Mesoscale Tiger Team -...

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MOSAC-7

Mesoscale Tiger Team

Bruce Macpherson


Motivation Rainfall and cloud verification

What trend ?


…. though trend depends on measure

T+18-T+24 rainfall accumulationETS Benefit odds ratio skill score

0.2mm/6h1 mm/6h4 mm/6h


UK-index for cloud

ETS-based index Benefit odds ratio based index


Motivation -2High profile forecast failures

No-one for tennis ?


Motivation -3Spin-up in cloud cover


Sub-projects

short-period precipitation forecast

convective precipitation forecast quality

quality control of input cloud data

analysis bias and spin-up in cloud cover

instability, initialisation and lateral boundary updating


Instability, initialisation &lateral boundary updating

occasional failures in convection over France– two sweeps convection per timestep

occasional failures in tropics– set orography > 0 for inland lakes

noise in pmsl– increased boundary rim width from 4 ->8 points

– dynamics solver settings tuned for better convergence


Short-period precipitation forecast

Mes New Dynamics trial verification

Dec ‘01 -Mar ‘02


Short-period precipitation forecast -2

Mes ND trial verification

Frequency bias for

hourly totals > 0.17mm

(v Nimrod radar)



Impact of cloud data

12 cases



Mes Autumn ‘02 upgrade– new covariances

– weaker nudging of cloud data

24 forecasts



examine sensitivity to other components of assimilation

– radar

– sonde rh

– IAU initialisation….


Convective precipitation forecast quality

“CMODS” changes– new convective momentum transport

– new definition & triggering of shallow, mid-level/deep convection

Progress– 8 test cases run

– slightly better moderate/heavy accumulations

– aim for spring ‘03 change


Quality control of input cloud data

Cloud top height (CTH) assignment


Quality control of input cloud data -2

CTH error

model

radiosonde


Quality control of input cloud data -3CTH assignment - “low level inversion change”

New logicOld logic


Quality control of input cloud data -4

“Low level inversion change” implemented, July ‘02

further spurious rain cases reported post ND implementation, August ‘02

further CTH changes under test, autumn ‘02

meeting on short-term way forward, Dec ‘02

workshop on strategy for cloud (and ppn) assimilation to follow


Analysis bias and spin-up in cloud cover

Mes New Dynamics trial verification

Jan/Feb ‘02


Analysis bias and spin-up in cloud cover -2

Weaker nudging to cloud data

12 cases


Analysis bias and spin-up in cloud cover -3

Assimilate cloud data within 3d-Var(instead of nudging) by spring ‘03

AMSU-B data in Mes

compare verification– v satellite imagery

– v surface stations


Questions?

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