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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
Atmospheric boundary layer top height in South Africa: Measurements with lidar and radiosonde compared to three atmospheric models
Atmospheric Chemistry and Physics, Volume 14, No. 8, Year 2014
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Description
Atmospheric lidar measurements were carried out at Elandsfontein measurement station, on the eastern Highveld approximately 150 km east of Johannesburg in South Africa throughout 2010. The height of the planetary boundary layer (PBL) top was continuously measured using a Raman lidar, PollyXT (POrtabLeLidar sYstem eXTended). High atmospheric variability together with a large surface temperature range and significant seasonal changes in precipitation were observed, which had an impact on the vertical mixing of particulate matter, and hence, on the PBL evolution. The results were compared to radiosondes, CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) space-borne lidar measurements and three atmospheric models that followed different approaches to determine the PBL top height. These models included two weather forecast models operated by ECMWF (European Centre for Medium-range Weather Forecasts) and SAWS (South African Weather Service), and one mesoscale prognostic meteorological and air pollution regulatory model TAPM (The Air Pollution Model). The ground-based lidar used in this study was operational for 4935 h during 2010 (49% of the time). The PBL top height was detected 86% of the total measurement time (42% of the total time). Large seasonal and diurnal variations were observed between the different methods utilised. High variation was found when lidar measurements were compared to radiosonde measurements. This could be partially due to the distance between the lidar measurements and the radiosondes, which were 120 km apart. Comparison of lidar measurements to the models indicated that the ECMWF model agreed the best with mean relative difference of 15.4%, while the second best correlation was with the SAWS model with corresponding difference of 20.1%. TAPM was found to have a tendency to underestimate the PBL top height. The wind speeds in the SAWS and TAPM models were strongly underestimated which probably led to underestimation of the vertical wind and turbulence and thus underestimation of the PBL top height. Comparison between ground-based and satellite lidar shows good agreement with a correlation coefficient of 0.88. On average, the daily maximum PBL top height in October (spring) and June (winter) was 2260 m and 1480 m, respectively. To our knowledge, this study is the first long-term study of PBL top heights and PBL growth rates in South Africa. © 2014 Author(s).
Authors & Co-Authors
Korhonen, Kimmo
Finland, Helsinki
Finnish Meteorological Institute
Finland, Kuopio
Itä-suomen Yliopisto
Giannakaki, Elina
Finland, Helsinki
Finnish Meteorological Institute
Mielonen, Tero
Finland, Helsinki
Finnish Meteorological Institute
Pfüller, Anne
Finland, Helsinki
Finnish Meteorological Institute
Laakso, Lauri
Finland, Helsinki
Finnish Meteorological Institute
South Africa, Potchefstroom
North-west University
Vakkari, Ville
Finland, Helsinki
Finnish Meteorological Institute
Finland, Helsinki
Helsingin Yliopisto
Baars, Holger
Germany, Leipzig
Leibniz Institute for Tropospheric Research
Engelmann, Ronny
Germany, Leipzig
Leibniz Institute for Tropospheric Research
Beukes, Johan Paul
South Africa, Potchefstroom
North-west University
van Zyl, Pieter Gideon
South Africa, Potchefstroom
North-west University
Ramandh, Avishkar
South Africa, Sasolburg
Sasol Technology Pty Ltd
Ntsangwane, Lucky
South Africa, Pretoria
South African Weather Service
Josipovic, Miroslav
South Africa, Potchefstroom
North-west University
Tiitta, Petri T.
Finland, Kuopio
Itä-suomen Yliopisto
South Africa, Potchefstroom
North-west University
Fourie, Gerhardus D.
South Africa, Sasolburg
Sasol Technology Pty Ltd
Ngwana, I.
South Africa, Pretoria
South African Weather Service
Chiloane, Kgaugelo Euphinia
South Africa, Johannesburg
Eskom
Komppula, Mika
Finland, Helsinki
Finnish Meteorological Institute
Statistics
Citations: 84
Authors: 18
Affiliations: 8
Identifiers
Doi:
10.5194/acp-14-4263-2014
ISSN:
16807316
e-ISSN:
16807324
Research Areas
Environmental
Study Locations
South Africa