WMOD00306

• Project Name: Sierra Cooperative Pilot Project
• Title: Sierra Cooperative Pilot Project - Operations Plan - 1986-1987
• Date: 10/1/1986
• Weather Modification - Doc Type: Report

Several storms will be set aside for monitoring ground seeding. Since the
randomization is known these periods can be coordinated ahead of time. Since
ground seedi ng encompasses 6 hours, a 9-hour collect i on peri od is needed
beginning 1 hour after generator on time and completing 2 hours after the
generators are turned off. Since this length of data taking will severely tax
a 11 ground personne 1, a mi n i mum of 18 hours wi 11 be requ i red before the
Kingvale and Tahoe-Donner sites can be staffed again.

2. Radiometer Measurements
The dual-frequency (20.6 and 31.54 GHz) microwave radiometer developed by NOAA
will be deployed at the HALO from October 14, 1986, through January 9, 1987.
The radiometer will be used to measure path integrated LWC (liquid water con-
tent) in mm and PWV (precipitable water vapor) in em. Characteristics of this
instrument are shown in table 3-2.

The radiometer is controlled by an LSI-ll computer which controls antenna
movement as well as data collection. Data will be recorded every 2 minutes on
disk. The data disk will last about 10 days before a new disk must be
installed. Procedures for doing this can be found in the dual-channel
radiometer reference manual, which was provided by NOAA.

Tipping curves are a means of calibrating the system. Tipping curves should
be carrie~ out every 2 weeks under conditions of clear skies and steady PWV
environment. The procedure for executing tipping curves can be also found in
the dual-channel radiometer reference manual located in the radiometer
trailer.

In order to keep the outside microwave dish clear of water and wet snow an
extremely hydrophobic substance will be applied to the dish. The substance

I II -16

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