Cold Wave Climate Characteristics and Risk Zoning in Jilin Province

Using the meteorological data of 50 stations in Jilin Province from 1961 to 2016, the demographic and economic data, and geographical information of all counties and cities aims to conduct the risk zoning of cold wave disasters in Jilin Province. The results show that, since 1961, the average number of cold wave occurrences per year in Jilin Province is 8.3 days, of which the highest number of occurrences occurred in February, followed by December and January, and the spring cold wave occurred mostly in March. From the map of cold-sea disaster risk zoning in Jilin Province, due to factors such as topography and land use distribution, the west and east of Jilin Province have a certain resilience to the disasters caused by cold waves, and the risk of disasters is low. The distribution of agricultural facilities and large areas of farmland in the central region are extremely sensitive to cold wave disasters and have a high risk of disasters. Areas with high risk of cold wave are mainly concentrated in Siping City, Changchun City, Liaoyuan City, Jilin City, northern Tonghua City and most of Baishan City. Areas with low cold wave risk are mainly concentrated in most of Baicheng City, most of Songyuan City and Yanbian Prefecture. And other places are moderately risky areas of cold waves.

Water vapor transport over China and its relationship with drought and flood in Yangtze River Basin

The characteristics of water vapor transport(WVT) over China and its relationship with precipitation anomalies in the Yangtze River Basin(YRB) are analyzed by using the upper-air station data in China and ECMWF reanalysis data in summer from 1981 to 2002.The results indicate that the first mode of the vertically integrated WVT is significant whose spatial distribution presents water vapor convergence or divergence in the YRB.When the Western Pacific Subtropical High(WPSH) is strong and shifts southward and westward, the Indian Monsoon Low Pressure(IMLP) is weak, and the northern part of China stands behind the middle and high latitude trough, a large amount of water vapor from the Bay of Bengal(BOB), the South China Sea(SCS) and the western Pacific forms a strong and steady southwest WVT band and meets the strong cold water vapor from northern China in the YRB, thus it is likely to cause flood in the YRB.When WPSH is weak and shifts northward and eastward, IMLP is strong, and there is nearly straight west wind over the middle and high latitude, it is unfavorable for oceanic vapor extending to China and no steady and strong southwest WVT exists in the region south of the YRB.Meanwhile, the cold air from northern China is weak and can hardly be transported to the YRB.This brings on no obvious water vapor convergence, and then less precipitation in the YRB.

Quasi-3-yr Cycle of Rainy Season Precipitation in Tibet Related to Different Types of ENSO during 1981–2015

The rainy season precipitation in Tibet（RSPT） is a direct cause for local floods/droughts. It also indirectly affects the thermal conditions of the Tibetan Plateau, which can result in anomalous patterns of atmospheric circulation over East Asia. The interannual variability of the RSPT is often linked with the El Ni？o–Southern Oscillation（ENSO）, but the relevant mechanisms are far from being understood, particularly for different types of ENSO events. We investigated the interannual variation of the RSPT in association with different types of ENSO. A quasi-3-yr period of the RSPT（less–more–more precipitation） was significant at the 95% confidence level. A joint multi-taper method with singular value decomposition analysis of the coupled field between the RSPT and the sea surface temperature（SST）revealed that the developing eastern Pacific type El Ni？o was accompanied by a decrease in the RSPT. The shift from the central Pacific type El Ni？o to the eastern Pacific La Ni？a was accompanied by an increase in the RSPT. Weakening of the central Pacific La Ni？a was accompanied by an increase in the RSPT. Analysis of the mechanism of this coupling, using the same analysis method but other climatic factors, indicated that the gradually strengthening eastern Pacific El Ni？o can inhibit the Walker circulation, weakening the South Asian summer monsoon, and resulting in transport of less water vapor from the Bay of Bengal to Tibet. The change from the central Pacific El Ni？o to the eastern Pacific La Ni？a led to continued strengthening of the Walker circulation with westward movement of the ascending area. This enhanced the South Asian summer monsoon over the Arabian Sea and transported more water vapor to Tibet. The decreasing central Pacific La Ni？a accompanied by persistent cooling of SSTs in the equatorial Pacific led to a strong eastern North Pacific summer monsoon, causing an anomaly in the easterly transport of water vapor from the Sea of Japan to Tibet and increased RSPT.