Seasonal Variation of Stratospheric Gravity Waves in the Asian Monsoon Region Derived from COSMIC-2 Data

Abstract

COSMIC-2 (Constellation Observing System for Meteorology, Ionosphere and Climate- 2) dry temperature profile data from December 2019 to November 2021 are used to study stratospheric gravity waves (GWs) in the Asian monsoon region. The stratosphere between 20 and 50 km is divided into the lower, middle, and high layers based on the vertical distribution of the mean potential energy (Ep) and the horizontal distribution of GW Ep in these three layers, and their seasonal changes are analyzed. The source and propagating mechanism of GWs in middle latitudes in winter are revealed. The results show that GWs in the stratosphere have distinct distribution features during different seasons. The significant Ep in winter appears mainly in middle latitudes north of 30°N, whereas in summer, it appears in the low latitudes south of 30°N. There are significant areas of GW activity in both low and middle latitudes in spring and autumn, but their intensity is significantly weaker than in winter and summer. Areas with significant GWs and the seasonal variation of their intensity are accompanied by the Asian monsoon activity. In winter, there is a northward and upward propagating column for GWs above the Sichuan Basin, and in summer, there is an eastward and upward propagating column for GWs in the zonal band 15–25°N. The occurrence of GWs in northwestern China in winter is the result of the subtropical jet stream and topography. Once GWs enter the stratosphere, they are regulated by the winter stratospheric environment, and the GWs acquire a northerly component by the wind shear. The meridional wind shear in the background field is an important factor affecting the development and propagation of GWs.

Seasonal Variations in the Vertical Wavenumber Spectra of Stratospheric Gravity Waves in the Asian Monsoon Region Derived from COSMIC-2 Data

“…The data were downloaded from https://cdaac-www.cosmic.ucar.edu/ (accessed on 1 August 2022). The Asian monsoon is selected as the study area, with the specific domain being 70-150 • E and 15-45 • N. Qu et al [18] reported the monthly average sampling density of COSMIC-2 data to be 25 times at 15-30 • N and 15 times at 30-45 • N, with a 2.5 • × 2.5 • grid resolution during this period. The vertical range of the COSMIC-2 dry temperature profile data is 0-60 km.…”

“…For the COSMIC-2 temperature profiles, the individual temperature profiles (T) consist mainly of background (T) and perturbation (T ) components (i.e., T = T + T) [16]. Due to the irregular vertical resolution of the raw observational data, each raw dry temperature profile was interpolated to a regular 100 m resolution [18]. All temperature profiles were then processed horizontally and vertically.…”

“…Therefore, based on these data, we have limited knowledge of the distribution of the vertical wavenumber spectra in a given region. The vertical resolution of COSMIC-2 data is 20 m, and the data density is higher than that of previous satellite data [18]; consequently, COSMIC-2 data are suitable for studying seasonal variations in the vertical wavenumber spectra in the Asian monsoon region. Qu et al [18] studied the distribution and seasonal variations of GW potential energy (Ep) at different heights in the stratosphere in the Asian monsoon region based on COSMIC-2 data, and found that the middle and low latitude GW Ep distribution exhibited seasonal variations.…”

“…Qu et al [18] studied the distribution and seasonal variations of GW potential energy (Ep) at different heights in the stratosphere in the Asian monsoon region based on COSMIC-2 data, and found that the middle and low latitude GW Ep distribution exhibited seasonal variations. However, Qu et al [18] did not undertake spectral analysis.…”

“…The main objective of this study was to investigate the vertical wavenumber spectra of GWs and its seasonal variations in the stratosphere using COSMIC-2 data, based on the study of Qu et al [18]. The remainder of this paper is organized as follows.…”