Investigation into spatiotemporal characteristics of coastal winds around the Taiwan Island

Abstract

Temporal and spatial variation characteristics of winds and their relationship with terrain environment in the Taiwan Island were investigated in this research. Based on the empirical orthogonal function (EOF) analysis, the monthly-averaged wind speed and direction at eight observation stations around Taiwan island from 1980 to 2015 were analyzed. Then the temporal and spatial variation characteristics of wind direction and wind speed as well as the abrupt change characteristics of wind speed were studied. Main results are: (1) The first EOF modal variance contribution rate of wind speed reaches 43%, and its spatial distribution numerical center shows that the positive value center is at S10, and the negative value center is at S1. The value at other areas does not change significantly. The contribution rate of the second EOF mode is 22%, which is also reflected in the positive center at S10, and the variance contribution rate of the third EOF mode is 16%. At the same time, the analysis of the wind direction EOF results shows that the first EOF modal variance contribution rate is 35%, which is lower than that of wind speed. Only stations S1 and S12 are positive but have small values, while S5 and S8 have the maximum negative value. In combination with the local terrain, it shows that wind speeds are significantly affected by topography. The wind speed is stable, but the wind direction is unstable near the plain along the Taiwan Strait. Additionally, the wind speed is less stable and the wind direction is more stable at the north and south of Taiwan Island due to the influence of the central mountains. (2) Analysis on the main contribution modal time coefficient of wind speed EOF indicate that the value is mostly negative in winter and positive in summer, which shows that the wind speed around Taiwan Island has significant variation at a seasonal scale, with a strong northeast wind in winter significantly affected by the northeast monsoon and a weak southwest wind in summer affected by the southwest monsoon.