臺灣大氣垂直結構之氣候長期分析

Atmospheric vertical motions play a crucial role in sustaining the Earth’s atmosphere system. Although vertical motions are much smaller than horizontal motions in spatial scale, most of the energy in the atmosphere is released and conveyed through vertical motions. The intensity of vertical motions is much affected by the atmospheric stability, which is essentially determined by the environmental lapse rate and the condition of saturation. Based on this knowledge, scientists are able to identify atmospheric conditions through conducting radiosonde observation tasks, and apply the results to the forecast for severe weathers. The history of Taiwan’s radiosonde observations can be traced back to the Japanese colonial era. Nowadays, several operating radiosonde stations operated and maintained by the Central Weather Bureau and the R.O.C. Air Force work together to construct a vertical atmospheric profile above Taiwan. This project has obtained observational temperature and rainfall data from numerous agencies spreading around Taiwan. Together with the radiosonde observation network and reanalysis datasets, our work examined atmospheric characteristics in different regions on the island and at various elevations from a climatology perspective. The first year progress of this project is summarized in the following published paper entitled “Warming Trends of the Upper Troposphere in Taiwan Observed by Radiosonde and Surface Meteorological Stations at Various Altitudes”. In recent decades, a more prominent warming trend in the upper troposphere above the tropical western Pacific has been proposed in the literature derived from model simulations, satellite-borne observations, or reanalysis datasets. Rather than applying these “indirect” approaches, this study obtains surface-based and radiosonde observations in Taiwan in order to investigate long-term changes in temperature at different altitudes within the troposphere under the conditions of ongoing global warming. These surface-based observations indicate more pronounced warming in areas of high terrain, and the radiosondes reveal faster warming trends in the upper troposphere, with the maximum temperature increase between 400 hPa and 250 hPa. The upper-tropospheric warming becomes even more pronounced during boreal winter and spring; however, the intense warming does not carry over near the tropopause. Notable warming is also observed near the surface in Taipei, which may be related to the urban heat island effect caused by the rapid development of anthropic activities. Since Taiwan is located right on the edge of the tropics in the western Pacific, the upper-tropospheric warming, particularly between December and March, above the island should be contributed by the radiative and non-radiative processes, which were previously proposed by other studies.