Preprints
https://doi.org/10.5194/amt-2022-286
https://doi.org/10.5194/amt-2022-286
 
27 Oct 2022
27 Oct 2022
Status: this preprint is currently under review for the journal AMT.

Near Global Distributions of Overshooting Tops Derived from Terra and Aqua MODIS Observations

Yulan Hong, Robert J. Trapp, Stephen W. Nesbitt, and Larry Di Girolamo Yulan Hong et al.
  • Department of Atmospheric Sciences, University of Illinois Urbana-Champaign, Urbana, Illinois, USA

Abstract. Overshooting cloud tops (OT) form in deep convective storms when strong updrafts overshoot the tropopause. An OT is a well-known indicator for convective updrafts and severe weather conditions. Here, we develop an OT detection algorithm using thermal IR channels and apply this algorithm to about 20-year MODIS data from both Terra and Aqua satellites to form an extensive, near global climatology of OT occurrences. The algorithm is based on a logistic model which is trained using A-Train observations. We demonstrate that the overall accuracy of our approach is about 0.9 when the probability of the OT candidates is larger than 0.9. The OT climatology reveals a pattern that follows the climatology of deep convection, as well as shallow convection over the mid-latitude oceans during winter cold air outbreaks. OTs appear most frequently over the Intertropical Convergence Zone (ITCZ), central and southeast North America, tropical and subtropical South America, southeast and south Asia, tropical and subtropical Africa, and northern middle-high latitudes. OT spatial distributions show strong seasonal and diurnal variabilities. Seasonal OT variations shift with large-scale climate systems such as the ITCZ and local monsoonal systems, including the South Asian Monsoon, North American Monsoon and West African Monsoon. OT diurnal variations agree with the known diurnal cycle of convection: Maximum OT occurrences are in the afternoon over most land area and around midnight over ocean; and the OT diurnal cycle is stronger and more varied over land than over ocean. OTs over land are usually colder than over ocean except around 10:30 am. The top 10 coldest OTs from both Terra and Aqua mostly occur over land and at night. This study provides OT climatology for the first time derived from two-decade MODIS data that represents the longest and stable satellite records.

Yulan Hong et al.

Status: open (until 02 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-286', Anonymous Referee #1, 10 Nov 2022 reply

Yulan Hong et al.

Yulan Hong et al.

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Short summary
Deep convective updrafts form overshooting tops (OT) when they extend into the upper troposphere and lower stratosphere. An OT often indicates hazardous weather conditions. Global distribution of OTs is useful for understanding global severe weather conditions. Moderate Resolution Imaging Spectroradiometer (MODIS) on both Aqua and Terra satellites has provide two-decade records of Earth-atmosphere system with stable orbits, which is used in this study to derive a 20-yr OT climatology.