Local Wave Driving of the Annual Cycle in Tropical Tropopause Temperatures

Diagnostics from ECMWF analyses indicate that a significant factor in controlling the mean state and annual cycle of the tropical tropopause is breaking by synoptic-scale waves on the equatorial side of the subtropical jets. This wave breaking extends further into the tropics during northern hemisphere winter than northern hemisphere summer where is displaced northward by the Asian monsoon. This annual cycle in wave breaking local to the tropopause explains the large annual cycle in temperatures just above the tropical tropopause and non-local wave breaking above 50 hPa is not important.