The 11-year Solar Cycle Influences On Stratospheric Circulation In Northern Winter

In consideration of the solar signals can propagate in the stratosphere-troposphere system, the influences of 11-year solar cycle on stratospheric circulation in northern winter are investigated based on the monthly ERA-Interim reanalysis data from the European Center for Medium-Range Weather Forecasts (ECMWF) and the daily solar spectrum data from the Spectral Irradiance Monitor (SIM) measurements, with the methods of the radiative transfer scheme of Beijing climate center (BCC-RAD), multiple linear regression, harmonic analysis, correlation analysis and synthesis analysis. Moreover, the diagnosis of wave activity flux is used to discuss the response mechanism of the stratospheric circulation to solar activities. The conclusions are as follows:(1) The interaction between the anomalies of solar shortwave radiation from the tropical upper stratosphere (’top-down’) and the planetary waves from mid-latitude troposphere (’bottom-up’) notably affects the dynamic and thermal structure in the stratosphere. During strong solar activity phases, the warm anomaly in tropical upper stratosphere is linked with the positive ozone ultraviolet (UV) heating in December, which enhances the meridional temperature gradient in mid-latitudes and hence the westerly jet strengthens. Consequently, the upward propagation of wave-1 strengthens while the wave-2 weakens. The negative anomaly of wave-2 is greater than the positive wave-1 anomaly. Therefore, it is shown that the anomaly of wave activity flux (wavel-2) in the extratropical upper stratosphere is negative. The weak wave dissipation drives a weak Brewer-Dobson circulation (BDC). The reduced upwelling of BDC warms the tropical lower stratosphere and the reduced downward BDC cools the mid-latitude upper stratosphere through the adiabatic process. (2) With the heating center of solar shortwave anomaly in the low latitudes of upper stratosphere accelerates to jump northward in February during strong solar activity phases, the seasonal stratospheric circulation anomalies occur a sudden change, and the weak SSW events increase, which correspond to a decrease of upward propagation of wave-1 and an increase of wave-2. The effect of wave-2 is dominant in the total wave activity flux. The anomaly of wave dissipation in the polar mid-upper stratosphere leads to the warm anomaly and the easterly wind anomaly in the polar mid-upper stratosphere. (3) The regional response of stratospheric circulation to solar activity occurs over Asian-Pacific region. During strong solar activity phases, above 10 hPa, the cold temperature center is located in Asian-Pacific region, and the upward propagation of wave-1 is weaker in the upper stratosphere. Below 10 hPa, the temperature anomaly is characterized by two wave structure, the cold temperature centers are over the Atlantic (Ocean) and Eastern Asia. It is the wave-2 that results in the reduction of wave activity flux (wave 1-2) in the Asian-Pacific. In the lower stratosphere (100 hPa,50 hPa), the equatorward propagation of wave activity flux and the suppressed high latitude waveguide in the Asian-Pacific region during strong solar activity phases are contributed from the wave-2.