@misc{10481/72126,
year = {2021},
month = {12},
url = {http://hdl.handle.net/10481/72126},
abstract = {This paper investigates the mechanisms involved
in the dispersion, structure, and mixing in the vertical column
of atmospheric pollen. The methodology used employs observations
of pollen concentration obtained from Hirst samplers
(we will refer to this as surface pollen) and vertical
distribution (polarization-sensitive lidar), as well as nested
numerical simulations with an atmospheric transport model
and a simplified pollen module developed especially for this
study. The study focuses on the predominant pollen type,
Pinus, of the intense pollination event which occurred in
the region of Barcelona, Catalonia, NE Spain, during 27–
31 March 2015. First, conversion formulas are expressed to
convert lidar-derived total backscatter coefficient and modelderived
mass concentration into pollen grains concentration,
the magnitude measured at the surface by means of aerobiological
methods, and, for the first time ever, a relationship
between optical and mass properties of atmospheric pollen
through the estimation of the so-called specific extinction
cross section is quantified in ambient conditions. Second,
the model horizontal representativeness is assessed through
a comparison between nested pollen simulations at 9, 3, and
1 km horizontal resolution and observed meteorological and
aerobiological variables at seven sites around Catalonia. Finally,
hourly observations of surface and column concentration
in Barcelona are analyzed with the different numerical
simulations at increasing horizontal resolution and varying
sedimentation/deposition parameters. We find that the 9 or
3 km simulations are less sensitive to the meteorology errors;
hence, they should be preferred for specific forecasting applications.
The largest discrepancies between measured surface
(Hirst) and column (lidar) concentrations occur during nighttime,
where only residual pollen is detected in the column,
whereas it is also present at the surface. The main reason
is related to the lidar characteristics which have the lowest
useful range bin at  225 m, above the usually very thin nocturnal
stable boundary layer. At the hour of the day of maximum
insolation, the pollen layer does not extend up to the
top of the planetary boundary layer, according to the observations
(lidar), probably because of gravity effects; however,
the model simulates the pollen plume up to the top of the
planetary boundary layer, resulting in an overestimation of
the pollen load. Besides the large size and weight of Pinus
grains, sedimentation/deposition processes have only a limited
impact on the model vertical concentration in contrast to the emission processes. For further modeling research, emphasis
is put on the accurate knowledge of plant/tree spatial
distribution, density, and type, as well as on the establishment
of reliable phenology functions.},
organization = {BSC	RES-AECT-2019-3-0001	
RES-AECT-2020-1-0007},
publisher = {Copernicus},
title = {Measurement report: Characterization of the vertical distribution of airborne Pinus pollen in the atmosphere with lidar-derived profiles – a modeling case study in the region of Barcelona, NE Spain},
doi = {10.5194/acp-21-17807-2021},
author = {Sicard, Michaël and De Linares Fernández, Concepción},
}