WMOD00268

• Applicant: CWCB
• Sponsor Name: USBR
• Project Name: Final Report Weather Damage Mitigation Program
• Title: Numerical Simulations of Snowpack Augmentation for Drought Mitigation Studies in the Colorado Rocky Mountains
• Prepared For: USBR - WDMP
• Prepared By: Curt Hartzell, Dr. William Cotton, Joe Busto
• Date: 9/1/2005
• State: CO
• Weather Modification - Doc Type: Scientific Study

cycle began, the existing procedure had been that all of the old products from the
previous cycle were deleted from the CSU Real-time Forecast Web site. This
was to avoid confusion by users, who otherwise might not realize that when they
were examining a time sequence of products. the valid time might cross over
discontinuously from the new forecast cycle to the old cycle. (The model run
produces 2-hr forecasts out to 48 hours. The new 2-hr forecasts are posted right
after the 0000 UTC model run completes them.) However, particularly with the
slow runs, the deletion of the old cycle products resulted in no high-resolution
forecast guidance for the first day or so of the new cycle, until the new cycle
reached that far.

It was thus decided to keep the old forecast cycle's products until they
were superceded and over-written by each two-hourly increment of the new
cycle. In this way, the products valid at 36 hours in the old cycle (or 1200 UTC
on Day 2), for Instance, were retained to provide guidance at 1200 UTC on Day 1
of the new cycle, until the new cycle's products were produced. To help the user
avoid the possible confusion of not realizing the discontinuity, prominent labels
were updated and displayed on each menu that give the initialization time of the
current cycle and how far out in the 48-hr cycle it has reached. Thus, any
products beyond that point were more easily recognized as being from the older
cycle, but were still available for high-resolution guidance. This change was
made beginning with the January 19, 2004 forecast cycle.

The real-time RAMS 0000 UTC forecast runs, originally intended to
constitute the set of control (no-seed) runs for the entire season, were
determined to be unusable for that purpose due to several problems that
became evident deep Into the cold season. The problems were traced to three
factors, two of which Involved overly warm soil temperatures that resulted in
too much surface sensible heat flux and low-level warming. One problem was
a soil initialization scheme that prevented the soil temperature from initializing
colder than aoe and the soil moisture from being initialized in frozen form,
when those conditions should have been allowed at high elevations deep into
winter. The second problem was a coding error with the thermal energy
content applied to soil, where sub-freezing soil improperly warmed rapidly to
aee when the slightest initial frost or frozen precipitation occurred in the
topmost soil layer.

The third problem was the use of an alternate horizontal diffusion
scheme that esu had used in previous winter seasons in order to avoid
runaway cooling at the lowesllayer that sometimes occurred with the standard
diffusion scheme. The alternate scheme was not strictly mass conserving,
however, and in many runs it apparently resulted in too much mass and
moisture convergence into the high country.

These three problems resulted in unrealistically warm low.level
(basically below ridge crest) temperatures and overestimates of precipitation in

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
4
4
4
4
4

32