| dc.description.abstract | In summer, the land-sea breeze associated with the development of deep cumulus convection in afternoon is the most significant character in Taiwan. A number of previous experiments and studies have analyzed the time series, physical mechanism, structure and the interaction with large scale circulation about the phenomenon of land-sea breeze. They showed that the sea breeze and deep cumulus convection are with fairly strong relationship. However, in summer, Taiwan faces strong intra-seasonal variation of its environmental flow, undergoes the subtropical high and south-west monsoon. In between these two climatologies, the see breeze evolution in Taiwan should be deeply influenced by the background systems. There must be a certain kind of structure of the background circulation that can help the land-sea breeze develop best. Therefore, here we analyzed the climate character of the large-scale background to determine the most suitable season and month. From such the season, we tried to set some criteria to classify the structure for best inducing the sea breeze and deep cumulus convection.
We used NCEP wind (u,v) data from 1993 to 1998, totally six years, to translate into streamfunction and velocity potential, performed the Fourier analysis to filter the extraseasonal period out. Then we calculated the area average around Taiwan to get the daily time series of July. The GMS IR image and CWB surface stations’’ wind are adopted to check the result of our classification by making composites form the selected cases. Our final criteria are: Based on the anticyclone of streamfunction at 850mb, we searched for the cases of cyclonic 200mb streamfunction for the clear condition. In addition, the 200mb streamfunction with the same phase but stronger of the 850mb one are also adopted.
The result showed as follow:
a. From the analysis of station data, we verify that July is the break of summer monsoon in Taiwan.
b. July is the season with the most significant land-sea breeze structure in Taiwan.
c. The criteria of our classification can efficiently filter out the large-scale circulation that help the land-sea breeze develop. | en_US |