Investigation of the diurnal pattern of the vertical distribution of pollen in the lower troposphere using LIDAR

摘要

The diurnal pattern of the vertical distribution of biogenic pollen in thelower troposphere was investigated by LIDAR. Meteorological data were takenat the ground. Pollen concentrations were measured at the surface using aBurkard 7-day-recording volumetric spore sampler. Aerosol extinctioncoefficients and depolarization ratios at 532 nm were obtained from LIDARmeasurements in spring (4 May–2 June) 2009 in Gwangju, South Korea. Linearvolume depolarization ratios varied between 0.08 and 0.14 and were observedonly during daytime (09:00–17:00 local time (LT)) during days of high pollenconcentration (4 to 9 May). Daily average pollen concentrations ranged1000–2500 cm?3 in the same period. The temporal evolution of thevertical distribution of the linear volume depolarization ratio showed aspecific diurnal pattern. Linear volume depolarization ratios of more than0.06, were measured near the surface in the morning. High depolarizationratios were detected up to 2 km aboveground between 12:00 and 14:00 LT,whereas high depolarization ratios were observed only close to the surfaceafter 17:00 LT. Low values of depolarization ratios (≤0.05) weredetected after 18:00 LT until the next morning. During the measurementperiod, the daily variations of the high depolarization ratios close to thesurface showed correlation to number concentration measurements of pollen.This finding suggests that high depolarization ratios could be attributed toenhanced pollen concentrations. The diurnal characteristics of the highvalues of depolarization ratios are thought to be closely associated withturbulent transport. Diurnal and vertical characteristics of pollen, ifmeasured continuously, could be used to improve the accuracy ofpollen-forecasting models via data assimilation studies.