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TITLE:
Observations of Atmospheric Transport of Water Vapor Structures Via Microwave Interferometry
INVESTIGATORS:
Bob Carlos, Matt Kirkland, and Xuan-Min Shao (LANL)
OBJECTIVES:
1. To quantify the amplitude, size, structure and transport of water vapor structures in the convective boundary layer.
2. To quantify atmospheric turbulence near the surface, using water vapor as a passive tracer.
APPROACH:
A 10 element array of commercial Ku-band (i.e. microwave) receiver antennas will be deployed near the San Pedro river to observe, using interferometric techniques, the passage of water vapor structures as they drift over the array's field of view. A microwave carrier from a cable television satellite in geosynchronous orbit will pass through the overhead atmosphere, which is refractive at microwave frequencies due to the presence of water vapor. The satellite signal's electrical phase at each receiver varies proportionally to the total water vapor content integrated along the line-of-sight from the antenna to the satellite beacon. Thus the difference in the signal electrical phase between any two antennas is directly proportional to the horizontal gradient in the total water vapor content between the two antennas. The largest concentrations of water vapor affecting the signal will be in the lower troposphere, which is the region of interest. Given an array of antennas, the perturbation amplitude and horizontal velocity of water vapor structures can be extracted. It may also be possible to deduce information concerning the evolution of the structures as they drift across the array. Studies of the structures' evolution and motion will provide information concerning the turbulent transport of air parcels carrying the water vapor. To clarify, these measurements provide knowledge of gradients and water vapor amplitudes relative to background concentrations; these measurements do not provide knowledge of the absolute water vapor content.
These measurements will be taken for the entire month of August, 1997. Additional long-term monitoring will occur should additional funding become available in October 1997.
DATA COLLECTION:
1. Variable: water vapor perturbation amplitude. Units: g/cm3. Method: microwave interferometry. Location: 800 meters SW of BM 4074 on Lewis Springs 7.5-min Quadrangle. Frequency: 30-400 seconds (entire range) for duration of campaign.
2. Variable: water vapor structure velocity. Units: 2-D vector, m/s. Method, Location and Frequency same as 1.
3. Variable: water vapor structure 2-D scale size. Units: meters. Method, Location and Frequency same as 1.
4. Variable: water vapor structure 2-D location. Units: TBD Method, Location and Frequency same as 1.
5. Variable: wind velocity. Units: 2-D vector, m/s. Method, Location and Frequency same as 1.
6. Variable: boundary layer turbulence. Units: Method, Location and Frequency same as 1.
DATA REQUESTED FROM OTHER INVESTIGATORS:
1. Cooper: Zenith pointing LIDAR measurements of background water vapor content, if possible.
2. Balloon sonde measurements of H20 vapor profile.
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