The Investigation Of Dust Storm's Frequency And Its General Trend In Arid And Semi-Arid Sudan

Abstract

Dust /sand storms are common meteorological phenomena in the arid and semi-arid regions of Sudan. The Sahara and drylands in North Africa are the main dust storm sources. It is usually caused by thunderstorms, and strong pressure gradients associated with cyclones, which increase wind speed over a wide area, lifting large amounts of dust storm from the barren ground, the site of low converge vegetation into the atmosphere. The location of the study area is in the arid and semi-arid zones, where dust storm frequency has often been regarded as one of the most important manifestations of desertification, fragile ecosystems, and frequent droughts, and thus, the interest in this phenomenon has increased in recent years.

The main objectives of this study, are first, to identify temporal and spatial dust storm distribution and characteristics of dust storms over the study area during the 11 years (2004-2014). Second, to investigate dust storm frequency and its general trend in the mentioned period. Finally, to obtain correlation coefficient values to reveal rainfall variability that reduces and increases dust storm frequency. 

There are a variety of methods used such as, (i) an average of dust storms was obtained to consider the monthly, seasonal, and annual distribution of this phenomenon across the study area, while the annual average rainfall was used to determine the variations of rainfall amount between the stations. (ii) The Pearson Correlation Analysis method was applied to determine the correlation coeffi[1]cient between the two variables. (iii) both deviations of dust storm from its arithmetic mean and Simple Liner Regression analysis are used to identify the general trend of a dust storm, based on dust storm values.

These methods are based on two meteorological variables, namely dust storm days and monthly rainfall amount. These data were collected from the Archive of Meteorological Authority in Sudan for seven stations during the period of 11 years (2004-2014).

The outlines of this study showed that Khartoum station has the highest annual dust storm frequency with a number of about 145 dust days, while Abu Hamad station has the lowest dust storm with 33 days. Generally, Kassla and Al Fasher stations experience fewer dust storm days than the mean of all stations (81 dust storms per 11 years).

The monthly averages of dust storms increased during the summer season (June-August), whilst, it decreased in the winter season (December-February).

The general trend of dust storm frequencies showed an increase in six stations out of seven during the entire period, with an exception for the Khartoum station which showed a decrease in the general trend.