Downslope winds along the wasatch front
Download
1 / 42

Downslope Winds Along the Wasatch Front - PowerPoint PPT Presentation


  • 86 Views
  • Uploaded on

Downslope Winds Along the Wasatch Front. Lacey Holland. Outline. Objectives A Climatology of Downslope Events at Hill AFB (HIF) Synoptic Overview of 7 Oct 2000 Mesoscale Overview Valley flows Tethersonde and lidar data ADAS analyses. Objectives.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Downslope Winds Along the Wasatch Front' - nathan-mueller


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Outline
Outline

  • Objectives

  • A Climatology of Downslope Events at Hill AFB (HIF)

  • Synoptic Overview of 7 Oct 2000

  • Mesoscale Overview

  • Valley flows

  • Tethersonde and lidar data

  • ADAS analyses


Objectives
Objectives

  • To what extent are strong winds on the east benches due to “canyon winds”?

  • To what extent are the strong winds on the east benches due to cold air flowing down and across the slope (i.e. bora winds)?

  • Why are the strongest winds confined to near the base of the Wasatch?

  • Why do the windstorms occur further away from the base of the mountains so infrequently?



Conditions favorable for downslope windstorms along the wasatch front
Conditions favorable for downslope windstorms along the Wasatch Front

  • Strong cross-barrier flow at crest-level (700 mb closed low to SSW)

  • Pool of cold air to the ENE (relatively high pressure over Wyoming)

  • Wind reversal above crest-level (presence of a critical level) and elevated stable layer



A composite of downslope wind events at hif
A Composite of Downslope Wind Events at HIF Wasatch Front

  • Most stations in valley of limited use

    • Records too short

    • Not in proximity of affected areas

  • Top 0.5% events used to create composite

  • NCEP Reanalysis


Top 10 downslope windstorms at hif 1949 1999

4 Apr 1983 (46 m/s) Wasatch Front

16 May 1952 (42 m/s)

20 Feb 1971 (38 m/s)

22 Oct 1953 (38 m/s)

18 Mar 1961 (37 m/s)

3 June 1949 (35 m/s)

11 Nov 1978 (35 m/s)

6 May 1949 (34 m/s)

16 Nov 1964 (34 m/s)

26 Jan 1957 (33 m/s)

Top 10 Downslope Windstorms at HIF (1949-1999)




Vertical transport and mixing experiment vtmx iop 2 6 7 october 2000
Vertical Transport and Mixing eXperiment (VTMX) IOP#2, Wasatch Front6-7 October 2000

  • IOP#2: 2200 UTC 6 Oct – 1600 UTC 7 Oct

  • Tethered balloon at Mt. Olivet Cemetery lost from its tether in strong winds

  • URBAN2000 scientists report tracers stagnating downtown


Synoptic overview
Synoptic Overview Wasatch Front

RUC2 500 mb heights

RUC2 700 mb heights


Mesoscale overview
Mesoscale Overview Wasatch Front

2300 UTC 6 October 2000


Chronology
Chronology Wasatch Front

  • Prior to 0700 UTC: Developing Stage

    • progression of cold air across Wyoming

    • drainage circulations in Salt Lake Valley (SLV)

  • 0700 -1000 UTC: Initial development

    • Initial penetration of cold air across Wasatch

    • Gap flows through Parley’s Canyon

    • Lidar

  • After 1000 UTC- Downslope wind event into SLV


Conceptual model of 7 oct 2000 0400 utc
Conceptual model of 7 Oct 2000 (0400 UTC) Wasatch Front

VTMX9

ACS

SLC


Cross section across wyoming
Cross-section Across Wyoming Wasatch Front

RWL

RKS

EVW


Surface plot
Surface plot Wasatch Front


Salt lake valley flows

WBB Wasatch Front

U42

Salt Lake Valley Flows

VTMX9

VTMX6

UT5

VPN10


Asu tethersondes
ASU Tethersondes Wasatch Front

  • Located at Mt. Olivet Cemetery

  • 3 sondes on one balloon

  • Each sonde separated by 50 m

  • Highest sonde 10 m below balloon


Sonde 2
Sonde #2 Wasatch Front


Tethersondes at 0400 utc
Tethersondes at 0400 UTC Wasatch Front

__ = WF

__ = T2

__ = T3

__ = T4


Noaa etl lidar
NOAA ETL Lidar Wasatch Front

  • Located at U42 (SLC Airport #2)

  • Traverse Excitation Atmospheric pressure CO2 (TEACO2) lidar

  • 10.6 mm wavelength

  • Detection range: 1-30 km

  • Radial velocity accuracy: 0.3-1 ms-1


Lidar
lidar Wasatch Front


Description of adas analyses
Description of ADAS Analyses Wasatch Front

  • Rawinsonde (PNL,NCAR,NWS), tethersonde (ASU), and surface station (PNL, Mesowest) data ingested into analyses

  • 1 km resolution

  • Adjustment made to analysis for dense data

  • Further adjustments to be made


Adas evening
Adas evening Wasatch Front


Conceptual model at 0700 utc
Conceptual Model at 0700 UTC Wasatch Front

VTMX9

ACS

SLC


Downslope winds along the wasatch front
sfc Wasatch Front


Tethersondes at 0530 utc
Tethersondes at 0530 UTC Wasatch Front

__ = WF

__ = T2

__ = T3

__ = T4


Conceptual model at 0830 utc
Conceptual Model at 0830 UTC Wasatch Front

VTMX9

ACS

SLC



Tethersondes at 1000 utc
Tethersondes at 1000 UTC Wasatch Front

__ = WF

__ = T2

__ = T3

__ = T4


Conceptual model at 1030 utc
Conceptual Model at 1030 UTC Wasatch Front

VTMX9

ACS

SLC


Lidar observations

Lidar graphics courtesy of Lisa Darby, NOAA ETL Wasatch Front

Lidar Observations


Adas analyses
ADAS Analyses Wasatch Front


Summary
Summary Wasatch Front

  • To what extent are strong winds on the east benches due to “canyon winds”?

    • Lidar indicates jet out of canyon (gap flow) but spatial extent is larger than simply the canyon opening ; Direction of flow out of the canyon determined by larger-scale flow

  • To what extent are the strong winds on the east benches due to cold air flowing down and across the slope (i.e. bora winds)?

    • 7 Oct 2000 (and other times) are primarily bora events; radiational inversions can erode and warm the surface, however.


Summary con t
Summary (con’t) Wasatch Front

  • Why do the windstorms occur further away from the base of the mtns so infrequently?

    • East benches can stop mechanical penetration of cold air into surface inversion in the valley

    • Radiatively cooled air in the valley is often cooler than air crossing the barrier

  • Why are the strongest winds confined to near the base of the Wasatch?

    • Need a mechanism to penetrate or to erode the surface inversion


Acknowledgments
Acknowledgments Wasatch Front

  • John Horel

  • My committee (S. Lazarus, E. Zipser)

  • Those who have contributed data (Sradik - ASU, Coulter - PNL, Darby - ETL)

  • Many unnamed others who have provided support, help, and motivation

THANKS!