WMOD00263 ‎(2)‎

• Applicant: CWCB
• Sponsor Name: USBR
• Project Name: Response to RFP
• Title: Numerical Simulations of Snowpack Augmentation for Drought Mitigation Studies in the Colorado Rocky Mountains
• Prepared For: USBR
• Prepared By: Joe Busto, CWCB
• Date: 8/20/2003
• Weather Modification - Doc Type: Application

I
I
I
I
I
I
I
I
I
I
II
;1
:1
!I
I
I
I
I
il
il

2. Technical Approach

2.1 Basic Research Study

The research proposed below is in support ofthe Colorado Water Conservation Board,
Flood Protection & Weather Modification Permitting Section's objective to further the
science of weather modification in Colorado by linking scientific analysis with an
operational winter-season program. For the 2003-2004 season, they desire to use the
CSU RAMS for precipitation forecasting and cloud seeding evaluation. The research
study is piggy-backed onto the Denver Water Department's operational cloud seeding
program in which Western Weather Consultants (Larry Hjermstad) provide the cloud
seeding operations.

The goal of the proposed research is to provide a physical evaluation of operational cloud
seeding in Colorado by using a well-established numerical model system. The model
will explicitly simulate the chain of events following seeding and if it shows a consistent
positive yield of precipitation, it will increase the credibility of the operational cloud
seeding program. Up to this point, no one has run a model with the advanced physics of
RAMS on a daily basis for an entire winter season to evaluate the consequences of
seeding. The model should determine if seeding material is likely to enter clouds,
nucleate ice crystals and augment precipitation processes in a beneficial way such that
monthly and seasonal precipitation is enhanced. This should be compared to a long-term
statistical evaluation of an operational seeding program, which, not being randomized, is
not likely to lead to convincing conclusions by the scientific community. A major
concern in such model-based studies is can the model replicate observed precipitation
amounts and spatial distributions, with sufficient skill to distinguish between seeding-
induced precipitation and naturally produced precipitation. To alleviate this concern we
propose to evaluate the performance of model precipitation forecast skill at several sites
for a selected one-month period.

It is thus proposed to run RAMS each day in real time for the 2003-2004 winter season.
A refined grid having 3 km grid spacing within a 240 kIn x 240 kIn box will be placed
over the region covering the seeding generators and the DWD project basins. The area
shown in Figure 3 includes not only the DWD program collection basins, but also the
region upwind of it where seeding is also done in the Vail Ski Area. Larry Hjermstad has
agreed to provide us outputs of his generators there as well so that we can examine its
potential impacts on the DWD program. Background IFN concentrations will be
determined from the Meyers et a1. (1992) formula described in the Background section,
unless specific measurements ofIFN are made available to us. Likewise CCN and
GCCN concentrations will be based on our best guess of what one should expect in the
region of interest, unless specific measurements are made available to us. Each daily
forecast simulation will run through 48 h, covering the next operational day and into Day
2. Output products will include precipitation rate at 2 h intervals and accumulated
precipitation for 6, 12 and 24 h increments through the 48 h forecast. Accumulated
precipitation for a given 24 h period (e.g., 6-30 h period) from each daily forecast
simulation will be used for the simulated monthly and seasonal totals. These 24-hour
model forecast precipitation amounts will be provided to WWC/Larry Hjermstad, via the

II-II