Recently, Dr. Xin Zhou (corresponding author) from the school of atmospheric science of our university cooperated with experts from Beijing normal university in Environmental Research Letter, an international Top journal in the field of geosciences (SCI journal of the Chinese academy of sciences sub-division: major subject — geoscience 2 zone; IF= 4.541) published an academic paper entitled “The key role of background sea surface temperature over The cold tongue in asymmetric response of The Artic stratosphere to El Nino — Southern Oscillation”. She reported the key role of background SST in the cold tongue region of the tropical Pacific in the asymmetric feedback of the arctic stratospheric polar vortex.

The asymmetric feedback of the arctic stratospheric polar vortex to ENSO is a proven phenomenon, that is, the polar vortex’s feedback to El Nino is stronger than its feedback to La Nina. Previous studies have suggested that the asymmetric feedback under the positive and negative phase is caused by the remote correlation of ENSO. This study found that the background SST of the tropical Pacific plays an important role in this asymmetric feedback process. When a tropical sea surface temperature in 26 to 30 ° C range, convection is sensitive response to the SST turbulence. In the case of El Nino, the SST in the cold tongue area is usually within this temperature range after the superposition of El Nino anomalies, so the atmospheric feedback is strong. However, in the case of La Nina, the SST in the cold tongue usually cannot reach the minimum threshold in this range, so the atmospheric feedback is weak. These results are confirmed in both observation and numerical experiments.

The study provides a new perspective for the asymmetric feedback of the northern hemisphere’s stratospheric polar vortex on ENSO and reveals the important role of the background SST in the cold tongue region of the tropical Pacific. Especially under the background of global warming, the change of the tropical SST background field may cause the change of climate response.

Thesis information: Xie, F., X. Zhou*, J. Li, C. Sun, J. Feng and X. Ma, 2018: The key role of background sea surface temperature over the cold tongue in asymmetric responses of the Arctic stratosphere to El Niño–Southern Oscillation. Environmental Research Letters,13, Doi: 10.1088/1748-9326/aae79b.

Links to papers: https://doi.org/10.1088/1748-9326/aae79b