28 Jan

1815 UTC 2135 UTC

Clear patches due to canyon drainage/Exchange from Utah Valley?

PCAPS IOP9 26-31 January 2011

Interesting Science Questions in IOP9

• Cadillac PCAPS observations (everything working!! Lots of sondes!!)

• Synoptic flow relatively weak 27-28 Jan.• Role of lake/ lake breezes• Role of clouds (large differences N to S)• Role of ‘clear’ Utah Valley• Role of increasing channeled southerly flow• Role of canyon slope flows (number of sondes on

slopes/canyons)• Role of surface variations (variable snow cover)

WRF Model Initial Set-up• Test ‘standard’ NWP setup• Following Alcott and Steenburgh (2012) and Lu and Zhong

(2012) • Computationally inexpensive—entire IOP9 period (~120 hrs)

runs on 100 parallel computers in ~20 hours• 3 nested grids (12 km, 4 km, 1.33 km), 72 vertical levels• Currently testing various combinations of microphysics, PBL,

radiation, etc… (including NEW Jimenez surface layer for stable conditions in WRF V3.4.1 release)

• This is what we will be showing output from today (LES pending)

WRF 12 km/ 4 km/ 1.33 km Domains

WRF Model Real-Case LES Set-up

• Following general approach of Talbot et al. 2012: Nested mesoscale-large eddy simulations with WRF: performance in real test cases J Hydrometeorology early online release

Computationally expensitve-- on 100 parallel computers 1 hour of simulation time takes 24 hours!!

• 3 nested grids (5 km, 1 km, 200 m), 72 vertical levels

• No output to show yet—still testing--will be forthcoming in next few weeks

WRF LES Domain 5 km/ 1 km/ 200 m domains

200m

1000m

5000m

PLOTS IN THIS PRESENTATION OF COARSE DOMAIN MODEL FIELDS (LES to FOLLOW)

• LES has been ‘blowing up’, need to make smaller time step which further increases computation time

IOP9: Development of surface inversion (lowest model level temp and winds plotted)

6 hr 0600 UTC 26 Jan 30 hr 1200 UTC 27 Jan—cooler airForming around lake basin

54 hr 0600 UTC 28 Jan—cooler airForming around lake basin

78 hr 0600 UTC 28 Jan—warming aloft increases temp difference. Utah valley too warm

102-108 hr 0600-1200 UTC 30 Jan—premature mix out

Vertical Cross-Sections

North

East

South

Center_EW

Will show

Center_NS

Vertical Cross-Sections

Will show

Center_NS

48 hr 0000 UTC 28 Jan Large horizontal temp differences and ‘lake surge’ relatively well-captured

3 hr later 0300 UTC 28 Jan cool lake surge has now filled valley as shown in observations…

Traverseridge

63 hr 1500 UTC 28 Jan Southerly channeled/drainage flow is bit too strong in model.

Hr 69 2100 UTC 28 Jan lake breeze with onshore low-level flow and channeled southerly/elevated drainage jet ~800 mb

Vertical Cross-Sections

Center_EW

18 UTC 28 Jan Weak slope flows21 UTC Lake breeze penetration on west side starts easterly cross-valley flow

00 UTC Interesting how lake breeze is on ‘west slope!’

06 UTC light cross-valley winds and homogeneous T

0900 UTC very weak slope flows

Black = westerly wind White = easterly

East

Outflow from parley’s and millCreek 1-2 m/s night til noon day… no Other canyon flow resolved at 1.33 km

Low RH

High RH

Modulating Cloud Cover

Utah Valley

Salt Lake Valley

WRF MODEL vs OBS (Temperature 27 Jan) at ISFS 1, 4, and 7 (wrf under-predicts surface temp swings ISFS7 and over-predicts near

lake

WRF MODEL vs OBS (Wind Speed 27 Jan) at ISFS 1, 4, and 7. For this period model underestimates wind speeds both from Utah

Valley and lake breeze on late 27th