The Sensitivity of Mesoscale Convective System Development to Land Surface Conditions in Semi-Arid Environments

Suny At Albany, Albany NY

Investigators

Abstract

The mesoscale convective system (MCS) is an organized ensemble of deep convective clouds with a contiguous precipitation area of about 100 km or more in horizontal scale. In semi-arid regions with seasonal rainfall, agricultural productivity, stream flow, and aquifer recharge depend greatly on the size and characteristics of the MCS population. MCSs are a critical component of the hydrological cycle on local, regional and global scales. The purpose of this research is to quantify the influence of land surface characteristics on the initiation and development of MCSs in a semi-arid environment. The study will focus on Sub-Saharan Africa. The research has two components. In the first component, contemporaneous meteorological and land-surface satellite data products will be compared for four wet seasons, May-September 1998-2001. From Tropical Rainfall Measuring Mission microwave imager data, convective cloud clusters will be identified and classified (e.g., location, size, intensity, percentage convective/stratiform). The Normalized Difference Vegetation Index data product will be the proxy for land surface conditions. The strength of the correlation between the characteristics of MCSs and the underlying land surface state will be assessed from the accumulation of statistics on convective systems at various stages of their life cycles. In the second component of the research, a three-dimensional coupled cloud-resolving and land surface model will be used to simulate MCSs. MCS development will be simulated over four common land covers in Sub-Saharan Africa, semi-desert, savanna grassland, woody savanna, and evergreen broadleaf forest. The experiments will vary vegetation density, vegetation type, and soil moisture and calculate the differences in MCS thermodynamic and dynamic profiles resulting from changes in the initial land surface conditions. Because precipitation from an MCS is a function of system size, structure and longevity, the spatial and temporal variability of precipitation will be the most important result used to evaluate differences among simulations. Successful completion of this research could lead to improved understanding and management of water resources in semi-arid climates.