PNNL

Abstract

This study is the first to relate Saharan dust and tropical cyclone (TC) movement over the eastern and central Atlantic Ocean (ECAO) using observations and modeling. An eastward position forecast bias for TCs over ECAO has been noticed and is potentially related to the neglect of dust-radiative forcing in numerical models. Using 11-year observations we found that aerosol optical depth and TC westward speed over ECAO are correlated (0.62) with a confidence level of 99%. The Weather Research and Forecasting dust model was used to quantitatively study the impact of the dust-radiative forcing on Helene’s (2006) track forecasts with 3 different microphysics schemes. The dust-radiative forcing increases the temperature in the warm Saharan Air Layer, thus increases the temperature gradient and modifies wind speed and/or direction along the southern flank of the dust plume, improving Helene’s track. Including dust-radiative forcing reduces the error in 7-day position forecasts by 27% (~205km).