first results of validation and hydrological impact studies for eumetsat h-saf satellite...

First Results of Validation and Hydrological Impact Studies for EUMETSAT H-SAF

Satellite Precipitation Products

Bożena Łapeta1, Jerzy Niedbała2, Jadwiga Niedbała2, Piotr Struzik1, Danuta Serafin1, Jakub Walawender1 and Rafał.Iwański1

1Satellite Remote Sensing Centre, Institute of Meteorology and Water Management, Kraków, Poland2 Hydrological Forecating Office, IMWM, Kraków, Poland

• H-SAF products validated• Comparison with rain gauge data

– ground data used, quality control – Example results for the several months– Results for case study;

• Validation using hydrological model– Catchment used and approach applied– Results

• Conclusions

4th IPWG Meeting, Beijing, China, 13-17 October 2008

Presentation Overview

Three out of four H-SAF precipitation products have been validated:H-01 (PR-OBS-1) - Precipitation rate at ground by MW conical scanners (with indication of phase)H-02 (PR-OBS-2) - Precipitation rate at ground by MW cross-track scanners (with indication of phase)H-03 (PR-OBS-3) - Precipitation rate at ground by GEO/IR supported by LEO/MW.

Current versions of product available since December 2007.Comparison for the period Dec 2007 – May 2008.


Precipitation Products validated

• Measurements from automatic rain gauges posts (2 rain gauges at each post);

• 10 minute cumulative values from the closest time slot (max. span: 10 min);

• Point to piksel comparison


Standard validation- instruments used

Each post is equipped with 2 rain gauges (heated and non-heated). QC is performed in the following way:•the data time series for heated and non-heated RG are compared in order to eliminate the cases of clogged instruments (rain rate increases continuously);•if both work properly, higher values is taken (automatic RG are known to lower the real precipitation);

During winter (November-March) data only from heated RG are available, so the quality of ground data is lower than during other months


Quality control of ground data

Validation Methodology: Validation Methodology: common and specific validation common and specific validation

1. The Common Validation is the result of the validation activities done by all the Institutes involved in the HPPVG:

– both rain gauges (4100 posts) and radar data (40 C band radars) are used;– it is based on statistical scores evaluated on multi-categorical and

continuous statistics;– the statistical scores are monthly averages;– the same up-scaling techniques by all the institutes (if proposed by

developers).

2. Specific validation Each Institute in addition to the common validation methodology has

developed a specific validation methodology based on its own knowledge and experience.

– lightning data, numerical weather prediction and nowcasting product– case studies: convective/stratiform precipitation, day/night, land/ocean

Station

here we will see the resuts obtained by the common validation methododlogy


H-SAF validation methodology: common and specific validation

1. The Common Validation is the result of the validation activities done by all the Institutes involved in the HPPVG:

– both rain gauges (4100 posts) and radar data (40 C band radars) are used;

– it is based on statistical scores evaluated on multi-categorical and continuous statistics;

– the statistical scores are monthly averages;– the same up-scaling techniques by all the institutes (if proposed by

developers).

2. Specific validation Each Institute in addition to the common validation methodology has

developed a specific validation methodology based on its own knowledge and experience.

– lightning data, numerical weather prediction and nowcasting product– case studies: convective/stratiform precipitation, day/night, land/ocean


Common validation

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

Dec-07 Jan-08 Feb-08 Mar-08 Apr-08 May-08

Mea

n er

ror [

mm

/h]

H01 H02 H03


Cases selection

High RG measurements connected with heavy precipitation.

Days when H01 and H02 products were available more or less at the same time (max time span - 30 min);

18 May 2008 - both, stratiform and convective precipitation on the cold front moving across Poland.

The reasonably cold maritime polar air was moving over Northern-West Poland and the worm tropical air was coming to the Southern-East part of the country.

Big thermal contrast, high relative humidity in the frontal zones, and finally the collision of two frontal zones resulted in the intensification of meteorological phenomena ahead and within the frontal zones.

Numerous heavy storms; in many places, the stratiform precipitation that occurred in the cold front zone caused flooding.


