Abstract

In this study, the relationship between gravity wave (GW) potential energy (Ep) and the tropopause height and temperature over the globe was investigated using COSMIC radio occultation (RO) dry temperature profiles during September 2006 to May 2013. The monthly means of GW Ep with a vertical resolution of 1 km and tropopause parameters were calculated for each 5° × 5° longitude-latitude grid. The correlation coefficients between Ep values at different altitudes and the tropopause height and temperature were calculated accordingly in each grid. It was found that at middle and high latitudes, GW Ep over the altitude range from lapse rate tropopause (LRT) to several km above had a significantly positive/negative correlation with LRT height (LRT-H)/ LRT temperature (LRT-T) and the peak correlation coefficients were determined over the altitudes of 10–14 km with distinct zonal distribution characteristics. While in the tropics, the distributions of the statistically significant correlation coefficients between GW Ep and LRT/cold point tropopause (CPT) parameters were dispersive and the peak correlation were are calculated over the altitudes of 14–38 km. At middle and high latitudes, the temporal variations of the monthly means and the monthly anomalies of the LRT parameters and GW Ep over the altitude of 13 km showed that LRT-H/LRT-T increases/decreases with the increase of Ep, which indicates that LRT was lifted and became cooler when GWs propagated from the troposphere to the stratosphere. In the tropical regions, statistically significant positive/negative correlations exist between GW Ep over the altitude of 17–19 km and LRT-H/LRT-T where deep convections occur and on the other hand, strong correlations exist between convections and the tropopause parameters in most seasons, which indicates that low and cold tropopause appears in deep convection regions. Thus, in the tropics, both deep convections and GWs excited accordingly have impacts on the tropopause structure.

Highlights

  • The tropopause is the transition layer between the upper troposphere and the lower stratosphere, which are distinct from one another in vertical mixing timescales, static stabilities, trace constituents, and thermal balance [1]

  • Statistically significant positive/negative correlations exist between gravity wave (GW) Ep over the altitude of 17–19 km and lapse rate tropopause (LRT)-H/LRT temperature (LRT-T) where deep convections occur and on the other hand, strong correlations exist between convections and the tropopause parameters in most seasons, which indicates that low and cold tropopause appears in deep convection regions

  • While during the same season, strong correlations exist between outgoing longwave radiation (OLR) and LRT-T/cold point tropopause (CPT)-T, as revealed by the correlation coefficient of 0.63/0.64, which passes through the significance test of the confidence level of 99%

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Summary

Introduction

The tropopause is the transition layer between the upper troposphere and the lower stratosphere, which are distinct from one another in vertical mixing timescales, static stabilities, trace constituents, and thermal balance [1]. The variations of the tropopause, which are the responses to any changes in the physical, chemical, and thermal characteristics of the two regions, are linked closely to the stratosphere-troposphere exchange as well as climate variability and change [2,3,4]. The cold point tropopause (CPT), which is usually applied in the tropics, is the level of the temperature minimum as the temperature decreases with height from the surface up to certain altitude and increases at higher altitudes in the stratosphere [7]. The CPT is an import indicator of stratosphere-troposphere coupling and exchange [2]

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