Preprints
https://doi.org/10.5194/acp-2021-597
https://doi.org/10.5194/acp-2021-597
21 Jul 2021
 | 21 Jul 2021
Status: this preprint was under review for the journal ACP but the revision was not accepted.

Convection-Aerosol Interactions in the United Arab Emirates: A Sensitivity Study

Ricardo Fonseca, Diana Francis, Michael Weston, Narendra Nelli, Sufian Farah, Youssef Wehbe, Taha AlHosari, Oriol Teixido, and Ruqaya Mohamed

Abstract. The Weather Research and Forecasting (WRF) model is used to investigate convection-aerosol interactions in the United Arab Emirates for a summertime convective event. Both an idealised and scaled versions of a 7-year climatological aerosol distribution are considered. The convection on 14 August 2013 was triggered by the low-level convergence of the circulation associated with the Arabian Heat Low (AHL) and the daytime sea-breeze circulation. The cold pools associated with the convective events, as well as the low-level wind convergence along the Intertropical Discontinuity (ITD) earlier in the day, explain the dustier environment, with Aerosol Optical Depths (AODs) in excess of two.

Due to a colder surface and air temperature, the AHL is incorrectly represented in WRF, which leads to a mismatch between the observed and modelled clouds and precipitation. Employing interior nudging in the outermost grids of the three-nested simulation has a small but positive impact on the model predictions of the innermost nest. This is because the higher temperatures from more accurate boundary conditions are offset by colder temperatures from locally enhanced precipitation, the latter arising from a shift in the position of the AHL. Numerical experiments revealed a high sensitivity to the aerosol properties. In particular, replacing 20 % of the rural aerosols by carbonaceous particles has an impact on the surface radiative fluxes comparable to increasing the aerosol loading by a factor of 10, with a daily-averaged reduction in the UAE-averaged net shortwave radiation flux of ~90 W m−2 and an increase in the net longwave radiation flux of ~51 W m−2. However, in the former, WRF generates 20 % more precipitation than in the latter, due to a broader and weaker AHL.

The surface downward and upward shortwave and upward longwave radiation fluxes are found to scale linearly with the aerosol loading, while the downward longwave radiation flux varies by less than ±12 W m−2 when the aerosol amount and/or properties are changed. An increase in the aerosol loading also leads to drier conditions due to a shift in the position of the AHL and rainfall occurring in a drier region, with a domain-wise decrease in the daily accumulated rainfall of 16 % when the aerosol loading is increased by a factor of 10. In addition, the onset of convection is also delayed.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Ricardo Fonseca, Diana Francis, Michael Weston, Narendra Nelli, Sufian Farah, Youssef Wehbe, Taha AlHosari, Oriol Teixido, and Ruqaya Mohamed

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-597', Anonymous Referee #1, 21 Aug 2021
  • RC2: 'Comment on acp-2021-597', Anonymous Referee #2, 02 Sep 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-597', Anonymous Referee #1, 21 Aug 2021
  • RC2: 'Comment on acp-2021-597', Anonymous Referee #2, 02 Sep 2021
Ricardo Fonseca, Diana Francis, Michael Weston, Narendra Nelli, Sufian Farah, Youssef Wehbe, Taha AlHosari, Oriol Teixido, and Ruqaya Mohamed
Ricardo Fonseca, Diana Francis, Michael Weston, Narendra Nelli, Sufian Farah, Youssef Wehbe, Taha AlHosari, Oriol Teixido, and Ruqaya Mohamed

Viewed

Total article views: 1,387 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
1,013 329 45 1,387 32 28
  • HTML: 1,013
  • PDF: 329
  • XML: 45
  • Total: 1,387
  • BibTeX: 32
  • EndNote: 28
Views and downloads (calculated since 21 Jul 2021)
Cumulative views and downloads (calculated since 21 Jul 2021)

Viewed (geographical distribution)

Total article views: 1,377 (including HTML, PDF, and XML) Thereof 1,377 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 

Cited

Latest update: 20 May 2024
Download
Short summary
High-sensitivity of summer convection and precipitation over the United Arab Emirates to aerosols properties and loadings.
Altmetrics