WRF model exercise

Experimental Boundary layer meteorology

Björn Claremar 2012

Outline

• Why use models?• The WRF model

– Physics schemes• The computer lab

Use of models

• Observations are not always sufficient to find out meteorology between observational stations.

• Meteorological re-analysis data are good to fill in gaps between observations (e.g. NCEP, ERA-40, ERA-Interim)– Numerical weather model makes sub-sequent short-range forecast

with observations (at ground and in free atmosphere) as initial and boundary forcing

– too coarse resolution (>80 km) to catch the influences on weather from the complex topography.

Regional modelling gives more detail

Simulated precipitation GCM 300 km GCM interp. to 50 km RCM 50 km

RCA3 with higher resolution

Precipitation (DJF, 1987-2007) as a function of resolution

EXAMPLE OF DYNAMICAL DOWNSCALING

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• Gridded dataset, partly based on: – Direct meteorological

observations and satellite measurements

– Prognostic atmospheric model– Assimilation of observations to

physical consistent fields.– Precipitation fully prognostic

• Data available from 1990 and onwards.

Downscaling processERA-Interim re-analysis

Land share

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0.8

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• Developed at National Center for Atmospheric Research (NCAR)• Equations: Fully compressible, Euler non-hydrostatic, conservative for

scalar variables.• Vertical Coordinate: Terrain-following. • Physics schemes: interchangeable

• This study– Running WRF3 with ERA-Interim at the

boundaries (3-D fields and near surface parameters) and below (SST/ice/snow) to 8 and 2.7 km grid and 27 vertical levels.

Downscaling processWRF3 model

Advanced Research WRFERA-Interim

(6 h)

WRFTerrestrial data

30’’

Preprocessing and initialization 200 m contour lines

2.7 km

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100

150

200

250

300

350

400

• Precipitation becomes more influenced by the terrain and increases more than 100% locally.

• Precipitation is much larger in WRF compared to ERA-Interim (too much? Better with polar physics?)

Preliminary results (standard WRF)- precipitation

ERA-Interim WRFMean yearly precipitation 2000-2008 (mm)

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• Geostrophic wind (not influenced by surface friction)– Finer details

• 10-m– Finer details– Increase of wind at

mountain tops and as channeling and corner effects (note southern tip)

– Decrease of wind in lee areas

Results – wind case

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5

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15

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25

10 m (m/s)

ERA-Interim WRF

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Geostrophic (m/s) 10

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1525

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76 76

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81

1100 m (m/s)

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16

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412

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414

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1410

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12 10

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84

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76 76

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79

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81

10 m (m/s)

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3.5

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4.5

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5.5

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18

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24 26

28

79

79.5

80

80.5

10-m wind speed 2003-2008

B

D

A

• 10 m-wind– Lee in valleys and maxima over

the ice sheet– Distinct katabatic winds and

channeling

Nordaustlandet

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13

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Wind direction

What is WRF• http://wrf-model.org/index.php

• The Weather Research and Forecasting (WRF) is developed at National Center for Atmospheric Research (NCAR)

• Designed to serve both operational forecasting (NMM) and atmospheric research needs (ARW).

• Physics and dynamics schemes are interchangeable• Features multiple dynamical cores, a 3-dimensional variational

(3DVAR) data assimilation system, and a software architecture allowing for computational parallelism and system extensibility. (Not used here)

• WRF is currently in operational use at NCEP, AFWA and other centers

Dynamical equations• fully compressible• Non-hydrostatic (with a runtime hydrostatic option). • vertical coordinate is a terrain-following hydrostatic pressure

coordinate. grid-spacing can vary with height • Grid staggering is the Arakawa C-grid.

– u components at the centers of the left and right grid faces, and the v components at the centers of the upper and lower grid faces

• Runge-Kutta 2nd and 3rd order time integration schemes, and 2nd to 6th order advection schemes in both horizontal and vertical.

• time-split small step for acoustic and gravity-wave modes. The dynamics conserves scalar variables.

