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<p>Cirrus and deep convective clouds that extend up to the cold point tropopause (CPT) can alter the structure of the tropical tropopause layer and the temperature of the CPT. Penetration of deep convective clouds through the CPT can cause rapid transfer of ice crystals to the lower stratosphere and regulate its water content and chemistry. This study examines the seasonal mean spatial variations and characteristics of tropical deep convective and cirrus clouds that reach near and above the CPT, utilising a joint analysis of cloud vertical profiles from CloudSat and CALIPSO satellite observations from 2006 to 2018, along with collocated ERA5 reanalysis data. Uncertainty of the ERA5 CPT altitude is assessed by comparing with the collocated CPT derived from COSMIC Radio Occultation data during the study period, and the CPT altitude is considered here as ERA5 CPT + 300&#xa0;m for determining CPT crossing clouds. Averaged annually over the tropical trough zone (13°S to 19°N), the frequency of occurrence of all clouds having top extending up to and above the CPT is 1.94%, of which 0.19% are deep convective clouds. About 75% of these clouds extend less than 500&#xa0;m above the CPT, making the CPT-crossing cloud estimates sensitive to CPT uncertainty. The occurrences of cirrus and deep convective clouds that cross ERA5 CPT + 900&#xa0;m presented here provide a lower bound of the actual CPT-crossing clouds. Seasonal and spatial variations in the volumes of deep convective and cirrus clouds extending above the CPT are estimated.</p>

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Tropical clouds near and overshooting the cold point tropopause: effect of the Hadley and Walker circulations observed using CloudSat and CALIPSO

  • 期刊论文

  • 发表日期：

    2026年7月28日

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  • R. S. Aswathy,
  • K. Rajeev

摘要

Cirrus and deep convective clouds that extend up to the cold point tropopause (CPT) can alter the structure of the tropical tropopause layer and the temperature of the CPT. Penetration of deep convective clouds through the CPT can cause rapid transfer of ice crystals to the lower stratosphere and regulate its water content and chemistry. This study examines the seasonal mean spatial variations and characteristics of tropical deep convective and cirrus clouds that reach near and above the CPT, utilising a joint analysis of cloud vertical profiles from CloudSat and CALIPSO satellite observations from 2006 to 2018, along with collocated ERA5 reanalysis data. Uncertainty of the ERA5 CPT altitude is assessed by comparing with the collocated CPT derived from COSMIC Radio Occultation data during the study period, and the CPT altitude is considered here as ERA5 CPT + 300 m for determining CPT crossing clouds. Averaged annually over the tropical trough zone (13°S to 19°N), the frequency of occurrence of all clouds having top extending up to and above the CPT is 1.94%, of which 0.19% are deep convective clouds. About 75% of these clouds extend less than 500 m above the CPT, making the CPT-crossing cloud estimates sensitive to CPT uncertainty. The occurrences of cirrus and deep convective clouds that cross ERA5 CPT + 900 m presented here provide a lower bound of the actual CPT-crossing clouds. Seasonal and spatial variations in the volumes of deep convective and cirrus clouds extending above the CPT are estimated.