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A Climatology of extratropical cyclones over East Asia During 1958-2001

Acta meteorologica Sinica 2012年第3期26卷 261-277页

作者：张颖娴丁一汇李巧萍 Chinese Academy of Meteorological Sciences College of Atmospheric Science Nanjing University of Information Science & Technology National Climate Center

A climatology of extratropical cyclones （ECs） over East Asia （20~ 75~N, 60^-160~E） is analyzed by applying an improved objective detection and tracking algorithm to the 4-time daily sea level pressure fields from the European Centre for Medium-range Weather Forecasts （ECMWF） reanalysis data. A total of 12914 EC processes for the period of 1958-2001 are identified, with an EC database integrated and EC activities reanalyzed using the objective algorithm. The results reveal that there are three major cyclogenesis regions： West Siberian Plain, Mongolia （to the south of Lake Baikal）, and the coastal region of East China; whereas significant cyclolysis regions are observed in Siberia north of 60~N, Northeast China, and Okhotsk Se^Northwest Pacific. It is found that the EC lifetime is largely 1 7 days while winter ECs have the shortest lifespan. The ECs are the weakest in summer among the four seasons. Strong ECs often appear in West Siberia, Northeast China, and Okhotsk Sea-Northwest Pacific. Statistical analysis based on k-means clustering has identified 6 dominating trajectories in the area south of 55~N and east of 80~E, among which 4 tracks have important impacts on weather/climate in China. ECs occurring in spring （summer） tend to travel the longest （shortest）. They move the fastest in winter, and the slowest in summer. In winter, cyclones move fast in Northeast China, some areas of the Yangtze-Huaihe River region, and the south of Japan, with speed greater than 15 m s-1. Explosively-deepening cyclones are found to occur frequently along the east coast of China, Japan, and Northwest Pacific, but very few storms occur over the inland area. Bombs prefer to occur in winter, spring, and autumn. Their annual number and intensity in 1990 and 1992 in East Asia （EA） are smaller and weaker than their counterparts in North America.

关键词： extratropical cyclones objective detection and tracking algorithm cyclogenesis cyclolysis cyclone tracks explosively-deepening cyclones

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Variations in extratropical Cyclone Activity in Northern East Asia

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Advances in Atmospheric Sciences 2009年第3期26卷 471-479页

作者：王新敏翟盘茂王萃萃 Meteorological Observatory in Henan Province Zhengzhou 450003 Chinese Academy of Meteorological Sciences Beijing 100081

Based on an improved objective cyclone detection and tracking algorithm, decadal variations in extratropical cyclones in northern East Asia are studied by using the ECMWF 40 Year Reanalysis （ERA-40） sea-level pressure data during 1958-2001. The results reveal that extratropieal cyclone activity has displayed clear seasonal, interannual, and decadal variability in northern East Asia. Spring is the season when cyclones occur most frequently. The spatial distribution of extratropieal cyclones shows that cyclones occur mainly within the 40°- 50°N latitudinal band in northern East Asia, and the most frequent region of occurrence is in Mongolia. Furthermore, this study also reveals the fact that the frequency of extratropieal cyclones has significantly decreased in the lower latitude region of northern East Asia during 1958 2001, but deeadal variability has dominated in higher latitude bands, with frequent cyclone genesis. The intensity of extratropical cyclones has decreased on an annual and seasonal basis. Variation of the annual number of cyclones in northern East Asia is associated with the mean intensity of the baroelinie frontal zone, which is influenced by climate warming in the higher latitudes. Moreover, the dipole structure of extratopical cyclone change, with increases in the north and decreases in the southern part of northern East Asia, is related to the northward movement of the baroelinic frontal zone on either side of 110°E.

关键词： ERA-40 SLP extratropical cyclones variability East Asia cyclone detection and trackingalgorithms

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Characteristics of extratropical cyclone variability in the Northern Hemisphere and their response to rapid changes in Arctic sea ice

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Acta Oceanologica Sinica 2023年第10期42卷 10-22页

作者： Di Chen Qizhen Sun Ocean University of China Qingdao 266100China National Marine Environmental Forecasting Center Beijing 100081China

extratropical cyclones are critical weather systems that affect large-scale weather and climate changes at mid-high ***,prior research shows that there are still great difficulties in predicting extratropical cyclones for occurrence,frequency,and *** this study,mean sea level pressure(MSLP)data from the European Centre for Medium-Range Weather Forecasts(ECMWF)reanalysis(ERA5)are used to calculate the variance statistics of the MSLP to reveal extratropical cyclone activity(ECA).Based on the analysis of the change characteristics of ECA in the Northern Hemisphere,the intrinsic link between ECA in the Northern Hemisphere and Arctic sea ice is *** results show that the maximum ECA mainly occurs in winter over the mid-high latitudes in the Northern *** maximum ECA changes in the North Pacific and the North Atlantic,which are the largest variations in the Northern Hemisphere,are independent of each other,and their mechanisms may be ***,MSLP is a significant physical variable that affects *** North Atlantic Oscillation(NAO)and North Pacific Index(NPI)are significant indices that impact ECA in the North Atlantic and North Pacific,*** innovation of this paper is to explore the relationship between the activity of extratropical cyclones in the Northern Hemisphere and the abnormal changes in Arctic sea ice for the first *** mechanism is that the abnormal changes in summer-autumn and winter Arctic sea ice lead to the phase transition of the NPI and NAO,respectively,and then cause the occurrence of ECA in the North Pacific and North Atlantic,*** sea ice plays a crucial role in the ECA in the Northern Hemisphere by influencing the polar vortex and westerly *** is the first exploration of ECAs in the Northern Hemisphere using Arctic sea ice,which can provide some references for the in-depth study and prediction of ECAs in the Northern Hemisphere.

关键词： extratropical cyclones mean sea level pressure North Atlantic Oscillation(NAO) North Pacific Index(NPI) Arctic sea ice

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A Diagnostic Study of Moist Potential Vorticity Generation in an extratropical Cyclone

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Advances in Atmospheric Sciences 1998年第2期15卷 19-33页

作者： Zuohao Cao and G.W.K. Moore Department of Physics, University of Toronto, Toronto, Ontario, Canada, M5S 1A7 Department of Physics University of Toronto Toronto Ontario Canada

Moist potential vorticity (MPV) and its generation may be important in the development of mesoscale structures such as rainbands within cyclones. In an adiabatic and frictionless flow, MPV generation is possible if the flow is three-dimensional and the air is unsaturated. Moist potential vorticity can be generated through the combined effects of gradients in the potential temperature and moisture fields. The diagnosis of MPV generation in an extratropical cyclone was performed with the ECMWF objectively analyzed fields for a system that developed during February 1992. It was found that at various stages during the development of the cyclone, negative MPV was generated: at the north end of the cold front; along the occluded front and the cold front; and in the region of the warm core. This pattern of negative MPV generation is in excellent agreement with the predictions of previous theoretical and numerical studies. After the cyclone ceased to deepen, the region of negative MPV generated in the cyclone was horizontally advected into a saturated area. The area of negative MPV generated both along the occluded front in this case study and in the region of the bent-back warm front in a numerical simulation showed a mesoscale structure with a width of about 200-500 km. It was found that the intrusion of moist or dry air into baroclinic zones was important for MPV generation. In addition, baroclinicity increase (adjacent to the area of condensation) in the regions of high moisture gradients led to significant MPV production.

关键词： Moist potential vorticity (MPV) generation extratropical cyclones

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