Impacts of anomalies of thermal state over the Qinghai-Xizang Plateau and sea surface temperature on interannual variability of the Asian monsoon seasonal transition
Based on the reversal of the middle and upper tropospheric meridional temperature gradient near the ridge surface of the Asian subtropical anticyclone during seasonal transition, correlation and composite analyses are employed to study the interannual variability of the Asian monsoon seasonal transition and its relation to external forcing. Results show that ENSO and thermal state over the Qinghai-Xizang Plateau in the preceding winter and spring are two dominant factors responsible for the interannual variability of the Asian monsoon seasonal transition. When the E1 Ni?o event occurs during winter and spring, Walker circulation is weakened so that deep convection is suppressed over the western Pacific warm pool, while enhanced convection over the eastern equatorial Pacific induces adiabatic descending motion over the equatorial Indian Ocean. Consequently, air temperature over the equatorial Indian Ocean gets warmer, meridional temperature gradient over Asian sector becomes larger, and the seasonal transition is later than normal. The middle and upper tropospheric temperature anomalies over the Qinghai-Xizang Plateau in early spring are good indicative of predicting abnormal seasonal transition.
Seasonal transitionInterannual variabilityENSOThermal state over the Qinghai-Xizang Plateau
NETL
NSTL
万方数据
维普
