Lidar Atmospheric measurements of Tropospheric Refractivity During Developing Santa Ana Winds
Document ID: 350
Blood, David W.1
Philbrick, C. Russell
Presentation
1 1995 IEEE-APS & URSI Symposium
Presented: Newport Beach, California, June 20, 1995
Abstract
A multi-wavelength Raman lidar was used to measure profiles of water vapor, temperature and other atmospheric properties in the troposphere during the beginnings of the 1993 Los Angeles fire storm period with developing high velocity Santa Ana wind conditions. The PSU/LAMP lidar instrument was being is used to make measurements at Point Mugu, CA for an observational campaign called VOCAR (Variability of Coastal Atmospheric Refractivity). The Raman technique provides an accurate way to measure the profiles of water vapor from the ratio of the Raman vibrational backscatter signal from water vapor to that of nitrogen. The lidar has been used both to obtain water vapor profiles from molecular Raman vibrational scattering at several wavelengths, and temperature profiles from Raman rotational scattering at 528 and 530 nm. The water vapor measurements have been made using the vibrational Raman backscatter intensity from the 660/607 ratio from the 532 nm, 407/387 ratio from 355 nm, or the 294/285 ratio from 266 nm laser radiation.
The measurements of the atmospheric refractive environment on October 26 and 27th, 1993 at Point Mugu, CA during the developing wind storm, produced an intense temperature inversion and gradient further producing an RF ducting condition in the lower troposphere. The lidar temperature and water vapor data were used to compute profiles of refractivity, N, and modified refractivity, M at 75 m height intervals in the lower tropospheric region (surface to 5000 m). The lidar data, stored at one minute intervals, is examined with integration times of several minutes. The time history of these profiles shows a dramatic low altitude drying effect in the maritime boundary layer. This changes the atmospheric refractive condition from a strong refractive surface based duct to the complete absence of any ducting over a 5 hour period. Atmospheric variability decreases as the moisture is driven entirely out of the surface air layer. This anomalous type of refractive ducting is entirely different from the usual ducting conditions predeveloping atmospheric condition is shown and the corresponding physical parameters contributing to the refractivity effects are analyzed.oduced during more quiescent conditions, where an elevated or surface duct is frequently formed by a significant drop in water vapor near a temperature inversion. The time history of this rare
| Citation: | Lidar Atmospheric measurements of Tropospheric Refractivity During Developing Santa Ana Winds, Blood, David W., Philbrick, C. Russell, Presentation, June 1995, 13 pages |