Effects of urban agglomeration on surface-UV doses: a comparison of Brewer measurements in Warsaw and Belsk, Poland, for the period 2013–2015
Specific aerosols and cloud properties over large urban regions seem to generate an island, similar to the well-known urban heat island, leading to lower ultraviolet (UV) radiation intensity compared to the surrounding less polluted areas, thus creating a shield against excessive human exposure t...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-11-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/13641/2016/acp-16-13641-2016.pdf |
| Summary: | Specific aerosols and cloud properties over large urban regions seem to
generate an island, similar to the well-known urban heat island, leading to
lower ultraviolet (UV) radiation intensity compared to the surrounding less
polluted areas, thus creating a shield against excessive human exposure to UV
radiation. The present study focuses on differences between erythemal and UVA
(324 nm) doses measured by the Brewer spectrophotometers in Warsaw
(52.3° N, 21.0° E) and Belsk (51.8° N,
20.8° E). The latter is a rural region located about 60 km
south-west of the city. Ratios between erythemal and UVA partly daily doses,
obtained during all-sky and cloudless-sky conditions for the period
May 2013–December 2015, were analysed to infer a specific cloud and aerosol
forcing on the surface UV doses over Warsaw. Radiative model simulations were
carried out to find sources of the observed differences between the sites. It
was found that Warsaw urban agglomeration induced 8 and 6 % attenuation
of the erythemal and UVA doses respectively. This is mostly due to the lower
sun elevation in Warsaw during the near-noon measurements and the larger
optical depth of the city aerosols and increased cloudiness. It could be
hypothesised that the expected stronger absorption of the solar UV radiation
by urban aerosols is compensated for here by a higher surface reflectivity
over the city. |
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| ISSN: | 1680-7316 1680-7324 |