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LOW-FREQUENCY CIRCULATION AND EXTENDED-RANGE FORECAST IN CONNECTION WITH AUTUMN EXTREME HEAVY RAINFALL PROCESS IN HAINAN
  Revised:August 15, 2019
KeyWords:heavy rainfall process  extended-range forecast method  low-frequency oscillation  10每30d  CFSv2
Fund:
Author NameAffiliationE-mail
WEI Xiao-wen 1. Hainan Meteorological Services Center, Haikou 570203 China
2. Key Laboratory of Southern China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province, Haikou 570203 China
3. Shanghai Climate Center, Shanghai 200030 China
4. Hainan Climate Center, Haikou 570203 China 
 
LIANG Ping  liangping1107@163.com 
WU Hui   
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Abstract:
      Observed daily precipitation data from the National Meteorological Observatory in Hainan province and daily data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis-2 dataset from 1981 to 2014 are used to analyze the relationship between Hainan extreme heavy rainfall processes in autumn (referred to as EHRPs) and 10每30 d low-frequency circulation. Based on the key low-frequency signals and the NCEP Climate Forecast System Version 2 (CFSv2) model forecasting products, a dynamical-statistical method is established for the extended-range forecast of EHRPs. The results suggest that EHRPs have a close relationship with the 10每30 d low-frequency oscillation of 850 hPa zonal wind over Hainan Island and to its north, and that they basically occur during the trough phase of the low-frequency oscillation of zonal wind. The latitudinal propagation of the low-frequency wave train in the middle-high latitudes and the meridional propagation of the low-frequency wave train along the coast of East Asia contribute to the &north high (cold), south low (warm)* pattern near Hainan Island, which results in the zonal wind over Hainan Island and to its north reaching its trough, consequently leading to EHRPs. Considering the link between low-frequency circulation and EHRPs, a low-frequency wave train index (LWTI) is defined and adopted to forecast EHRPs by using NCEP CFSv2 forecasting products. EHRPs are predicted to occur during peak phases of LWTI with value larger than 1 for three or more consecutive forecast days. Hindcast experiments for EHRPs in 2015每2016 indicate that EHRPs can be predicted 8每24 d in advance, with an average period of validity of 16.7 d.
DOIㄩ10.16555/j.1006-8775.2019.04.010
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