Circulation pattern controls of summer temperature anomalies in southern Africa

Abstract: This study investigates the relationship between circulation patterns and austral summer temperature anomalies in southern Africa. The results show that the formation of continental lows tends to increase the partial atmospheric layer thickness. Further, the distinct variabilities of high and low pressure under the circulation types, influence air mass advection from the adjacent oceans, as well as atmospheric stability over land. Stronger anticyclonic circulation at the western branch of the Mascarene high enhances low-level cold air advection by southeast winds, decreases thickness, and lowers the temperature over a majority of the land in southern Africa. Conversely, a weaker Mascarene high, coupled with enhanced cyclonic activity in the southwest Indian Ocean increases low-level warm air advection and increases temperature anomalies over vast regions in southern Africa. The ridging of a closed South Atlantic anticyclone at the southern coast of southern Africa results in colder temperatures in the tip of southern Africa due to enhanced low-level cold air advection by southeast winds. However, when the ridge is weak and westerly winds dominate the southern coast of southern Africa, temperature increases in these areas. The northward track of the Southern Hemisphere mid-latitude cyclone, which can be linked to the negative Southern Annular Mode, reduces the temperature in the southwestern part of southern Africa. Also, during the analysis period, El Niño and the positive Subtropical Indian Ocean dipole were associated with temperature increases over the central parts of southern Africa.

Keywords:
• temperature,
• circulation types,
• Subtropical Indian Ocean dipole,
• Southern Annular Mode,
• Mascarene high,
• South Atlantic anticyclone,
• atmospheric thicknesses