WMOD00307

• Title: A Proposal for Cooperative Weather Research Between the Santa Barbara County Water Agency and the US Department of Interior Bureau of Reclaimation in the Context of the Weather Damage Modification Program through the State of CA 2002-2003 Winter Season
• Date: 10/17/2002
• State: CA
• Weather Modification - Doc Type: Report

over the mountains. WMI has successfully sought and obtained similar waivers for previous
research programs.

2.3.2 Data Collection

Project data will be collected from a number of sources. While some sources exist primarily for
other reasons, there are some that are project-specific. First and foremost among these is the
cloud physics aircraft. The various sensors are enumerated and described below.

Aircraft Data System Position
Aircraft latitude, longitude, and elevation are provided by GPS, and also by more traditional
aviation instruments, including VOR/DME, and the aircraft altimeter. The aircraft has dual
NA Vs. Pressure altitude is provided by a Setra Model S-270 transducer, which is interfaced with
the aircraft static system and provides a DC analog voltage output that is used by the WMI-DAS-
200. Long term reliability and stability in this application is achieved in the S-270 with the
combination of the capacitive sensor and custom IC analog circuit. The fundamentally simple
design and thermally stable glass fused ceramic sensing capsule is coupled with the sophisticated
capacitance charge-balance type IC circuit where accurate signal conditioning and environmental
compensation is performed. Standard accuracy is 0.05% with 0.01% non-repeatability and
0.1 %/lOooF thermal performance.

Airspeed
Airspeed is obtained with a Setra S-239 differential pressure transducer, interfaced with the
aircraft static and pitot systems and provides an analog DC voltage which is used by the WMI-
DAS-200. The S-239 applies a theory that has been proved to be simple and reliable. A stainless
steel diaphragm and an insulated electrode form a variable capacitor. As pressure increases or
decreases the capacitance changes. This capacitance is detected and converted to a linear D.C.
electric signal by WMI's unique electronic circuit. The S-239 provides a high-level 0-5 to 0-::1:2.5
volt output. High positive over-pressure protection is achieved by the sensor electrode acting as a
stop for the diaphragm. The high level output signals, excellent long term stability and fast
dynamic response make this transducer ideal for such an application.

Horizontal Winds
The horizontal environmental winds (u, v) are derived by comparison of the rate of change of
aircraft position and airspeed, heading, groundspeed. The difference is the wind vector at the
aircraft altitude.

Vertical Wind
The vertical environmental wind (w) is sensed through a Ball Variometer 4.0, a transducer which
measures instantaneous vertical velocities, or updrafts and downdrafts at rates up to 4,000 feet
per minute. The BV4.0 is interfaced with the aircraft pitot-static system, and with the WMI-
DAS-200 analog measurement portion.

"',

Temperature

Weather Damage Modification Program 34

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