18 May 2008


Data from lightning detection system

Standard validation18 May 2008


H01, 16:15 UTC

90.7

40.0

100.0

8.7

60.0

100.0

0.6

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

[0, 0.25] (0.25, 2.8] (2.8, 7.5] > 7.5Rain rate from RG

Rain rate from H01 v.1.0

> 7.5

(2.8, 7.5]

(0.25, 2.8]

[0, 0.25]

All-day data



H02, 15:49UTC

All-day data

91.1

42.432.3

14.3

8.1

40.1

38.7

28.6

0.9

16.922.6

42.9

0.66.5

14.3

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

[0, 0.25] (0.25, 2.8] (2.8, 7.5] > 7.5Rain rate from RG

Rain rate from H02 v.1.2

> 7.5

(2.8, 7.5]

(0.25, 2.8]

[0, 0.25]



H03, 15:42UTC

All-day data

18.0

59.944.0

54.3

69.6

28.9

30.818.9

11.9 11.123.3 25.0

0.4 0.1 1.8 1.8

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

[0, 0.25] (0.25, 2.8] (2.8, 7.5] > 7.5Rain rate from RG [mm/h]

Rain rate from H03 v 1.1

> 7.5(2.8, 7.5]

(0.25, 2.8][0, 0.25]



Temporal variability of RG and H-03 rain rates (selected posts)


0

1

2

3

4

5

6

7

8

9

10

0:12

1:27

2:42

3:57

5:12

6:27

7:42

8:57

10:1

211

:27

12:4

213

:57

15:1

216

:27

17:4

218

:57

20:1

221

:27

22:4

223

:57

Rain

rate

[mm

/h]

Time UTC

H03 RG

Point 1 -Stratiform and convectice precipitation

0

10

20

30

40

50

60

70

0:12

1:27

2:42

3:57

5:12

6:27

7:42

8:57

10:1

211

:27

12:4

213

:57

15:1

216

:27

17:4

218

:57

20:1

221

:27

22:4

223

:57

Rain

rate

[mm

/h]

Time UTC

H03

RG

Point 2 -Convective precipitation



Parameter H-01 H-02 H-03

POD 0.65 0.60 0.42 Proportion correct

0.86 0.86 0.34

FAR 0.43 0.44 0.49 Probability of False Detection

0.09 0.09 0.82

Bias 1.13 1.07 0.82 HSS 0.52 0.50 -0.37 Odds Ratio 17.70 15.27 0.16

Parameter H-01 H-02 H-03 Mean RG [mm/h] 0.26 0.38 1.18 Mean H01 [mm/h] 0.19 0.35 1.12 ME [mm/h] -0.08 -0.03 -0.06 MAE [mm/h] 0.28 0.45 1.54 RMSE 0.93 2.43 2.74


Conclusions I Reasonably good quality in precipitation recognition was found for both H-01

and H-02 products. High precipitation events connected with convection on cold front were not

recognized by H−01 at all, while H−02, underestimated the precipitation rate. Poor ability of H−03 to recognize precipitating grids – probably connected with

parallax effect (no correction at the moment) or applied cloud mask quality. High temporal resolution of H−03 enables analysis of diurnal variability of

precipitation over selected points. It has been found that: – moderate and high stratiform precipitation cases were properly recognized but not

properly estimated; – light stratiform precipitation were not recognized, what can be connected with

difficulties in recognition of low level, warm stratus clouds; – convection precipitation was properly recognized but significantly underestimated.

Hydro-validation background

Insufficient number/spatial resolution of ground data and their questionable quality make the validation of satellite derived precipitation products very difficult task.

High variability of the parameters in space and time causes additional difficulties in proper validation using conventional ground measurements and observations.

In the frame of H-SAF, the validation with the use of hydrological model has been agreed as the additional tool.

1st EUMETSAT H-SAF Workshop, 16-18 October 2007, Rome, Italy

Hydro-validation goals

To independently assess the benefit of satellite-derived data in practical hydrological applications with the use of operational hydrological models.

To provide the feedback to the data producers for possible products quality improvement.

The above are the main goals of H-SAF Cluster IV ‘Hydro-validation’, coordinated by Poland and the following participating countries: Belgium, Finland, France, Germany, Italy, Poland, Slovakia and Turkey.

1st EUMETSAT H-SAF Workshop, 16-18 October 2007, Rome, Italy

H-SAF– test catchments

• Variety of climatological conditions

• Variety of terrain conditions

• Variety of land cover

• Different hydrological regimes

• Catchment size: 242 – 102000 km2

• 902 rain gauges, 21 radars

Hydrological validation has already started – preliminary results are available for 5 catchments.

