Abstract
Abstract. The NASA Langley Research Center (LaRC) airborne High Spectral Resolution Lidar (HSRL) measures vertical profiles of aerosol extinction, backscatter, and depolarization at both 532 nm and 1064 nm. In March of 2006 the HSRL participated in the Megacity Initiative: Local and Global Research Observations (MILAGRO) campaign along with several other suites of instruments deployed on both aircraft and ground based platforms. This paper presents high spatial and vertical resolution HSRL measurements of aerosol extinction and optical depth from MILAGRO and comparisons of those measurements with similar measurements from other sensors and model predictions. HSRL measurements coincident with airborne in situ aerosol scattering and absorption measurements from two different instrument suites on the C-130 and G-1 aircraft, airborne aerosol optical depth (AOD) and extinction measurements from an airborne tracking sunphotometer on the J-31 aircraft, and AOD from a network of ground based Aerosol Robotic Network (AERONET) sun photometers are presented as a validation of the HSRL aerosol extinction and optical depth products. Regarding the extinction validation, we find bias differences between HSRL and these instruments to be less than 3% (0.01 km−1) at 532 nm, the wavelength at which the HSRL technique is employed. The rms differences at 532 nm were less than 50% (0.015 km−1). To our knowledge this is the most comprehensive validation of the HSRL measurement of aerosol extinction and optical depth to date. The observed bias differences in ambient aerosol extinction between HSRL and other measurements is within 15–20% at visible wavelengths, found by previous studies to be the differences observed with current state-of-the-art instrumentation (Schmid et al., 2006).
Highlights
Tropospheric aerosols influence the radiative budget of the earth directly by scattering and absorbing solar radiation and indirectly by serving as cloud condensation nuclei
Rogers et al.: NASA Langley Research Center (LaRC) airborne high spectral resolution lidar aerosol measurements layers located at different altitudes; it is important to have an accurate measurement of aerosol optical properties and vertical profile measurements
We have presented NASA LaRC airborne High Spectral Resolution Lidar (HSRL) measurements of aerosol backscatter, extinction, and depolarization at two wavelengths (532 nm and 1064 nm) and aerosol optical depth at 532 nm acquired during the Megacity Initiative: Local and Global Research Observations (MILAGRO) field campaign
Summary
Tropospheric aerosols influence the radiative budget of the earth directly by scattering and absorbing solar radiation and indirectly by serving as cloud condensation nuclei. Aerosols have highly variable optical and physical properties, relatively short atmospheric lifetimes, and large spatial and temporal gradients; these factors complicate efforts to account for their radiative forcing impacts in climate models. Another key component directly affecting the radiative forcing is the aerosol vertical profile In this paper we present the NASA Langley airborne HSRL measurements from the MILAGRO field campaign (Molina et al, 2009) This campaign was designed to study the evolution of trace gases and aerosols above and downwind of Mexico City and employed ground-based instrumentation in and around the urban megacity along with numerous airborne instruments on seven aircraft. The HSRL extinction profile measurements are validated for the first time via comparisons with three state-of-the-art measurement techniques on board three different aircraft, and the HSRL aerosol optical depth measurements are validated via comparison with airborne and ground based sunphotometer measurements
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