1 Impact of the large-scale wind and mesoscale shallow flows on the development of cumulonimbus...
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Transcript of 1 Impact of the large-scale wind and mesoscale shallow flows on the development of cumulonimbus...
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Impact of the large-scale wind and mesoscale shallow flows on the development of
cumulonimbus clouds over Istria
Karmen Babić, Marko Kvakić & Maja Telišman Prtenjak
Department of Geophysics
http://www.gfz.hr/
2
CONTENTS:
1. Introduction, aim & motivation
2. WRF model
3. Numerical simulations
4. Summary and conclusions
Department of Geophysics
http://www.gfz.hr/
3
Introduction
Department of Geophysics
http://www.gfz.hr/
• The role of the SB circulation, including SB front in triggering convection has long been recognized
•Convection initiation often takes place when 2 or more features (fronts and /or rolls, thunderstorm outflows) collide or merge.
•Locations of the very extensive Cb and SB research, e.g: Florida (e.g. Pielke, 1974; Yuter and Houze, 1995; ) Australia & Indonesian archipelago (MCTEX; e.g. Saito et al., 2001) Japan, Kanto plain (e.g. Sano and Tsuboki, 2006) Spain (e.g. Azorín-Molina et al., 2009) ……
Holland and McBride (1989)
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Department of Geophysics
http://www.gfz.hr/
Italy
CroatiaAlps
Istria: an area with the highest frequency of thunder in Croatia
The mean annual number of days withthunderstorms (1948-1966); Penzar et al. (2001)
Perod: 2006-2009
0
10
20
30
40
50
60
IV V VI VII VIII IX X
months
num
ber
of d
ays
wit
h lig
htni
ng
East Croatia
CentralCroatiamountainousCroatiaNorth Adriatic
CentralAdriaticSouth Adriatic
Lightning data from LINET network
the analysis of some spatial and temporal characteristics of lightning in 4-years warm period (2006-2009)
Arbitrary choiceConvective day = a day with more than
10 strokes of the total discharge data (CG+IC) detected per hour
across limited area
402 convective days
Mikuš et al. (2012)
Climatology of convection in Croatia
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Department of Geophysics
http://www.gfz.hr/
Above northeastern Adriatic
the most common summer weather types during convective days:
non-gradient (NG) pressure conditions & low pressure pattern (C, T)
the peak in daytime convective activity during NG weather type in July
in 82% of overall days with convective activity 3 dominant large-scale windregimes SW, NE, NW
Mikuš et al. (2012)
01020304050607080
IV V VI VII VIII IX Xrela
tiv
e f
req
ue
nc
y (
%)
NG C T A
0
10
20
30
40
50
60
IV V VI VII VIII IX Xrela
tiv
e f
req
ue
nc
y (
%)
SW NW NE W
weather types
wind regimes
6
Department of Geophysics
http://www.gfz.hr/
SB climatology over Istria (1997–2006)
∆T → prime peak in August, → secondary max in Junedue to dominance of daytime
convection
SLB frequency→ max in August up to65%of all summer days(June-September)
Pula-airport
1
2
3
4
5
6
7
8
9
10
11
12
VI VII VIII IXmonths
DT
(°C
)
15
25
35
45
55
65
75
SL
B f
req
ue
nc
y (%
)
Pazin
13
16
19
lE
10
l7224
N
1
W
u (m s-1)
v (
m s
-1)
-1
0
1
2
-3 -2 -1 0 1 2
S
hodograph
0
1
2
3
4
5
1 4 7 10 13 16 19 22
t (CET)
Mea
n w
ind
sp
eed
(m s
-1)
0
10
20
30
40
50
60
70
80
90
100
ste
ad
ine
ss
(%
)
Pula-airport
CW rotation of wind vectors
mean SB speed about 3.5 m/s
mean LB speed about 2 m/s
low steadiness of SB between 10-13 CET
In average during summerAt least every second day with SB
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Department of Geophysics
http://www.gfz.hr/
QUESTION:
Sea breeze + large-scale wind
Convective activity?????
Cb development????
QUESTION:
Sea breeze + large-scale wind
Convective activity?????
Cb development????
