Transcript Global Weather Services in 2025

Advancd Regional Prediction
System (ARPS)
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Ming Xue
[email protected]
School of Meteorology
and
Center for Analysis and Prediction of Storms
University of Oklahoma
Model Dynamics, Equations and
Numerical Formualtions
See PDF file
Initial Condition
ARPS Components
Incoming
data
Lateral bo und ary co nditions
fro m larg e-scale mo dels
Gridd ed first gu ess
Mob ile Mesonet
R awinso ndes
ACAR S
C LASS
SAO
Satellite
Profilers
ASOS/AW OS
Oklahoma Mesonet
WS R-88 D Wideb and
AR PS Data Ass imilation Sys tem (A RPSDA S)
Data Acquisition
& Analysis
AR PS Data Analysis
System (ADA S)
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Ingest
Quality con trol
Objective analysis
Arch iv al
Forecast Generation
AR PS Numerical Model
– Multi-scale n on-hy drostatic predictio n
mod el with comprehen siv e phy sics
Parameter Retri eval and 4DD A
Single-Doppler Velocity
Retrieval (SDVR)
4-D
Variational
Data
As similation
Variational Velocity Adjustment
& Thermodynamic Retrieval
Product Generation and
Data Support System
AR PSPLT and AR PSVIEW
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Plots and imag es
Animations
Diag nostics an d statistics
Fo recast evaluatio n
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Ways to Initialize ARPS
• Idealized, single sounding
• Interpolation from GFS, Eta, RUC, etc
• ADAS
ARPS Data Analysis System (ADAS)
• Manages the real time ingest, QC, objective analysis of observations
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Doppler radar data (NIDS, base Level II from n systems, VAD)
MDCRS commercial aircraft wind and temperature reports
Wind profilers
RAOBS (conventional, CLASS, dropsondes)
Mobile and fixed mesonets
SAO and METAR observations
GOES satellite visible and IR data for cloud analysis
NCEP gridded model output
• Based on Bratseth successive correction method
• Handles retrieved radar data (from SDVR et al)
• Had its root in FSL LAPS. Data format is about the only one left though.
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Braseth Analysis Scheme
• ADAS use the Bratseth analysis scheme which is a
successive correction scheme
• The scheme theoretically converges to optimal interpolation
(O/I), but without explicit inversion of large matrices
• Multi-pass strategy used where more detailed data can be
introduced after a few iterations using broad-scale data.
• Like OI, the Bratseth method accounts for the relative error
between the background and each observation source, and is
relatively insensitive to large variations in data density.
• Vertical correction in terms of z or q
Formulation of Bratseth Scheme
Formulation (Continued …)
ARPS Data Analysis System (ADAS)
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User specifies background error covariances and structure functions.
Codes to calculate background error statistics being developed.
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Performed on ARPS native (terrain-following) grid
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3-D cloud analysis and diabatic initialization package using GOES,
Doppler radar and surface data.
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Water vapor, cloud, rain, ice and temperature fields are affected by the
cloud analysis
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Used to initialize realtime high-res (~kms) forecasts at CAPS since
1996
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Linked closely with ARPS data assimilation system (via, e.g.,
intermittent assimilation, incremental analysis update method)
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Incremental Analysis Update
Cycles
(from Brewster 2003)
ADAS analysis –
Total u
Background
ADAS
73x73x43 grid, dx=12km
ADAS Analysis
– Total q
Background
ADAS
Example of Initial Condition with
cloud analysis on a 3km Grid
Application to fine-scale analysis
at Kennedy Space Center (Case et al
2002 Wea. Forecasting)
Boundary Conditions
• Lateral Boundary Conditions
 Rigid, zero-gradient, periodic
 Open/radiative LBC (only applied to normal velocity)
 Externally (can be from the same model) forced
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Davies-type relaxation zone, arbitrary width
w not forced
variables (e.g., water) not found in exbc are excluded
from relaxation – zero gradient is usually applied
Ensure same terrain at nesting boundaries
 Carpenter (1982) – radiation BC with external
forcing(?)
o
Carpenter, K. M., 1982: Note on radiation conditions for the lateral
boundaries of limited-area numerical models. Quart. J. Roy. Meteor.
Soc., 108, 717-719.