• 1- or 2-way nesting available • Moving nests (prescribed moves and vortex tracking)• nudging

ARAKAWA grids

Application fields

• suitable for a broad spectrum of applications across scales ranging from meters to thousands of kilometers. Idealized simulations (e.g. LES, convection, baroclinic waves) – Parameterization research – Data assimilation research – Forecast research– Real-time NWP– Hurricane research– Regional climate research (dynamical downscaling)

• of re-analysis fields or atmosphere-ocean coupled general circulation models (AOGCMs)

– Coupled-model applications– Teaching

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Descriptions and references at http://www.mmm.ucar.edu/wrf/users/docs/user_guide_V3/users_guide_chap5.htm#Phys

• Long wave radiation physics• Short wave radiation physics• Cumulus physics (small scale convective clouds) (important only over

sea in the Arctic)• Land-surface model

We concentrate on:• Cloud physics (microphysics): simulates cloud and precipitation

processes• Boundary layer physics• Surface layer physics

7 different physics types

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Present land surface model (LSM) in WRF

4 soil layers (10, 30, 60, 100 cm)

Runoff and infiltration

Soil layers can turn into snow layers

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Polar WRF

• The key modifications for Polar WRF are in the land surface model (LSM) Noah : – Optimal surface energy balance and heat transfer

over sea ice and permanent ice surfaces – Implementation of a variable sea ice thickness and

snow thickness over sea ice– Implementation of seasonally-varing sea ice albedo

• Also specific physics suitable for Arctic conditions (in dark blur in following slides)

Microphysics (mp_physics)• X-class: number of different “particles”• Single-moment: Particle mixing ratio• Double-moment: Particle mixing ratio + particel number concentration

Some examplesSingle moment• c. WRF Single-Moment 3-class scheme: A simple, efficient scheme with ice and snow processes suitable for

mesoscale grid sizes (3).• d. WRF Single-Moment 5-class scheme: A slightly more sophisticated version of (c) that allows for mixed-

phase processes and super-cooled water (4).• e. Eta microphysics: The operational microphysics in NCEP models. A simple efficient scheme with diagnostic

mixed-phase processes. For fine resolutions (< 5km) use option (5) and for coarse resolutions use option (95).• f. WRF Single-Moment 6-class scheme: A scheme with ice, snow and graupel processes suitable for high-

resolution simulations (6).

Double-moment• h. New Thompson et al. scheme: A new scheme with ice, snow and graupel processes suitable for high-

resolution simulations (8). This adds rain number concentration and updates the scheme from the one in Version 3.0. New in Version 3.1.

• j. Morrison double-moment scheme (10). Double-moment ice, snow, rain and graupel for cloud-resolving simulations. New in Version 3.0.

• k. WRF Double-Moment 5-class scheme (14). This scheme has double-moment rain. Cloud and CCN for warm processes, but is otherwise like WSM5. New in Version 3.1.

• l. WRF Double-Moment 6-class scheme (16). This scheme has double-moment rain. Cloud and CCN for warm processes, but is otherwise like WSM6. New in Version 3.1.

Surface Layer (sf_sfclay_physics)Scheme must be working with PBL physics• a. MM5 similarity: Based on Monin-Obukhov

– with Carslon-Boland viscous sub-layer – standard similarity functions from look-up tables (sf_sfclay_physics =

1).

• b. Eta similarity: Used in Eta model. Based on Monin-Obukhov– with Zilitinkevich thermal roughness length– standard similarity functions from look-up tables (2).

• d. QNSE surface layer. Quasi-Normal Scale Elimination PBL scheme’s surface layer option (4). – new theory for stably stratified regions

• e. MYNN surface layer. Nakanishi and Niino PBL’s surface layer scheme (5). • Includes better interaction of the turbulence with microphysics and radiation in the PBL,

compared to the MYJ2.5 scheme

PBL turbulence closure• First order closure (K-theory): 2nd order moments are parameterized

• 1.5 order closure– TKE and potential temperature variance budgets– KM = f(TKE, q’ variance)

• Higher order closures– Only higher order moments are parameterized– Example: 2nd order closure uses budgets for 2nd order moments and

parameterizes 3rd order moments, dissipation terms and pressure gradient correlations

z

ew

z

wpw

T

g

z

uwu

x

eu

t

e

oo

)()(1

' ' , ' '

, , in surface layer

, , is height of boundary layer

M H

M Hm h

M

Uu w K w K

z zu kz u kz

K K

K f z h h

4. Planetary Boundary layer (bl_pbl_physics)• a. Yonsei University scheme: Non-local-K scheme with explicit

entrainment layer and parabolic K profile in unstable mixed layer (bl_pbl_physics = 1).

• b. Mellor-Yamada-Janjic scheme (MYJ2.5): Eta operational scheme. One-dimensional prognostic turbulent kinetic energy scheme with local vertical mixing (2).

• e. Quasi-Normal Scale Elimination PBL (4). A TKE-prediction option that uses a new theory for stably stratified regions. Daytime part uses eddy diffusivity mass-flux method with shallow convection (mfshconv = 1) which is added in Version 3.4.

