Downslope windstorms with WRF
Experiment #5 at end
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Basics
• Introduce the idealized WRF • Simula?ons are “effec?vely” 2D • Sounding provided via input file (input_sounding) – Change ver?cal profiles of poten?al temperature and horizontal winds
• Mountain shape mimics terrain across Cuyamaca Peak in San Diego county
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Set up WRF environment mkdir MOUNTAIN!cd MOUNTAIN!cp /home/c115-test/MOUNTAIN/make_all_links.csh .!cp /home/c115-test/MOUNTAIN/namelist.input .!cp /home/c115-test/MOUNTAIN/input_sounding .!!cp /home/c115-test/MOUNTAIN/control_file* .!cp /home/c115-test/MOUNTAIN/*.gs .!!!./make_all_links.csh!!
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input_sounding (open in text editor)
1022.93 291 0!10. 291. 0 -5.00E+00 0.00E+00!2500. 300. 0 -5.00E+00 0.00E+00!5000. 311. 0 -5.00E+00 0.00E+00!10000. 326. 0 -5.00E+00 0.00E+00!15000. 378. 0 -5.00E+00 0.00E+00!20000. 430. 0 -5.00E+00 0.00E+00!
Sfc. Pressure (mb) sfc. poten?al temp (K) and sfc. mixing ra?o (g/kg)
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input_sounding!
1022.93 291 0!10. 291. 0 -5.00E+00 0.00E+00!2500. 300. 0 -5.00E+00 0.00E+00!5000. 311. 0 -5.00E+00 0.00E+00!10000. 326. 0 -5.00E+00 0.00E+00!15000. 378. 0 -5.00E+00 0.00E+00!20000. 430. 0 -5.00E+00 0.00E+00!Height (m) Pot. temp. (K) vapor (g/kg) u wind (m/s) v wind (m/s)
• no moisture in this sounding • u wind is set to -‐5 m/s (easterly flow), no ver;cal shear • v wind is zero because we’re 2D with no Coriolis force
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namelist.input! &time_control! run_days = 0,! run_hours = 24,! run_minutes = 0,! run_seconds = 0,! start_year = 0001, 0001, 0001,! start_month = 01, 01, 01,! start_day = 01, 01, 01,! start_hour = 00, 00, 00,! start_minute = 00, 00, 00,! start_second = 00, 00, 00,! end_year = 0001, 0001, 0001,! end_month = 01, 01, 01,! end_day = 01, 01, 01,! end_hour = 00, 00, 00,! end_minute = 00, 00, 00,! end_second = 00, 00, 00,! history_interval = 30, 30, 30,! frames_per_outfile = 1000, 1000, 1000,!
30 min history interval
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namelist.input &domains! time_step = 12,! time_step_fract_num = 0,! time_step_fract_den = 1,! max_dom = 1,! s_we = 1, 1, 1,! e_we = 100, 43, 43,! s_sn = 1, 1, 1,! e_sn = 3, 43, 43,! s_vert = 1, 1, 1,! e_vert = 91, 91, 91,! dx = 2000, 666.6666667, 222.2222222! dy = 2000, 666.6666667, 222.2222222! ztop = 18000, 18000, 18000,!
• One domain (so extra columns irrelevant) • 100 x 3 x 91 (x by y by z) domain • 2 km horizontal resolu?on • 18 km deep
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namelist.input &physics! mp_physics = 1, 1, 1,! ra_lw_physics = 0, 0, 0,! ra_sw_physics = 0, 0, 0,! radt = 30, 30, 30,! sf_sfclay_physics = 1, 1, 1,! sf_surface_physics = 1, 1, 1,! bl_pbl_physics = 1, 1, 1,!
• “warm rain” microphysics (but no moisture) • no radia?on scheme • rudimentary surface scheme on, so there is surface fric?on and
a small surface moisture flux
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namelist.input
&dynamics! w_damping = 1,! rk_ord = 3,! diff_opt = 2,! km_opt = 2,! damp_opt = 2,!!
• subgrid turbulent mixing and ver?cal velocity damping are on
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Make control run • ulimit –s unlimited!• ./ideal.exe!– Reads in input_sounding!– Creates wrfinput_d01!
• nohup ./wrf.exe > wrf.out &!– Model configured to create one wrfout file, containing all output ?mes
– Simula'on should take 3-‐5 min on an idle machine
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While your simula?on is running…
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Sta?ons in the San Diego Gas & Electric mesonet
Cuyamaca Peak
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101 mph gust at Sill Hill (1710Z 30 Apr 2014)
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Red numbers = gusts in mph
101 mph gust at Sill Hill (1710Z 30 Apr 2014)
0
15
30
45
60
75
90
105
4-‐29-‐2014 0:00 GMT 4-‐29-‐2014 12:00 GMT 4-‐30-‐2014 0:00 GMT 4-‐30-‐2014 12:00 GMT 5-‐1-‐2014 0:00 GMT
wind speeds (m
ph)
date
SILSD winds/gusts during 29 April 2014 event
SKNT mph GUST mph
101 mph gust @1710Z
10h
90+ mph gusts recorded 32 7mes in 10 h period (of 60 total reports)
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10m winds ≥ 20 mph
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PX/ACM2
NBCSD
May 2014 – Bernardo fire
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NBCSD
Ver?cal cross-‐sec?on
WRBSD
KRNM NBCSD 17
Anima?on
WRBSD
KRNM NBCSD 18
Finished running?
