[Show abstract][Hide abstract] ABSTRACT: Based on 1961-2003 NCEP/NCAR reanalysis treated with EOF, wavelet and cross wavelet techniques we investigate different space patterns of July-September precipitation over Fujian in relation to summer monsoon over the NW Pacific and Indian Ocean at a range of time scales. Results show that 1) the uniform rainfall all over the province and opposite distribution of precipitation in the SE to the NW part are the dominant modes, 2) the NW Pacific summer monsoon exerts steadier impacts on rainfall in the former case, manifested dominantly in the interannual variation especially after the mid 1980s, depending on the strong (weak) monsoon for excessive (insufficient) precipitation, with the response center in the eastern seaboard of the province whereas the Indian Ocean monsoon has rather stable influence on rainfall differing in amount between SE and NW Fujian, mainly in the interdecadal variation, and it also exerts remarkable effects on the interannual variation subsequent to the mid 1980s, relying on the intense (weak) monsoon for more (less) precipitation in the SE and less (more) in the NW part in this season. It follows that the NW Pacific (Indian) monsoon has its effect on the rainfall amount (space distribution) during July to September, and 3) with the strong monsoons over the two oceans the difference in rainfall between SE and NW Fujian is increased and in the opposite case precipitation is lower over much of the province, and when the monsoons are contrary in intensity the departure field shows a complicated pattern, manifesting pronounced locality.
[Show abstract][Hide abstract] ABSTRACT: The paper investigates the multiple time scale features of the annual frequency of tropical cyclones (TC) affecting Fujian and the air - sea background in abnormal TC frequency years in 1884~2003, leading to the conclusions as follows: (1) The province experiences two (three) stages of more (fewer) TC hitting, with the turning years being 1902,1931, 1955 and 1971, and the last in particular serves as the strong turning point for the frequency change on a yearly basis. The frequency experiences oscillations in quasi-13, -4 and -2.5 years, and especially the quasi-4 year oscillations are the most significant;(2) examining the summertime 500hPa height field in the years of more (fewer) TC striking the province, we find the geopotential heights over the Okhotsk Sea to be lower (higher) than in normal years, and the anomaly to be characterized by a "- + -" ("+ - +") pattern from high to lower latitudes, the zonal (meridional) circulations to prevail, the westerly trough, the northern limit of the subtropical high (sub-high) and its ridge line to be northward (southward) of average; (3) a noticeable negative (positive) SSTA band is found over the eastern equatorial Pacific as well as a swathed positive (negative) SSTA in the western Pacific dominant source region of TC and also the NW Pacific, indicating that the frequency of TC affecting Fujian depends not only on SST in the TC genesis area but the position and intensity of atmospheric circulations that play a crucial role in the TC track, which thus affects the yearly frequency of TC influencing Fujian.