ANALYSES OF INTRASEASONAL OSCILLATION CHARACTERISTICS OF FLOOD-CAUSING RAINSTORMS IN XIJIANG RIVER VALLEY DURING THE ANNUALLY FIRST RAINING SEASON IN THE PAST YEARS

• Published in: Journal of Tropical Meteorology Vol. 17; no. 2; pp. 136 - 146
• Main Author: 罗秋红 纪忠萍 吴乃庚 蔡洁云 孙汉明
• Format: Journal Article
• Language: English
• Published: Guangzhou Guangzhou Institute of Tropical & Marine Meteorology 01.06.2011; Guangdong Meteorological Observatory, Guangzhou 510080 China
• Subjects: filter; rainstorms; intraseasonal oscillation; annually first raining season; Xijiang River valley
• ISSN: 1006-8775
• DOI: 10.3969/j.issn.1006-8775.2011.02.006

Based on the daily precipitation data of nine stations representing the Xijiang River valley and the National Center for Environmental Prediction/National Center for Atmospheric Research （USA） reanalysis data, this study uses the wavelet analysis and band-pass filter methods to investigate the atmospheric intraseasonal oscillation characteristics of flood-causing rainstorms in the valley during the annually first raining seasons in 1968, 1994, 1998, 2002 and 2005. Results show that the daily precipitation in the valley exhibits significant quasi-biweekly （10 to 20 days） oscillations. The flood-causing rainstorms in the valley were mainly associated with the confluence of low-frequency warm and humid airflow in the lower latitudes and cold and dry airflow in the higher latitudes. The low-frequency vortexes were propagating or in control when this type of rainstorms took place over the valley, being favorable for the convergence of moisture at lower levels and thus vital to the formation of the rainstorms.