LASE measurements of aerosol and water vapor profiles during TARFOX

The Lidar Atmospheric Sensing Experiment (LASE) was operated autonomously f rom the NASA high-altitude ER-2 aircraft on nine flights during July 1.0-26 , 1996, as part of the Tropospheric Aerosol Radiative Forcing Observational Experiment(TARFOX). LASE measured high-resolution profiles of water vapor and aerosols in regions of urban haze plumes over the U.S. eastern seaboard . Real-time LASE aerosol measurements were used to guide the in situ aircra ft to sample haze layers. In this paper the vertical and horizontal distrib utions of aerosol backscatter measured by LASE are presented along with the temporal evolution of the haze layers. The aerosol backscatter data also i dentify the presence of gradients in the aerosol plumes, the presence of lo w-altitude clouds, and optically thin cirrus. This information is useful fo r many of the radiometeric observations made during TARFOX and can help exp lain observational differences among ground, airborne, and satellite observ ations. An iterative procedure is discussed which was used to invert lidar data to retrieve aerosol scattering ratios, extinction, and total optical d epths from the LASE measurements. The sensitivity of these retrievals to as sumed parameters is discussed and the results of retrievals are also compar ed to the well-known Bernoulli method. LASE water vapor measurements were m ade across the entire troposphere using a three "line pair" method to cover the range of water vapor mixing ratio from <0.01 g/kg near the tropopause to similar to 20 g/kg near the surface in a single aircraft pass over the e xperiment region. These measurements also show two-dimensional distribution s of large spatial gradients in water vapor in the lower and upper troposph ere. These observations are useful in the calculation of IR radiation field s and relative humidity fields, since relative humidity has a strong influe nce on the growth of aerosols and their scattering properties. Water vapor profiles, aerosol scattering ratios, aerosol extinction coefficients and ae rosol optical depths were derived using the methodology presented in this p aper from LASE measurements during TARFOX. These measurements are compared with other in situ and remote measurements during TARFOX in the companion p apers [Ferrare et al., this issue (a, b)].