Global zonal wind variations and responses to solar activity, and QBO, ENSO during 2002–2019

Abstract

Abstract. Variations of global wind are important in changing the atmospheric structure and circulation, in the coupling of atmospheric layers, in influencing the wave propagations. Due to the difficulty of directly measuring zonal wind from the stratosphere to the lower thermosphere, we derived the global balance wind (BU), which captured the main feature of the monthly zonal mean wind, to study its variations (i.e., annual, semiannual, terannual, and linear) and responses to QBO (quasi-biennial oscillation), ENSO (El Niño/Southern Oscillation), and solar activity. Same procedure is performed on the MERRA2 zonal wind (MerU) to validate BU and its responses below 70 km. The annual, semiannual, terannual oscillations of BU and MerU have similar amplitudes and phases. The semi-annual oscillation of BU has peaks around 80 km, which are stronger in the southern tropical region and coincide with previous satellite observations. The responses to QBO shift from positive to negative and extend from the equator to higher latitudes with the increasing height. The responses to ENSO and F10.7 are strongest (positive and negatively, respectively) in the southern stratospheric polar jet region below 70 km and exhibit hemispheric asymmetry. While above 70 km, the responses of BU to F10.7 and ENSO are mainly positive. Both BU and MerU exhibit similar linear changes, but the negative linear changes of BU at 50° N are absent in MerU during October–January. The discussions on the possible influences of the temporal intervals and sudden stratospheric warmings (SSWs) on the variations and responses of BU illustrate that: (1) the seasonal variations and the responses to QBO are almost independent on the temporal intervals selected; (2) the responses to ENSO and F10.7 are robust but slightly dependent on the temporal intervals; (3) the linear changes of both BU and MerU depend strongly on the temporal intervals; (4) SSWs affect the magnitudes but do not affect the hemispheric asymmetry of the variations and responses of BU at least in the monthly mean sense. The variations and responses of global zonal wind to various factors are based on BU, which is derived from observations, and thus provide a good complementary to model studies and ground-based observations.