The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Nowcasting and Short Range NWP at the

The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

Nowcasting and Short Range NWP at the Australian Bureau of Meteorology

Peter Steinle

Earth System Modelling Group

Alan Seed

Weather & Environmental Prediction Group

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology

• Rainfall Nowcasting in the BoM …• Short Term Ensemble Prediction System (STEPS)

• Estimation & Nowcast (radar & gauge)• Short forecast (radar, gauge & NWP)

• NWP in the BoM … • Aust. Community Climate & Earth System Simulator (ACCESS)

• Met Office Unified Modelling System

• Bringing them together …. • Strategic Radar Enhancement Program (SREP)


Initializing the nowcast:Multi-radar QPE

• Mosaic of Sydney area radars

• 10 min, 2 km resolution

• Gauge adjusted QPE for each radar

• Advect images to a common time:

• 1-5 min forecasts

• Blend the radars:• inverse error variance as

weights


STEPS QPNSpectral decomposition of a rainfall field

128-256-512 km

64-128-256 km

32-64-128 km

16-32-64 km 8-16-32 km 2-4-8 km4-8-16 km

Use Fourier notch filters to isolate narrow bands of wavelengths in the field


STEPS QPN60 minute rainfall accumulation forecasts

Forecast – ensemble mean

Radar accumulation


STEPS QPN60 minute probability products

Probability accumulation > 10 mm Probability accumulation > 20 mm


STEPS QPF: 0 – 6 hours

• Melbourne, Sydney, Brisbane – 500 km domain, 2 km & 10 min resolution

• Blends radar forecasts with Numerical Weather Prediction • 30 member ensemble updated every hour• 10-min forecasts of rainfall intensity out to 6 hours• Probability products for hourly accumulations for next 6 hours

Probability of rain > 1 mm for 2 & 3 hour lead times, Melbourne

Rainfall intensity forecast, 150 min lead time, Sydney


STEPS QPF 0 – 6 hour with NWP blending

• Skill of nowcast is a function of scale and lead time• Skill of NWP is a function of scale• Decompose the NWP into components• Blend the NWP and nowcast components, weights a function of lead

time and scale• Generate the ensemble by adding statistical noise that represents the

error in the deterministic blended forecast for each component• Combine the components into the forecasts


STEPS QPFWeights for nowcast & NWP

Ble

nd

ing

500 km scale

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 100 200 300 400

Lag (minutes)

Wei

gh

t Extrapolation

NWP

Noise

125 km scale

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 100 200 300 400

Lag (minutes)

Wei

gh

t Extrapolation

NWP

Noise


NWP systems

Global: N320 (~40km) + 4dVAR

Regional 0.11o +4dVAR

City: 4km ; no DA

• Met Office Unified Model (UM7.5,L70)• 6 hourly 4dVAR : Global, Region & TC

• 4km City Systems• No Assimilation (3dVAR expt.)

• 1.5km UM7.6/L70 (Experimental)• 3dVAR

• + radar winds & precip(LHN)

• Relocatable

• Ensembles• Global & Regional EPS in research• Need deterministic high res.


SREP to deliver:

• 4 new radars delivering QPE & F products as appropriate for radar location

• STEPS blending radar nowcasts with NWP in the Capital Cities

• NWP assimilating radar data operationally• Start with Latent Heat Nudging for simplicity & baseline• Begin moving to VAR soon

• Rapid update cycle and relocatable domains tested and made ready for transition into operations

• Prototype radar QC system ready for transition into operations


Extensive testing on Brisbane Jan2-14 2011

Radar+Gauge

Analysis

SREP 1.5km

6hr forecast

Operational 0.05o

6hr forecast

Hourly precipitation


Have STEPS & NWP…So all done & dusted???

• Apart from one or two problems…

• Rainfall estimation• Systematic errors from clutter and quality control

• Model calibration• Overdoes heavy precipitation in tropics

• Assimilation • Large initial rainfall in the tropics

• Dirty laundry time…..


QPE Errors Climatology – truth from rain gauges

Melbourne Mean daily rain rateGauge data only


QPE ErrorsClimatology – radar

Blocking from hills

Clutter

Systematic errors areobvious in long accumulations

Radar clutter rejection


Area & Volume vs Rainfall Rate (2-11 Jan)

• 1.5km – too much convection & too strong• 4,5 & 6 hour forecasts

• Model calibration

• Latent Heat Nudging needs calibration

• One of the worse events• Sydney events looked much better

• 0.05o & 0.11o problems with heavy precipitation too

• 3,4,5,….,14 hour forecasts

• Little sensitivity to forecast length

• 3dVAR / no 3dVAR similar

Obs3dVAR+LHN3dVAR only

Obs3dVAR+LHN0.05o (FC only)0.11o 4dVAR


After effects from Latent Heat Nudging …

Radar+Gauge

Analysis

SREP 1.5km

4hr forecast

Operational 12km

4hr forecast

Hourly precipitation


Summary

• Rainfall nowcasting established• In the queue for operations

• Improved radar quality control being tested

• NWP “developing”• Seems better much behaved away from tropics

• More extensive trials in Sydney underway

• Tropical NWP still a challenge• Restrain LHN

• Systems are in place• Analysis → Nowcast → NWP blend → NWP

• Calibration/tuning of components ongoing

Documents

The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Nowcasting and Short Range NWP at the