WMOD00293 ‎(2)‎

• Contract/Permit #: 14-06-D-6467
• Project Name: Project No. 15-1371-1113
• Title: A Case Study of the Water Budget of an Orographic Cloud
• Prepared By: L. K. Balick, J. L. Rasmussen
• Date: 5/1/1972
• State: CO
• Country: United States
• Weather Modification - Doc Type: Report

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atmosphere by cloud evaporation on the downslope side of the ridge has

to be removed from the final water balance computation. This is done

by obtaining an estimate of the downslope evaporation and eliminating

this estimate from the net condensation already computed for between

Camp Hale and Fairplay.

Estimation of the downslope evaporation is done by computing tem-

perature and mixing ratio profiles for an imaginary station at the top

of the ridge (designated TOP). The air above this station is assumed

to be initially saturated and travelling adiabatically between the top

and Fairplay. For each 8e channel, the temperature at TOP is equal to

the temperature at Fairplay minus the dry adiabatic warming due to

descent and compression, plus the cooling due to evaporation between

Camp Hale and Fairplay. Expressed as an equation.

TTOP

TFPY + yd 62 + 1-- (w w)
Cpd TOP - FPY

(7)

Here yd is the dry adiabatic lapse rate (-9.80C/km.), 62 is the distance

the parcel descends between the top of the ridge and Fairplay, L is the

latent heat of evaporation and Cpd is the specific heat of dry air,

wTOP is the mixing ratio at the top (assumed saturated) and wFPY is the

mixing ratio at Fairplay. wTOP is an exponential function of TTOP so

equation (7) can be evaluated numerically. An initial guess of TTOP

(and thus wTOP) is found by time interpolation on the Camp Hale temper-

.

ature time series. Evaluated for each 8e channel, equation (7) gives

a temperature profile at TOP.