碩士 / 國立臺灣大學 / 大氣科學研究所 / 99 / The characteristics of precipitation in tropical oceans were examined in this study. We focused on the influence of the atmospheric thermal condition and the boundary condition, such as sea surface temperature (SST).
Previous studies show that the relationship between precipitation and SST could be either positive or negative. When SST is between 26 ℃ and 30℃, the correlation is positive, which SST plays an active role in the air-sea interaction. On the other hand, a negative correlation appears with SST greater than 30℃, so SST plays a passive role. The relationship between precipitation and SST discussed above is usually obtained from monthly data with a relatively coarse resolution, so it might not be able to represent a realistic relationship between these two variables. Here we examine the relationship between precipitation and SST by using daily satellite data with a high spatial resolution. Only a positive correlation is found between SST and precipitation. Precipitation shows a delayed impact on SST, i.e. a cooling 2-3 days after the peak of precipitation. This delayed impact might be the reason causing the negative correlation between SST and precipitation in monthly data with a relatively coarse resolution.
The strength of precipitation is related to water vapor, which is strongly linked to temperature. We examined the differences of precipitation between summer and winter. We focus on monsoon regions, where moisture presumably varies a lot between these two seasons. When temperature increases, water vapor in the atmosphere increases by about 7%/K, which is close to the Clausius-Clapeyron thermal expansion under the condition that the relative humidity is constant. The increased rate of extreme precipitation is much greater than the increase in water vapor, which implies that vertical velocity is more important. The vertical structure of temperature differences between summer and winter is consistent with the atmospheric stability, which can affect the strength of upward motion. In model simulations, changes in extreme precipitation vary a lot among models, which might be due to differences in vertical velocity.
| Identifer | oai:union.ndltd.org:TW/099NTU05022036 |
| Date | January 2011 |
| Creators | Yi-Chun Liao, 廖怡君 |
| Contributors | 周佳 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 77 |
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