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

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Presentation on theme: "The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Alan Seed Centre for Australian Weather."— Presentation transcript:

1 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Alan Seed Centre for Australian Weather and Climate Research Short Term Ensemble Prediction System: STEPS

2 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Outline Statistical structure of rainfall Modelling the errors in a nowcast Temporal development Radar reflectivity to rain rate conversion Tracking Nowcast ensembles Radar only nowcasts Radar + NWP blending Products Ensembles for end users Expected rainfall – ensemble mean Probability of exceeding various thresholds Meteograms Products Developments Conclusions

3 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology 15-min rainfall over the UK 1000 km (15 min)

4 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Adelaide Radar – 250 km (10 min)

5 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Auckland 10 km (2 min) 15 km x 7.5 km box, 100 m resolution

6 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Variability as a function of scale Modelling 1000 km domain, eastern half of the HRRR region

7 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Nowcast skill as a function of scale and lead time Widespread rain in Sydney

8 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Outline Statistical structure of rainfall Modelling the errors in a nowcast Temporal development Radar reflectivity to rain rate conversion Tracking Nowcast ensembles Radar only nowcasts Radar + NWP blending Products Ensembles for end users Expected rainfall – ensemble mean Probability of exceeding various thresholds Meteograms Developments Conclusions

9 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Conceptual model for rainfall Rainfall usually has areas of higher intensity rainfall inside areas of lower intensity rainfall, and we get clusters of storms and not just a random pattern of storms- variability over a wide range of scales The lifetime of a storm increases with the size of the storm as a power law The simplest model is a multiplicative cascade model (used to model turbulence) for the spatial scaling and a hierarchy of AR(1) models for the Lagrangian temporal evolution so as to reproduce the dynamic scaling of the field Temporal development of rainfall

10 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Multiplicative Cascade Model for Turbulence Lovejoy et al., 1987 J. Geophys. Res. Each cascade level evolves in time Rate of development decreases with increasing scale Hierarchy of AR(1) models used for temporal development Temporal development of rainfall

11 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Spectral decomposition of a rainfall field km km km km km km km Temporal development of rainfall

12 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Radar Z-R error is coherent over scales that are significant for urban hydrology RadarGauge Radar measurement error Z - R Error

13 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Space & Time correlations of radar z-r error Villarini et al, WRR 45, W Z - R Error

14 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Errors due to observing above ground level Correlation as a function of height separation for pairs of radar observations where one observation is at the base scan and the other is below the wet bulb freezing level. Sampling Error

15 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Model of radar ZR and sampling errors Observed and ensembles for 10-min rainfall Radar measurement error Ensemble 1Ensemble 2 Observation Radar observation error model includes Z-R and sampling errors due to observing at a height above the ground Modelling QPE Error

16 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Verification of radar error model Reliability of probabilities Power specta of observed and perturbed fields Modelling QPE Error

17 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Other radar observation errors are tricky, depending on the situation and the QC algorithms used Radar measurement error Beam blocking Clutter Daily rainfall accumulation for Melbourne Modelling QPE Error

18 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Modelling the tracking error We do not have a complete description of tracking error Generating fields of U,V error components that are correlated with each other and in space and time is VERY tricky- at least I do not know how to do it Not the most important source of error in the first 6 hours so we can keep it simple Multiply the radar U,V components by a random number that has a mean of 1 and some (small) variance Modelling Tracking Error

19 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Outline Statistical structure of rainfall Modelling the errors in a nowcast Temporal development Radar reflectivity to rain rate conversion Tracking Nowcast ensembles Radar only nowcasts Radar + NWP blending Products Ensembles for end users Expected rainfall – ensemble mean Probability of exceeding various thresholds Meteograms Developments Conclusions

20 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Short Term Ensemble Prediction System- radar only 1.Estimate the advection field using rainfall fields 2.Estimate the AR(1) and cascade parameters using the current observed field 3.For each ensemble member a)Perturb the radar analysis with the observation error model b)Perturb the advection field c)Generate a conditional stochastic field for the next 90 minutes Modelling STEPS-nowcast

21 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Beijing Olympics: 1 hr forecast & observation STEPS-nowcast

22 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Beijing 2008 inter-comparison Compared STEPS against 5 other international systems during the Beijing Games STEPS-nowcast

23 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Short Term Ensemble Prediction System- NWP blend Decompose NWP into a cascade Decompose the rainfall field into a cascade Use radar field to estimate stochastic model parameters Calculate the skill of the NWP at each level in the cascade using the correlation between NWP and radar Blend each level in the radar & NWP cascades using weights that are a function of the forecast error at that scale and lead time For each forecast Add noise component to the deterministic blend, the weight of the noise is calculated using the skill of the blended forecast Combine the cascade levels to form a forecast STEPS-NWP

24 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Blending with NWP – calculating the weights STEPS-NWP

25 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Nowcast explained variance as a function of scale and lead time STEPS-NWP

26 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology NWP explained variance as a function of scale STEPS-NWP

27 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Weights for nowcast & NWP Blending STEPS-NWP

