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© Crown copyright Met Office
DICE project
Adrian Lock and Martin Best
© Crown copyright Met Office
Apologies
• For not looking at submitted data in sufficient detail until last week
• Especially to Maria whose model output from stage 1 missed stage 3 as a result
• For sending and resending stage 3a forcing
• All the other problems that I’ve now forgotten!
© Crown copyright Met Office
Outline of DICE
• These stages test:
• LSM and SCM stand-alone performance against observations (stage 1)
• What is the impact of coupling? (stage 2)
• How sensitive are different LSM and SCM to variations in forcing? (stage 3)
© Crown copyright Met Office
CASES-99 case studySteeneveld et al (2006)
• Field experiment in Kansas, USA
• Copy Steeneveld et al (2006) and run a 3 day simulation from 2pm local time on 23rd October 1999 (to 26th)
• Recall GABLS II ran for from 2pm on 22nd for 2.5 days
• Clear skies throughout
• Gives 3 nights of varying character
• intermittent turbulence
• continuous turbulence
• very stable, almost no turbulent fluxes
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CASES-99 location
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CASES-99 locationPoulos et al 2002
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CASES-99 location
Main 60m tower
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CASES-99 locationGoogle streetview
Looking north
Looking SW
“The area consisted of relatively flat homogeneous terrain (average slopes are 0.2°) with a relatively dry soil and lacks obstacles in the near surroundings.” Steeneveld et al
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CASES-99?
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CASES-99 photosJoan Cuxart
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CASES-99 photosJoan Cuxart
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CASES-99 photosPoulos et al 2002 – 60m tower
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CASES-99 photosWebsite – from 60m tower
Looking south
Looking SSW
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Stage 1a set-up
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DICE set-upAtmosphere model forcing
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Single column modelForcing for surface-obs-forced and coupled
• Based on Steeneveld et al (2006) who used:
• Time-varying geostrophic wind (uniform with height)
• Large-scale horizontal advective warming (~4K/day), for day 2 only
• Subsidence
• Relaxation to observed sondes above the BL top
© Crown copyright Met Office
How much subsidence?
• From sondes (descent of base of moist layer):
• D=5x10-6 s-1 (w=-Dz) until 26th October, as in Steeneveld et al
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Large-scale advection problems (1)
• Lack of daytime warming on first afternoon
• Suggestive of cold advection not picked up by Steeneveld et al’s mesoscale analysis using MM5
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Large-scale advection problems (2)• Wind stress and 10m wind drop simultaneously on
evening of 25th Oct, as does the “geostrophic” wind• Something other than surface drag is slowing the wind• For DICE I’ve taken it to be horizontal advection
U at 800m (Steen et al)
U average below 3km
© Crown copyright Met Office
Large-scale forcing for DICE
• So what to do about it?
• Easy enough to run SCM with relaxation to sondes
• What timescale?
• Doesn’t really allow model to develop the PBL structure it wants – gets imposed by sonde
© Crown copyright Met Office
Large-scale forcing for DICE
• Use a simple budget analysis to derive large-scale advection, eg for temperature:
advectionhsubsidenceBLrad dt
dT
dt
dT
dt
dT
dt
dT
dt
dT
.
Sonde evolution
From SCM radiative transfer scheme
Estimated from sonde evolution
From SCM with prescribed surface heat flux
Use relaxation to sondes in SCMfor this calculation
© Crown copyright Met Office
Large-scale forcing for DICE
• To reduce the signature of the Met Office PBL scheme(!):
• Integrate PBL increment over PBL depth + 250m and redistribute uniformly over that depth
• Finally use a simple 1-2-1 filter in time and space on the resulting advection increment
© Crown copyright Met Office
Large-scale forcing (5)
• Do the same for moisture:
© Crown copyright Met Office
Large-scale forcing (6)• …and momentum: Strong nocturnal jet
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Large-scale forcing summaryUsed in all atmosphere simulations (stages 1b, 2, 3b)
• Use the following large-scale forcing
• Time-varying geostrophic wind (uniform with height)
• Large-scale horizontal advective tendencies for T, q, u, v
• Subsidence for T, q
• No relaxation
• Note that radiation should be switched on in all simulations (as well as all other physics!)
© Crown copyright Met Office
Surface forcing for stage 1b (atmosphere-only simulation)
• Surface flux observations
• from Oscar Hartogensis, Wageningen U (via Gert-Jan)
• Average observations to 30 minutes and smooth (1-2-1 filter)
• Observed surface sensible and latent heat fluxes
• Observed u*
• Ideally explicitly specify surface stresses too
• Alternatively set cD1/2 = u* / V1 for observed u* and model V1
• Observed surface T and albedo
• For upward LW, SW (or use observed – did anyone?)
