Backscatter properties of hygroscopic aerosols using models, combined multiwavelength Raman lidar, GPS and radiosonds

摘要

In this paper, we explore the possibility of determining the nature and variability of urban aerosol hygroscopic properties using multi-wavelength Raman lidar measurements at 355nm, as well as backscatter measurements at 532nm and 1064nm. The addition of these longer wavelength channels allow us to more accurately validate the homogeneity of the aerosol layer as well as provide additional multiwavelength information that can be used to validate and modify the aerosol models underlying the hygroscopic trends observed in the Raman channel. In support of our hygroscopic measurements, we also discuss our calibration procedures for both the aerosol and water vapor profiles. The calibration algorithm we ultimately use for the water vapor measurements are twilight measurements where water vapor radiosonde data from the OKX station in NYS, are combined with total water vapor obtained from a GPS MET station. These sondes are then time correlated with independent near surface RH measurements to address any bias issues that may occur due to imperfect calibration due to lidar overlap issues and SNR limitations in seeing the water vapor at high altitudes. In particular, we investigate the possibility of using ratio optical scatter measurements which eliminate the inherent problem of variable particle number and illustrate the sensitivity of different hygroscopic aerosols to these measurements.