Our goal was to obtain high-resolution profile measurements of water vapor and wind velocities in the marine boundary layer using the mini-MOPA DIAL/Doppler lidar system. The milestone was undertaken to enhance an existing lidar system by developing new capabilities for water vapor and ship-borne measurements. This is a contribution to NOAA's Strategic Plan objective Implement Seasonal to Interannual Climate Forecasts by obtaining much needed, high resolution data in regions where little data exists in an effort to understand the present and pending states of the complex ocean/atmosphere system.

The Environmental Technology Laboratory (ETL) mini-MOPA lidar system was successfully deployed aboard the NOAA Ship Ronald H. Brown obtaining over 400 hours of atmospheric measurements from August 24th through October 22nd, 2001.

During our two month cruise from Seattle, Washington, to Arica, Chile, the lidar obtained high-resolution DIAL (water vapor) and Doppler (wind speed and direction) profiles and cloud measurements from the surface up to as high as 6 km. The lidar data set spans a variety of atmospheric regions; from the northern U.S. coastal zone where we observed water vapor pressures of 13 mb, to the tropical warm pool where water vapor pressures were as high as 31 mb and finally into the equatorial cold tongue region where water vapor dramatically dropped to 18 mb. In addition to the water vapor data, the lidar simultaneously measured wind speed and direction. The lidar documented many different wind features throughout the cruise including low-level wind shear layers, jets, and occasional thunderstorm outflow boundaries. Wind speeds ranged from dead-calm to 13 m/s. Boundary layer depths (deduced from aerosol returns) and cloud heights are also documented as part of the lidar data set. Detailed stratus cloud measurements were obtained as well as turbulent kinetic energy information in a variety of cloud conditions and transitions.

The main customer for this project was the EPIC sponsor NOAA. Additionally, we are collaborating with scientists from Scripps, Wood's Hole Oceanic Institute, University of Washington and University of Mexico. Our lidar results will be presented at EPIC science meetings in addition to being available on the EPIC data archive.

This deployment marked several significant firsts for the mini-MOPA system; the first ship cruise, the first motion-compensated data set, and the first DIAL measurements. Water vapor and wind measurements will allow us to quantify energy exchanges between key sub- tropical regions. This will provide much needed observational validation for modeled ocean atmosphere processes with the end result being improved model prediction.

The project was completed by October 22, 2001, and lidar system met all of our instrument performance goals by providing water vapor measurements on a moving platform and in harsh oceanic conditions. It is our aim to relate the lidar water vapor pressure and wind measurements to the further understanding of the energy exchanges and processes between the atmosphere and ocean that contribute to seasonal-to-interannual climate variability as part of conducting research for improved climate predictions under the NOAA Strategic Plan element Implement Seasonal to Interannual Climate Forecasts.

Our next step with the lidar EPIC data set will be to 1) process the wind velocity data to correct for ship's motion, 2) process the water vapor data to correct for atmospheric and system offsets, and finally to 3) produce a full time-series of the adjusted water vapor and wind velocity profiles. This corrected data set will then be compared to the wind speed and water vapor pressure point measurements taken on the Ron Brown for calibration/validation. Finally the lidar profile measurements will be used to characterize and understand the boundary layer structure of winds and water vapor and energy exchanges through the different marine temperature regimes we traversed.

Radial Doppler velocities (fig 1.) are fit to a sinusoid at each range bin (fig 2.) and then used to create high-resolution profiles of wind speed (fig 3.) and direction (fig 4.) throughout the depth of the marine boundary layer.

Fig. 1 - Radial Doppler velocities

Fig. 2 - Radial Doppler velocities fit to a sinusoid at each range bin.

Fig. 3 - High-resolution profiles of wind speed throughout the depth of the marine boundary layer.

Fig. 4 - High-resolution profiles of wind direction throughout the depth of the marine boundary layer.