Climatology of super‐refraction and trapping layers conditions over Central and West Africa
Abstract The propagation of radio electric waves emitted from ground‐based meteorological instruments is determined through stratification of the atmosphere. In super‐refractive cases characterized by strong temperature inversions or strong vertical moisture gradients, the radar beam can be deflecte...
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| Format: | Article |
| Language: | English |
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Wiley
2021-07-01
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| Series: | Meteorological Applications |
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| Online Access: | https://doi.org/10.1002/met.2016 |
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| author | Samuel Kaissassou L. Djiotang A. Komkoua B. Ekobo B. Ndzana R. Tanessong M. Guenang A. Vondou |
| author_facet | Samuel Kaissassou L. Djiotang A. Komkoua B. Ekobo B. Ndzana R. Tanessong M. Guenang A. Vondou |
| author_sort | Samuel Kaissassou |
| collection | DOAJ |
| description | Abstract The propagation of radio electric waves emitted from ground‐based meteorological instruments is determined through stratification of the atmosphere. In super‐refractive cases characterized by strong temperature inversions or strong vertical moisture gradients, the radar beam can be deflected towards the ground (trapping). This phenomenon often results in spurious returned echoes and misinterpretation of radar images such as erroneous precipitation, wind, and temperature detection. In this study, a 5‐year Central and West Africa (CWA) climatology of the frequency of super‐refractive and trapping‐layer base height has been produced using refractivity computations from European Centre for Medium‐Range Weather Forecasts (ECMWF) analyses at a 40‐km horizontal resolution and 60 levels in the vertical direction. The aim of this climatology is to improve the understanding on how frequent such anomalous propagations conditions are, which is a prerequisite for fully benefiting from radar data information for the multiple purposes of model validation, precipitation analysis, and data assimilation. First, the main climatological features are summarized for the whole CWA: Sahara and inlands seldom experience super‐refraction, whereas coastal areas are strongly affected, especially in regions where the temperature inversion and the trade winds are intense lying near the surface. Over land, seasonal averages of super‐refraction frequencies reach 80% (40%) over moist areas year‐round but remain below 40% (15%) in most other regions. Seasonal statistics exhibit a pronounced diurnal cycle of super‐refraction occurrences, with averaged frequencies peaking at 60% in summer late afternoon over the areas located on the Atlantic Ocean border but inlands region are less affected with super‐refractive cases by midday. |
| first_indexed | 2024-04-11T18:01:08Z |
| format | Article |
| id | doaj.art-7eb96eac58d948398b436c21734f1981 |
| institution | Directory Open Access Journal |
| issn | 1350-4827 1469-8080 |
| language | English |
| last_indexed | 2024-04-11T18:01:08Z |
| publishDate | 2021-07-01 |
| publisher | Wiley |
| record_format | Article |
| series | Meteorological Applications |
| spelling | doaj.art-7eb96eac58d948398b436c21734f19812022-12-22T04:10:32ZengWileyMeteorological Applications1350-48271469-80802021-07-01284n/an/a10.1002/met.2016Climatology of super‐refraction and trapping layers conditions over Central and West AfricaSamuel Kaissassou0L. Djiotang1A. Komkoua2B. Ekobo3B. Ndzana4R. Tanessong5M. Guenang6A. Vondou7Laboratory of Electric Mechatronic and Signal Processing, Department of Electric and Telecommunication Engineering, National Advanced School of Engineering University of Yaoundé I Yaoundé CameroonLEMAP, Department of Physics, Faculty of Science University of Yaoundé I Yaoundé CameroonFaculty of Science University of Dschang Dschang CameroonLaboratory of Electric Mechatronic and Signal Processing, Department of Electric and Telecommunication Engineering, National Advanced School of Engineering University of Yaoundé I Yaoundé CameroonLaboratory of Electric Mechatronic and Signal Processing, Department of Electric and Telecommunication Engineering, National Advanced School of Engineering University of Yaoundé I Yaoundé CameroonFaculty of Agronomy and Agricultural Sciences, School of Wood, Water and Natural Resources University of Dschang Ebolowa CameroonFaculty of Science University of Dschang Dschang CameroonLEMAP, Department of Physics, Faculty of Science University of Yaoundé I Yaoundé CameroonAbstract The propagation of radio electric waves emitted from ground‐based meteorological instruments is determined through stratification of the atmosphere. In super‐refractive cases characterized by strong temperature inversions or strong vertical moisture gradients, the radar beam can be deflected towards the ground (trapping). This phenomenon often results in spurious returned echoes and misinterpretation of radar images such as erroneous precipitation, wind, and temperature detection. In this study, a 5‐year Central and West Africa (CWA) climatology of the frequency of super‐refractive and trapping‐layer base height has been produced using refractivity computations from European Centre for Medium‐Range Weather Forecasts (ECMWF) analyses at a 40‐km horizontal resolution and 60 levels in the vertical direction. The aim of this climatology is to improve the understanding on how frequent such anomalous propagations conditions are, which is a prerequisite for fully benefiting from radar data information for the multiple purposes of model validation, precipitation analysis, and data assimilation. First, the main climatological features are summarized for the whole CWA: Sahara and inlands seldom experience super‐refraction, whereas coastal areas are strongly affected, especially in regions where the temperature inversion and the trade winds are intense lying near the surface. Over land, seasonal averages of super‐refraction frequencies reach 80% (40%) over moist areas year‐round but remain below 40% (15%) in most other regions. Seasonal statistics exhibit a pronounced diurnal cycle of super‐refraction occurrences, with averaged frequencies peaking at 60% in summer late afternoon over the areas located on the Atlantic Ocean border but inlands region are less affected with super‐refractive cases by midday.https://doi.org/10.1002/met.2016ECMWF operational analysessuper‐refractiontrapping layer |
| spellingShingle | Samuel Kaissassou L. Djiotang A. Komkoua B. Ekobo B. Ndzana R. Tanessong M. Guenang A. Vondou Climatology of super‐refraction and trapping layers conditions over Central and West Africa Meteorological Applications ECMWF operational analyses super‐refraction trapping layer |
| title | Climatology of super‐refraction and trapping layers conditions over Central and West Africa |
| title_full | Climatology of super‐refraction and trapping layers conditions over Central and West Africa |
| title_fullStr | Climatology of super‐refraction and trapping layers conditions over Central and West Africa |
| title_full_unstemmed | Climatology of super‐refraction and trapping layers conditions over Central and West Africa |
| title_short | Climatology of super‐refraction and trapping layers conditions over Central and West Africa |
| title_sort | climatology of super refraction and trapping layers conditions over central and west africa |
| topic | ECMWF operational analyses super‐refraction trapping layer |
| url | https://doi.org/10.1002/met.2016 |
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