Multiwavelength lidar measurements at the City College of New York in support of the NOAA-NEAQS and NASA-INTEX-NA experiments

Abstract

Satellite measurements do not provide the vertical information needed to assess aerosol transport mechanisms. To supply this information, multiwavelength lidar measurements are needed to study the vertical structure of aerosol events. In support of NASA-INTEX and NOAA-NEAQS transport experiments; we present lidar retrievals, which identify multiple stratified particulate plumes occurring over New York City on 2004 July 21 in support of MODIS imagery. In particular, multiwavelength measurements at CCNY are used to determine the /spl Aring/ngstro/spl uml/m coefficient of the plumes that unambiguously identifies them as fine mode particulates and not cloud particles. A description of our lidar system capabilities and processing algorithms used to process simultaneous backscatter lidar measurements with Aeronet CIMEL Optical Depth (OD) data is presented and back trajectory analysis is used to confirm the source of the plumes to be from Alaskan wild fires. Finally, surface measurements from in situ particle counters are presented and show no enhanced PM2.5 loading. This result is supported by lidar measurements, which confirm that nearly all of the aerosol plumes are located above the normal aerosol boundary layer showing that satellite measurements are often incomplete and is not useful to assess surface air quality. In particular, we show that high PM2.5 events are triggered from more local sources such as the Ohio Basin and climatological conditions which drive the pollution to the surface.