Transcript Winter Storm Studies along the Front Range of Colorado during FROST S. A.

Winter Storm Studies along the
Front Range of Colorado during
FROST
S. A. Rutledge*, M. R. Kumjian**, R. Rasmussen**
P. C. Kennedy* and R. Schumacher*
*Colorado State University, Ft. Collins, CO
**NCAR, Boulder CO
36th AMS Conference on Radar Meteorology
Breckenridge, CO
Front Range Orographic Storms
(FROST) Science Goals
• To examine the fine scale cloud and precipitation structure in winter
orographic storms over or near complex terrain.
• To determine through case studies and modeling simulations the role that
the fine scale cloud and precipitation features (such as embedded
convection, generating cells, and K-H waves) play in the formation of
precipitation in these storms. Building on the results from PLOWS.
• To improve the microphysical parameterizations for the simulation of
orographic precipitation, including the formation of mixed phase
precipitation.
• To provide a dataset and set of experiences by which we can design a
larger and more comprehensive orographic precipitation field program
along the Front Range.
FROST 2013
• A collaboration between CSU and NCAR
• CHILL X-band; NCAR X-band plus assortment of surface
measurements at NCAR Marshall Field site, soundings
• documented many winter storms, frequent overnight
(autonomous) operations conducted
A very snowy
March, April
and early
May………
Marshall Field Site
- A premier testbed for surface
measurements of winter precipitation
- Deployment of a large suite of
instrumentation,
including
snow
gauges,
hot
plate
sensors,
disdrometers,
traditional
meteorological observing stations,
etc.
http://www.ral.ucar.edu/projects/winter/sites/marshall/
Marshall Field Site
Soundings were launched during selected winter
storms to obtain in-situ thermodynamic data in
precipitating winter clouds.
Especially interested in
documenting layers of
convective instability
in relation to convective
scale snow generation
Students from Metro State Univ. (Denver)
participated in the sounding and snow
crystal collection phases
CSU sounding system
RADARS----NCAR XPOL
Deployed at the Marshall Field Site for the duration of FROST. Data were collected using
a series of PPIs, RHIs, and “birdbath” (vertically pointing) scans.
- Mobile, X-band polarimetric radar
- Magnetron transmitter
- 20 kW peak power, 0.1% duty cycle
- 1.8-m antenna (1.4° 3-dB beamwidth)
- Dual-polarization, simultaneous H/V
- Employed 90-m range resolution in
FROST operations
- Remote operation
CSU-CHILL RADAR X-BAND RADAR
Development of X-band
radar addition to CSU-CHILL
X-Band hardware adopted from
UPRM MRI radar (CSU ECE
collaboration effort)
CHILL X-band specifications
75 m gate
spacing used
in FROST
DUAL FREQUENCY, DUAL POLARIZATION
ANTENNA
1 deg
0.3 deg
S-Band, G=43 dB
X-Band, G=53 dB
lS-band » 3lX -band
q=
kl
d
G=
4pAe
l2
HEAVY AGGREGATE SNOWFALL CAUSED
MAJOR TRAFFIC ACCIDENT ON I-25
25 car pileup due to reduced visibility
15 April 2013
1709 UTC
145 degree RHI
Impressive convective scale
generating cells; generating cells
were ubiquitous during FROST. Colocated
with layers of convective instabiity.
Listen to the next talk!
Several km in width
Small scale features
Convergence
Fallstreak
Low Zdr
High Zdr
OLDER CELL
NEWER CELL
CONVECTIVE UPDRAFT
-15C
-12C
Thompson et al. 2014
Rapid formation of aggregates…from dendrites
Comparison of radar observations with CSU-WRF model simulations
(4 km resolution; GFS initiation data; two moment microphysics, Morrison
scheme)
Aggregates
Pristine crystals
Shallow tops
2 km
1 km winds and reflectivity
Forecast at 1000 UTC
The WRF simulations hint at the
banded structure but the bands
are considerably east of the radar
location
0.5 – 3 km shear, reflectivity
Shear parallel bands
“evident” in model
Examine model vertical x-sec
Deep
convective
band with
graupel
predicted
N-S Cross section
1000 UTC
Radar
indicates
pristine
ice precipitation
with tops to
2 km AGL
SOUTH
NORTH
Conclusions
• FROST provided radar, sounding and ground
based particle measurements in many winter
storms
• High resolution CHILL X-band data providing
detailed look at microphysical processes,
surface observations important for HID
verification
• Obviously more work to be done on radarmodel intercomparison---finer resolution
needed, microphysical parameterizations?