WMOD00558

• Project Name: Project Skywater, Sierra Cooperative Pilot Project
• Title: Project Skywater, Sierra Cooperative Pilot Project - Fall 1984 Status Report
• Date: 12/1/1984
• Weather Modification - Doc Type: Report

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Precipitation measurements are made by a network of recording

precipi ta tion gages. The number of gages has varied from 30 to 60.

Some of the gages are in remote areas and require servicing by

helicopter. The snowfall at the ground is also studied by the GML

(ground microphysics laboratory). The GML consists of a camper truck

equipped with instruments for counting and measuring snow crystals

and for studying their shapes. In addition, snow samples sometimes

are collected for analysis of trace impurities, including silver, to

see if changes in precipitation rate can be related to changes in silver

content in the snow.

A relative newcomer to the SCPP instrumentation list is a dual-channel

microwave radiometer. This instrument, operated for the past two seasons

at high elevations in the ARB, will be discussed in the next section

on program results.

3. Results from Physical Observations Within Sierra Storms

3. 1 Supercooled Liquid Wa ter and its Rela tion to Sierra Nevada

Meteorology

It is generally agreed that the presence of SLW (supercooled liquid

water) is a necessary although not always sufficient condition for

precipitation increases to occur due to cloud seeding in winter storms

over mountains. It is therefore necessary to understand the synoptic

and mesoscale controls which determine when supercooled water will

exist over the ARB. Therefore SCPP scientists have given close attention

to the problem of finding and measuring SLW and relating its occurrence

to the meteorological setting.

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