Consortium Meeting June 14th 2012 Cliff Mass University of Washington

Web Statistics

Hits 168… is WA School Information Processing Coop

Data (KB)

Finally…Canadians in Check

Rainshadow Verification West minus East Precipitation East: Yakima, Ellensburg and Wenatchee West: Spada Lake, Gold Bar ES, South Fork Tolt Reservoir

Observed versus WRF 1.3 km

Model Improvement The expanded 1.3 km domain is completely reliable. But it has revealed/accentuated some issues we knew where there and now should deal with it. One example: how we handle the upper portion of our domain.

Problems with our model top In the past we have had a relatively low top (100 hPA) and used the simple diffusive upper layer to attenuation reflections off the model top. 100 hPA is too low for a number of reasons and the diffusive upper layer was not effective enough. We had done some experiments before that did not suggest a huge impact on 12 and 4 km domains..that is why we had left it alone.

4km

1.3 km

700 hPa Vertical Velocity

Solution Completed an extensive series of experiments, working with Dale Durran. The Solution Move the model top to 50 hPa Switch to the WRF Rayleigh damping parameterization Move enough levels to the upper troposphere to insure 5-7 levels over a vertical wavelength of upwardly propagating waves (roughly 6 km wavelength)

Test Summary Web Page

Current

Proposed

Before After

Dealing with the stable PBL problem Would hyper-resolution help? Version 3.3 of WRF and later allows adding more levels in PBL without it going unstable Inspired by overmixing last December and January. Tried an extra 10 levels below 200 m and 1000m. Tried a few December 2011 dates and several in January 2012.

Conclusion We can do this now without issues. Hyperresolution helps a small amount in getting very shallow inversions. Keeps a bit more moisture at low levels…better low level fog No big fix and is probably not worth slowing down the system.

New Surface Drag Parameterization For over a year we have had in place a new surface drag parameterization for the 36, 12 and 4 km domains, in which zo depends on the variance of subgrid scale terrain. Substantial overall improvement in surface winds and temperature. Even our past critics at the NWS were satisfied!

But we were still not satisfied… Although we profoundly helped in stable conditions, we hurt when wind speed were strong (lots of mechanical mixing) or during the day during summer (lots of convective mixing). This made sense since local terrain or roughness features are less important when there is a large amount of mixing of higher momentum down from aloft.

Solution (or at least a partial one) Fade out the sub-grid scale drag when the vertical lapse rate is large or when vertical wind shear is large. Or just one of them. We have tried all the combinations.

Bottom Line During the winter, all the approaches are similar at low wind speeds, but current is more harmful at high winds (> 20 knots) In summer during day, new approach is better during the day at all wind speeds, but similar at night.

An Issue to Work On: Shallow Cumulus Convection We appears to underplay the development and precipitation from shallow convection. Classic: destabilization over the Cascades, which sometimes drifts over the lowlands. Problem is seen in all domains. Origin: lack of shallow convective parameterization? PBL problems? Convective parameterizations on outer domains suppressing in 1.3 km? Try Grell or other convective schemes?

Adding Requested Graphics

Trajectories: Close to Being Ready…next week

Low Level Stability Plots

Something to Look at Over the Summer

Other tasks for the next several months Evaluate new release of WRF 3.4, which has a number of potentially useful additions and fixes (we are using 3.1.1-July 2009 version), . Some examples: NOAH MP Land Surface Model: lots of enhancements including multilevel snowpack A number of fixes and enhancements to PBL schemes…need to test them again. Also new schemes in 3.2 and 3.3, many we had tested already.

EnKF Greg will talk about recent advances and UW research. Dave Ovens has taken over the real-time EnKF and stabilized it. Next steps: Improve web page (Mark Albright and Dave Ovens working on this. move research improvements (e.g., pressure assimilation) over to real time system Hourly data assimilation and adding more observation types (e.g., radar)

Testing the analog/reforecast approach

The end