Tropical orographic rainfall regimes according to the tropical rainfall measuring mission

Reed, Kimberly

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https://hdl.handle.net/2142/29678 Copy

Description

Title

Tropical orographic rainfall regimes according to the tropical rainfall measuring mission

Author(s)

Reed, Kimberly

Issue Date

2012-02-06T20:10:33Z

Director of Research (if dissertation) or Advisor (if thesis)

Nesbitt, Stephen W.

Department of Study

Atmospheric Sciences

Discipline

Atmospheric Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• orographic precipitation
• Tropical Rainfall Measuring Mission (TRMM)
• tropical precipitation
• precipitation radar

Abstract

Observing precipitation in tropical regions of complex terrain is a challenging problem. While ground-based instrumentation including rain gauge networks and radar data offer some insights, the lack of spatially complete gauge networks and radar artifacts such as severe beam blockage lead to large errors in the precipitation retrievals. The goals of this study are to understand what atmospheric variables and parameters influence tropical orographic precipitation and how these variables and parameters govern the precipitation intensity and patterns. Twelve years (1998-2009) of data are used to determine which dynamic and thermodynamic variables and derived parameters interact to influence precipitation development and mode in multiple regions with varying orographic characteristics. NASA Modern Era Retrospective-Analysis for Research and Applications (MERRA) data over the tropical Andes, Hawaii, Eastern Himalayas, Sierra Madre Occidental, and Western Ghats are used to evaluate thirteen variables and parameters including convective available potential energy, convective inhibition, lifting condensation level, level of free convection, 700 hPa specific humidity, total precipitable water, 1000-700 hPa layer relative humidity, 700-300 hPa layer relative humidity, cross-barrier flow, mean virtual potential temperature, lapse rate of the mean virtual potential temperature, Brunt-Väisälä Frequency, and the moist Froude number. The variables and parameters are then organized into regimes specific to each individual region of complex terrain. The Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) 2A25v6 data is used to determine the vertical and horizontal structure and propagation of the precipitation systems as well as precipitation frequency and intensity. The resulting regimes defined by the variables and parameters are compared to the TRMM PR data to examine how changes in the controlling atmospheric conditions impact the mode, propagation, and structure of the precipitation systems. Results indicate multiple variables and parameters have strong controls on regional orographic precipitation. Sounding and stability parameters tend to control precipitation patterns and locations while moisture variables tend to influence both frequency and intensity of the precipitation. On a multi-regional scale, moisture variables including 1000-700 hPa and 700-300 hPa layer relative humidities as well as 700 hPa specific humidity exhibit strong relationships with precipitation rate and frequency, and demonstrate the greatest universal applicability.

Graduation Semester

2011-12

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http://hdl.handle.net/2142/29678

Copyright and License Information

Copyright 2011 Kimberly Ann Reed

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