the zonal circulation and the movement and adjustment of the ultra-long waves, and are closely linked to the surface CORW process. [ABSTRACT FROM AUTHOR]