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Federal Department of Home Affairs FDHAFederal Office of Meteorology and Climatology MeteoSwiss

Cometa

Fribourg, 17th April 2008

Meteorological Metadata Combination Framework

DIVA Group

University of Fribourg, Switzerland

Master thesis of Lorenzo Clementi

Second presentation

2 MEMcaf | MEteorological Metadata CombinAtion FrameworkLorenzo Clementi

Presentation outline

• Framework architecture: reminder

• Use case description• Overview• Forecast evaluation

• Demo

• Result discussion

• Conclusion





• Demo


• Conclusion


Architecture (1/2)

• Goals of the framework• Support for combining meteorological data• Help in developing and validating nowcasting

algorithms

• Use of metadata to describe data types and processing information

• “Nowcast validation and comparison with extrapolation is incomplete” [J.W.Wilson, National Centre for Atmospheric Research, Boulder]


Configuration +Metadatacombination

Architecture (2/2)

IdeaTesting, validation

Exp

erim

ent

Procedure file

Data combination


Key features

• Products metadata hierarchy / inheritance

• Metadata: XML to Java mapping thanks to JAXB

• Parameter perturbation

Experiment1Experiment2 …ExperimentN

Metadata 1

Metadata 2

Combinationmethod

Param

eter P

erturbation





• Demo


• Conclusion


Use case: overview

• Precipitation field extrapolation based on satellite displacement vectors in the Alpine region

• Goals• Illustrate the contribution of the Cometa framework• First assessment of forecast reliability• First optimization experiments


Use case: some details

• Atmospheric motion field (vector field) is computed on satellite images (external software) and then applied onto radar images to generate a forecasted image

• Satellite channel: IR 10.8 μm (cloud top temperature)

• Radar products• OMC (reflectivity)• PJC (precipitation estimate)

• Note that other satellite and radar products over different resolutions could be used (metadata extensibility)


Evaluation: visual inspection

• Residual vectors: AMF between forecasted and extrapolated images

• Visual inspection• Systematic shift → synchronization, parallax (limb view)

• Speed and direction analysis (RMS)


Evaluation: quality flag

Difference between the extrapolated image and the measured one.

q = Ngood / (Ngood + Nbad)

• Simple approach

• Improvements:• CRA• Root mean square error

tolerance

q=Mean f x ,y f x , y

2





• Demo


• Conclusion


OMC versus PJC

Tolerance ± 1Mean difference: 0.08

July 18, 2005

00.10.20.30.40.50.60.70.80.9

1

11.3

0 h

11.4

5 h

12.0

0 h

12.1

5 h

12.3

0 h

12.4

5 h

13.0

0 h

13.1

5 h

13.3

0 h

13.4

5 h

14.0

0 h

14.1

5 h

14.3

0 h

time

qu

alit

y fl

ag

OMC

PJC


Pattern size perturbation

Pattern = window used for the pattern matching algorithm

• Pattern of size 60 to 80 pixels, best result

OMC extrapolation, July 12, 20065 minutes step, tolerance +/- 1

0.7

0.75

0.8

0.85

0.9

0 20 40 60 80 100 120 140 160

pattern size (pixels)

ex

tra

po

lati

on

qu

alit

y


Pattern size perturbation

• Pattern size: cost - benefit

• The AMF algorithm uses a pattern matching technique

• Computational complexity:

O(m2 ∙ n)

m: pattern size n: number of grid points

• Outside optimum: • Big effort (computational resources)

but small benefit (quality increase)


Prediction reliability over time

Strong relation: R2 > 0.9

March 8, 2006 (11:00 - 14:45 UTC)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

5 25 45 65 85 105

extrapolation time [minutes]

qu

alit

y quality

Logarithm





• Demo


• Conclusion


Outlook

Limitations• Quality flag needs to be improved• The creation of metadata files has to be done manually

Future works• Simultaneous perturbation of several parameters

• Assess correlations• Combinatorial problem

• Machine learning approach


Timeline

November December January February March April

November 5

Project start

December 14

1st milestone- Literature study- Implementation choices- First prototype

February 8

2nd milestone- End to end use case

April 4

Final deadline- Project delivery (source code +thesis)

April 17

Final presentation- in Fribourg


Conclusion

• The use case proved the validity of Cometa• We have found some interesting result• There is place for improvement

Thank you!

Questions?

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