ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 44 Issue 3 > 2018,44(3):372-381. DOI:10.7519/j.issn.1000-0526.2018.03.004 Prev Next
Distribution of East Asian Subtropical Westerly Jet High Frequency Baroclinic Wave Packet in Summer
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Abstract:
By using the daily reanalysis data of National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP) and daily precipitation data at 20:00 BT from Chinese meteorological stations during 1950-2015, and based on the methods of Morlet wavelet analysis and wave-packet propagation diagnosis (WPD), in this paper, we put emphasis on the research of high frequency baroclinic wave packets distribution and propagation climate characteristics of East Asian subtropical westerly jet (EASJ) in summer (June to August) and their corresponding relationships with the typical rainy season in eastern China. The results show that (1) after filtering out the monthly scale (30 days) cycle signals, highlighted 3-7 d high frequency narrowband signals of the EASJ are obvious in the 200 hPa zonal winds, covering the high frequency narrowband signals of 2-4 d and 5-7 d in South China in the rainy season, 5-7 d in Jianghuai Region in Meiyu season and 2-4 d and 6-8 d in the rainstorms in the northern China from late July to August, which reflects the step changes of summer narrowband signals and the relationship with the typical rainy season in eastern China. (2) The 3-7 d high-frequency baroclinic wave packets corresponding to the East Asian subtropical westerly jet are quasi-zonal distribution, which represents the strong disturbance area, i.e., the dynamic instability zone of the strong west wind shears. The low-value region of the wave packet corresponds to the high pressure in South Asia, which represents the weak perturbation region, i.e., the weak wind pressure stability zone. The distribution characteristics of wave packets during the Meiyu season shows that the two 5-7 d high-frequency baroclinic wave-band and high value zones in the mid latitude and high latitude have a good correspondence with the high energy values of the baroclinic energy dispersive waveguides and the critical areas influencing the precipitation of the Yangtze River and the Meiyu season. (3) The 3-7 d high-frequency baroclinic wave band, located at 40°-55°N, corresponding to the subtropical westerly jet, has the regularity of meridional displacement and intensity changes. Its meridional displacement shows that it falls on the south and rises on the north and then fluctuates, and its intensity gradually weakens and then strengthens. The latitudinal evolution of the zonal winds is divided into two stages, which are characterized by significant differences in the distribution of the wave packets. The first stage has two large wave areas, which are the Black Sea to the Caspian Sea region and the northeast of China to the island of Japan; and the second stage has three large wave areas, including the Black Sea to the Caspian Sea, the west side of the Balkhash Lake and the northeastern region of Japan, of which the disturbance of 3-7 d high frequency baroclinic wave on the west side of the Balkhash Lake has an important contribution to the precipitation in eastern China.
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Clc Number:
P466
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