Study of tropical deep convective processes and water vapor variations using nasa a-train data and geostationary satellite observations
Item
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Title
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Study of tropical deep convective processes and water vapor variations using nasa a-train data and geostationary satellite observations
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Identifier
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d_2009_2013:17edf6dae337:12081
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identifier
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12536
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Creator
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Takahashi, Hanii,
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Contributor
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Zhengzhao Johnny Luo
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Date
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2013
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Language
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English
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Publisher
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City University of New York.
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Subject
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Atmospheric sciences | Meteorology | CloudSat | ISCCP | Level of Neutral Buoyancy | NASA A-Train | Tropical Deep Convection | Water Vapor
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Abstract
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The theme of this dissertation is to use various satellite observations to seek new insights into our understating of tropical deep convective processes and water vapor variations. Three subjects are investigated: 1) observational determination of level of neutral buoyancy (LNB) for deep convection, 2) characters and life stage view of tropical overshooting convection (OSC), and 3) variations of water vapor and clouds during East Pacific (EP)- and Central Pacific (CP)-El Ninos. The first study conducts a near-global survey of LNB for tropical deep convection using CloudSat (LNB_observation) and makes comparison with the corresponding LNB based on the parcel theory using ambient sounding (LNB_sounding). The principal findings are as follows: First, although LNB_sounding provides a reasonable upper bound for convective development, ambient sounding contains limited information for predicting the actual LNB. Second, LNB_sounding significantly overestimates the "destination" height level of the detrained mass. Third, LNB_observation is consistently higher over land than over ocean, although LNB_sounding is similar between land and ocean, suggesting some fundamental differences between land and ocean convection. The second study uses CloudSat data together with ISCCP CT to study tropical OSC properties and the convective systems in which they are embedded. Our results find that, nearly 21 % of tropical deep convection is overshooting; the occurrence frequency is only slightly higher over land (~ 50.2 %) than over ocean (~ 49.8 %). Various proxies of convective strength are analyzed showing consistently that continental OSC is stronger than the oceanic counterpart. Moreover, majority (2/3) of the OSC occurs during the growing stage of the convective systems. About 1/3 occurs during the mature stage, which are more abundant over land during noontime. The third study shows that EP- and CP-El Nino events produce different patterns of water vapor and cloud anomalies over the tropical ocean. Regression of water vapor anomalies onto the Nino-3.4 sea surface temperature shows a clear "upper tropospheric amplification" of the fractional water vapor change. Furthermore, water vapor and cloud anomalies in different circulation regimes are examined. Finally, Geophysical Fluid Dynamics Laboratory AM2.1 model simulations of water vapor and clouds are compared with the satellite observations.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Earth & Environmental Sciences