• f. Mellor-Yamada Nakanishi and Niino (MYNN) Level 2.5 PBL (5).– Predicts sub-grid TKE terms. – Includes better interaction of the turbulence with microphysics and radiation in

the PBL, compared to the MYJ2.5 scheme

QNSE scheme for PBL/surface layer(Quasi-Normal Scale Elimination)

• k-e model• uses a new theory for stably stratified regions.

accounts for anisotropic turbulence and gravity waves and is not based on the shortcomings of Reynolds stress models in very stable stratifications.

Computer lab

Model Microphysics Turbulence/surface layer

Vertical resolution

Eva Polar WRF Morrison MYJ 28

Jakob Polar WRF WRF3 MYJ 28

Christian Polar WRF Morrison QNSE 28

Adam Polar WRF Morrison MYJ 32

Jenny Standard WRF Morrison MYJ 28

• Run WRF model during 36 h with different physical parameterizations and vertical resolution.

• You are also welcome to extend the test if you have time!

• Look at:• time evolution of temperature at

Nordenskiöldbreen in comparison to measurements.

• time evolution of wind speed at Nordenskiöldbreen in comparison to measurements.

• time evolution of temperature profile• time evolution of wind profile

Running WRF

• You will use the KALKYL computer cluster at UPPMAX

• The environment is scientific Linux and you will reach the system via the program Putty and WinSCP

• In Putty you can run the programs• WinSCP is better to use when downloading

data and changing in text files.• You will do your analyses in MATLAB (or excel).

UPPMAX• Uppsala Multidisciplinary Center for Advanced Computational

Science (UPPMAX) is Uppsala University's resource of high-performance computers, large-scale storage, and know-how of high-performance computing (HPC). The center is a member of the national metacenter Swedish National Infrastructure for Computing (SNIC).

• UPPMAX was founded in 2003, but builds on a much longer successful history of HPC activities at Uppsala University.

• UPPMAX is hosted by the Department of Information Technology, Faculty of Science and Technology at Uppsala University and is one of the six centra in the national metacenter Swedish National Infrastructure for Computing (SNIC).

• UPPMAX is part of the SweGrid national grid.• UPPMAX is funded by the Faculty and by SNIC.

The KALKYL cluster•

Technical Summary• 348 Compute Nodes with 2784 CPU cores• 9504 Gigabyte total RAM• 113 Terabyte total disk• interconnected with a 4:1 oversubscribed DDR Infiniband fabric• 696 CPU's in 348 dual CPU, quad core, nodes• HP SL170h G6 compute servers• Quad-core Intel® Xeon 5520 (Nehalem 2.26 GHz, 8MB cache)

processors– 316 nodes with 24 GB memory and 250 GB hard disk– 16 nodes with 48 GB memory and 250 GB hard disk– 16 nodes with 72 GB memory and 2 TB hard disk

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• This study– Running WRF with ERA-Interim at the

boundaries (3-D fields and near surface parameters) and below (SST/ice/snow) to 24 and 8 km grid and 27 vertical levels.

Downscaling processWRF3 model

Advanced Research WRFERA-Interim

(6 h)

WRFTerrestrial data

30’’

Preprocessing and initialization 200 m contour lines

2.7 km

Done!

Namelist• &time_control• run_days = 0,• run_hours = 1,• run_minutes = 0,• run_seconds = 0,• start_year = 0001,• start_month = 01,• start_day = 01,• start_hour = 00,• start_minute = 00,• start_second = 00,• end_year = 0001,• end_month = 01,• end_day = 01,• end_hour = 01,• end_minute = 00,• end_second = 00,• history_interval = 10,

Namelist• &domains• time_step = 3,• time_step_fract_num = 0,• time_step_fract_den = 1,• max_dom = 1,• s_we = 1,• e_we = 202,• s_sn = 1,• e_sn = 3,• s_vert = 1,• e_vert = 81,• dx = 250,• dy = 250,• p_top_requested = 5000,• eta_levels = 1.000, 0.997, 0.993, 0.988, 0.982,• 0.975, 0.965, 0.952, 0.937, 0.917,• 0.891, 0.860, 0.817, 0.766, 0.707,• 0.644, 0.576, 0.507, 0.444, 0.380,• 0.324, 0.273, 0.228, 0.188, 0.152,• 0.121, 0.093, 0.069, 0.048, 0.029,• 0.014, 0.000,

Namelist• &physics• mp_physics = 2,• ra_lw_physics = 0,• ra_sw_physics = 0,• radt = 0,• sf_sfclay_physics = 0,• sf_surface_physics = 0,• bl_pbl_physics = 0,• bldt = 0,• cu_physics = 0,• cudt = 0,• isfflx = 0,• ifsnow = 0,• icloud = 0,• num_soil_layers = 5,• mp_zero_out = 0,