Effects of two typical gravity wave processes on stratospheric ozone over the Tibetan Plateau based on radiosonde data

Abstract

This study analyzes the formation process and propagation characteristics of two typical gravity wave events that occurred over the Tibetan Plateau, based on the radiosonde data from Naqu Station on August 4, 2011 at 7:00-12:00UTC and August 13, 2011 at 8:00-12:00 UTC, as well as the global climate fifth-generation atmospheric reanalysis dataset (ERA5) provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). The effects of the two gravity wave events on ozone are also analyzed. The results show that two gravity wave processes were broken in the tropopause and upper stratosphere respectively. The gravity wave event on August 4 captured the signal well at 400 hPa, showing a northwest-southeast structure and gradually tilting eastward. The signal decayed between 7:00-9:00 UTC, and the gravity wave completely broke and released energy near 150 hPa at 10:00 UTC. The ozone significantly decreased in the region of 200-50 hPa due to ozone exchange between the upper troposphere and lower stratosphere (UTLS). The results on August 13 showed that the gravity wave propagated from the middle stratosphere to the upper stratosphere, exhibiting a northeast-southwest structure and gradually tilting eastward. The signal weakened from the middle stratosphere at 8:00 UTC, and it broke and released energy near 7 hPa at 10:00 UTC. The ozone concentration increased in the region of 20-3 hPa. Both gravity wave events resulted in a decrease in ozone at the tropopause (200-150 hPa) and upper stratosphere (20-3 hPa), mainly due to the mixing of the upper and lower atmospheric layers caused by the gravity wave breaking, leading to ozone exchange.