Vertical profiles of optical scattering were obtained using a multi-wavelength Raman lidar to
describe the distribution of airborne particulate matter in the lower atmosphere.  The signal profiles from Raman scatter wavelengths at 607, 530 and 285 nm and the lidar backscatter at 532 nm were used to measure optical extinction, while at the same time Raman lidar measurements of water vapor, temperature, and ozone profiles were obtained.  Correlation between backscatter and extinction measurements provides a means of  describing atmospheric aerosol and particulate matter in the lower atmosphere.  It is important to obtain improved ways of measuring the distribution of airborne particulate matter, which has been shown to have a strong correlation with health and respiratory problems. Measurements were taken using the Lidar Atmospheric Profile Sensor (LAPS), which was developed and demonstrated as an operational prototype instrument for the U.S. Navy.  An algorithm for the telescope geometrical form factor was developed to aid in analyzing signals near the surface.  The measured Raman signals, which represent the molecular density, are directly analyzed to determine the optical extinction profiles in the far field (1000-5000 m).  However, special care must be given to analysis of the near field data because of overfilling of the detector which is located in the far field focal plane.  The variation of optical extinction associated with water vapor, aerosols, and ozone in the atmosphere is useful in understanding the evolution of pollution events.  Scattering at optical wavelengths provides information on small airborne particles and corresponds well with the PM2.5 particulate matter.  Most pollution and atmospheric episodes occur near the surface within the planetary boundary layer.  Several cases of extinction measurements from the NARSTO-NE-OPS investigations in Philadelphia during summer 1998 and 1999 have been analyzed and compared with other measurements.