Episodic Dust Events of Utah’s Wasatch Front and Adjoining Region Jeffrey D. Massey 1, W. James...
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Episodic Dust Events of Utah’s Wasatch Front and Adjoining Region Jeffrey D. Massey 1, W. James Steenburgh 1, and Thomas H. Painter 2 1 Department of Atmospheric
Episodic Dust Events of Utahs Wasatch Front and Adjoining
Region Jeffrey D. Massey 1, W. James Steenburgh 1, and Thomas H.
Painter 2 1 Department of Atmospheric Sciences, University of Utah,
Salt Lake City, UT 2 Jet Propulsion Laboratory, Pasadena, CA
Contact: [email protected] Introduction Episodic dust events
produce hazardous air quality in the Salt Lake City metropolitan
area. From 20022010, wind-blown dust events produced 13 exceedances
of the National Ambient Air Quality Standard for PM2.5 or PM10.
Derived from: 1.North American Regional Reanalysis (NARR) 2.GOES
satellite imagery 3.Salt Lake City (KMTX) radar imagery 4.Hourly
observations and remarks from DS-3505 Long term climatology
(1930-2010) Dust loading in the nearby Wasatch Mountains affects a
snowpack that serves as the primary water resource for ~400,000
people and enables a $1.2 billion winter sports industry, known
internationally for the Greatest Snow on Earth. Observations from
Colorados San Juan Mountains indicate that dust loading increases
the snowpacks absorption of solar radiation, thus decreasing the
duration of snow cover by several weeks 12 MST 13 MST 14 MST 15 MST
Snowpack impacted by episodic dust events Alta, UT, 30 Apr 2009
NARR analyses of 850-hPa geopotential height (black) and
temperature (color shaded) at 17 MST 10 May 2004. Type 3:
Stationary Baroclinic Trough or Cold Front (18%) Example: 10 May
2004 Conclusions Dust events at KSLC occur throughout the
historical record, with considerable interannual variability Dust
events have a bimodal distribution, with a peak in Apr and a
secondary peak in Sep, and are most common during the afternoon
KSLC dust events are mainly caused by Intermountain baroclinic
troughs, cold fronts, and airmass convection Emission sources are
concentrated in low elevation Late Pleistocene to Holocene alluvial
environments in southern and western Utah and southern and western
Nevada Dust generated in prefrontal environment of upstream
baroclinic trough or quasi-stationary front Baroclinic trough or
cold front does not pass reporting station within 24 hrs of initial
dust observation Dust free snowpack Ben Lomond Peak, 26 Apr 2005
Dust Event: A day (MST) at Salt Lake City International Airport
(KSLC) with at least one blowing dust, dust in suspension, or dust
storm report with visibility < 10 km in the Global Integrated
Surface Hourly Database (DS-3505) Type 1: Baroclinic trough or cold
front (48% of events) Example: 10 May 2004 Type 2: Airmass
Convection (33% of events) Example: 19 May 2006 Elevation (m) 1350
1700 2050 2400 Reflectivity (DbZ) 10 20 30 40 50 60.5 degree NEXRAD
KMTX reflectivity for 16:06 MST 19 May 2006 Time (MST) Direction
Speed (m s -1 ) Gust (m s -1 ) Visibility (km) 16:001905.6n/a16
16:0720027.831.96.4 17:0013022.626.216 18:001104.6n/a16 11:30 MST
12:30 MST 13:30 MST 14:30 MST NARR analyses of 850-hPa geopotential
height (black) and temperature (color shaded) at 11 MST 19 April
2008. Dust Source regions Wasatch Mtns KSLC. Carson Sink Sevier
Desert Escalente Desert Milford Valley Frontal Passage > 3 hrs
before < 3 hrs before < 3 hrs after > 3hrs after
25%50%87.5%12.5% Dust reports relative to surface frontal passage
for all baroclinic trough or cold front events Dust plumes are
typically generated in the prefrontal environment and extend to the
Wasatch Front. Dust may be entrained into the post-frontal airmass
through cold-frontal convergence Airmass convection events are
produced by thunderstorm outflow and are typically short-lived, but
intense, events Dust plume starting locations and orientations for
all recent Intermountain West dust days from GOES imagery Major
Sources: 1.Carson Sink 2.Sevier Desert 3.Sevier Lakebed 4.Milford
Valley 5.Escalente Desert 6.West Desert Wind rose of conditions at
the onset of each dust event Considerable interannual variability
(4.3 per WY) A bimodal monthly distribution with a primary maximum
in Apr and secondary maximum in Sep An afternoon peak Predominately
southerly winds at the onset U13B-07 Dust events exhibit: KSLC
observations surrounding 16:07 MST dust observation KSLC Recent
Event Characteristics (2001-2010) GOES visible imagery with applied
dust detection algorithm (red) Emission sources are concentrated in
low elevation Late Pleistocene to Holocene alluvial environments in
southern and western Utah and southern and western Nevada. Sevier
Lakebed