28 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Outline Statistical structure of rainfall Modelling the errors in a nowcast Radar reflectivity to rain rate conversion Tracking Temporal development Nowcast ensembles Radar only nowcasts Radar + NWP blending Products Ensembles for end users Expected rainfall – ensemble mean Probability of exceeding various thresholds Meteograms Developments Conclusions

29 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Status QPE and STEPS-nowcast running on LINUX workstations in operational mode STEPS-NWP (radar + NWP blend) running on a super computer 16 radars with QPE, 15 QPF domains Generating 1000 products (100 Mbytes) per hour Up to 100 clients inside the Bureau being served with products on a busy day QPE live to the public for capital city radars Planning to go live to the public with QPF in May 2011 Products

30 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Rainfall Estimates Melbourne, Sydney, Brisbane, Adelaide 30, 60, 120 min, since 9 AM, daily accumulations blended with rain gauges and updated every 30 min 10 min accumulations radar only with real-time gauge adjustments and updated every 6 or 10 minutes Products

31 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Rainfall Forecasts: 0 – 90 minutes 4 major cities, 1 km & 6 min resolution, 250 km domain 3 Regional forecasts, 2 km & 10 min resolution, 500 km domain 30 member ensemble updated every 6,10 minutes 30, 60, 90 min accumulations of ensemble mean (expected rain) Probability that rain accumulation will exceed 1,2,5,10,20,50 mm in next 60 minutes 60 min accumulationProbability of rain > 50 mm Forecast time series at a point with uncertainty shown Products

32 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Rainfall forecasts: 1 – 6 hours Melbourne, Sydney, Brisbane – 500 km domain, 2 km & 10 min resolution 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, Brisbane Products

33 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Example from east Victoria – NWP

34 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Example from east Victoria- STEPS Ensemble member 1

35 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Met Service Canada: Point Mode Paul Joe, 2010

36 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Met Service Canada: Point-Time Mode PDF of rainrates at a point for all time lagged nowcasts Paul Joe, 2010

37 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Met Service Canada: POP for a validtime and rainrate threshold Rainrate threshold is 1 mm/h; number of hits exceeding threshold / number of samples (60) Paul Joe, 2010

38 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Probability Probability of 60 min accum > 5 mm

39 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Outline Statistical structure of rainfall Modelling the errors in a nowcast Radar reflectivity to rain rate conversion Tracking Temporal development Nowcast ensembles Radar only nowcasts Radar + NWP blending Products Ensembles for end users Expected rainfall – ensemble mean Probability of exceeding various thresholds Meteograms Developments Conclusions

40 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Qualitative severe weather warning THESPA Calculates the probability of a TITAN cell passing over a point in the next 60 minutes based on the current velocity and cell size and a climatological TITAN tracking error Being developed for aviation applications and use in TIFS TIFS Operational in most Regional Forecast Centres Automatic version for aviation is operational Revising the software architecture Graphical and automated text editing feature development 25 km Developments

41 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Development: Closing the gap between NWP & nowcasts Strategic Radar Enhancement Project $48 M project over 7 years, 8 people for three years in CAWCR 4 new radars Radar data assimilation in ACCESS Roll out of a new radar data quality control system for ~50 radars Characterise radar errors for use in data assimilation (and QPE) Assimilate radar data (LH nudging, Doppler radial winds, reflectivity) into high res (~2 km) NWP meso-scale models over capital cities Seamless rainfall prediction Integrate rainfall forecasts from 0 – 10 days lead time into a seamless forecast Use STEPS to blend the forecasts from the various models Develop a portal for convenient access to the rainfall forecasts

42 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Seamless rainfall forecasts Rainfall portal Data source transparent to user Aggregation Disaggregation New science STEPS downscaling Blending strategy Verification (esp. transition periods) 3-10 day forecasts km 2 x daily 1-2 day forecasts ACCESS-A ACCESS-C AGREPS-R ECMWF EPS PME/GOCF GFE 5-25 km 2-4 x daily 1-24 hour forecasts ACCESS-A ACCESS-C GFE 2-10 km 4-8 x daily 1-6 hour forecasts ACCESS-C STEPS-NWP 1-2 km hourly min nowcasts STEPS-nowcast every 10 min 1 km Down- scaled and blended using STEPS ACCESS-G AGREPS-G ECMWF EPS PME/GOCF GFE TIGGE? Cross-cutting programs: ESM, CWD, OEB, NMOC

43 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Issues Limited capacity in the Regional Forecast Centres Head Office support branches to deploy and learn new nowcasting systems, busy with the Next Generation Forecast and Warning System – slows the adoption of new algorithms Focus has been on improving the service adoption of existing nowcasting science through Delivering the products through a range of platforms – 3drapic, Google maps, web pages Using formats that are carefully designed and that conform to formal geo- spatial standards (eg CF compliant netCDF) Serving the data on a range of platforms (ftp, SOAP, directories) Formalising the use of QPE&F products in the forecast process Training Developments

44 The Centre for Australian Weather and Climate Research A partnership between CSIRO and the Bureau of Meteorology Conclusions Nowcasting rainfall is an uncertain business Have incomplete description of the error structure of QPE and QPF Have enough of a description to make useful stochastic ensemble models There is still a lot of work to do to make the stochastic models include more meteorological knowledge There is even more work to do to help the end-users make full use of the ensemble members in their decision support systems


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