Observation of the moist convective environment of West Africa by the Atmospheric InfraRed Sounder

Abstract

The seasonal migration of the Intertropical Discontinuity (ITD) is critical for monitoring seasonal moist convective processes and associated rainfall over West Africa. This study constitutes a new analysis of the seasonality of moist convection over West Africa, relative to the ITD, based on NASA's Atmospheric Infrared Sounder (AIRS) measurements from 2003-2018. Results show that AIRS resolves the seasonal march of the ITD, including its inherent diurnal-scale variations. AIRS captures the north - south daytime skin temperature dipole around the ITD, with greater relative temperatures to the north, especially during March - August. In the vicinity of the nighttime ITD, AIRS profiles indicate increased instability that is characteristic of nocturnal thunderstorm propagation. On thunderstorm days, the mean latitude of the AIRS-derived ITD is displaced 3o , 0.2o, and 2o north of its DJF, MAM, and SON climatological positions, respectively, and 1.2o south in JJA. The findings of this study are critical to building local tropical weather forecasting capacity and capabilities in West Africa.