A Strengthened Teleconnection of the Quasi‐Biennial Oscillation and Tropical Easterly Jet in the Past Decades in E3SMv1
The simulations by E3SMv1 provide more evidence that the QBO has an impact on the summer monsoon, specifically on the tropical easterly jet (TEJ). A strengthened teleconnection between the QBO and TEJ in the past decades can be detected not only in observation but also in the cutting-edge climate model. The warming in sea surface temperatures over the Indian Ocean and opposite trends in the air temperature in the upper troposphere and lower stratosphere are considered the essential reasons responsible for the strengthened teleconnection between the QBO and TEJ.
Improving the S2S predictability of the monsoon has an important social-economic value. Windows of opportunity for forecasting this can open up if the relevant external drivers are active. As a periodic oscillation in the stratosphere, the QBO is expected to provide predictability to the monsoon. This research shows that E3SMv1 can capture the teleconnection between the QBO and tropical easterly jet (TEJ), which is an important member of the Asian summer monsoon system. This research also reveals reproducing precisely the trends in sea surface temperature over the Indian Ocean and temperature in the upper troposphere is essential for models to capture the interdecadal change of teleconnection between QBO and TEJ.
E3SMv1 can generate the QBO internally and simulate the response of the tropical easterly jet (TEJ) to different QBO phases. A stronger correlation between the QBO and TEJ in the period after 1980 observed in reanalysis is reproduced by the AMIP-historical simulations. A possible explanation of this strengthened teleconnection between QBO and TEJ is the long-term trend of decrease in stability and enhancement in upward motion in the upper troposphere over the Indian Ocean driven by a warmer Indian Ocean and increased greenhouse gasses. Therefore, the performance of reproducing the temperature trend in the upper troposphere and lower stratosphere and tropical sea surface temperature is critical for the model to capture the long-term trend in the teleconnection between QBO and TEJ.