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Stage 1b resultsatmosphere only simulations forced by observed surface fluxes
© Crown copyright Met Office
ModelsModel Contact
scientistInstitute Stages
submittedLevels Sensitivity
testsArome Eric Bazille Meteo France All 60/70 resolution
Arpege Eric Bazille Meteo France All 60/70 resolution
ECEARTH Reinder Ronda Wageningen SCM only 91 LAI
GDPS3.0 Ayrton Zadra CMC All 79
GFDL Sergey Malyshev Princeton All 24
GISS_E2 Ann Fridlind, Andy Ackerman
GISS All 40
IFS/HTESSEL Irina Sandu, Gianpaolo Balsamo
ECMWF All 137 LAI
MESO_NH Maria Jimenez UIB All 85 Bare soil
UM/JULES Adrian Lock, Martin Best
Met Office All 70 Vegetation
WRF-NOAH Weiguo Wang NUIST All 60 Lots!
WRF Wayne Angevine NOAA ? 119 PBL scheme
CAM5, CLM4 David Lawrence NCAR 1a, 1b ?
PBCM Pierre Gentine Columbia Not yet
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NUIST sensitivity tests
Stage 1a
Stage 1b
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Model grids• Solid lines = control model
• Dotted/dashed lines = experiment
L70!
L60
Control lowest level
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Stage 1b: basic checkIs LS forcing working correctly?
Time evolution at 1500m (above PBL) No radiation
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Stage1b surface fluxes
LW up – emissivity differences?
Surface SW down differ• be nice to check TOA SW down
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Stage 1b: SCM forced by obs fluxes
• Driving with observed u* too successfully achieved
• Two models show small departures
• One model has apparent minimum u* of 0.1ms-1
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Stage 1bClouds and rain! Cirrus (9 km)
Fog
?
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Stage 1b: SCM forced by obs fluxesPBL evolution
• Some oddities
• Quite consistent features
• more gradual growth on 25th than 26th
• shallow SBL on 1st and 3rd nights
• big differences over SBL depth on middle night
© Crown copyright Met Office
Profile comparison with sondes
• Sondes available at 2am, 6am, 2pm, 10pm
= every 8 hours plus a 2am sonde
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Stage 1b: PBL evolution at 300m
SW’ly wind implies from the pond?
Warm bias develops in most models
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Stage 1bNear surface evolution
20m 55m
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Stage 1bProfiles – first night, pot. temperature
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Stage 1bProfiles – first night, moisture
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Stage 1bProfiles – first night, winds
Missing data!
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Stage 1bProfiles – first night, heat fluxes
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Stage 1bProfiles – second night, winds: LLJ?
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Stage 1bProfiles – second night, temperature
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Stage 1bProfiles – second night, heat fluxes and stress
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Stage 1bProfiles – third night, temperature
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Stage 1bProfiles – all 3 nights
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Stage 1bProfiles – final state
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Stage 1b summary
• Simulations successfully completed
• Overall doing a reasonable job
• Lots to look at
• SCM forcing issues:
• I‘m not happy with the wind forcing
• Can geostrophic wind be set better?
• simply use 1-3km average instead of below 3km?
• Remove fine-scale structure in wind ICs and forcing?
• Subsidence slightly too weak?
• Check cirrus on 26th (is it spurious?)
• Check SW TOA between models
• Check temperature budgets for all models
• What should be happening with near surface night-time moisture (LHF~0)?
© Crown copyright Met Office
Stage 2 resultsCoupled atmosphere-land models
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Stage 2: coupled land-atmosphereCloud and rain!
Still foggy
Still get cirrus (9 km)
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Stage 2: coupled land-atmosphere Near surface wind and wind stress
Stress overdone for a given windspeed?
• U* OK when winds are too weak
• U* too strong when winds are OK
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Stage 2: coupled land-atmosphereSurface fluxes
SHF too large on stable nights
LHF generally far too large by day (and night?)
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Stage 2: coupled land-atmosphereNet surface fluxes
SWnet+LWnet-H-L = G
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Stage 1 vs 2Bulk PBL sensitivity
• Coupling removes some oddities
• Some significant differences in PBL height…
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Stage 1 vs 2Bulk PBL sensitivity
• Some significant differences in PBL height…
• Linked to surface Bowen ratio?
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Stage 1 vs 2Bulk PBL sensitivity
• Extract mean PBL depth and EF for early afternoon…
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PBL depth sensitivityStage 2 – stage 1b, control simulations
• More evaporation gives shallower PBL and vice versa
SHFLHF
LHFEF
◊= 24th
x= 25th
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Stage 2 sensitivity tests
• Some sensitivity of PBL depth to EF
• PBL depth depends on other things too!
SHFLHF
LHFEF
◊= 24th
x= 25th
Small symbol=test
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Stage 1 vs 2Bulk PBL sensitivity
• More spread between models in stage 2
• Interesting lack of spread within (some) models
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Stage 2Little LHF sensitivity to increasing PBL humidity
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Stage 2 summary
• Excessive SHF on stable nights
• Daytime LHF mostly greatly overdone
• “the grass is dead” (Larry Mahrt)
• coupled simulations don’t appear sensitive to atmospheric humidity
• Significantly more spread between models in coupled simulations (stage2 vs 1b)
• Night-time u* much better (weaker) in coupled that stand-alone LSM driven by 55m data (where MO not applicable)
• Need lowest model level << 55m
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Thank you