detailed flow, hydrometeor and lightning characteristics ... · icam 2011, aviemore, scotland (uk),...
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Folie 1
Detailed flow, hydrometeor and lightning characteristics of an isolated, hail
producing thunderstorm during COPS
Kersten Schmidt, Martin Hagen, Hartmut Höller, Hans Volkert
Institut für Physik der Atmosphäre, DLR Oberpfaffenhofen
Abteilungsseminar > Wolkenphysik mit dem Wolkenradar > Kersten Schmidt > 02.03.2010
Folie 2ICAM 2011, Aviemore, Scotland (UK), 23-27 May 2011 Kersten Schmidt Folie 2
Results from previous studies of IOP 8b (15 July 2007)
Observation
• Kottmeier et al. 2008, MetZet• Aoshima et al. 2008, MetZet• Kalthoff et al. 2009, AR• Behrendt et al. 2011, QJRMS
Modelling
Barthlott et al. 2009, AR Kirshbaum et al. 2010, JAS Richard et al. 2011, QJRMS Barthlott et al. 2011, QJRMS
• General observation results with
special focus on convection initiation• Evaluation of triggering mechanism
(radar convergence line)• Evaluation of moist condition
• no deep convection by using COSMO-DE
but triggering of convection matches well• Intercomparison of different model results• Comparison with observed moisture,
changing of Meso-NH-model parameters
current step: evaluation of mature state and dissipation
Abteilungsseminar > Wolkenphysik mit dem Wolkenradar > Kersten Schmidt > 02.03.2010
Folie 3ICAM 2011, Aviemore, Scotland (UK), 23-27 May 2011 Kersten Schmidt Folie 3
Approach: Synergy of sensors
Multiple-Doppler radar analysis of 15 July 2007,
additional validation with photos, lightning and MSG data
Development of cloud-top height evaluated from radar
and MSG data
Analysis of microphysics of clouds by using polarimetric
radar data
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Initiation: Horizontal development
parallax corrected positions of BT10.7µm
≤ 5°C Radar sites
multiple-Doppler area~ 80 km
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Life cycle and vertical development
Initiation
Mature state
Decay
Tropopause
discrepancy between radar cloud height and
MSG related cloud height (ice shield)
lapse rate:
0.6 K per 100 m
3 km at 5 min
-> vertical motion
~ 10 m/s
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Life cycle and vertical development
Tropopause
reference time steps for triple
Doppler calculation
lapse rate:
0.6 K per 100 m
3 km at 5 min
-> vertical motion
~ 10 m/s
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radar volume scan time intervals
Feldberg radar Türkheim radar Karlsruhe radarreference time for Multiple Doppler
calculation
14:30 – 14:37 14:30 – 14:37 14:30 – 14:34 14:35
14:45 – 14:52 14:45 – 14:52 14:50 – 14:54 14:50
15:00 – 15:07 15:00 – 15:07 15:00 – 15:04 15:05
15:15 – 15:22 15:15 – 15:22 15:20 – 15:24 15:20
POLDIRAD RHI scan Feldberg radar Türkheim radar Karlsruhe radar
reference time for Multiple Doppler
calculation
14:43 - 14:45 14:45 – 14:52 14:45 – 14:52 14:30 – 14:34 14:43
Validation case
Data
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Multiple Doppler calculation
● radar data interpolation by using REORDER (by NCAR)
● GRID distance in all 3 dimensions: 500m (tested: 300m, 1km)
● Cressman weighting scheme
● Determination of storm motion (best overlap of reflectivity)
● multiple doppler calculation by using CEDRIC (by NCAR)
● calculation horizontal wind components u,v
● smoothing of wind field
● calculation of vertical wind by using variation integration
procedure with boundary conditions
Method
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Mid cloud flow structure at 5 km (msl) Result
km
km
• Contour of reflectivity (10 dbZ interval, starting from 10 dBZ)• Horizontal wind vectors relative to the storm motion• updraft downdraft
inflow
outflow
in
out
con
ne
ct
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Mean vertical velocity
Standard deviation of
vertical velocity
average of updrafts
(w>0)
average of downdrafts
(w<0)
Statistics: Vertical wind from triple Doppler
14:35 14:50
15:05 15:20
• Updraft higher than downdraft at the early phase (14:35)
• Dominating wind direction changes from updraft to downdraft:
decreasing of storm intensity
• Decreasing of absolute vertical wind speed indicate decay state
(15:20)
• Mean values and standard deviation
decreases at top and bottom (influence
of boundary condition)
• Low border limited to 1.7 km: radar
beam cannot reach the ground
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first photo from serie:
timestamp: 14:43 UTC location: POLDIRAD
Validation
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add scale: elevation, azimuth
Validation
ele
vatio
n [
°]
azimuth [°]
