CODOS Dust Alert - Event D3-WY2013,
new research on dust enhancement of precipitation
I've just returned from the Swamp Angel Study Plot where I collected new dust-on-snow samples for event D3-WY2013, from the snowpack surface. This comparatively low-mass, brown dust layer was delivered "dry", at very low intensity, on sustained SSW and S'ly winds sometime since Tuesday evening, March 5th (see wind rose below). Although very minor haze was sometimes seen in the sky from Silverton, no significant dust was observed during daylight hours on Wednesday (March 6th) or Thursday (March 7th). However, images captured by the USGS Abajo Peak camera late Thursday afternoon did show what appeared to be some dust in the air, reducing visibility of distant landmarks, whereas the Mesa Verde and Island in the Sky cameras did not.
This D3 dust enhanced the development of a melt-freeze crust at the snow surface at SASP during the very sunny and warm weather of Wednesday and Thursday, March 6 and 7. Fresh snowfall began as I finished the sampling and it was not clear whether that new snow was sustaining the deposition of dust event D3. (This will be Storm #17 and may total up to 20" by Sunday morning, according to the NWS Storm Warning). A snowpit following the storm will reveal whether D3 simply continued or not.
This storm is also traversing the Colorado Plateau and NWS Flagstaff has issued the following Hazardous Weather statement:
DAY ONE...TODAY
A STRONG PACIFIC STORM SYSTEM WILL MOVE ACROSS THE SOUTHWEST TODAY
BRINGING WIDESPREAD MODERATE-TO-HEAVY RAIN AND SNOW TO THE REGION.
WINTER STORM WARNINGS AND WINTER WEATHER ADVISORIES REMAIN IN EFFECT
FOR MUCH OF NORTHERN ARIZONA. SEE PRODUCT PHXWSWFGZ FOR ADDITIONAL
DETAILS.
.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY
WINTER WEATHER CONDITIONS WILL CONTINUE ON SATURDAY WITH ADDITIONAL
SNOW ACCUMULATIONS ACROSS THE MIDDLE AND HIGHER ELEVATIONS OF
NORTHERN ARIZONA.
As always, fresh precipitation in the Plateau may delay subsequent dust emmissions, until soils re-dry. This storm will exit the Colorado mountains quickly on Saturday night and NWS expects high pressure with mostly sunny skies and unseasonably warm temperatures over most of western Colorado for Sunday through Thursday.
More soon,
Chris
PS - some of you may have seen recent press coverage of new research by NOAA scienctists and others showing that Saharan and Asian dust has enhanced precipitation during winter storms in the Sierra Nevada. I've had a very interesting discussion of that result with the lead author, Dr. Jessie Creamean. Many of you have asked me whether Colorado Plateau dust could act as a cloud 'seeding' agent, and I've had to say that 'we' simply don't know. An abstract is available online through
Science Express. The February 28 article is titled "Dust and Biological Aerosols from the Sahara and Asia Influence Precipitation in the Western U.S". Dr. Creamean is going to provide me with the full citation as soon as their article appears in
Science, proper, later this month and I will forward it to you then.
Chris Landry, Executive Director
clandry@snowstudies.org
Center for Snow and Avalanche Studies
PO Box 190, Silverton, CO 81433 USA
(970) 387-5080
www.snowstudies.org
