Update on the Northwest
Regional Modeling System
Cliff Mass, Dave Ovens, Jeff Baars, Mark Albright,
Phil Regulski, Dave Carey
University of Washington
The
current
model
domains
36-124/1.33
km
Major Changes and Improvements
• Beginning with the December 31, 2009 0000
UTC run, the WRF-GFS, our flagship system, has
switched to the latest version of WRF (3.1.1.)
– Bug fixes in several of parameterizations we use.
– Better microphysics (should get start of light rain
better).
– More boundary layer options (a major problem)
– More stable.
– But as we will see, the new system has created some
problems too.
Added an Operational Ultra High Resolution
1.33 km Nest to Our Current 36 km/12 km/4 km
system
• Western WA only
• Once a day (0000 UTC
cycle) to 36 h
• Attempt to answer
questions:
• What is the payoff in
getting the land-water
boundaries and smaller
scale terrain much
better (4-km hardly has
Puget Sound!)
• Does ultra high
resolution improve
objective verification or
subjective structures?
4 km
1.3
1.3
Land Use
4 km
Precip Verification
Wind Direction
Future Evaluation
• Beginning intensive objective
verification
• Improving boundary layer schemes,
surface drag, and surface physics may
preferentially help 1.3 km (more later)
The Greenest Computer Facility in
the U.S.?
• We have roughly 150 processors for the high
resolution and ensemble runs
• Approximately, 200 Terabytes of storage.
• Needs very little air conditioning and we had
no trouble getting through the 103F heat last
summer.
• Why?
Suck in Cool Outside Air!
Blow the
hot air out!
Why AC
when you
can dump
it?
Three big
fans on
each
enclosure!
But is it better?
Nighttime Temps are Fine
The new system is too cold during
the day on average.
But why?
Problem over the Interior.
The Problem: Where There is Snow
on the Ground and High Elevation
The Problem Is Probably in the
Land Surface Model
Model Wack a Mole!
Wind Direction Errors: Stable and
Generally Better than NWS 12-km
NAM
Wind Speed is Another Issue: UW WRF too
strong, NWS NAM too Weak
A Major Problem Has Been Surface
Winds Over Land
• Winds too strong over land
• Winds too geostrophic over land
• Winds over land and water too similar
Fixing the Problem
• No magic bullet in testing various planetary
boundary layer (PBL) schemes
• Recently, we tried two approaches that are
very promising:
• Increasing the friction veloc (ustar) in the PBL.
Essentially adds low-level drag.
• Decreasing vertical diffusion in the model (less
vertical mixing of high momentum air down to the
surface).
Changing Surface Drag
Standard
Low Diffusion
The Fix
• We are testing these new approaches singly
and together.
• Verification statistics show we can reduce the
wind bias without harming other parameters.
• Next month we should put the fix into place
and expect a radical improvement in the wind
bias.
Testing the Fixes: Ustar *1.5
3 weeks of statistics
A Lot More To Talk About But no
Time
• A high resolution local data assimilation
system (EnKF) is being tested and developed.
• Very high quality local analyses and very good
short-term forecasts should be available this
year.
• We are testing this system for use with the
new coastal radar: may see much better local
short-term forecasts if this works.
The End