WMOD00550

• Title: Scientific Weather Modification Experimentation in the United States
• Weather Modification - Doc Type: Report

',I-~~'~le 1. Cloud Selection Criteria for HIPLEX-l
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I Class A-I Cloud Criteria

1. Average cloud liquid water concentration greater than 0.5 g/m3 over approximately a l-km-long cloud
region determined by 10 s of flight at approximately 100 m/s

2. Average ice-crystal concentrations less than 1.0 per liter in the 1-km-long (10 s of flight) cloud region
of maximum average liquid water concentration

3. Maximum ice-crystal concentration less than 5.0 per liter for any 1-km-long (10 s of flight) cloud region'
(defined by FSSP liquid water concentration greater than 0.01 g/m3) during the test pass

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4. Vertical air velocity greater than -1.0 m/s in the region defined by item I, but if the vertical velocity:
is greater than 10.0 m/s and the buoyancy is greater than 1 oC, reject the candidate

5. Length of the test penetration more than 2 km and less than 8 km as defined by an FSSP liquid water con-
centration greater than 0.01 g/m3 i I

6. No radar echo detectable on the aircraft weather radar

7. Cloud-top temperature lower than -6 oC but higher than -12 oC
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8. Cloud-base temperature higher than 0 oC i

9. Minimum separation between the current test cloud and previous test clouds greater than 15 km to insure
the meteorological independence of the clouds i

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2. An average wind direction between the surface fnd 80~ kPa from 2500 to 0400 true
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3. A 30-kPa-thick st.able layer present with its b~se between 0 to -10 oC and its top temperature at least
1.5 oC higher than the temperature extrapolated from the base of the layer to the top using pseudoadiaba-
tic ascent I I

4. A 10 oC dewpoint depressing present somewhere Within the 30-kPa layer of B.3 above
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1. Items A.l through A.3, A.5, A.6, A.8, and A.9 above i
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2. Cloud-top temperature lower than -6 oC but higher than -20 oC
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3. Vertical air velocity greater than -1.0 m/s in! the region defined by Item A.1, but no other vertical
velocity or buoyancy restrictions I

Class A-2 Cloud Criteria

1. Items A.l to A.9 above

Class B Cloud Criteria

I Table 2. HIPLEX-1 Primary response variables

1. CIC2
2. CIC5
3. CCR5
4. PIC8
5. MVD8
6,' AWC8
,'7. TFPI

8. TFE
9a. TIPA
b. TI PR
lOa. RERC
b. AER

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Cloud ice concentration, 2 min after treatment
Cloud ice concentration, 5 min after treatment
Concentration of crystal s rimed, 5 mi n after treatment
Precipitating ice number concentration, 8 min after treatment
Mean volume diameter of precipitating ice particles, 8 min after treatment
Average liquid water concentration, 8 min after treatment
Time to first precipitating ice (particles with diameters> 0.6 mm in concentrations> 0.1 per
liter) I I
Time to first SWR-75 radar echo (15 dBZ)
Time to-initial precipitation at +10 oC level. aircraft measurement
Time to initial precipitation at +10 oC level. SWR-75 radar (15 dBZ)
Radar-estimated rainfall at +10 oC level, using a constant Z-R relationship
Ai rcraft-estimated rainfall at +10 oC level

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