Abstract:

    This study investigates the effect of stratospheric sudden warmings (SSWs) on planetary wave (PW) activ- ity in the mesosphere–lower thermosphere (MLT). PW ac- tivity near 95km is derived from meteor wind data using a chain of eight SuperDARN radars at high northern lati- tudes that span longitudes from 150◦ W to 25◦ E and latitudes from 51 to 66◦ N. Zonal wave number 1 and 2 components were extracted from the meridional wind for the years 2000– 2008. The observed wintertime PW activity shows com- mon features associated with the stratospheric wind reversals and the accompanying stratospheric warming events. On- set dates for seven SSW events accompanied by an elevated stratopause (ES) were identified during this time period us- ing the Specified Dynamics Whole Atmosphere Community Climate Model (SD-WACCM). For the seven events, a sig- nificant enhancement in wave number 1 and 2 PW ampli- tudes near 95 km was found to occur after the wind reversed at 50 km, with amplitudes maximizing approximately 5 days after the onset of the wind reversal. This PW enhancement in the MLT after the event was confirmed using SD-WACCM. When all cases of polar cap wind reversals at 50 km were considered, a significant, albeit moderate, correlation of 0.4 was found between PW amplitudes near 95 km and westward polar-cap stratospheric winds at 50 km, with the maximum correlation occurring ∼ 3 days after the maximum westward wind. These results indicate that the enhancement of PW am- plitudes near 95 km is a common feature of SSWs irrespec- tive of the strength of the wind reversal.

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