LUNAR-SYNODIC COMPONENT IN THE EAST ASIAN WINTER MONSOON

This study is an extension of the lunar-synodic influence on the weather and climate. Using data from satellite observations and model reanalysis in a lunar month during East Asian winter monsoon (EAWM), the atmospheric condition surrounding the semi-permanent anticyclone (SPA) is investigated. The SPA in the EAWM exists at lower-tropospheric atmosphere center near Taiwan. Between the first and the last quarter of the moon, the northward movement of the SPA ridge is assessed, to be the cause of the enhancement of windward coastal precipitation in East and Southeast Asia. Corresponding to the SPA variation across the full moon, the geopotential height over the SPA region (17.5–27.5°N; 115–135°E) increased at lower-tropospheric atmosphere and decreased at higher-tropospheric atmosphere. Associated with the squishing atmosphere, the middle- and low-level clouds with thick optical thickness (MLTC) increased significantly, which was highly related to the increased precipitation (there was 1/4 MLTC enhancement in the SPA region calculated by three-fifths of the lunar months between 1985 and 2006). It is suggested that the lunar-synodic cycle might modulate the EAWM precipitation when the atmospheric conditions change and favor development of thick clouds.