ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 47 Issue 12 > 2021,47(12):1457-1468. DOI:10.7519/j.issn.1000-0526.2021.12.003 Prev Next
Characteristics of Spring Persistent Rains in Hunan and Its Anomaly Causes
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Abstract:
In this study, the key area of upwind southwest wind speed is established, which is closely associated with spring persistent rains in Hunan (SPRH). The monitoring indicators of SPRH from 1980 to 2014 are defined. The temporal and spatial patterns of SPRH rainfall are analyzed. Besides, the anomaly of the atmospheric circulations during the strong/weak SPRH period and sea surface temperature (SST) during the early period are discussed. Results show that the climate average of SPRH occurs from the 13th pentad to the 27th pentad, whereas the starting date and ending date of SPRH vary in different years. The rainfall of SPRH exceeded normal conditions during the periods before the mid-1980s and after 2014, but it was lower than normal conditions during the periods of the mid-1980s to 2013. The rainfall of SPRH decreased from south to north and from east to west in spatial distribution. The spatial pattern of more (less) precipitation in the whole province can show the main spatial distribution of SPRH. In the strong SPRH years in whole province, the Western Pacific subtropical high (WPSH) remarkably becomes stronger and westward, the Indo-Burmese trough tends to become weaker, and an anomalous anticyclone exists in the southern Yangtze River regions in low-level wind field. Hunan is located in the center of anomalous anticyclone, causing heavy SPRH. However, in the weak SPRH years, WPSH evidently becomes weaker, the Indo-Burmese trough tends to become stronger, and an anomalous anticyclone is found in southern China. Additionally, Hunan is located in the center of anomalous water vapor divergence, resulting in weaker SPRH in whole province. In the following year of the occurrence of El Ni〖AKn~D〗o events, SPRH starts earlier, persists longer and has more intensive rainfall amount compared with the normal years. On the contrary, during the following year of the occurrence of La Ni〖AKn~D〗a, SPRH starts later, has short rainy periods, lower rainfall amount and weaker rainfall intensity compared with the normal years.
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