Six-year observations of aerosol optical properties at a southern African grassland savannah site

Autor: Aki Virkkula, Miroslav Josipovic, Lauri Laakso, Markku Kulmala, Johan P. Beukes, Marcell Venter, Ville Vakkari, Pieter G. van Zyl
Přispěvatelé: Institute for Atmospheric and Earth System Research (INAR), Department of Physics, 10092390 - Beukes, Johan Paul, 22648143 - Josipovic, Miroslav, 10710361 - Van Zyl, Pieter Gideon, 33371210 - Vakkari, Ville T., 21240442 - Laakso, Lauri, 22120017 - Venter, Marcell
Jazyk: angličtina
Rok vydání: 2020
Předmět:
Atmospheric Science
Angstrom exponent
Absorption coefficient (σAP)
Absorption coefficient (sigma(AP))
010504 meteorology & atmospheric sciences
SURFACE
Single scattering albedo (ω0)
010501 environmental sciences
VOLATILE ORGANIC-COMPOUNDS
Atmospheric sciences
REGIONAL BACKGROUND SITE
CHEMICAL-COMPOSITION
01 natural sciences
Population density
114 Physical sciences
Grassland
Aerosol scattering coefficient (σSP)
Radiative transfer
ABSORPTION
Absorption (electromagnetic radiation)
Ångström exponent of scattering (αSP)
0105 earth and related environmental sciences
General Environmental Science
Angstrom exponent of scattering (alpha(SP))
CONTINENTAL BOUNDARY-LAYER
geography
geography.geographical_feature_category
Single-scattering albedo
Scattering
15. Life on land
Welgegund measurement station
LIGHT-SCATTERING
Aerosol
Single scattering albedo (omega(0))
VARIABILITY
ATMOSPHERIC AEROSOLS
13. Climate action
BLACK CARBON
Environmental science
Aerosol scattering coefficient (sigma(SP))
Popis: Atmospheric aerosols have a significant effect on earth's radiative budget, particularly on regional scales. This paper presents a similar to 6 year, in situ, ground level aerosol scattering and absorption dataset, measured at a background site strategically positioned to enable differentiation of the effect of anthropogenic, population density and open biomass burning activities on a regional scale. Relatively well-defined seasonal and diurnal patterns were observed for all the aerosol optical properties, i.e. scattering coefficient (sigma(SP)), absorption coefficient (sigma(AP)), single scattering albedo (omega(0)) and Angstrom exponent of scattering (sigma(SP)). These patterns were explained by considering southern African specific sources and metrological conditions. Using a receptor modelling method (auto-generated source maps) it was found that air masses that had higher sigma(SP), sigma(AP) and omega(0), and lower alpha(SP), if compared with the relatively clean background, passed over source regions with significant industrial or other anthropogenic activities, higher population density, re-circulation of polluted air masses and higher open biomass burning frequency. To quantify differences, four source regions were defined, i.e. Karoo, Kalahari, anti-cyclonic recirculation pattern and the industrial hub of South Africa. Air masses that had passed over the Karoo source region represented the cleanest regional background conditions, while air masses that had passed either over the industrial hub and/or the anti-cyclonic recirculation pattern represented the most significant anthropogenically impacted, as indicated by the aerosol optical properties. The omega(0) medians of air masses that had passed over the Karoo (0.80-0.86) were 9, 12 and 7% lower than in air masses that had passed over source regions with the highest omega(0) median, in the warmest/wettest, coldest, and driest, peak open biomass burning periods, respectively.
Databáze: OpenAIRE