Moist Potential Vorticity Vector for Diagnosis of Heavy Rainfall Events in Tanzania

Philbert Modest Luhunga,George Djolov,Edmund Mutayoba

doi:10.4236/gep.2016.49010

Abstract

In this paper, we modify the convective vorticity vector (CVV) defined as a cross product of absolute vorticity and gradient of equivalent potential temperature to moist potential vorticity vector (MPVV) defined as a cross product of absolute vorticity () and the gradient of the moist-air entropy potential temperature (). The patterns of (MPVV) are compared with the patterns of heavy rainfall events that occurred over different regions in Tanzania on 20th to 22nd December, 2011 and on 5th to 8th May, 2015. Moreover, the article aimed at assessing the relative contributions of the magnitude, horizontal and vertical components of (MPVV) detecting on the observed patterns of rainfall events. Dynamic and thermodynamic variables: wind speed, temperature, atmospheric pressure and relative humidity from numerical output generated by the Weather Research and Forecasting (WRF) model running at Tanzania Meteorological Agency (TMA) were used to compute MPVV. It is found that MPVV provide accurate tracking of locations received heavy rainfall, suggesting its potential use as a dynamic tracer for heavy rainfall events in Tanzania. Finally it is found that the first and second components of MPVV contribute almost equally in tracing locations received heavy rainfall events. The magnitude of MPVV described the locations received heavy rainfall events better than the components.

Highlights

The patterns of ( MPVV ) are compared with the patterns of heavy rainfall events that occurred over different regions in Tanzania on 20th to 22nd December, 2011 and on 5th to 8th May, 2015
We presented a first step of new paradigm, to use the Moist Potential Vorticity Vector MPVV as diagnostic variable of heavy rainfall events in Tanzania
The main purpose of the article was to compute and compare the patterns of MPVV derived from the gradient of the moist-air entropic potential temperature and heavy rainfall events that occurred over different regions in Tanzania on 20th to 22nd December, 2011 and on 5th to 8th May, 2015

Summary

Introduction

Extreme weather events such as heavy rainfall are common and have. Tanzania has witnessed many heavy rainfall events in recent years. Forecasting of these events is of considerable benefit to different sectors (agriculture, hydropower, health, water resources) and community at large. It is difficult to forecast these events accurately and reliably [3] [4]. In Tanzania, the difficulty to forecast heavy rainfall is associated with the country’s complex topographical landscapes, numerous large inland water bodies, variation in vegetation types and land-ocean contrast [5]

Objectives

Results

Conclusion