Mountain wave structures occurring

1
Mountain wave structures occurring within a
major orographic precipitation event Part 2
Observed and Modeled Precipitation Fields Matt
Garvert, Brad Smull and Cliff Mass IMPROVE-Meetin
g 13 July 2005
Photo by Greg Thompson- http//www.inclouds.com
2
Part-2 Discussion Topics

• Analysis of precipitation structures over complex
  terrain using dual-Doppler radar.
• Utilize MM5 to assist in explaining structures in
  reflectivity
• Large scale (gt 20-km) over mean crest
• Small scale (lt 20-km) over windward slopes

3
Observed Mean E-W Cross Section
1
2
3
4
P3-Reflectivity and MM5-Snow field 2300-0100 UTC
Snow (g kg-1)
MB
5
SBAND - Reflectivity
Reflectivity maximum between 4-5 km is attributed
to growth of dendrites which are then advected to
lee of mountain barrier.
6
Wave-like behavior in MM5-Kinematic and CLW
Fields
23 -01 UTC
MM5-w (m s-1)
MM5-CLW (g kg-1)
7
2200 -0030 UTC
MM5-w (m s-1)
8
2200 -0030 UTC
MM5-Clw (g kg-1)
9
Looking closer at leg-2
N
Latitude (Deg)
SPL
IB
MB
UW
Distance from Crest (km)
Distance from Crest (km)
10
JAS-Garvert (2005)
11
Dual-Doppler v-wind
V-Wind (m s-1)
gt40
36-40
32-36
28-32
24-28
20-24
16-20
12-16
08-12
lt08
0 10 20 30
40 50 60 70
80 90 100 110 Distance
(km)
S
N
12
Dual-Doppler v-wind and w
0 10 20 30
40 50 60 70
80 90 100 110 Distance
(km)
S
N
13
Dual-Doppler dBZ and w
0 10 20 30
40 50 60 70
80 90 100 110 Distance
(km)
S
N
14
Dual-Doppler dBZ and MM5-w
0 10 20 30
40 50 60 70
80 90 100 110 Distance
(km)
S
N
15
Latitude (Deg) 44.00 44.09 44.18
44.27 44.36 44.45 44.54 44.63
44.72 44.81 44.90 44.98
Height (km)
0 10 20 30
40 50 60 70
80 90 100 110 Distance
(km)
S
N
16
Latitude (Deg) 44.00 44.09 44.18
44.27 44.36 44.45 44.54 44.63
44.72 44.81 44.90 44.98
1.4
1.6
1.2
1.0
1.0
0.8
0.6
Height (km)
0.4
MM5-Precip (g kg-1)
0.2
snow
0 10 20 30
40 50 60 70
80 90 100 110 Distance
(km)
S
N
17
Latitude (Deg) 44.00 44.09 44.18
44.27 44.36 44.45 44.54 44.63
44.72 44.81 44.90 44.98
1.4
1.6
1.2
0.4
1.0
1.0
0.4
0.8
0.4
0.2
0.2
0.6
Height (km)
0.4
MM5-Precip (g kg-1)
0.2
snow
graupel
0 10 20 30
40 50 60 70
80 90 100 110 Distance
(km)
S
N
18
Latitude (Deg) 44.00 44.09 44.18
44.27 44.36 44.45 44.54 44.63
44.72 44.81 44.90 44.98
1.4
1.6
1.2
0.4
1.0
1.0
0.4
0.8
0.4
0.2
0.2
0.6
Height (km)
0.4
0.2
0.2
0.4
0.4
0.4
0.4
0 10 20 30
40 50 60 70
80 90 100 110 Distance
(km)
S
N
19
Effect of Terrain Resolution on Precipitation
Totals
Cascade Crest
Willamette Valley
Terrain (m)
20
Accumulated Precipitation from
22-01 UTC
1.33-km Precip
Elevation (km)
Precip (mm)
S
N
0 10 20 30
40 50 60 70
80 90 100 110 Distance
(km)
21
Accumulated Precipitation from
22-01 UTC
6-15 increase in accumulated precipitation over
windward slopes
1.33-km Precip
1.33-km Smooth Precip
Elevation (km)
Precip (mm)
S
N
0 10 20 30
40 50 60 70
80 90 100 110 Distance
(km)
22
Height (m)
N
SPOL
Coast
Willamette Valley
Latitude (Deg)
E
S
Longitude (Deg)
W
23
Height (m)
N
SPOL
Coast
Willamette Valley
Latitude (Deg)
E
S
Longitude (Deg)
W
24
Conclusions

• Interaction of two distinct air streams
  low-level barrier-parallel airflow and upper
  level flow-over regime resulted in heavy
  precipitation over windward slopes of Cascades.
• Larger-scale mountain wave atop Cascade-crest
  produced enhanced snow field which was
  subsequently advected to lee slopes.
• Low-level barrier parallel flow interacted with
  the complex terrain of windward slopes producing
  waves which enhanced accretional processes and
  QPF (7-15).
• Impact of coastal mountains was spatially
  focused, and evidently not related to wave-like
  behavior over windward slopes of Cascades (not
  shown).

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Future Work

• Improve derivation of Doppler vertical-velocity
  by altering boundary conditions (similar to
  Bousquet and Smull 2003).
• Simulate case with WRF model (improved numerics
  and physics) with Thompson-microphysics.
• Examine additional cases that have been seen to
  possess similar kinematic structures e.g.,
  November 29th-30th and possibly MAP-IOP8 case.
• Utilize the in situ microphysical observations to
  document and quantify the effect of smaller scale
  (gt20 km) waves on the snow and CLW fields.

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MM5-Accumulated Precipitation
1.33-km Precip
E
W
27
MM5-Accumulated Precipitation
1.33-km Precip
1.33-km Smooth Precip
E
W
28
MM5-Accumulated Precipitation
1.33-km Precip
1.33-km Smooth Precip
Increase in accumulated precipitation by
6-15 over windward slopes
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Observed E-W Cross-Section
Wind Speed
W-DIR
30
Height (m)
SLE
N
Coast
Willamette Valley
Latitude (Deg)
E
S
Longitude (Deg)
W
31
Height (m)
SLE
N
Coast
Willamette Valley
Latitude (Deg)
E
S
Longitude (Deg)
W
32
(No Transcript)
33
Average QPF E-W
E
W
34
Thanks to Dave Ovens, Stacy Brodzik, Socorro
Medina, Amy Haase, Dale Durran, Lucas Harris,
Brian Colle, John Locatelli and others.
THE END