Transcript 070606Chambery_ICAM_Medina.ppt

Detailed Structure of Moist, Sheared,
Statically Stable Orographic Flow
MAP IOP8 - 00 UTC 21 Oct
Socorro Medina1, Robert Houze1, and Nicole Asencio2
1University
of Washington, Seattle, USA; 2Météo-France, CNRS, Toulouse, France
29th International Conference on Alpine Meteorology, Chambéry, France, 4-8 June 2007
Detailed Structure of Moist, Sheared,
Statically Stable Orographic Flow
Height (km)
MAP IOP8 - 00 UTC 21 Oct
N2 (x10-4 s-2)
Socorro Medina1, Robert Houze1, and Nicole Asencio2
1University
of Washington, Seattle, USA; 2Météo-France, CNRS, Toulouse, France
29th International Conference on Alpine Meteorology, Chambéry, France, 4-8 June 2007
OBJECTIVES
• Examine flow and shear layer at lowlevels
• Misplacement of precipitation in
numerical simulations
• The nature of observed turbulent
motions
OBJECTIVES
• Examine flow and shear layer at lowlevels
• Misplacement of precipitation in
numerical simulations
• The nature of observed turbulent
motions
Orography (km)
S-Pol radial velocity (m s-1)
for elevation angle of 3.8°
4.0 (b)
32
3.5
24
3.0
16
2.5
8
2.0
0
1.5
-8
1.0
-16
0.5
-24
-32
0.0
00 UTC 21 Oct 1999
Constant Elevation Angle Scanning
Z1 < Z2
Orography (km)
S-Pol radial velocity (m s-1)
for elevation angle of 3.8°
4.0 (b)
RANGE  ALTITUDE
32
3.5
24
3.0
16
2.5
8
2.0
0
1.5
-8
1.0
-16
0.5
-24
-32
0.0
00 UTC 21 Oct 1999
Orography (km)
S-Pol radial velocity (m s-1)
for elevation angle of 3.8°
4.0 (b)
32
3.5
24
3.0
Low-level flow
16
2.5
8
2.0
0
1.5
-8
1.0
-16
0.5
-24
-32
0.0
00 UTC 21 Oct 1999
Orography (km)
S-Pol radial velocity (m s-1)
for elevation angle of 3.8°
4.0 (b)
32
3.5
24
3.0
Mid-level flow
16
2.5
8
2.0
0
1.5
-8
1.0
-16
0.5
-24
-32
0.0
00 UTC 21 Oct 1999
Orography (km)
S-Pol radial velocity (m s-1)
for elevation angle of 3.8°
MAP IOP8 - 00 UTC 21 Oct
4.0 (b)
32
3.5
24
3.0
Upper-level flow
16
2.5
8
2.0
0
1.5
-8
1.0
-16
0.5
-24
-32
0.0
00 UTC 21 Oct 1999
S-Pol radial velocity (m s-1) for elevation angle
= 3.8° in a rectangular azimuth-range plot
32
(b)
24
16
8
0
-8
-16
-24
-32
360
00 UTC 21 Oct 1999
OBJECTIVES
• Examine flow and shear layer at lowlevels
• Misplacement of precipitation in
numerical simulations
• The nature of observed turbulent
motions
Precipitation accumulation during 21 Oct
Rain-gauge observations
Frei and Häller (2001)
Meso-NH simulation of
Asencio and Stein (2006)
 Common thread in
simulations
S-Pol mean radial velocity (m s-1)
(00-09 UTC 21 Oct)
Simulated – Asencio and Stein
Observed
-32 -24 -16 -8
0
8 16 24 32
Milan sounding at 00 UTC 21 Oct
Observed Simulated
OBS SIM
(e)
OBJECTIVES
• Examine flow and shear layer at lowlevels
• Misplacement of precipitation in
numerical simulations
• The nature of observed turbulent
motions
Conceptual model of orographic enhancement
of precipitation by turbulent small-scale cells
Houze and Medina (2005)
S-Pol time-averaged variables and std deviation
(19 UTC 20 Oct – 01 UTC 21 Oct)
Radial velocity
(every 4 m s-1
in solid contours)
Topography
(at range = 20 km)
Terrain Height (km)
STD deviation
radial velocity
(m s-1; color)
S-Pol time-averaged variables
(19 UTC 20 Oct – 01 UTC 21 Oct)
Radial velocity
(every 4 m s-1
in solid contours)
Topography
(at range = 20 km)
Terrain Height (km)
Reflectivity
(dBZ; color)
Why kind of turbulence are
we observing?
DOW Radar observations
Radial velocity (m s-1)
Shear (m s-1 km-1)
Radar observations of Kevin-Helmholtz billows
in mid-latitude precipitating system
Radial velocity (m s-1)
Shear (m s-1 km-1)
Chapman and Browning (1997)
CONCLUSIONS
• Three flows: synoptically driven upper-level flow,
barrier-scale mid-level jet, and valley-scale lowlevel jet
• In comparison between observed and simulated
precipitation: fundamental to evaluate detailed
structure of windward flow
• In obs: Shear + Terrain = Turbulent flow and
enhanced precipitation