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Setup of the model: two-way nesting Lambert conformal projection
3 domains : x = 13.5 km, 4.5 km, 1.5 km 81 vertical levels (terrain- following)
Initial and boundary data from ECMWF
Schemes: MYJ scheme for the PBL; RRTM for the longwave radiation; Dudhia scheme for the shortwave
radiation; Lin microphysics scheme; Eta surface layer scheme; five-layer thermal diffusion scheme for the
soil temperature; Betts-Miller-Janjic cumulus
parameterization two outer domain
WRF-ARW model
mzkmztop 10)(,20 min D
Department of Geophysics
http://www.gfz.hr/
9
In the finest model domain
date Dominantlarge-scale
wind
Cb durationonset – end
(CET)
SB durationonset – end
(CET)
Max SB speed
Case A 09 July 2006 NE 10:50 – 16:00 9- 19 5.1
Case B 08 June 2003 SW 12:40 - 16:30 9- 20 3.6
Case C 08 August 2006 NW 11:10 – 16:30 9- 13 4.1
Department of Geophysics
http://www.gfz.hr/
For Case A sensitivity test: without microphysics
Three selected cases simulated by WRF
Similarities the Cb cloud over Istria weather type: almost non-gradient pressure conditions SB at the Pula-airport site (tip of the Istria peninsula).
The main dissimilarity wind regimes
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Department of Geophysics
http://www.gfz.hr/
LINET (CG+IC) data between 14-15 CET
MAX ECHO (DBZ) at 13 CET CASE A = large scale wind NE
-11 CET – formation of convergence zone ( 15 km inland, 75 km long )
- 12 CET – cloudiness and precipitatation 5 mm – 15 mm over Istria
Convective activity
- 13 CET – formation of Cb (Pazin)- 14 – 16 CET – disipation of Cb (moved to south) along convergence zone
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WRF 10-m surface wind at 14 CET
Department of Geophysics
http://www.gfz.hr/
Measured surface wind field
statistical indices at 14 CET
Wspeed (m/s)
Wdirection
(°)
Temp
(°C)
MAE 1.20 45.45 4.08
RMSE 1.54 64.31 3.39
IOA 0.66 0.89 0.65
20 km
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Department of Geophysics
http://www.gfz.hr/ Results
- large-scale NE wind enhanced the SB at the southeastern Istrian coast
- prevented deeper penetration of the dominant western SB over the peninsula - convergence zone is not moved to east too much
- indication for the superposition between SB front and outflow below Cb along convegence zone
- Sb weaker after the storm; - Cb act destrucive on the air-sea temp. diff.
17 CET
17 CET
Comparison between control A run and sensitivity test
CASE A = large scale wind NE
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WRF 10-m surface wind at 14 CET
11 CET – formation of convergence zone ( 30 km inland, 75 km long )
11 – 12 CET – cloudiness and precipitation 10 mm – 15 mm
Convective activity
Department of Geophysics
http://www.gfz.hr/
CASE B = large scale wind SWMeasured surface wind field
30 km
14
deeper penetration of SB inland
convergence zone is moved to east
Department of Geophysics
http://www.gfz.hr/
MAX ECHO (DBZ) at 13:50 CET
CG lightning data at 13:50 CET
13 CET – formation of Cb ( north part of Istria )14 – 16 CET – disipation of Cb
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WRF 10-m surface wind at 14 CET
Department of Geophysics
http://www.gfz.hr/
CASE C = large scale wind NWMeasured surface wind field
30 km -10 CET – formation of convergence zone (30 km, 50 km long – highly curved in space)
- 11 CET – penetration of SB deeper over land (in the central part of peninsula )
-12 – cloudiness and precipitation 5 – 25 mm
convective activity
30 km
16
13 CET – Cb moved southward of Istria, Rijeka and Cres (cloudiness and 45 mm precipitation) large-scale NW wind is superimposed on the western SB producing larger inland penetration and amplifying the magnitude of the SB speed 14 – 17 CET – dissipation of Cb
Department of Geophysics
http://www.gfz.hr/
CASE C = large scale wind NWMAX ECHO (DBZ) at 13:50 CET
LINET (CG+IC) data between 14-15 CET
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Summary
-The large-scale winds (LSW) influence the SB development and evolution, therefore creating the zone of convergence
-The interaction SB - LSW reinforces the convergence of the flow field in the boundary layer and consequently the intensity of SB fronts and its updrafts
- The certain amount of cloudiness and precipitation has been developed in the zone of the convergence between 12 CET and 13 CET
- The ZC, cloudiness and percipitation depended on the type of the LSW
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THANK YOU FOR YOUR ATTENTION !!!!!!!!!!!!