LAKE EFFECT SNOW

SIMULATIONJohn D McMillen

John D McMillen

LAKE BONNEVILLE

EFFECT SNOW

27 Oct 2010 Event Trevor Alcott

found that the simulation and by extension, the GSLE are sensitive to the terrain around the lake Downstream

terrain is a strong positive impact on production of SWE

GSLE SIMULATION

I have replicated Trevor’s control and run several microphysics schemes This case is also sensitive to microphysics parameterization The most sophisticated schemes overproduce SWE

GSLE SIMULATION

This study views the additional moisture source of Lake Bonneville as a possible sensitivity

The results are compared with existing studies of the climate of the Pleistocene over Lake Bonneville

LAKE BONNEVILLE SIMULATION

Terrain raised to ~1550m Freshwater Lake Temp

286.5 K

Land Use Index, Land Use Fraction, and Landmask reset

BUILDING THE LAKE

WRF ARW 24 hour run from 18 UTC 26 Oct 2010 to 18 UTC 27 Oct 2010

Triple nested 12, 4, 1.33 km grid spacing Lake Bonneville added in domains two and three

Physics YSU PBL NOAH LSM RRTM LW radiation and RRTMG SW radiation Simple Diffusion Kain-Fritsch Cumulus for 12, 4 km domains. No Cumulus for 1.33km domain

Microphysics Thompson

WRF DETAILS

Total Accumulated Precipitation 0230-1700 UTC 27 Oct

RESULTS

3 UTC simulated reflectivity z=2.5 km, lowest model level wind

RESULTS

5 UTC simulated reflectivity z=2.5 km, lowest model level wind

RESULTS

7 UTC simulated reflectivity z=2.5 km, lowest model level wind

RESULTS

9 UTC simulated reflectivity z=2.5 km, lowest model level wind

RESULTS

11 UTC simulated reflectivity z=2.5 km, lowest model level wind

RESULTS

PALEOCLIMATE

Jewell 2010Lake circulation

model and stream incision indicate

surface westerlies

Jewell 2007, Schofield et al

2004Lake spits indicate strongest surface winds were from

the north-northwest unlike

modern southwesterly

Bromwich et al 2004

Polar MM5 month-long simulations indicate <5 m/s

surface easterlies in Jan; surface

westerlies in Jul

Laabs et al 2006, Refsnider 2008,

Monroe et al 2006Glacier signatures in Wasatch and Uintahs

indicate a west to east decline in precip requires

westerlies

Laabs et al 2009, Glaciers in northeast

Uintahs retreat earlier than in

southwest Uintahs indicating

shadowing by the range and southwest

flow

WESTERLIES AND GLACIERS

WESTERLIES AND GLACIERS

WESTERLIES AND GLACIERS

WESTERLIES AND GLACIERS

WESTERLIES AND GLACIERS

This event is sensitive to the addition of Lake Bonneville Total accumulated precipitation increases in maximum

amount and areal coverage The elevated low friction lake surface intensifies a

mesoscale vortex on the baroclinic trough Precipitation increases due to this feature Possibly decreases precip to the northeast of the lake

Paleoclimate assumptions based on Geographical proxies are highly variable The hypothesis of glaciation in the Uintah Mountains

declining eastward due to less influence of Lake Bonneville has merit based on this case and the modeling work by Hostetler and Giorgi 1992, Hostetler et al 1994

CONCLUSIONS