WMOD00299

• Title: Physical Structure of Northern Colorado River Basin Cloud Systems
• Date: 9/1/1985
• State: CO
• Weather Modification - Doc Type: Report

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(1) Aggregation in a deep cloud system.........................270
(2) Aggregation in a shallow cloud system......................281

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CHAPTER V

SUMMARY AND CONCEPTUAL MODELS OF PRECIPITATION FORMATION.290

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1. Summary of data analysis......................................... 290
A. Supercool ed wa ter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .290
(1) Temporal variations of the supercooled water field.........290
a. Pre-frontal and frontal cloud systems...................291
b. Post-frontal cloud systems..............................293
c. Orographic cloud systems................................293
(2) Location of the liquid water in Park Range cloud systems...294
(3) Microphysical characteristics of the supercooled droplet

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popul a ti on. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .296"

B. 'I'I1e ice phase..................................................2 97

(1) General characteristics....................................2 V7
a. Ice particle concentrations.............................297
b. Crystal habi ts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29'7
c. Precipitation rates.................................... .298
(2) Growth by vapor deposition.................................299
(3) Ice nuclea t1on. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .300
(4) Secondary ice particle production..........................301

(5) Accretion................................................. .302

(6) Aggregation............................................... .304

2. Conceptual models of Park Range cloud systems.....................305
A. The shallow stratiform cloud system with cloud top temperature

greater than -20oC.............................................30S
B. Deep stratiform cloud systems with tops colder than -20oC......310

c. Organized convection...........................................314

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CHAPTER VI

PRECIPITATION AUGMENTATION...............................316

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1. Requirements for modification of precipitation processes..........317
A. Supercooled liquid water.......................................317
B. Artificial ice nucleants.......................................320
2. Hypotheses for modification of precipitation processes............323
A. Precipitation modification by seeding the -10oC to

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010 ud ba se r eg1 0 n. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 24

(1) Nucleat1o,n................................................ .324

(2) Growth processes...........................................325

( 3 ) Hypo the s1 s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .326

B. Precipitation modification by cloud top seeding................327

( 1) Nu c1 ea tio n. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . _ . .327

(2) Growth processes...........................................328
(3) Hypothesis...................................... __. . . . . . . . . .329

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C.

Precipitation modification by seeding the region of strong

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orographic lift............................................... .330

(1) Nucleation................................................ .330

(2) Growth processes.......................................... .330

(3) Hypothesis................................................. 331

3. Hypothesis testing............................................... .332

A. Instrum.entation............................................... .332

B. Physical experiments.......................................... .334

(1) Seeding the low level region...............................33S

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