Areal rainfall statistics based on radar observations - ESSL
Transcript of Areal rainfall statistics based on radar observations - ESSL
Areal rainfall statisticsbased on radar observations
Edouard Goudenhoofdt and Laurent DelobbeRoyal Meteorological Institute of Belgium (RMIB)
June 3, 2013, European Conference on Severe Storms
RMIB operates a C-band radar since 2001
I Single-polarisation
I Doppler filtering (clutter)
I Located 600 m asl,range of 240 km
I 5-elevation every 5 min(during 2 min)
I Resolution : 1° in azimuth,250 m in range
Quantitative precipitation estimates��
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��I PCAPPI 800 m above
radar level
I Z = 200R1.6
I Hail:Z > 53 dBZ → 53 dBZ(75 mm/h)
I Cartesian grid 500 mresolution.
I Accumulation by linearinterpolation.
To be validated : clutter mitigation and profilecorrection.
Quantitative precipitation estimates��
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��I PCAPPI 800 m above
radar level
I Z = 200R1.6
I Hail:Z > 53 dBZ → 53 dBZ(75 mm/h)
I Cartesian grid 500 mresolution.
I Accumulation by linearinterpolation.
To be validated : clutter mitigation and profilecorrection.
Merging and verification with denseraingauge networks.
50 km
100 km
Radar and rain gauge networks
SPW (69)RMI(84)Radar
I hourly automaticraingauge network (blue)
I 1E 6 scale difference !I mean field bias : simple
and robustI max range 120 kmI min value 0.1 mmI min 10 valid pairs
A 8-year verification reveals relatively goodaccuracy.
Merging and verification with denseraingauge networks.
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I hourly automaticraingauge network (blue)
I 1E 6 scale difference !I mean field bias : simple
and robustI max range 120 kmI min value 0.1 mmI min 10 valid pairs
A 8-year verification reveals relatively goodaccuracy.
Mean hourly rainfall depth 2005-2012
150 100 50 0 50 100 150
150
100
50
0
50
100
150
0.06
0.07
0.08
0.09
0.10
0.11
0.12
0.13
0.14
['A
CR
R']
['bewid - 2012-01-01 00:00:00 - STAT(scan1_cap_aclPT1H_mfb_stmeanP8Y)']
I unconditional mean(dry periods are included)
I minimum 0.07 mm(600 mm/year) in theplains
I maximum 0.14 mm(1200 mm/year) in thehills
I clear correlation withtopography (cluttereffect?)
Those results are consistent with raingaugeclimatology.
Mean hourly rainfall depth 2005-2012
180 km
0 200 400 600 800
Elevation [m]
I unconditional mean(dry periods are included)
I minimum 0.07 mm(600 mm/year) in theplains
I maximum 0.14 mm(1200 mm/year) in thehills
I clear correlation withtopography (cluttereffect?)
Those results are consistent with raingaugeclimatology.
Mean hourly rainfall depth 2005-2012
150 100 50 0 50 100 150
150
100
50
0
50
100
150
0.06
0.07
0.08
0.09
0.10
0.11
0.12
0.13
0.14
['A
CR
R']
['bewid - 2012-01-01 00:00:00 - STAT(scan1_cap_aclPT1H_mfb_stmeanP8Y)']
I unconditional mean(dry periods are included)
I minimum 0.07 mm(600 mm/year) in theplains
I maximum 0.14 mm(1200 mm/year) in thehills
I clear correlation withtopography (cluttereffect?)
Those results are consistent with raingaugeclimatology.
Max hourly rainfall depth 2005-2012
200 100 0 100 200
200
100
0
100
200
10
15
20
25
30
35
40
45
50
55
60
['A
CR
R']
['bewid - 2013-01-01 00:00:00 - STAT(scan1_cap_aclPT1H_mfb_stmaxP8Y)']
I High small scalevariations.
I No significant large scaletrend.
I Slightly more max inSouth-East.
Highest values are due to stationary cells and/orhail.
Max hourly rainfall depth 2005-2012
200 100 0 100 200
200
100
0
100
200
10
15
20
25
30
35
40
45
50
55
60
['A
CR
R']
['bewid - 2013-01-01 00:00:00 - STAT(scan1_cap_aclPT1H_mfb_stmaxP8Y)']
I High small scalevariations.
