The Characters Analysis Of Climate And Anomaly On MJO Of China Precipitation

By using the daily precipitation data of 490 stations in China from 1960 to 2000, the characters of climate and anomaly for intraseasonal oscillation (MJO) of China precipitation are studied in this paper. The work concerns the choice of filter in separating MJO, seasonal variation of China precipitation MJO, area difference and interannual anomalies of summer precipitation MJO in East China, the relationship between summer precipitation MJO in East China and 500hPa circulation MJO, and El Nino/La Nina, and drought/flood respectively. The main results are as follows. 1) For long data sequences of △t = 1d, Lanczos filter is better than Butterworth filter when n≥69d. By using Lanczos filter of n = 182d, this paper obtains 40 years MJO data of high quality of China precipitation and East Asia-Western Pacific wind field which will be studied further. 2) There are evident seasonal variation and area difference in China precipitation MJO. The absolute intensity of China precipitation MJO is strong in summer, weaker in spring and autumn, weakest in winter. The grade of relative intensity is converse. In summer the absolute intensity in southeast is evident stronger than in northwest along the dividing line from Yunnan to northeast of China. The East China can be divided into four regions as Northeast of China, North China, Changjiang-Huaihe region, South China. 3) There is prominent correlation between East China precipitation MJO and East Asia-Western Pacific wind MJO in summer. For their first couple of characteristic vector after SVD analyzing, the zero line of precipitation MJO is consistent with the ridge line of anticyclone circulation in 500hPa wind MJO. The positive anomaly area of precipitation matches the southwest air flow on the north of ridge line. There is evident interannual difference in the amplitude and phase of the left and right time correlation for the first mode. In strong MJO years, the amplitudes are great and phases are similar for the left time correlation. In strong MJO years, precipitation anomaly and precipitation MJO change synchronously, so the latter plays an important role in deciding the former. 4) There is no evident relationship between the MJO intensity of summer precipitation in the whole East China and El Nino/La Nina, but weak relationship between MJO intensity in each region and El Nino/La Nina exist. In El Nino summer and La Nina summer, MJO energy is mostly weak in two north regionswhile slightly strong in two south regions. 5) There is evident difference between summer precipitation MJO in each eastern region in drought years and in flood years. The MJO intensity is stronger in flood years than in drought years. This character is prominent in Changjiang-Huaihe region, weaker in North China and South China, weakest in Northeast.