Hydrological validation – the Soła basin

Soła catchment - mountainous river with small retention capacity of river valleys, rapid water rising and high risk of flash floods. The most hazardous floods originate in upper parts of the Soła river.

• Surface: 784.8 km2

• Length of main river: 38.7 km

• Vegetation type: 80% forest

• 18 RG, 15 of them are

telemetric stations

Exercise

The simulations include all events during the period from December 2007 to May 2008. The experiment was run in two steps:

1.Comparison with rain gauges data on the catchment base – results for the whole data set

2.Hydrological model simulationsa. Calibration of the model using historical, long time series of RG datab. Using RG data as an inputc. Using H-03 product (accumulated to 1 hour values) as an inputd. Compare the obtained run-off with the measurements

1st step resultsThe values of PR-OBS-3 rain rate:

aggregated over one hour 1 hour cumulative

integrated over the Soła catchment

compared with the values by interpolating rain gauge data with the Thiessen

method.

Data collated on the basis of:

min value per hour [mm]

max value per hour [mm]

mean value per hour [mm]

standard deviation [mm]

Satellite data 0.00 6.17 0.065 0.240 Ground based data 0.00 7.95 0.067 0.267

10-1-2008 20-1-2008 30-1-2008 9-2-2008 19-2-2008 29-2-2008 10-3-2008 20-3-2008 30-3-2008

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

110.0

120.0

130.0

140.0[m^3/s] Time Series Discharge

2nd step- results for winter

Time series of catchment run-off [mm/day], Dec 2007 – Mar 2008measured, simulated using H-03, simulated using RG

1-1-2008 11-1-2008 21-1-2008 31-1-2008 10-2-2008 20-2-2008 1-3-2008 11-3-2008 21-3-2008 31-3-2008

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

110.0

120.0

130.0

140.0

150.0

[] Acc_Q

2nd step - results for winter

Accumulated catchment run-off [106 m3], Dec 2007 – Mar 2008measured, simulated using H-03, simulated using RG

6-4-2008 11-4-2008 16-4-2008 21-4-2008 26-4-2008 1-5-2008 6-5-2008 11-5-2008 16-5-2008 21-5-2008 26-5-2008

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

11.0

12.0

13.0

14.0

15.0

16.0

17.0

18.0

19.0

20.0

21.0

22.0

23.0

24.0[m^3/s] Time Series Discharge

2nd step- results for spring

Time series of catchment run-off [mm/day], Apr 2008 – May 2008measured, simulated using H-03, simulated using RG

5-4-2008 10-4-2008 15-4-2008 20-4-2008 25-4-2008 30-4-2008 5-5-2008 10-5-2008 15-5-2008 20-5-2008 25-5-2008 30-5-2008

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

55.0

60.0[] Acc_Q

Accumulated catchment run-off [106 m3], Apr 2007 – May2008measured, simulated using H03, simulated using RG

2nd step - results for spring

2nd step - results

Data collated on the basis of:

R2

Observed run-off height

for the season [mm]

Simulated run-off height for the season

[mm]

Error of simulated

run-off height [%]

Winter satellite data 0.306 773 577 25.4 ground based data

0.571 773 579 25.2

Spring

satellite data 0.653 438 406 7.40 ground based data

0.740 438 440 -0.40


Conclusions II The comparison of RG data and H-03 product averaged over the Soła

catchment confirmed that H03 underestimates the observed precipitation.

At the moment, hydrological validation for winter does not take into account the snow retention and melting - results obtained using H-03 were different from the measurements but were coherent with the ones obtained with RG.

Although introducing of H03 to hydrological model caused slight decrease of the results quality, very good agreement with observed run-off was obtained.

The results for water balance were reasonably good while the individual waves were not proper recognised. This refers both to satellite product and RG data.

Performed exercise indicates that H-03 can be used for hydrological modeling for spring season.


Conclusions II

Longer time series of satellite products is needed for hydrological model calibration using these data.

Although the present versions of H−SAF precipitation products are still pre−mature, the obtained results are promising.

The validation activities performed in the frame of H−SAF, including the hydrological one, provided necessary information for further tuning and improvement of these products (example of PR-OBS-5).


Thank you for your attention!

first results of validation and hydrological impact studies for eumetsat h-saf satellite...

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