© Crown copyright Met Office DICE project Adrian Lock and Martin Best.

© Crown copyright Met Office

DICE project

Adrian Lock and Martin Best


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!


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)


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


CASES-99 location


CASES-99 locationPoulos et al 2002


CASES-99 location

Main 60m tower


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


CASES-99?


CASES-99 photosJoan Cuxart


CASES-99 photosPoulos et al 2002 – 60m tower


CASES-99 photosWebsite – from 60m tower

Looking south

Looking SSW


Stage 1a set-up


DICE set-upAtmosphere model forcing


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


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


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


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


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



• 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



• 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


Large-scale forcing (5)

• Do the same for moisture:


Large-scale forcing (6)• …and momentum: Strong nocturnal jet


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!)


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?)


Stage 1b resultsatmosphere only simulations forced by observed surface fluxes


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


NUIST sensitivity tests

Stage 1a

Stage 1b


Model grids• Solid lines = control model

• Dotted/dashed lines = experiment

L70!

L60

Control lowest level


Stage 1b: basic checkIs LS forcing working correctly?

Time evolution at 1500m (above PBL) No radiation


Stage1b surface fluxes

LW up – emissivity differences?

Surface SW down differ• be nice to check TOA SW down


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


Stage 1bClouds and rain! Cirrus (9 km)

Fog

?


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


Profile comparison with sondes

• Sondes available at 2am, 6am, 2pm, 10pm

= every 8 hours plus a 2am sonde


Stage 1b: PBL evolution at 300m

SW’ly wind implies from the pond?

Warm bias develops in most models


Stage 1bNear surface evolution

20m 55m


Stage 1bProfiles – first night, pot. temperature


Stage 1bProfiles – first night, moisture


Stage 1bProfiles – first night, winds

Missing data!


Stage 1bProfiles – first night, heat fluxes


Stage 1bProfiles – second night, winds: LLJ?


Stage 1bProfiles – second night, temperature


Stage 1bProfiles – second night, heat fluxes and stress


Stage 1bProfiles – third night, temperature


Stage 1bProfiles – all 3 nights


Stage 1bProfiles – final state


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)?


Stage 2 resultsCoupled atmosphere-land models


Stage 2: coupled land-atmosphereCloud and rain!

Still foggy

Still get cirrus (9 km)


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


Stage 2: coupled land-atmosphereSurface fluxes

SHF too large on stable nights

LHF generally far too large by day (and night?)


Stage 2: coupled land-atmosphereNet surface fluxes

SWnet+LWnet-H-L = G


Stage 1 vs 2Bulk PBL sensitivity

• Coupling removes some oddities

• Some significant differences in PBL height…



• Some significant differences in PBL height…

• Linked to surface Bowen ratio?



• Extract mean PBL depth and EF for early afternoon…


PBL depth sensitivityStage 2 – stage 1b, control simulations

• More evaporation gives shallower PBL and vice versa

SHFLHF

LHFEF

◊= 24th

x= 25th


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



• More spread between models in stage 2

• Interesting lack of spread within (some) models


Stage 2Little LHF sensitivity to increasing PBL humidity


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


Thank you

© Crown copyright Met Office DICE project Adrian Lock and Martin Best.

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Transcript of © Crown copyright Met Office DICE project Adrian Lock and Martin Best.