Diurnal variability of the global tropical tropopause: results inferred from COSMIC observations
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Short and long-term variability of the tropical tropopause controls the exchange of minor constituents between the troposphere and the stratosphere. We present the diurnal variability of the global tropical tropopause altitude and temperature using 7 years of COSMIC observations. The aim of the study is to extract diurnal tropopause signals and their impact on stratosphere-troposphere exchange processes. The possible role of atmospheric tides and convection in controlling the tropopause characteristics are discussed. The most significant and new observation is that in the deep tropics the cold-point tropopause altitude is higher and temperatue is cooler over the land (ocean) during evening to late evening hours (afternoon to early evening). Lower tropopause altitude allows the stratospheric air intrusion into the troposphere during the day time. The combined effect of diurnal tropopause altitude changes and turbulent mixing increases the possibility of stratospheric intrusions. A warmer forenoon tropopause allows increased injection of water vapor from the troposphere to the lower stratosphere. Over the tropical land (ocean), the zonal mean diurnal amplitude is 130–200 m (140–180 m) for tropopause altitude and 0.6–0.9 K (0.6–0.8 K) for tropopause temperature.
KeywordsTropopause Stratosphere–troposphere exchange Diurnal variability COSMIC
Authors would like to acknowledge UCAR/CDAAC team for providing the data. Thanks to Director, Space Physics Laboratory (SPL) and Head, Atmospheric Dynamics Branch, SPL for their constant supports extended during this study. The first author KVS thankful to Indian Space Research Organization (ISRO) for providing doctoral fellowship during this study period. Authors would like to sincerely thank both the anonymous reviewers and the editor for their constructive comments and suggestion, which helped the manuscript significantly during the review process.
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