Date of Award

1-1-2020

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Atmospheric and Environmental Sciences

Content Description

1 online resource (xviii, 142 pages) : color illustrations, color maps.

Dissertation/Thesis Chair

Liming Zhou

Committee Members

Aiguo Dai, Brian E. J. Rose, Paul E Roundy

Keywords

Climate variability, Congo rainforest, Madden–Julian oscillation, Satellite remote sensing, Tropical Convection, WRF model, Rain and rainfall, Rain forests, Convection (Meteorology), Madden-Julian oscillation, Atmospheric waves

Subject Categories

Atmospheric Sciences

Abstract

The hydrological cycle over tropical rainforests includes some of the most intense thunderstorms and rainfall totals. The energy associated with this convective activity plays an important role in the Earth’s weather and climate system. Therefore, the interannual variability, trends, and future climate projections of the hydrological cycle over tropical rainforests are important topics for research. The Congo rainforest situated over equatorial Africa is the second largest rainforest in the world, and recent studies have documented a >30-year large-scale and long-term drying trend over the Congo since the late-1970s. However, unlike the Amazon rainforest in South America, the Congo rainforest is relatively understudied. The challenges associated with meteorological research over the Congo basin is also exacerbated by the declining trend in surface observations (e.g., rain gauges) and the complex topography surrounding the Congo basin. In this dissertation, rainfall variability and trends over the Congo basin are explored by analyzing satellite and surface observations, global atmospheric reanalysis data, sub-seasonal/seasonal teleconnection indices, and convection-allowing simulations from a mesoscale numerical model. Since there is a strong relationship between rainfall and convective activity over the tropical latitudes, trends in thunderstorm activity was explored. Next, convectively coupled atmospheric equatorial waves (CCAEW) and the Madden Julian oscillations (MJO) were investigated as a possible mechanism to explain thunderstorm activity. The relationship between the MJO and rainfall over the Congo basin was investigated in more detail to clarify the method-dependent findings reported in previous works. Finally, the interaction of precipitation with orography was studied by perturbing orography by using a high-resolution, convection allowing, mesoscale numerical model. The findings presented in this work include the following:

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