The June 2013 Alberta Catastrophic Flooding: Water vapor transport analysis by WRF simulation

Yanping Li1, Kit Sezto2, Ron Stewart3, Julie Theriault4, Xuebin Zhang2, Bob Kochtubajda5, Sudesh Boodoo6, Ron Goodson5, Anthony Liu5

1School of Environment and Sustainability, University of Saskatchewan 2Climate Data and Analysis, Environment Canada, Toronto3Dept of Environment and Geography, University of Manitoba4Dept of Earth and Atmospheric Sciences, Université du Québec à Montréal5Environment Canada, Edmonton6Environment Canada, King City

WRF (Weather Research and Forecast) real case simulations to examine –

storm evolution and rainfall distribution during June 2013 Alberta Flooding

-> Synoptic precondition-> Water vapor sources-> the role of terrain -> the role of evaporation

Outline

WRF setup

• Initial and Boundary ConditionNCEP reanalysis with 1 degree resolution every 6 hours.

• Regional domainDomain-1, Domain-2

• ResolutionD1: 3km, D2: 27km

• PhysicsLongwave Radiation scheme (=1): RRTM (Rapid Radiative Transfer Model) scheme. Shortwave Radiation scheme (= 2): Goddard shortwave. Surface Layer (=2): Eta similarity. Planetary Boundary layer (=2): Mellor-Yamada-Janjic scheme. Cumulus Parameterization (=2 for D2, none for D1): Betts-Miller-Janjic scheme.

Microphysics (=6): WRF Single-Moment 6-class scheme. • Land Surface: Noah /CLM /RUC.

D1D2

WRF simulation vs CaPA

WRF CaPAUTC

UTC

Canadian precipitation analysis (CaPA): every 6 hrs, at 15km resolution

WRF CaPA06/19 – 06/21 06/19 – 06/21

WRF simulated total rain

Simulation vs Station Obs

With different Land Surface Model (CLM, Noah, RUC)

. Houly Precip obs

. Hourly Soil Moisture obs

Synoptic Preconditions

L L

200hPa 500hPa

L

H

700hPa 850hPa

Lateral Water Vapor flux

Water Budget

Effects of Orographic Lifting-Original - 0.5 X Mtn

q0=0.007 g/kg, U0=3~4 m/s=> =0.01

Effects of Orographic Lifting

ε

hhUq

hRain

a′

= 00ερ-Original - 0.5 X Mtn

Effects of Soil Moisture-Original -Soil Moisture +0.1

Soil Moisture ↗ => q ↗ => . =>… => Precip ↘ ？

Effects of Soil Moisture-Original -Soil Moisture +0.1

Soil Moisture ↗ => q ↗ => LH ↗ => SH ↘ => sfs pressure ↗

Effects of Soil Moisture-Original -Soil Moisture +0.1

Soil Moisture ↗ => q ↗ => LH ↗ => SH ↘ => sfs pressure ↗ => u ↘ => E Flux ↘ => Precip ↘indirect effect

Conclusions

• Rainfall structure and evolution play a critical role: large-scale dynamics, especially in settings with strong moisture convergence, determine flood properties.

• A reduction in mountain elevation decreases maximum precipitation significantly over the mountains and foothills, indicating that heavy precipitation was mainly contributed by the orographic lifting of the mountains.

• Land surface processes is a secondary factor in flooding. The major role of local evaporation is to change the buoyancy instead of providing additional moisture to the already plentiful moisture influx from the Prairies.

Next Step…

• WRF model Calibration by performing test simulations of extreme rain events like June 2013 Alberta flooding to determine the optimal model configuration (domain size and location, resolutions, nesting strategy, etc) for the western Prairies.

• The future change of the Prairies’ convective environment, i.e. the wind shear and low-level moisture under global change background, may lead to possible convective regime shift and the potential geographical redistribution of precipitation: Regional Climate Change Studies Using WRF to improve the projection of the occurrence of extreme rainfall and flooding under the future climate condition.