I No significant large scaletrend.
I Slightly more max inSouth-East.
Highest values are due to stationary cells and/orhail.
Probability of hourly rainfall (1 mm).
150 100 50 0 50 100 150
150
100
50
0
50
100
150
1.2
1.6
2.0
2.4
2.8
3.2
3.6
4.0
%
['bewid - 2013-01-01 00:00:00 - STAT(scan1_cap_aclPT1H_mfb_spe1P8Y)']
I ranges from 2 % to4 %
I positive effect oftopography
Highly correlated with mean hourly rainfall
Probability of hourly rainfall (1 mm).
150 100 50 0 50 100 150
150
100
50
0
50
100
150
1.2
1.6
2.0
2.4
2.8
3.2
3.6
4.0
%
['bewid - 2013-01-01 00:00:00 - STAT(scan1_cap_aclPT1H_mfb_spe1P8Y)']
I ranges from 2 % to4 %
I positive effect oftopography
Highly correlated with mean hourly rainfall
Probability of rainfall exceeding 10 mm.
200 100 0 100 200
200
100
0
100
200
0.016
0.024
0.032
0.040
0.048
0.056
0.064
0.072
%
['bewid - 2013-01-01 00:00:00 - STAT(scan1_cap_aclPT1H_mfb_spe10P8Y)']
I ranges from 0.02 %to 0.06 %
I less effect oftopography
I higher probabilitySouth-East of radar
Partially correlated with max hourly rainfall
Probability of rainfall exceeding 10 mm.
200 100 0 100 200
200
100
0
100
200
0.016
0.024
0.032
0.040
0.048
0.056
0.064
0.072
%
['bewid - 2013-01-01 00:00:00 - STAT(scan1_cap_aclPT1H_mfb_spe10P8Y)']
I ranges from 0.02 %to 0.06 %
I less effect oftopography
I higher probabilitySouth-East of radar
Partially correlated with max hourly rainfall
Exceedance probability of four differentriver catchment.
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I catchment ofdifferent size
I smooth andlogarithmicbehavior
I smallest catchment: max 20 mm
I largest catchment :max 8 mm
Computation of return periods is limited (8 years).
Exceedance probability of four differentriver catchment.
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I catchment ofdifferent size
I smooth andlogarithmicbehavior
I smallest catchment: max 20 mm
I largest catchment :max 8 mm
Computation of return periods is limited (8 years).
Exceedance probability of four differentriver catchment.
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I catchment ofdifferent size
I smooth andlogarithmicbehavior
I smallest catchment: max 20 mm
I largest catchment :max 8 mm
Computation of return periods is limited (8 years).
Exceedance probability of adjacentequal-area squares.
0.1 0.2 0.5 1 2 5 10 20 50Mean rainfall depth [mm]
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
Pro
babili
ty
Area = 25 km2
I simpleapproximation of acatchment
I distance less than100 km for bestaccuracy
I space and timestationarity
I independencebetween windows?
Possibility to compute longer return periods?(theoretically 8 years x number of windows)
Exceedance probability of adjacentequal-area squares.
0.1 0.2 0.5 1 2 5 10 20 50Mean rainfall depth [mm]
10-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
Pro
babili
ty
Area = 100 km2
I simpleapproximation of acatchment
I distance less than100 km for bestaccuracy
I space and timestationarity
I independencebetween windows?
Possibility to compute longer return periods?(theoretically 8 years x number of windows)
Exceedance probability of adjacentequal-area squares.
0.1 0.2 0.5 1 2 5 10 20 50Mean rainfall depth [mm]
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
Pro
babili
ty
Area = 400 km2
I simpleapproximation of acatchment
I distance less than100 km for bestaccuracy
I space and timestationarity
I independencebetween windows?
Possibility to compute longer return periods?(theoretically 8 years x number of windows)
Conclusions
I Weather radar provide good areal rainfall estimates.
I Areal rainfall exceedance probability can be computed.
I Important application to river catchment.
I Longer return periods could be computed using a largerdomain.
Outlook
I Best single radar QPE reanalysis (almost ready)
I Radar composite to mitigate attenuation and beambroadening
I Effect of rainfall depth duration
I Proof using a proper theoretical framework