The Mozambique Channel trough variability and its influence on regional precipitation variability in Mozambique in austral summer

Abstract

The Mozambique Channel trough (MCT) is one of the weather systems that affect Southern Africa including Mozambique, but has not received much attention. Through the empirical orthogonal function (EOF) analysis applied for austral summer-mean sea level pressure (SLP), interannual variability of the MCT is categorized into that of its intensity and zonal shift. The MCT intensity is significantly correlated to ENSO but is not correlated to regional precipitation in Mozambique. In contrast, the zonal shift of the MCT is not significantly correlated to ENSO but is correlated to regional precipitation there. A westward shift of the MCT is accompanied by the positive subtropical Indian Ocean dipole (SIOD) and strengthened Mascarene High (MH) that enhance moisture convergence over the Southern Indian convergence zone, inducing increased precipitation in southern and central regions of Mozambique. An eastward shift of the MCT is not necessarily accompanied by the SIOD but accompanied by weak suppression of the MH and precipitation there. However, if the eastward shift occurs simultaneously with the negative SIOD, it accompanies El Niño and prominent weakening of the MH, which should lead to stronger precipitation decrease in southern and central regions and increase in the northeast region of Mozambique.