Observational evidence of African desert dust intensification of easterly waves

Abstract

This paper presents indirect observational evidence that desert dust can modulate the amplitude of easterly waves in the Atlantic Ocean. Twenty two years of NCEP/NCAR reanalysis and dust from a global transport model are used to characterize the evolution of enhanced easterly waves. Lag composites of analysis increments (analysis minus first-guess) of geopotential height (700-hPa) anomalies indicate larger amplitudes in the analysis than in the first-guess fields. The results indicate that the temperature structure in the lower troposphere associated with easterly waves is warmer in the analysis than in first-guess fields by about 0.25 K per day. We hypothesize that the differences in the amplitudes are due to radiative effects associated with African dust, which have been incorporated in the reanalysis by data assimilation but absent in the model first-guess. Copyright 2004 by the American Geophysical Union.