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Post-‐process control run • w2g control_file.z windz05 – Note control_file.z has been changed to refer to the wrfout files created by this model run, to declare the model output as “ideal” rather than “real” and to turn the map off
– This creates a GrADS file that interpolates to higher resolu?on below 5 km height, but cuts off there
• w2g control_file wind05 – This version of the control file has lower resolu?on near surface but retains the en?re domain depth
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From wind05 GrADS file
ga-> open wind05!ga-> set display color white!ga-> set t 1!ga-> set x 1!ga-> d theta!ga-> draw xlab pot. temp. (K)!ga-> draw ylab height (km)!
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Easily manipulated in input_sounding!
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Wind flow at 0 h
ga-> set t 1!ga-> ww_color.gs!
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Plots theta (black contours) and wind speed (colored field) and topography (grey) (looks a liWle beWer in the windz05 file)
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set t 2 ww_color.gs
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set t 3 ww_color.gs
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set t 4 ww_color.gs
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set t 5 ww_color.gs
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set t 49 [final ;me] ww_color.gs
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Stepping and anima?on
ga-> step.gs u 2 49 2.5!ga-> step.gs theta 2 49 2![hit return to move on to next time]!
ga-> vert_movie.gs![wind speed thin contours,!theta thick contours,!Richardson number shaded.!If you save gif files, they are named/numbered movie_###.gif]!
!!
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U, theta and Ri at 24 h.
Why is the Richardson number so low here?
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Anima;on created using vert_movie.gs
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vert_movie.gs!
if(frame < 10)!'printim movie_00'frame'.gif gif '!else!if(frame < 100)!'printim movie_0'frame'.gif gif '!else!'printim movie_'frame'.gif gif '!endif!endif!frame=frame+1!endif!pull dummy!
Change name of movie s7ll images here
To avoid himng return between frames, comment out this line with an asterisk; i.e., * pull dummy 33
Conver?ng a series of *.gif images into a movie
!!convert -delay 30 -loop 0 movie_*.gif OUT.GIF!
Uses ImageMagick “convert” program -‐loop = 0 endless looping -‐loop = 1 just play once -‐delay ## decrease to speed up play
You can play the movie OUT.GIF in a web browser
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Hovmoller diagram
ga-> c!ga-> reset!ga-> set t 1 49!ga-> hov.gs![by default, a contour x vs. t diagram! of near-surface 10m wind speed]!
!!
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Edi?ng input_sounding to make new cases
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Cases to explore • Change the wind speed – Control run is -‐5 m/s (east to west) – What does stronger or weaker easterly flow do? – You can guess what making the wind westerly would do, right?
– What happens if you force wind shear on the ini?al wind profile?
• Change the poten?al temperature profile – Create a less stable layer aloq – Change the height of the lower, more stable layer
• Add moisture (be careful) • Feel free to edit the GrADS scripts, or make new ones
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input_sounding z theta
N = 0.011
N = 0.016
You can change the heights, too, and add levels, but I’d keep the lowest level at 10 m and highest at 20 km
Average tropospheric and stratospheric N values are 0.01 and 0.02, respec?vely.
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A possible sounding
• This sounding puts a more stable layer beneath 2.5 km and a less stable (neutral layer) between 2.5-‐5 km.
• How does this alter the downslope flow? • If the depth of the lower stable layer is changed, how
would that alter the downslope flow? • If the easterly wind speed is altered, how does that
affect the downslope flow? 40
Experiment #5 • Alter the input_sounding in some fashion and observe how it changes
the flow over the mountain rela;ve to the control run • Think about crea'ng a “parameter space” and exploring it. Example:
changing depth of lower stable layer and wind speed. • Write a report that describes your results. Include figures. Cap?on your
figures appropriately. • Due: December 19th (end of finals week). • More comments:
– Changing the surface pressure is not relevant – Keep the poten?al temperature of the surface and lowest level in sounding equal to
each other (presently both are 291 K) – What happens if you make the lower layer less stable and the upper layer more stable? – There is a small moisture source from the surface that isn’t turned off – You can add atmospheric moisture but make sure vapor mixing ra?os are realis?c. Once
moisture is added, mp_physics is relevant and may be altered as well. Since flow may become much more vigorous, time_step may have to be reduced. Using the no_mp_heating = 1 flag may help keep things under control. 41