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Atmospheric response to the 20 March 2015 solar eclipse along the whole aerosol column by lidar measurements
摘要： Lidar measurements at 355, 532, and 1064 nm have been performed at Lecce (40.3°N, 18.1°E), in south-eastern Italy, to investigate for the first time the impact of the 20 March 2015 solar eclipse on both the planetary boundary layer (PBL) height and the aerosol optical and microphysical properties along the whole aerosol column. The partial solar eclipse lasted from 08:30 up to 10:47 UTC and reached the full phase at 09:37 UTC. The maximum percentage obscuration of the solar disk was 43.6%. The eclipse cooling effect was responsible at the full phase time (tF) for the downward solar irradiance decrease at the top of the atmosphere, at the surface, and within the atmosphere of 429.2 ± 0.6, 373 ± 25, and 56 ± 26 W m-2, respectively. The turbulent kinetic energy, the potential temperature flux, the sensible heat flux, the variance of air temperature, and the vertical wind speed at the surface revealed that the turbulence activity reached the maximum weakening at the time tF. The standard deviation (SD) technique has been applied to both the lidar range corrected signals (RCS) at 1064 nm and the linear volume depolarization ratio (δV) profiles at 355 nm to determine the time evolution of the shallow PBL height and the aloft aerosol layers. The SD technique applied to RCS and δV profiles revealed similar results within experimental uncertainties. The PBL height, which was equal to 380 ± 40 m above ground level (AGL) at the eclipse full phase (09:37 UTC), decreased up to 220 ± 20 m at 09:45 UTC because of the eclipse cooling effect, and then increased up to 320 ± 30 m at 10:17 UTC. The determined PBL height time evolution was in good agreement with the ones of the main turbulence parameters at the surface after tF. The vertical profiles of the aerosol backscatter coefficient (β), the δV at 355 nm, and the extinction-related ?ngstr?m exponent (?), calculated at the 355-1064 nm wavelength pair revealed a marked decrease of β, δV, and ? at the eclipse full phase, within the aloft aerosol layers. The abrupt β, δV, and ? decrease due to the aerosol concentration and type changes has mainly been associated with the decrease of the fine-mode particle contribution.
关键词： solar irradiance,Solar eclipse,lidar measurements,atmospheric aerosols,turbulence parameters,planetary boundary layer
更新于2025-09-23 15:21:01
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Enhancing Double-Beam Laser Tweezers Raman Spectroscopy (LTRS) for the Photochemical Study of Individual Airborne Microdroplets
摘要： A new device and methodology for vertically coupling confocal Raman microscopy with optical tweezers for the in situ physico- and photochemical studies of individual microdroplets (? ≤ 10 μm) levitated in air is presented. The coupling expands the spectrum of studies performed with individual particles using laser tweezers Raman spectroscopy (LTRS) to photochemical processes and spatially resolved Raman microspectroscopy on airborne aerosols. This is the first study to demonstrate photochemical studies and Raman mapping on optically levitated droplets. By using this configuration, photochemical reactions in aerosols of atmospheric interest can be studied on a laboratory scale under realistic conditions of gas-phase composition and relative humidity. Likewise, the distribution of photoproducts within the drop can also be observed with this setup. The applicability of the coupling system was tested by studying the photochemical behavior of microdroplets (5 μm < ? < 8 μm) containing an aqueous solution of sodium nitrate levitated in air and exposed to narrowed UV radiation (254 ± 25 nm). Photolysis of the levitated NaNO3 microdroplets presented photochemical kinetic differences in comparison with larger NaNO3 droplets (40 μm < ? < 80 μm), previously photolyzed using acoustic traps, and heterogeneity in the distribution of the photoproducts within the drop.
关键词： optical levitation,optical traps,photochemical reactions in Earth’s atmosphere,atmospheric aerosols,laser tweezers Raman spectroscopy (LTRS)
更新于2025-09-12 10:27:22