NOTES AND CORRESPONDENCE Annual and Semiannual Variations of Surface Pressure in Taiwan

Corresponding author address: Tsing-Chang (Mike) Chen, Atmospheric Science Program, 3010 Agronomy Hall, Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA 50011. E-mail: [email protected] Recently, the ps observations of 59 stations (Fig. 1, including 26 original surface stations of the Taiwan Weather Bureau analyzed by CY) during 1993–98 were made available to us. In our analysis of the ps annual variation over Taiwan, a distinct semiannual signal emerged from the ps observations at some tall mountain stations. Although this signal at Yu-Shan was pointed out by CY, it was not discussed in detail. Several studies have examined the structure and cause of the semiannual oscillation in low latitudes (e.g., van Loon and Jenne 1969, 1970; Weickmann and Chervin 1988; Chen et al. 1996). However, as far as we know, this short-term climate signal in the low latitudes has not previously been explored with ps observations at a high-elevation station. Also, for the opposite-phase annual variation of ps between high and low elevations, CY only contrasted ps(Yu-Shan) with ps at the low-elevation stations of the Taiwan Weather Bureau. Is this ps inverse relationship common in Taiwan between tall mountains and the low plains? Since more ps observations are now available, it is of interest to examine this question as well.