Master of Science (MS)
Meteorology and Physical Oceanography (Marine)
Date of Defense
First Committee Member
Shuyi Chen - Committee Chair
Second Committee Member
Chidong Zhang - Committee Member
Third Committee Member
Brian Mapes - Committee Member
Fourth Committee Member
Chris Landsea - Outside Committee Member
The tropical cyclone (TC) and environmental interaction is not fully understood. Previous studies have demonstrated that this interaction affects intensity change. The studies found that intensification is favored in low shear, moist environments, with high sea surface temperatures (SST). However, little precise quantification was provided, especially in terms of the impact of environmental water vapor on TC intensity change. This work addresses the TC interaction with the environmental water vapor. Results from a comprehensive statistical study show that TC intensification is more likely to occur in an anomalously moist environment than a dry environment. However, only a small amount of the total variance is explained. When assessing the effect of vertical wind shear along with environmental water vapor, more of the variance is explained. Water vapor not only affects TC intensity. Prior modeling studies have demonstrated impacts from environmental water vapor on TC structure. These impacts can also affect intensity change. Specifically, enhanced water vapor content within the TC enhances the rainbands, which can lead to an eyewall replacement cycle, causing a temporary weakening, followed by re-intensification. This thesis evaluates observational and high resolution MM5 model output from Hurricanes Katrina and Rita from the Hurricane Rainband and Intensity Experiment (RAINEX) to evaluate the effects of varying water vapor distributions on TC structure. While the two hurricanes were of similar intensity, they had different water vapor distributions and structures. Rita underwent an eyewall replacement cycle while under RAINEX surveillance while Katrina did not. Rita was also located within a dry environment and had a strong horizontal moisture gradient, while Katrina was in a moist environment and had a weak moisture gradient. Results suggest that a strong horizontal water vapor gradient, with a moist TC and dry outer environment may confine the hurricanes into a pattern that causes them to have high circularity, promoting the formation of a secondary eyewall. The dry outer environment had strong atmospheric stability and was less favorable for deep convection far from the center in the Rita case. The moist environment in the Katrina case was more unstable. This may have allowed for the rainbands to be farther from the center in a less circular pattern than Rita. The results presented in this thesis suggest that this pattern is less favorable for an eyewall replacement cycle.
Hurricane Intensity; Water Vapor; Eyewall Replacement; Katrina; Rita
Ortt, Derek, "Effects of Environmental Water Vapor on Tropical Cyclone Structure and Intensity" (2007). Open Access Theses. 90.