Transcript Rapid Update Cycle Model

Rapid Update Cycle Model
William Sachman
and
Steven Earle
ESC452 - Spring 2006
Primary uses of RUC
► Making
short range forecasts
 Initialized with very recent data
► Monitoring
analyses
hourly conditions with hourly
 Useful when overlaid with satellite, radar
and other hourly observations
► Evaluating
models
trends of longer range
 Used to confirm other models
History
► With
the birth of an increase in automated
observations from commercial aircraft and
the newly developed wind profilers came
the means to create short term forecasts
based on the frequent observations.
► It was designed to provide accurate 0-12h
forecasts for weather sensitive users such
as the aviation community.
► Significant weather events occur in such a
short time frame, including severe
weather.
RUC Implementation
► Mesoscale
Analyses and Prediction System
(MAPS) was developed at the Forecast Systems
Laboratory (FSL) and began testing in 1988
 used only for research.
► RUC-1
was the first short range operational
forecast model, September 1994 at NCEP
 3h data assimilation cycle
 60-km resolution and 25 levels
► RUC-2 developed in April, 1998
 1h data assimilation cycle
 40-km resolution and 40 levels
► RUC-20 April 16, 2002
► RUC-13 June 28, 2005
RUC-20
Replaces RUC-2.
► 50 hybrid isentropic-sigma levels
► 20-km grid spacing
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RUC-13
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Model Changes
 13-km resolution
 Still has 50 levels
New observations in data assimilation
 METAR
 Mesonet
 Radio Acoustic Sounding System (RASS)
Improved Post-processing
 precipitation type, CAPE, visibility
1-hour version of the RUC model
RUC-13 now provides a 9 hour forecast every hour, with a 12 hour forecast every third hour
RUC-20 Mean Orography
http://www.meted.ucar.edu/nwp/pcu2/index.htm
http://www.meted.ucar.edu/nwp/pcu2/index.htm
http://maps.fsl.noaa.gov/
Soil Moisture (Top 2cm)
February 21, 3005 22z
• More detailed coastline with 13km RUC
http://maps.fsl.noaa.gov/
Horizontal Domain
Consists of a rectangular mesh (451 by 337 grid
points)
o
► Grid length measures 13.545 km at 35 N and 12.4
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km at 45 N
► Grid length decreased to 10 km at the northern
boundary
► East-West boundaries are well off the coastline
providing good coastal forecasts
► Local circulation is better resolved including
differential heating and orographic precipitation
patterns
► Very detailed output
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 Could lead to problems?
Vertical Domain
Sigma Coordinates
Isentropic (Theta) Coordinates
http://www.meted.ucar.edu/nwp/pcu2/index.htm
Surfaces are terrain following
-resolve boundary layer well
May not correctly portray weather
events on the lee side of mountains
Increases resolution in baroclinic regions
-fronts and tropopause
Incompletely depicts low level adiabatic flow
RUC-13 Vertical Resolution
Observations used to initialize RUC model
Data Type
~ Number Frequency
Rawinsonde
80
12h
Wind Profilers
30
1h
VAD Winds
110-130
1h
Aircraft (V, Temp)
1400-4500
1h
Surface METAR
1500-1700
1h
Buoy/Ship
100-150
1h
GOES Precip. Water
1500-3000
1h
GOES Cloud Winds
1000-2500
1h
GPS Precip. Water
300
1h
Mesonet
5000
1h
METAR cloud-vis-wx
1500
1h
RUC Diagnosed Variables
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Relative Humidity
Surface Temperature
Dew Point
Sea-level pressure
Precipitation
Snow accumulation
Snow depth
Precipitation type
Freezing levels
3h Pressure changes
CAPE/CIN
Lifted Index
Precipitable water
Helicity
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Soil Moisture
Tropopause pressure
Vertical Velocity
PBL depth
Gust wind speed
Cloud base height
Cloud top height
Cloud fraction
Visibility
Pressure of max Theta-E in
column
Convective cloud top height
Equilibrium level height
Strengths of the RUC model
► Initializes
every hour
► Hybrid isentropic-sigma vertical coordinates
 Eliminates problem of isentropic (theta)
surfaces intersecting the ground.
► Horizontal
Domain
 Finer definition of terrain features which leads
to better representation of topographically
induced features.
Weaknesses of the RUC model
► Hybrid
isentropic-sigma vertical coordinates
 Difficult to blend coordinates at their interfaces
► Horizontal
Domain
 Detailed (sometimes noisy) output compared to
other models.
 Resolution still insufficient to depict local details
of most topographically induced circulations
In Conclusion...
► Operational
forecast model that provides
accurate short range forecasts.
► The most recent model is the RUC-13 model,
providing a 13km resolution.
► RUC uses hybrid isentropic-sigma vertical
coordinate system.
► Combines upper air and surface data to
initialize model.
References
FSL
► NOAA
► NCEP
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