Preprints
https://doi.org/10.5194/angeo-2021-67
https://doi.org/10.5194/angeo-2021-67
 
15 Dec 2021
15 Dec 2021
Status: a revised version of this preprint was accepted for the journal ANGEO and is expected to appear here in due course.

Determination of Tropical Belt Widening Using Multiple GNSS Radio Occultation Measurements

Mohamed Darrag1,2, Shuanggen Jin1,3, Andrés Calabia1, and Aalaa Samy2 Mohamed Darrag et al.
  • 1School of Remote Sensing and Geomatics Engineering, Nanjing University of Information Science and Technology, Nanjing, China
  • 2National Research Institute of Astronomy and Geophysics-NRIAG, 11421- Helwan, Cairo, Egypt
  • 3Shanghai Astronomical Observatory, Chinese Academy of Science, Shanghai, China

Abstract. In the last decades, Global navigation satellite systems (GNSS) have provided an exceptional opportunity to retrieve atmospheric parameters globally through GNSS radio occultation (GNSS-RO). In this paper, data of 12 GNSS-RO missions from June 2001 to November 2020 with high resolution were used to investigate the possible widening of the tropical belt along with the probable drivers and impacts in both hemispheres. Applying both lapse rate tropopause (LRT) and cold point tropopause (CPT) definitions, the global tropopause height shows increase of approximately 36 m/decade and 60 m/decade, respectively. Moreover, the tropical edge latitude (TEL) estimated based on two tropopause height metrics, in the northern hemisphere (NH) and southern hemisphere (SH), are different from each other. For the first metric, subjective method, the tropical width from GNSS has expansion behavior in NH with ~ 0.41°/decade and a minor expansion in SH with ~ 0.08°/decade. In case of ECMWF Reanalysis v5 (ERA5) there is no significant contraction in both NH and SH. For Atmospheric Infrared Sounder (AIRS), there are expansion behavior in NH with ~ 0.34°/decade and strong contraction in SH with ~ −0.48°/decade. Using the second metric, objective method, the tropical width from GNSS has expansion in NH with ~ 0.13°/decade, and no significant expansion in SH. In case of ERA5, there is no significant signal in NH while SH has a minor contraction. AIRS has an expansion with ~ 0.13°/decade in NH, and strong contraction in SH with ~ −0.37°/decade. The variability of tropopause parameters (temperature and height) is maximum around the TEL locations at both hemispheres. The total column ozone (TCO) shows increasing rates globally, and the rate of increase at the SH is higher than that of the NH. There is a good agreement between the spatial and temporal patterns of TCO variability and the TEL location estimated from GNSS LRT height. Carbon dioxide (CO2), and Methane (CH4), the most important greenhouse gases (GHGs) and the main drivers of global warming, have a global increasing rate and the increasing rate of the NH is similar to that of the SH. The spatial pattern in the NH is located more pole ward than its equivalent at the SH. Both surface temperature and precipitation increase in time and have strong correlation with GNSS LRT height. Both show higher increasing rates at the NH, while the precipitation at the SH has slight decrease and the surface temperature increases. The surface temperature shows a spatial pattern with strong variability, which broadly agrees with the TEL locations. The spatial pattern of precipitation shows northward occurrence. In addition, Standardized Precipitation Evapotranspiration Index (SPEI) has no direct connection with the TEL behavior.

Mohamed Darrag et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on angeo-2021-67', Anonymous Referee #1, 11 Feb 2022
  • RC2: 'Comment on angeo-2021-67', Anonymous Referee #2, 18 Mar 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on angeo-2021-67', Anonymous Referee #1, 11 Feb 2022
  • RC2: 'Comment on angeo-2021-67', Anonymous Referee #2, 18 Mar 2022

Mohamed Darrag et al.

Mohamed Darrag et al.

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Short summary
We investigated the possible widening of the tropical belt along with the probable drivers and impacts based on high accuracy, high resolution GNSS RO data (2001–2020). The results show that the tropical belt has significant expansion in Northern hemisphere while the Southern hemisphere has no significant expansion.