First Results of Validation and Hydrological Impact Studies for EUMETSAT H-SAF Satellite Precipitation Products Bożena Łapeta 1, Jerzy Niedbała 2, Jadwiga Niedbała 2, Piotr Struzik 1, Danuta Serafin 1, Jakub Walawender 1 and Rafał.Iwański 1 1 Satellite Remote Sensing Centre, Institute of Meteorology and Water Management, Kraków, Poland 2 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, 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 Comparison for the period Dec 2007 – May th IPWG Meeting, Beijing, China, October 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 4th IPWG Meeting, Beijing, China, October 2008 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 4th IPWG Meeting, Beijing, China, October 2008 Quality control of ground data

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

4th IPWG Meeting, Beijing, China, October 2008 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

4th IPWG Meeting, Beijing, China, October 2008 Common validation

4th IPWG Meeting, Beijing, China, October 2008 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 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.

4th IPWG Meeting, Beijing, China, October May 2008

4th IPWG Meeting, Beijing, China, October 2008 Data from lightning detection system Standard validation 18 May 2008

4th IPWG Meeting, Beijing, China, October 2008 H01, 16:15 UTC All-day data Standard validation 18 May 2008

4th IPWG Meeting, Beijing, China, October 2008 H02, 15:49UTC All-day data Standard validation 18 May 2008

4th IPWG Meeting, Beijing, China, October 2008 H03, 15:42UTC All-day data Standard validation 18 May 2008

4th IPWG Meeting, Beijing, China, October 2008 Temporal variability of RG and H-03 rain rates (selected posts) Standard validation 18 May 2008

4th IPWG Meeting, Beijing, China, October 2008 Standard validation 18 May 2008

4th IPWG Meeting, Beijing, China, October 2008 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, 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, 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 – km 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: 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 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 simulations a.Calibration of the model using historical, long time series of RG data b.Using RG data as an input c.Using H-03 product (accumulated to 1 hour values) as an input d.Compare the obtained run-off with the measurements

1st step results The 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.

2nd step- results for winter Time series of catchment run-off [mm/day], Dec 2007 – Mar 2008 measured, simulated using H-03, simulated using RG

2nd step - results for winter Accumulated catchment run-off [10 6 m 3 ], Dec 2007 – Mar 2008 measured, simulated using H-03, simulated using RG

2nd step- results for spring Time series of catchment run-off [mm/day], Apr 2008 – May 2008 measured, simulated using H-03, simulated using RG

Accumulated catchment run-off [10 6 m 3 ], Apr 2007 – May2008 measured, simulated using H03, simulated using RG 2nd step - results for spring

2nd step - results

4th IPWG Meeting, Beijing, China, October 2008 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.

4th IPWG Meeting, Beijing, China, October 2008 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).

4th IPWG Meeting, Beijing, China, October 2008 Thank you for your attention!