WMOD00372

• Project Name: High Plains Cooperative Program
• Title: The Design of HIPLEX-1
• Date: 4/1/1979
• Weather Modification - Doc Type: Report

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D. Second Posttreatment Pass

The cloud will be penetrated 5 minutes after treatment, 300 m below
treatment altitude, to document the following response variables:

1. The average concentration of ice crystals (CIC5) over the 2-km
distance having the maximum ice-crystal concentration out of the
4-km distance centered on the closest distance to the initial
pointer.

2. The concentration of ice crystals rimed (CCR5) ~s determined
by a decelerator slide exposed within a 2-km distance that is
centered on the second pointer.

E. Third and Additional Posttreatment Passes

The cloud will be penetrated 8 minutes after treatment at the -5 oC
level, and at about 3-min intervals thereafter, to document the
following response variables:

1. The average cloud liquid water concentration (AWC8), the
average precipitating ice* number concentration (PIC8), and the
mean volume diameter of precipitating ice partic"es (MVD8) over a
4-km distance centered on the closest distance to the vertical
projection of the initial pointer. These variables will be
updated on subsequent passes.

2. The time of first precipitating ice (TFPI) with sizes greater
than or equal to 0.6-,mm diameter and concentrations greater than
0.1 per liter.

TFPI is not now available in real time. However, the aircraft will
stay at the -5 oC level, continuing to fly through the pointer
location after the 8-min pass, until 17 minutes have elapsed since
treatment or until the onboard radar indicates a first echo within 5
km of the pointer. If a first echo appears, the aircraft will
proceed to fly through the center of the echo. The ice-particle
concentrations and sizes measured on this pass should be in excess
of those occurring at TFPI. After the pass through the echo, or

* Particles greater than or equal to 0.6 mm in diameter as measured
by the 2D precipitation probe.

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