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Interannual Variability of Temperature, Water Vapor, and Clouds in the Tropical Tropopause Layer
  • Aodhan John Sweeney,
  • Qiang Fu
Aodhan John Sweeney
University of Washington

Corresponding Author:aodhan@uw.edu

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Qiang Fu
Department of Atmospheric Sciences ,University of Washington
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Water vapor and cirrus clouds in the Tropical Tropopause Layer (TTL) are important for the climate and are largely controlled by temperature in the TTL. On interannual timescales, both stratospheric and tropospheric modes of variability affect temperatures in the TTL. In this study, we use satellite observations to investigate the explained variance in cold point temperature (CPT), 83 hPa water vapor (WV83), and TTL cirrus cloud fraction (TTLCCF) over the equatorial region (15°N - 15°S) using a multiple linear regression (MLR) model where predictors are stratospheric and tropospheric modes of variability. The MLR model can explain 68%, 60%, and 52% of the variance in CPT, WV83, and TTLCCF. The model suggests that these variables are dominated by stratospheric ‘top-down’ processes associated with the Quasi-Biennial Oscillation (QBO) and Brewer Dobson Circulation (BDC) as opposed to tropospheric ‘bottom-up’ processes associated with the El Nino Southern Oscillation (ENSO) and the Madden-Julian Oscillation (MJO). Although cold point temperature is controlled by ‘top-down’ mechanisms, the cold point tropopause height is related to both ‘top-down’ stratospheric and ‘bottom-up’ tropospheric processes. Our MLR model explains more variance during boreal winter. We also investigate how these modes of variability correlate with zonal mean temperature, water vapor, and cloud fraction globally in the upper troposphere and lower stratosphere (UTLS) and find significant relationships between clouds and the modes of variability.
06 Apr 2023Submitted to ESS Open Archive
16 Apr 2023Published in ESS Open Archive