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

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provided by Larry Hjermstad. Predicted seed vs. no-seeded precipitation amounts will be
calculated for each day as well as for monthly and seasonal total accumulations.

On selected days, Lagrangian transport of the seeding material will be analyzed in detail
to determine if and how efficiently the seeding material is getting into the simulated
clouds under different wind and stability regimes. The Lagrangian transport model
implemented in RAMS by Uliasz (1994) and Uliasz et al. (1996) will be used. We expect
that 6 to 12 cases should suffice to span the relevant range of synoptic storm types and
wind and stability regions.

Model skill for predicted precipitation will be evaluated for a selected month using
Multivariate Randomized Block Permutation statistics (MRBP; Mielke, 1984; 1991) as
implemented by Cotton et al. (1994) and Gaudet and Cotton (1998). Snotel and gauge
data will be used for the evaluations. This step is important to determine if the model
forecast skill is sufficient to say something definitive about seed vs. no-seed differences
or if those differences are within the noise level or level of uncertainty of the model. (See
Option below.)

The reliability of model predictions of seed vs. no-seed differences depends not only on
model simulations of the source strengths, transport and diffusion of seeding material,
and its activation in clouds, but also on the natural background ofIFN. In this first phase
we have proposed to use the Meyers formula for estimates of background IFN
concentrations. However, our experience in the Arctic during FIRE-ACE (see Curry et
aI., 2000) and in CRYSTAL-FACE has shown that there can be wide variations from
estimates with this formula.

The current generally accepted standard for ice nuclei measurements is the continuous-
flow diffusion chamber (CFDC; Rogers 1988). Currently there is a laboratory device and
one airborne version in the U.S. and another in the U.K. The CFDC in the U.S. is fully
committed to projects. We encourage Reclamation to find support for the construction of
another transportable CFDC for future use on WDMP research projects not only in
Colorado, but also other state-supported cloud seeding operations in the WDMP. The
estimated cost for its construction is $48,600. However, even without the new CFDC, we
assure Reclamation that the base modeling research study proposed is a meaningful and
significant effort with distinct deliverables that stand on their own.

2.2 Option in addition to Basic Proposal

Option to Extend Period of MRBP Evaluation of Model Performance

This option extends the MRBP evaluation of model performance from one selected
month to include five months of winter seeding operations. The MRBP statistical
analyses are labor intensive; consequently, it was necessary to limit this task in the base
proposal. Extending the MRBP to cover additional months would increase the
confidence in the evaluation of the model's performance.

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