Haboobs and instability in the sudan

Abstract

Abstract The dust‐storms of the Sudan, called haboobs, are shown to be associated with thunder squalls. Several haboobs are discussed with particular reference to upper winds and upper air temperatures, an indication of the speeds of the vertical currents associated with a haboob being obtained on one occasion by means of a series of pilot balloon observations in close sequence. A value of 10 8 for the coefficient of eddy diffusivity in a haboob is derived. Conditions associated with instability in the Sudan are investigated and it is suggested that they may be referred to a discontinuity between southwest monsoon and northeast trade, the slope of which is given by the expression: the symbols having the usual‐significance. A series of photographs taken with the co‐operation of the R.A.F. illustrates the conditions in some of the haboobs.