Orographic Precipitation in Potentially Unstable Alpine Storms:

1
Orographic Precipitation in Potentially Unstable
Alpine Storms MAP IOPs 2b, 3, and 5 Socorro
Medina and Robert A. Houze
2
Lago Maggiore region
3
IOP2b
4
Equivalent Potential Temperature
IOP2b
12Z 20 Sep 99
Milan sounding
5
MAP IOP2b 33-hour Mean Radial velocity

NNW
S-Pol radar
6
MAP IOP2b 33-hour Mean Reflectivity
NNW
S-Pol radar
7
MAP IOP2b Frequency of occurrence of particle
types accumulated over 33 Hours
NNW
S-Pol radar
8
MAP Conceptual Model for precipitation
enhancement inPotentially Unstable Upstream
Conditions
0ºC
ALPS
Medina and Houze 2003
9
Other potentially unstable upstream flow cases
MAP IOPs 3 and 5
10
IOP3
11
IOP5
12
Equivalent Potential Temperature
IOP3
00Z 26 Sep 99
Milan sounding
13
Equivalent Potential Temperature
IOP3
IOP5
00Z 26 Sep 99
12Z 03 Oct 99
Milan sounding
14
MAP IOP3 24-hour Mean Reflectivity
NNW
S-Pol radar
15
MAP IOP5 4-hour Mean Reflectivity
NNE
S-Pol radar
16
MAP IOP3 24-hour Mean Radial velocity
NNW
S-Pol radar
17
MAP IOP5 4-hour Mean Radial velocity
NNE
S-Pol radar
18
MAP IOP3 Frequency of occurrence of particle
types accumulated over 24 Hours
NNW
S-Pol radar
19
MAP IOP5 Frequency of occurrence of particle
types accumulated over 4 Hours
NNE
S-Pol radar
20

• CONCLUSION
• Despite differences in the upper-level flow
  direction, the lower slope precipitation
  processes were similar in 3 IOPs.
• The observations were consistent with the
  conceptual model for potentially unstable
  upstream flow.
• Convective cells formed intermittently on the
  first major peak of terrain as a radial velocity
  jet rose over it.
• Both riming and coalescence were key
  microphysical processes in the cells.

21
Mixed caseMAP IOP 14
22
Equivalent Potential Temperature
IOP14
00Z 4 Nov 99
Milan sounding
23
MAP IOP14 Mean wind shear from Lonate profiler
Mean and SD over 16 hours
24
MAP IOP14 34-hour Mean Reflectivity
NNW
S-Pol radar
25
MAP IOP14 34-hour Mean radial velocity
NNW
S-Pol radar
26
MAP IOP14 Polarimetric Particle Identification
over 34 Hours
NNW
S-Pol radar
27
MAP IOP14 Reflectivity from vertically pointing
S-band radarat Locarno Monti
Height (km)
Time UTC
OPRA radar