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Precipitation and Mesoscale Convective Systems: Explicit versus Parameterized Convection over Northern Africa

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Název: Precipitation and Mesoscale Convective Systems: Explicit versus Parameterized Convection over Northern Africa
Autoři: Reinares Martínez, Irene, Chaboureau, Jean-Pierre
Přispěvatelé: Chaboureau, Jean-Pierre
Zdroj: Monthly Weather Review
Informace o vydavateli: American Meteorological Society, 2018.
Rok vydání: 2018
Témata: [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, 0207 environmental engineering, Mesoscale systems, Precipitation, 02 engineering and technology, 01 natural sciences, [SDU] Sciences of the Universe [physics], Cloud resolving models, 13. Climate action, Convective parameterization, Africa, Meso-NH model, Deep convection, 0105 earth and related environmental sciences
Popis: Precipitating systems are analyzed during a dust event from 9 to 14 June 2006 over northern Africa. A common analysis is applied to satellite observations and two Meso-NH simulations: one convection permitting (grid spacing x = 2.5 km) and the other with parameterized convection (x = 20 km). The precipitating systems are identified as cloud objects and classified as deep convective clouds (DCCs) or other clouds according to their infrared signature. Large DCCs [hereafter named mesoscale convective systems (MCSs)] are tracked, characterized in terms of precipitation and thermodynamic profiles, and analyzed in southern West Africa (SWA), central Africa, and Ethiopia. Precipitation is mostly observed along 0°–15°N, with 71% of the total precipitation produced by all DCCs and 55% by long-lived MCSs. It shows a marked diurnal cycle with a peak in the evening, mainly due to long-lived MCSs, which are characterized by an increase in size, zonal speed, and duration from east to west, with the largest, fastest, and longest-lived ones found over SWA. This is due to an enhanced African easterly jet (AEJ) and monsoon flow leading to stronger shear and greater conditional instability. The simulation with parameterized convection fails to distribute precipitation correctly. The convection-permitting simulation captures most of the observed precipitation features, but lacks the increase in organization of the long-lived MCSs over SWA. Excess moisture in a too zonal AEJ flow suggests that the long-lived MCSs in SWA are poorly located with respect to African easterly waves. The convection-permitting model improves the representation of precipitation but without fully resolving the long-lived MCSs.
Druh dokumentu: Article
Other literature type
Popis souboru: application/pdf
Jazyk: English
ISSN: 1520-0493
0027-0644
DOI: 10.1175/mwr-d-17-0202.1
Přístupová URL adresa: https://journals.ametsoc.org/view/journals/mwre/146/3/mwr-d-17-0202.1.xml
https://ui.adsabs.harvard.edu/abs/2018MWRv..146..797R/abstract
https://journals.ametsoc.org/mwr/article/146/3/797/103152/Precipitation-and-Mesoscale-Convective-Systems
http://journals.ametsoc.org/doi/pdf/10.1175/MWR-D-17-0202.1
Rights: implied-oa
URL: http://www.ametsoc.org/PUBSReuseLicenses
Přístupové číslo: edsair.doi.dedup.....311982adbe72b1358e6c56cb7897e56f
Databáze: OpenAIRE
Popis
Abstrakt:Precipitating systems are analyzed during a dust event from 9 to 14 June 2006 over northern Africa. A common analysis is applied to satellite observations and two Meso-NH simulations: one convection permitting (grid spacing x = 2.5 km) and the other with parameterized convection (x = 20 km). The precipitating systems are identified as cloud objects and classified as deep convective clouds (DCCs) or other clouds according to their infrared signature. Large DCCs [hereafter named mesoscale convective systems (MCSs)] are tracked, characterized in terms of precipitation and thermodynamic profiles, and analyzed in southern West Africa (SWA), central Africa, and Ethiopia. Precipitation is mostly observed along 0°–15°N, with 71% of the total precipitation produced by all DCCs and 55% by long-lived MCSs. It shows a marked diurnal cycle with a peak in the evening, mainly due to long-lived MCSs, which are characterized by an increase in size, zonal speed, and duration from east to west, with the largest, fastest, and longest-lived ones found over SWA. This is due to an enhanced African easterly jet (AEJ) and monsoon flow leading to stronger shear and greater conditional instability. The simulation with parameterized convection fails to distribute precipitation correctly. The convection-permitting simulation captures most of the observed precipitation features, but lacks the increase in organization of the long-lived MCSs over SWA. Excess moisture in a too zonal AEJ flow suggests that the long-lived MCSs in SWA are poorly located with respect to African easterly waves. The convection-permitting model improves the representation of precipitation but without fully resolving the long-lived MCSs.
ISSN:15200493
00270644
DOI:10.1175/mwr-d-17-0202.1