thunderstorm and lightning activities over the tibetan plateau xiushu qie asm-ste, lhasa, china,...
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Thunderstorm and lightning activities ovThunderstorm and lightning activities ov
er the Tibetan Plateauer the Tibetan Plateau
Xiushu QIEXiushu QIE
ASM-STE, Lhasa, China, July 21-23, 2010
Key Laboratory of Middle Atmosphere and Global Environment Observation (LAGEO), Institute of Atmospheric Physics,
Chinese Academy of Sciences, Beijing, China
Motivation• Tibetan Plateau exerts profound thermal and dynamical
influence on atmospheric circulation; It also plays an important role in the Asian monsoon circulation.
• Three major programs:– National experiment: May-August, 1979: Qinghai-Xizang
(Tibetan) Plateau Meteorology Experiments (QXPMEX):– National Experiment: May-August 1998, Tibetan Plateau
Experiments (TIPEX)– International Experiment (China-Japan-South Korea):
1997-? May- September, 1998: IOP of GEWEX ASIAN MONSOON EXPERIMENT (GAME-TIBET)
Water cycles; radiation budget; boundary layer; Energy processes; Influence of the plateau thermodynamics on the circulation, monsoon, climate change, and formation and development of disastrous weather system.
• Lightning is one of the main features of severe convection, and can be an indication of deep convection. The knowledge of lightning and thunderstorm is important to understand the heating and convective processes on the Plateau.
• Hydrological cycle maybe difficult to be estimated without a better understanding of variation of thunderstorms.
• Lightning and thunderstorm is important to the stratosphere and troposphere chemistry, and stratosphere-troposphere exchange as well.
• Lightning and thunderstorm could be unique because of the high elevation of the Plateau.
Importance of lightning research on the Plateau
Scientific issues
• What is the lightning distribution on the Plateau? And how does it related to the topography?
• What parameters control the lightning production?
• Are the lightning physics and charge structure inside the thunderstorm different from the lower regions? Why?
Data Sources
• Space-based lightning data: LIS/TRMM & OTD/Microlab-1
•PR radar on TRMM • NCEP data:• First lightning campaign on the Central TP
Spatial distribution of lightning activity over Tibetan Plateau
• The mean flash density is 3 fl·yr-1·km-2, and the max. is around (32ºN, 88ºE) with a peak value of 5.1 fl·yr-1·km-2.
7 8 8 0 8 2 8 4 8 6 8 8 9 0 9 2 9 4 9 6 9 8 1 0 0
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63 fl·yr-1·km-2
5.1 fl·yr-1·km-2
Lhasa
NaquAnduo
NCEP climatology of CMAP precipitation on the Tibetan Plateau in summer season.
Topography of the Tibetan Plateau
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NCEP climatology of surface wind field
• Response to the topography and surface thermodynamics.
Lightning distribution
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20
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Seasonal variation of lightningMaximum in June and July
Spreads out to whole TP along the valleys from the southeast of TP
Mainly occurs in the south of Himalayas
Enhancement clearly in JuneThe maximum moves westward
The maximum continues to move westward
Deceases clearly
April May
Jun Jul
Aug Sept
Time of maximum flash rate (LT)
78 80 82 84 86 88 90 92 94 96 98 100
78 80 82 84 86 88 90 92 94 96 98 100
26
28
30
32
34
36
26
28
30
32
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36
1112131415161718192021222324
15 13
14
12
13
16 15
15
15
16
16
17
1312
18
20
L / Eo
L/
No
12
18
14
16
15
Tarmu Base
Chaidamu Base
Mt. Kala
Kunlun
Mt. Kokoxili
Diurnal variation of max. flash rate peaks during 14:00-15:00 LT with exceptions of the prominent high mountain region, which peak earlier, and prominent low basins, which peak later.
Seasonal variation of flash rate and precipitation
0
0.00005
0.0001
0.00015
0.0002
0.00025
1-Jan 1-Mar 1-May 1-Jul 1-Sep 1-Nov
Prec
ipita
tion
rate
(kg/
m2 /s
)
0
0.003
0.006
0.009
0.012
0.015
0.018
Flas
h (f
l/km
2 /day
)
NCEPCMAPFlash
0
0. 5
1
1. 5
2
2. 5
3
J an Feb Mar Apr May J un J ul Aug Sep Oct Nov Dec
fl/r
ain
(10-
8 fl
/kg/
day)
• The flash density and rainfall shows maximum in early July.
• The most striking feature is the large amount of lightning in the relatively dry pre-monsoon season (March to May), 11% in May.
Ratio of lightning to rain • An interesting seasonal change in the lightning activity and rainfall relationship.
• The relative share of lightning activity as a proportion of the precipitation is largest at the beginning of the season.