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verify: Black Forest silhouette from SRTM topography data
Validation
ele
vatio
n [
°]
azimuth [°]
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add all lightning locations (cloud and ground stokes) 14:34 – 14:45 UTC photo time: 14:43 UTC
Validation
ele
vatio
n [
°]
azimuth [°]
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Reflectivity composit from triple-Doppler analysis
at 14:35 UTC (7 minutes before the photo was taken)
Validation
ele
vatio
n [
°]
azimuth [°]
0 dBZ
10 dBZ
20 dBZ 30 dBZ
40 dBZ
motiondirection
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maximum updraft in line of sight from multiple-Doppler analysis
Validation
ele
vatio
n [
°]
azimuth [°]
2 m/s
7 m/s
12 m/s
2 m/s
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maximum downdraft in line of sight from multiple-Doppler analysis
Validation
ele
vatio
n [
°]
azimuth [°]
-3 m/s
-3 m/s
-3 m/s
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Consistency check for triple Doppler results
measured radial velocity from each
radar site
derived radial component corresponding to radar site
from 3D triple Doppler calculation
Higher dynamics (e.g. more turbulence)
in the early Mature state?
rms v3D = 1n ∑ v r Measured
i− v r 3D
i
2
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14:43 – 14:45 UTC
Scan position of POLDIRAD RHI scans
ele
vatio
n [
°]
azimuth [°]
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Quality check by using POLDIRAD
main part of discrepancy corresponds with
occurrences of turbulence
denoted by low ρHV
and high spectral width
retrieved vr
5 m/s higher than measured
correlation coefficient
retrieved vr
5 m/s lower than measured
Measured and retrieved radial velocities v
r
low ρHV
: high particle variation in type, shape and orientation
high σ: broad range of radial velocity values
lightning
σ
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Estimation of hydro-meteors by only using of
ZDR and LDR after Höller et al. 1994
Estimation of hydrometeor content
Comparison:
Estimation of hail signal (HDR) by using ZDR and Z
after Aydin et al. 1986
mixing zone (water, ice)
evidence of hail below melting zone:
• HDR (Z+ZDR)
• classification (LDR+ZDR)
• hail spike at reflectivity
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Temporal evolution of hydrometeor content
• counting of radar range bins for each hydrometeor type per altitude level (1km)
• normalizing by dividing through total count
• summarizing 5 RHI scans per time interval
14:43 14:53 15:03 15:13
• fraction of hail is negligible
• Early phase dominated by ice particles (snow, graupel)
• Mean altitude level of ice particles decreases with time, but ice shield seen at photos and MSG data not detected by radar
method results
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Contours: Triple-radar derived cloud-top heights ( 8km, 12km, 13km )
Points: Parallax corrected cloud-top positions (MSG IR-channel) with color coded BT
Cloud-top height
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Cloud-top height
Discrepancy of cloud-top location during the dissipation state
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Triple-Doppler results
horizontal wind
Maximum reflectivity in line of sight
Radar cross section reflectivity
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• Documentation of full life cycle by using
– radar data (inclusive multiple Doppler approach)
– MSG and lightning data
• Most active phase between 14:35 and 14:45
– cloud extended to tropopause
– raised updraft, high cloud dynamic (turbulence), lightning, hail
• Temporal evolution of hydrometeor profiles (consistent with simulations?)
• Discrepancy between radar and satellite & photo due to small ice particles
• Future work: comparison with model results
Conclusion
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Spatial resolution: 500 m
altitude level: 5 km
Outlook: MesoNH-model results from E. Richard48.6
48.4
48.3
48.2
48.18.33 8.44 8.54 8.64 8.75 8.44 8.54 8.64 8.75 8.44 8.54 8.64 8.75 8.44 8.54 8.64 8.75
10
7.5
5.0
2.5
-2.5
-5.0
-7.5
-10
w [m/s]
Small spatial (or temporal) discrepancies between model and observation
Different role of southern cell
Same inflow and outflow characteristics
14:5014:35 15:05 15:20
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Thank you for your attention!
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Mean horizontal wind speed with standard deviation
Mean wind direction derived from mean u and v wind components
Statistics: Horizontal wind from triple Doppler
•wind shear decreases during life time•profiles of mean wind speed ~ constant•standard deviation of mean horizontal
wind correlated with cloud dynamics