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![Page 1: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/1.jpg)
Validation of Satellite Rainfall
Estimates over the Mid-latitudes
Chris Kidd
University of Birmingham, UK
![Page 2: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/2.jpg)
The European Context
Geographically diverse• Large extent of coastlines and interiors• Plains & mountains• Variable background – snow cover, sand etc.
Meteorologically diverse – hence climatologically• Maritime and continental influences• Stratiform vs convective precipitation• Seasonal variations – frigid vs stifling temperatures
Plenty of light rain intensities…
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 3: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/3.jpg)
The European
Region
![Page 4: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/4.jpg)
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
3B40 3B41 3B42
CMORPH
ECMWF
CPCMW
Validation Data
Europeanradar data
Production of web pages
Statistics at 20km and 50km
Remap data to PSG
Data Products
Raw Data
Data processing
PMWIR
GPIPMIR FDA
Data processing
![Page 5: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/5.jpg)
Results generation
Visual analysis• Imagery of observations and estimates
In addition:• Cumulative distribution of accumulation• Analysis of occurrence of precipitation• Cumulative distribution of occurrence by intensities
Descriptive statistics• Contingency tables, conditional rain rates
Statistical analysis• Bias, ratio, RMSE, Correlation, Heidke score etc
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 6: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/6.jpg)
IPWG European validation
![Page 7: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/7.jpg)
Resampled/remapped imagery
![Page 8: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/8.jpg)
Scatterplot
![Page 9: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/9.jpg)
Rainfall intensity distribution
![Page 10: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/10.jpg)
Occurrence of rainfall by intensity
![Page 11: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/11.jpg)
Accumulation of rainfall by intensity
![Page 12: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/12.jpg)
Statistics
![Page 13: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/13.jpg)
![Page 14: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/14.jpg)
![Page 15: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/15.jpg)
21-day moving average
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 16: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/16.jpg)
Ratio of occurrence >0 (21-day)
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 17: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/17.jpg)
Ratio of occurrence >1 (21-day)
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 18: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/18.jpg)
Rainfall ratio (21-day)
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 19: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/19.jpg)
Heidke Score >=0 (21-day)
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 20: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/20.jpg)
Heidke Score >=1 (21-day)
![Page 21: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/21.jpg)
Initial results
• Satellite observations show significant seasonality
• Rainfall occurrence is underestimated, except by the ECMWF model reanalysis (resolution?)
• Model results suggest an element of inconsistency
• Day-to-day variations in performance are large
and…
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 22: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/22.jpg)
Future strategy
Broaden range of algorithms/products• (more please!)
Back-date study as far as possible• (radar/gauge and algorithm radar)
Include other radar data where available• (Baltex, Spain, Italy?)
Incorporate gauge data when available• (available <1999 for UK, European?)
BUT….
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 23: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/23.jpg)
Light rainfall detection
An algorithm with a rain/no-rain boundary of 1mm/hr should underestimate the rainfall by the contribution of rainfall below 1mm/hr
• Algorithms that cannot identify all the rain should underestimate rainfall totals
• Algorithms that are bias-corrected must compensate the lack of light-rainfall contribution with rainfall at higher intensities – i.e. they will underestimate the low rainfall and overestimate high rainfall.
(In reality algorithms might detect some light rain, but not all)
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 24: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/24.jpg)
radar e40 3B40 3B41 3B42
“Ideal” algorithms
All algorithms produce identical results to any validation data set…
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
Acc
umul
atio
n
![Page 25: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/25.jpg)
radare40
3B40
3B41 3B42
… reality
Algorithms tend to be tuned to minimise the longer-term biases – but are they ‘correct’?
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
Acc
umul
atio
n
![Page 26: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/26.jpg)
radare40
3B40
3B41 3B42
Rainfall accumulation
The make-up of the ‘intensities’ to the total is of critical importance:
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
Acc
umul
atio
n
![Page 27: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/27.jpg)
radare40
3B40
3B41 3B42
Rainfall accumulation
The make-up of the ‘intensities’ to the total is very important:
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
Acc
umul
atio
n
![Page 28: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/28.jpg)
Jan2004
Feb2004
Mar2004
Apr2004
May2004
Jun2004
Accumulation of precipitation
Radar e40 3B40 3B41 3B42 Radar e40 3B40 3B41 3B42 Radar e40 3B40 3B41 3B42
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
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Jan 2004 Feb 2004 Mar 2004
Apr 2004 May 2004 Jun 2004
Occurrence of precipitation
Radar e40 3B40 3B41 3B42 Radar e40 3B40 3B41 3B42
Radar e40 3B40 3B41 3B42
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 30: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/30.jpg)
Accumulation of precipitation
<1 mm/hr
<2 mm/hr
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 31: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/31.jpg)
Occurrence of precipitation
<1 mm/hr
<2 mm/hr
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
![Page 32: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/32.jpg)
Rain/no-rain induced biases
TRMM 2A25 data
mean rainrates mean rainrates > thresholds
Generate ‘global’ ratio
Bias (ratio) correct mean rainrates
Plot grid-sized ratios
![Page 33: Validation of Satellite Rainfall Estimates over the Mid-latitudes Chris Kidd University of Birmingham, UK.](https://reader035.fdocuments.us/reader035/viewer/2022062511/5513c72b55034646298b4c7d/html5/thumbnails/33.jpg)
-0.5
Rain/no-rain induced biases
-1.0-2.0-4.0
• Differences in rain/no-rain boundaries reveal regional variations that do not exist in reality• Further complicated since rain/no-rain boundaries tend to differ over land/sea areas
2nd IPWG working group workshop, Monterey, CA. 25-28 October 2004
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Recommendations
• There is a need to identify regions over which climate change can be observed with a high degree of confidence
• Parameters need to be chosen that can be retrieved with a high degree of confidence – basic ones means that the causes of changes can be understood
• Cross-talk between parameters needs to be reduced as much as possible
• Long-term changes need to consider RFI contamination, particularly for coastal regions