The Use of Moist Potential Vorticity Vector as Diagnostic Variable of Rainfall Events in Tanzania

Philbert Modest Luhunga, Agnes Kijazi, Ladislaus Chang a, Chuki A Sangalugembe, Doreen Mwara Anande, Hashim Ng ong olo, Habiba Mtongori

Abstract


The work of this paper is a first step of the new paradigm, to use the Moist Potential Vorticity Vector (MPVV) as a diagnostic variable of rainfall events in Tanzania. The paper aims at computing and assessing the usefulness of MPVV in the diagnosis of rainfall events that occurred on 08th and 09th May 2017 over different regions in Tanzania. The relative contributions of horizontal, vertical components and the magnitude of MPVV on diagnosis of rainfall events are assessed. Hourly dynamic and thermodynamic variables of wind speed, temperature, atmospheric pressure and relative humidity from the numerical output generated by the Weather Research and Forecasting (WRF) Model, running at Tanzania Meteorological Agency (TMA) are used in computation of MPVV. The computed MPVV is then compared with WRF model forecasts and observed rainfall. It is found that in most parts of the country, particularly over coastal areas and North-Eastern Highlands, MPVV exhibited positive values in the lower troposphere (925hPa) and (850hPa) indicating local instability possibly associated with topographic effects, and continent/ocean contrast. MPVV is mostly positive with slightly negative values indicating instabilities (due to possible convective instability). Moreover, MPVV provides remarkably accurate tracking of the locations received rainfall, suggesting its potential use as a dynamic diagnostic variable of rainfall events in Tanzania.


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DOI: https://doi.org/10.5539/apr.v9n5p1

Copyright (c) 2017 Philbert Modest Luhunga, Agnes Kijazi, Ladislaus Chang a, Chuki A Sangalugembe, Doreen Mwara Anande, Hashim Ng ong olo, Habiba Mtongori

License URL: http://creativecommons.org/licenses/by/4.0

Applied Physics Research   ISSN 1916-9639 (Print)   ISSN 1916-9647 (Online)   Email: apr@ccsenet.org

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