Validation of aerosol extinction and water vapor profiles from routineAtmospheric Radiation Measurement Program Climate ResearchFacility measurements

摘要

The accuracy with which vertical profiles of aerosol extinction aep(A) can be measuredusing routine Atmospheric Radiation Measurement Program (ARM) Climate ResearchFacility (ACRF) measurements and was assessed using data from two airborne fieldcampaigns, the ARM Aerosol Intensive Operation Period (AIOP, May 2003), and theAerosol Lidar Validation Experiment (ALIVE, September 2005). This assessment pertainsto the aerosol at its ambient concentration and thermodynamic state (i.e., o-ep(A) eitherfree of or corrected for sampling artifacts) and includes the following ACRF routinemethods: Raman lidar, micropulse lidar (MPL), and in situ aerosol profiles (IAP) with asmall aircraft. Profiles of aerosol optical depth rp(A), from which the profiles of o-ep(A)are derived through vertical differentiation, were measured by the NASA AmesAirborne Tracking 14-channel Sun photometer (AATS-14); these data were used asbenchmark in this evaluation. The ACRF IAP o-ep(550 nm) were lower by 11% (duringAIOP) and higher by 1% (during ALIVE) when compared to AATS-14. The ACRFMPL Uep(523 nm) measurements were higher by 24% (AIOP) and 19-21% (ALIVE)compared to AATS-14, but the correlation improved significantly during ALIVE. In theAIOP, a second MPL operated by NASA showed a smaller positive bias (13%) withrespect to AATS-14. The ACRF Raman lidar Uep(355 nm) measurements were larger by54% (AIOP) and by 6% (ALIVE) compared to AATS-14. The large bias in the Ramanlidar measurements during AIOP stemmed from a gradual loss of Raman lidarsensitivity starting about the end of 2001 going unnoticed until after AIOP. A majorrefurbishment and upgrade of the instrument and improvements to a data processingalgorithm led to the significant improvement and very small bias in ALIVE. Finally, wefind that during ALIVE the Raman lidar water vapor densities p, are 8% larger whencompared to AATS-14, whereas in situ measured p, aboard two different aircraft aresmaller than the AATS-14 values by 0.3-3%.