advecon$correcon$of$$ radar@based$probability$of$hail
TRANSCRIPT
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8th European Conference on Severe Storms – ECSS 2015 Wiener Neustadt, Austria, 14-‐18 September 2015
AdvecBon correcBon of radar-‐based probability of hail
in Belgium Maryna Lukach, Loris ForesB, Laurent Delobbe Royal Meteorological InsBtute of Belgium (RMI).
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Hail damage
M. Lukach
7-‐9 June 2014
≈ 500 MEUR
total loses
13-‐14 August 2015
≈ 1000 ha
fruit gardens
1/12
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Radar-based hail detection in Belgium Zaventem
Belgocontrol (2003)
Wideumont RMI (2001)
radius = 100 km
Jabbeke RMI (2012)
☐ Hail detec0on ☐ Advec0on ☐ Sta0s0cs 2/12 M. Lukach ✔
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Raw radar data archive
☐ Hail detec0on ☐ Advec0on ☐ Sta0s0cs 3/12 M. Lukach ✔
Radar in Wideumont (2002) mean availability 97%
scan 1 5 elevaBons, 5 minutes
scan 2 10 elevaBons, 15 minutes
Radar in Jabbeke (2012) mean availability 89%
Radar in Zaventem (2004) mean availability 95%
monitor mode 11 elevaBons, 5 minutes
single scan (from 2014) 15 elevaBons, 5 minutes
single scan (from 2012)
15 elevaBons, 5 minutes
hazardous mode 14 elevaBons, 5 minutes
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Radar-based probability of hail
H0 is a (00 C) – isotherm height
ETOP45 is a height of 45dBZ echotop
POH = 0.319 + 0.133(ETOP45 – H0) Holleman, (2000)
Waldvogel’s method ETOP45 ≥ H0 + 1.4
POH – Probability of Hail ETOP 4
5
H0
☐ Hail detec0on ☐ Advec0on ☐ Sta0s0cs 4/12 M. Lukach ✔
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Daily Maximum Probability of Hail
☐ Hail detec0on ☐ Advec0on ☐ Sta0s0cs 5/12 M. Lukach ✔
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Advection Scheme
The Op0cal Flow Constraint (OFC)
• Par0al deriva0ves es0mated using finite-‐difference method
• Domain split into a number of blocks
• OFC solved for each block using least squares
• Between block con0nuity imposed by Laplacian minimiza0on
• Interpola0on of block veloci0es on the fine observa0on grid
• Constant vector backward-‐in-‐0me advec0on of precipita0on field
€
DtR = u∂R∂x
+ v∂R∂y
+∂T∂t
= 0
☐ Hail detec0on ☐ Advec0on ☐ Sta0s0cs 6/12 M. Lukach ✔ ✔
(Bowler, Pierce and Seed, 2004)
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Velocity Vectors
☐ Hail detec0on ☐ Advec0on ☐ Sta0s0cs 7/12 M. Lukach ✔ ✔
calculated per block interpolated on fine grid
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Velocity Vectors Calculation
☐ Hail detec0on ☐ Advec0on ☐ Sta0s0cs 8/12 M. Lukach ✔ ✔
based on rain rates based on probability of hail
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Daily Maximum Probability of Hail
☐ Hail detec0on ☐ Advec0on ☐ Sta0s0cs 9/12 M. Lukach ✔ ✔
Not advected Advected
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Advection & number of hail days
☐ Hail detec0on ☐ Advec0on ☐ Sta0s0cs 10/12 M. Lukach ✔ ✔
Not advected mean 10 days
Advected mean 16 days
✔
Number of hail days in ten hail seasons 2002-‐2012 (60% POH threshold)
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Mean number of hail days Num
ber of days
☐ Hail detec0on ☐ Advec0on ☐ Sta0s0cs 11/12 M. Lukach ✔ ✔ ✔
0
20
40
60
80
100
120
0
10
20
30
40
50
60
70
10 20 30 40 50 60 70 80 90 100
Threshold, %
Number of hail days (POH > % threshold) during 2003-‐2012.
<-‐ Non advected
<-‐ Advected
% added advected -‐> right axis
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Conclusions
☐ Hail detec0on ☐ Advec0on ☐ Sta0s0cs 12/12 M. Lukach ✔ ✔ ✔
! The advection correction influence is significant for 15 minutes scan.
! Velocity field estimation is better with POH than with rain rates.
! Advection correction is important for hail statistics
! Will it be the case for 5 minutes scan?