| Summary: | 碩士 === 中國文化大學 === 地學研究所大氣科學組 === 104 === In recent years, many studies have indirectly use gross moist stability (Yu 1997) to analyze climatic phenomena (e.g., Madden-Julian Oscillation, MJO). The gross moist stability is determined by atmospheric most static energy profile associated with the depth of convection. This index is used to display atmospheric stability and change.
The main purpose of this study is to use reanalysis data and International Satellite Cloud Climatology Project (ISCCP) data to examine gross moist stability. In climatic mean, it is found that gross moist stability is positive and its gradient is small in the tropics. In the original way of estimating gross moist stability, the saturated layer is assumed at 1000hPa. In this study, several different saturation levels are used to estimate gross moist stability and compare with observational data. The results show that the saturation level and the maximum height of convection are important to the estimate of gross moist stability. Minimum values occur when the level of free convection is chosen as the saturation level.
Because the maximum height of convection is idealized, the difference between the maximum height of convection and ISCCP data is large in generally. In the western Pacific convergence zone, the differences range from 100hpa to 150hpa. In the eastern Pacific convergence zone, the differences range from 300hpa to 350hpa. According to the normalized gross moist stability (Raymond 2009, NGMS), the moisture budget equation is used to examine gross moist stability. The results show that ratio of gross moist stability over gross moisture stratification (Mq) is smoother than NGMS in the Pacific convergence zone. In analysis by using moisture budget equation, we found that while the vertical moisture advection term is in general balanced by the difference between rainfall and evaporation, but the errors are large.
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