GAUGES – RADAR – SATELLITE COMBINATION Prof. Eng. Ezio TODINI
Improvements in Rainfall Estimates are obtained by combining together the different available Rainfall Measurement Sources RAIN GAUGES Reliable but point measures
Improvements in Rainfall Estimates are obtained by combining together the different available Rainfall Measurement Sources RADAR Spatial but less reliable
Improvements in Rainfall Estimates are obtained by combining together the different available Rainfall Measurement Sources METEOSAT Spatial but too coarse resolution
The MUSIC Prototype Integrates: Hydrologic & Hydraulic models GIS and Advanced Visual User Interface THE MUSIC INTEGRATED SYSTEM PROTOTYPE RAINFALL INPUTS CAN BE FROM: Gauges, Radar, Satellite and Meteorological Models Forecasts
Rain-gauge measurements KRIGED measurements from gauges Radar measurements, A PRIORI estimates Combination of radar estimates and gauges measurements, A POSTERIORI estimate BLOCK KRIGING KALMAN FILTER SPATIAL MEASUREMENTS over the radar pixels Eliminating the BIAS and producing MINIMUM VARIANCE precipitation estimates on pixels ORIGINAL TECHNIQUE TO COMBINE, IN A BAYESIAN SENSE, AREAL PRECIPITATION FIELDS (RADAR) TO POINT MEASUREMENTS OF PRECIPITATION (RAIN-GAUGES) GROUND BASED TELE- METERING RAIN- GAUGE MEASUREMENTS - accurate in a point - spatial significance decays with the distance and with the area BLOCK KRIGING estimating the average field over the radar pixels and its Variance from the point rain-gauge measurements SPATIAL MEASUREMENTS POINT MEASUREMENTS RADAR MEASUREMENTS - good spatial representation - poor quantitative estimates - biased measurements SPATIAL MEASUREMENTS KALMAN FILTER finding the a posteriori estimates by combining the a priori estimates provided by the radar with the block Kriged measurements provided by the gauges, in a Bayesian framework 1
RAIN-GAUGES Meteorological RADAR Meteorological SATELLITE Measurements of the rainfall field at different scales. combine measurements at multiple resolution. MODEL: UP-SCALING: disaggregated estimate at the RADAR scale (from the Bayesian combination) covariance of the estimation errors at the RADAR scale aggregated RADAR estimate variance of the estimation errors of the aggregated RADAR estimate RAIN-GAUGES, RADAR AND SATELLITE COMBINATION The true rainfall at the upper scale can be obtained simply by summing the true rainfall at the lower scale RAD Scale SAT Scale x y DOWNSCALING RAD Scale SAT Scale x y UPSCALING
BAYESIAN APPROACH at SATELLITE Scale TRUEBK-RADSATBK-RAD- SAT
BAYEISAN APPROACH at RADAR scale TRUEBKRADBK-RADBK-RAD-SAT
RESULTS (1000 time-steps) BIASVARIANCE RADAR RADAR BLOCK KRIGING BLOCK KRIGING BLOCK KRIGING + RADAR (RADAR scale) BLOCK KRIGING + RADAR (RADAR scale) SATELLITE SATELLITE BK+RADAR AGGREGATED BK+RADAR AGGREGATED (SATELLITE scale) (SATELLITE scale) BK+RADAR + SATELLITE (SATELLITE scale) BK+RADAR + SATELLITE (SATELLITE scale) BK+RADAR + SATELLITE (RADAR scale) BK+RADAR + SATELLITE (RADAR scale)
BLOCK KRIGING RADARSATELLITE BK+RADARBK+RADAR+SATELLITEBK+SATELLITE 6.5 mm 0.0 mm 2.2 mm 4.4 mm
The present status: - Block-Kriging software package Completed(*) - Raingauge – Radar combination Completed - Raingauge – Satellite combination Completed - Raingauge-Radar-Satellite comb. Completed - Coupling with TOPKAPICompleted (*) Under revision