Vertical Boundary Condition
• Radiation top BC based on cosine Fourier
transform (Klemp and Durran 1983)
 periodicity requirement at the top relaxed
 Still based on linearized equations – difficult to apply to
large domain
• Upper boundary sponge/absorbing layer
 relaxation to coarse grid/external model solution in the
layer
 or relaxation to the mean state
• Rigid, zero-gradient and periodic top-bottom BC
• Semi-slip lower BC
Stratiform Clouds and
Precipitation
• Microphysics parameterization for grid-scale
precipitation
• Can be used together with cumulus
parameterization schemes
• Option to allow condensation at subsatuation
(<100% RH)
 helps retaining clouds in IC for large grid spacing
 improves surface temperature forecast at low-resolution
by introducing clouds earlier
• Sedimentation term treated implicitly or using
time splitting
Model Physics
• SGS Turbulence
 Smagorinsky-Lilly, 1.5-order TKE, Germano dynamic closure
 Fully three dimensional formulation, including map factor
 Simplified 1-D option available for efficiency purpose
• Cumulus Parameterization
 Kuo scheme
 Old and New versions of Kain-Fritsch cumulus parameterizations
 Eta Betts-Miller-Jancic scheme
• Microphysics
 Kessler warm rain
 Lin-Tao ice microphysics
 Schultz NEM grid-scale microphysics
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Model Physics (continued)
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PBL scheme
 Convective PBL mixing parameterization based on 1.5-order TKE formulation (Xue et
al 1996)
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Surface Physics (fluxes)
 Stability-dependent bulk aerodynamic drag for surface heat, momentum, and moisture
fluxes
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Soil Model
 2-layer soil model (multiple soil types in 1 grid cell; API initialization)
 A new multi-layer soil model
 High-resolution surface characteristics data base (consistency among surface fields
important)
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Radiation
 Full long- and short-wave radiation (NASA code) including cloud interactions, cloud
shadowing, and terrain gradient effects
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ARPS Physical
Processes
Subgrid Scale Fluxes
(Land surface, surface layer, PBL
and SGS turbulence)
See PDF file
Radiation
Radiation Parameterization
• ARPS radiation package came from NASA GSFC.
 Shortwave is based on Chou (1990; 1992)
 Longwave based on Chou and Suarez (1994)
 Cloud-radiation interaction described in Tao et al (1996)
• Allows checkboard-type staggered calculations to save
computation
• Recently implemented terrain shading effect
• Terrain slope accounted for
• Cloud fraction diagnosed from RH and q’s
• Verifications against OK Mesonet radiation measurements
show good agreement, in clear sky conditions at least
Shortwave Radiation
• Solar spectrum is divided into the ultraviolet and visible
region (<0.69mm), and the near-infrared (IR) region
(>0.69mm),
• UV and visible region includes ozone absorption, Rayleigh
and cloud scattering. It is further divided into 4 bands, with
effective ozone absorption and scattering coefficients given
to each band
• The IR region includes absorption due to water vapor,
cloud, CO2, O3 and scattering due to clouds.
 Further division into 7 water vapor absorption bands, with kdistribution method used to calculate the absorption.
 Liou et al (1988) 4-stream discrete ordinate scattering algorithm
used for multiscattering in cloud layer
 Single scattering albedo from King et al (1990)
Longwave Radiation
• IR spectrum divided into 8 bands
• Water vapor transmission function computed used kdistribution method
• CO2 and O3 transmission functions computed using lookup
tables
• Includes aerosol effects
• Absorption due to cloud hydrometeors also included.
Clouds assumed to be gray and nonscattering
• Cloud optical properties
 Scheme 1: Broadband emissivity method of Stevens (1978, 1984)
 Scheme 2 follows Fu and Liou (1993), Sui et al (1996)
Radiation Fluxes Verification
Microphysics Schemes
• Kessler warm rain microphysics (qc and qr)
• Lin et al (1983) ice microphysics
 includes rain, cloud water, cloud ice, snow,
graupel/hail,
 lookup tables for power and exponential functions
 ice-water saturation adjustment procedure of Tao et al
(1989)
 modifications to hydrometeo fall speeds (Ferrier 1994
and updated coefficients)
• Shultz (1995) simplified ice scheme (also include
3 ice categories)
ARPS Ice
Microphysics
Processes
~ 30 processes
Accumulated
Precipitation
from 1977 Del
City Supercell
Storms with
warmrain and
ice
microphysics
Simulation of 1977 Del City
Supercell Storms with warmrain
and ice microphysics
Convective Parameterization
Convective Clouds and
Precipitation
• At high resolutions (=< 3km), use ‘explicit’
microphysics, hopefully the model can
resolve the convection well
• Cumulus parameterization schemes
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Kuo scheme
Old and new Kain-Fritch schemes
Betts-Miller-Janjic scheme
New K-F scheme used most
Use of Cumulus Scheme
• K-F scheme used most
• New K-F scheme using at 27 and 9km
during IHOP realtime forecast
• BMJ scheme tends to produce much
smoother precipitation field
• Cold pool important for propagation of
convective systems over the plains
• Triggering of spurious propagating
precipitation pattern observed during IHOP
CAPS Real Time Forecast
Domain during IHOP_2002
183×163
273×195
213×131
June 15, 2002, 9km Grid
NCEP Hourly Precip
9 km Forecast Precip Hourly Rate.
24 hour forecast
June 15, 2002 – 3km grid
NCEP Hourly Precip Analysis
3 km Forecast Hourly Precip Rate
11 hour forecast
00-12UTC, June 13, 2002, Hourly Precip