ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 49 Issue 11 > 2023,49(11):1285-1298. DOI:10.7519/j.issn.1000-0526.2023.032601 Prev Next
Climatology and Environmental Feaures of Tornadoes in Liaoning Province During 1971-2020
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Abstract:
A climatology, which includes interannual variability, annual and diurnal cycles, intensities according to the “Enhanced Fujita Scale”, geographic distribution, and environmental conditions derived from reanalysis data, is developed in this study for the tornadoes in Liaoning Province during 1971-2020 in order to understand the climatic characteristics of tornado. The tornado reports are obtained from the Chinese Meteorological Disaster Dictionary, Chinese Meteorological Disaster Yearbook and other associated data. The differences in environmental background between Liaoning Province in China and the tornado-prone areas in United States are compared, and the typical circulation conditions and atmospheric characteristics of Liaoning tornadoes are analyzed. The major findings are as follows. Over the 50 years (1971-2020), there were 105 tornadoes recorded (including 17 EF2 or stronger tornadoes) in 97 tornadic days in Liaoning Province, which suggests that Liaoning has 2.1 tornadoes per year with the annual generation density to be 1.4×10-5 km-2, approximately equal to 1/10 tornadoes in the United States. A total of 17 EF2 or stronger tornadoes are recorded, with an average annual occurrence of 0.3. The tornadoes occur mostly (95%) from May through September, and 67% of tornado genesis are between 14:00 BT and 19:00 BT. Significant tornadoes (EF2/EF3/EF4) mainly occur in the central and western part of Liao-ning, while weak tornadoes (EF0/EF1) happen more in the coastal region of the southeastern Liaoning. The tornadic season in the northwest of Liaoning is much earlier than in the southeast. CAPE and mid-level wind shear often change in opposite phases with seasons, and the appropriate configuration of the two is the prerequisite for the occurrence of tornadoes and other convective weather. Additionally, the lower low-level the storm relative helicity (SRH) is the major cause for the apparently lower tornado density in Liaoning relative to the United States. About 87% of tornadoes are related to the cold vortices, which can be mainly divided into the short-wave trough category at the cold vortex bottom and cold vortex front category dominated by low-level frontogenesis (65%), the mid-level dry cold air forcing category dominated by mid-to-high level dry cold airflow (12%), and the cold vortex central area category dominated by mesoscale near-storm environment under severe thermal instability (6%). The environmental conditions in the high-incidence area of Liaoning tornadoes have the following characteristics: the mid-level impact system is cold vortex, the ground corresponds to frontal cyclones, tornadoes often appear in the northwest quadrant of the center of SRH and in the large-value zone of CAPE gradient, corresponding to the east side of cold front and the dry line at surface as well as the top of the temperature ridge.
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