effects of terrain on precipitation The wind began to blow steadily out of the west and pour the water of the distant seas on the dark heads of the hills JRR Tolkien The Lord of the Rings ID: 660653
Download Presentation The PPT/PDF document "Chapter 12.4 (Houze 2014):" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Chapter 12.4 (Houze 2014): effects of terrain on precipitationThe wind began to blow steadily out of the west and pour the water of the distant seas on the dark heads of the hills … J.R.R. Tolkien, The Lord of the Ringsintroduction to this chapter(Robert Houze’s Symons gold medal lecture, RMS, May 2015)
Also check out
this
Meted
module:
Dynamics
& Microphysics of Cool-Season Orographic Storms
, by Jim Steenburgh, U
UtahSlide2
1. mechanisms in which terrain affects precip
stratified flow
release of potential instability
elevated
sfc
heating, anabatic convergence, and convection
ocean
katabatic flow / land breeze
reduced sub-cloud evaporation
seeder-feeder
trapped lee waves
blocked flow, cold air damming
low hill
u
sually embedded in stratiform precip
sfc heating, lee convergence
stratified flow, lee plunging & hydraulicjump
capped lee convergencearound isolated mtn
convergence over lee ridge
P
recipitation primarily due the triggering of convection by orographic flow.
Precipitation mainly due to
stratiform
orographic
ascent.Slide3
orographically triggered convection:(b) potential instability release
buoyancy
vertical
displacementSlide4
convection is often embedded in broad stratiform regions
orographically
triggered convection:
(b) potential instability release
LSlide5
orographically triggered convection:(m) convergence over lee ridge
Sierra
de
Córdoba
frequency of super-deep convection (>40
dBZ
up to 10 km) as seen by TRMM radar, DJF
Andes
Deep convection initiation in areas with much CAPE & CIN is common over lee ridges,
e.g. Palmer Divide, Cheyenne Ridge, Black Hills
broad ascentSlide6
pre-existing squall line moving across a terrain barrierSlide7
stratiform orographic precip(i) blocked flow
Rotunno
and Houze (2007)
Fr > 1
Fr < 1
south
nor
th
blocked flow example
AlpsSlide8
stratiform orographic precip(i) blocked flow
terrain map showing drainage flow in Alpine valleys
deep moisture fluxSlide9
stratiform orographic precip(i) blocked flow
barrier
jet
cross-mountain flow
IMPROVE experiment (2000), Oregon CascadesSlide10
stratiform orographic precip(i) blocked flow
AndesSlide11
2. frontal systems passing over mountainsbarrier jet
into page
out
6 hours later
21Z on 9 Dec 1995Slide12
precip evolution during frontal cyclone passageprefrontal
postfrontal
LLJ
LLJSlide13
atmospheric rivers intersecting terrainSlide14Slide15
3. Tropical cyclones intersecting terrainSlide16
deep convection near TC eyeheight (km)
height (km)