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Using reanalysis and the sea surface temperature (SST) analysis, the combined impact of El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) on the northern winter stratosphere is investigated. The warm and weak stratospheric polar vortex response to El Niño simply appears during positive PDO, whereas the cold and strong stratospheric polar vortex response to La Niña is preferable during negative PDO in the reanalysis. Two mechanisms may account for the enhanced stratospheric response when ENSO and PDO are in phase. First, the asymmetries of the intensity and frequency between El Niño and La Niña can be identified for the two PDO phases. Second, the extratropical SST anomalies in the North Pacific may also play a role in the varying extratropical response to ENSO. The North Pacific SST anomalies related to PDO superimpose ENSO SST anomalies when they are in phase but undermine them when they are out of phase. The superimposed North Pacific SST anomalies help to increase SST meridional gradient anomalies between tropical and extratropics, as well as to lock the local height response to ENSO. Therefore, the passages for the upward propagation of waves from the troposphere is more unimpeded when positive PDO is configured with El Niño, and vice versa when negative PDO is configured with La Niña.

Abstract:To further verify the ozone profile reliability of satellite remote sensing for the ozone valley over the Tibetan Plateau in the core area of the South Asian high in summer, we validate the ozone products from the microwave limb sounder (MLS) onboard the Aura satellite over the Tibetan plateau using electrochemical concentration cell (ECC) ozonesonde data of 2016 for Ngari, Tibet. The MLS version four ozone profiles have lower standard deviation in the middle stratosphere (38-10 hPa), whereas the ozonesonde profiles have lower standard deviation in the upper troposphere and lower stratosphere region (200-83 hPa). There are statistically significant differences between these two datasets in most of the stratosphere (10-83 hPa). The mean value of MLS ozone is about 0.8-1.5 mPa greater than that of ECC ozone, which corresponds to a relative deviation of 59 ± 24% at 83 hPa, 24 ± 13% at 68 hPa, 20 ± 5% at 56 hPa, 14 ± 4% at 46 hPa and 38 hPa, and 9 ± 4% in the layers between 32 and 10 hPa. However, there is no statistically significant difference between the two datasets in the upper troposphere (100-200 hPa).