Seasonal variation of flash rate and Cloud Work Function (Similar to CAPE)
• The cloud work function is much smaller in May than in September, but the flash density is almost the same. The cloud work function therefore only crudely captures the seasonal variation.• Parameterizations based on this variable would significantly underestimate the lightning activity in Spring.
0
150
300
450
600
750
1- J an 1-Mar 1-May 1- J ul 1-Sep 1-Nov
CW
F (J
/kg)
0
0. 003
0. 006
0. 009
0. 012
0. 015
0. 018
Flash
(fl/k
m2 /d
ay)
Flash rate and heat flux
0
100
200
300
400
1-Jan 1-Mar 1-May 1-Jul 1-Sep 1-Nov
Hea
t flu
x (W
/m2 )
0
0.003
0.006
0.009
0.012
0.015
0.018
Flas
h (fl
/km
2 /day
)
Flash
Sensible
Latent
Total
• Very different seasonality of the two fluxes add to give a smooth seasonal evolution which matches both the Spring and monsoon flash density.
Seasonal variation of products of S*CWF and B*CWF
• The role of the sensible heat
flux appears to primarily
modify the efficiency of
producing lightning for any
given CAPE.
• The cloud buoyancy and rainfall show a better seasonal relationship with flash when they are multiplied by Bowen ratio (ratio of sensible to latent heat flux)
0
10000
20000
30000
40000
50000
60000
70000
1- J an 1-Mar 1-May 1- J ul 1-Sep 1-Nov
S*C
WF
(W J/k
g m
2 )
0
0. 003
0. 006
0. 009
0. 012
0. 015
0. 018
Flash
(fl/k
m2 /d
ay)
Fl ash
S*CAPE
0
80
160
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320
400
1- J an 1-Mar 1-May 1- J ul 1-Sep 1-Nov
B*C
WF
(J/k
g)
0
0. 003
0. 006
0. 009
0. 012
0. 015
0. 018
Flash
(fl/k
m2 /d
ay)
First Lightning Campaign on the Plateau First Lightning Campaign on the Plateau
• June – Aug, 2003-2004
• Naqu Meteorology Bureau, central Plateau
• 31o28’47”N, 92o03’39.8”E, 4508 m asl
At 5300m asl At 4600m asl
Instrumentations
• Surface E : Field mill• Field change : Slow antenna
Fast antenna
• VHF/UHF radiation location: TOA & Interferometer techniques
• Optical : High speed camera(1000f/s) 、 Spectrum• NOx: NOx Anylazer• Surface meteorology observation• Sounding: at 07:00 and 19:00
• Small• Isolated• Weak• Frequently max: 5 storms/day
Developing stage of typical thundercloud
on the Plateau
Surface E filed underneath thunderstorm
- 20
- 10
0
10
20
30
40
Ti me
E (kV/m)
13: 57 14: 13 14: 30 14: 47
Hai l July 7, 2003-CG:3 +CG:0
• Thunderstorms are usually hailstorms on the Plateau with a hail fall period of about 10 min and the diameter of hailstone on the ground is less than 1 cm.
• Surface E field underneath thunderstorm was usually downward pointed on the Plateau, which suggests that there are a large positive charge region at the lower part of Tibetan Plateau thunderstorms.
E
Flash rate for 6 overhead thunderstorms in July
VHF pulse location results by using TOA method for IC discharge at 15:07 (LT) on July 8, 2004
0
0. 5
1
1. 5
2
2. 5
3
0 100 200 300 400 500
Ti me (ms)
Rela
tive
E c
hang
e
- 0. 2
0
0. 2
0. 4
0. 6
0. 8
1
1. 2
Rela
tive
E c
hang
e
Sl ow E
Fast E
a0
102030405060708090
270 280 290 300 310 320 330 340 350 360Azi muth ( o)
Elev
atio
n (
o )
1
2
23
4
b
0102030405060708090
0 50 100 150 200 250 300Ti me (ms)
Elev
atio
n (
o )
c0
60
120
180
240
300
360
0 50 100 150 200 250 300Ti me (ms)
Azim
uth
(o )
d
2-D development
Elevation evolution Azimuth evolution
E-field changes
• IC flashes take about 78.4% of the total.• IC discharges show polarity-inverted structure, and occur between up
per negative and lower positive charge region
Charge structure inside the thunderstorm over Tibetan Plateau
+-+
-+-
Naqu, Tibetan Plateau Lower altitude region
LPPC
23:12:17 23:32:17 23:52:17 0:12:17 0:32:17-20.0
-10.0
0.0
10.0
20.0
30.0
Inverted IC
IC
Spectrum
• Discharge is weak on the Plateau
Gungzhou
PlateauLower channel
temperaturenm
nm
Temporal variation of the maximumecho top of per day (From GAME-TIBET)
Uyeda et al., 2001; Feng et al., 2002
• The mean height of cloud base was 1.5-2 km above ground.• The cloud top was 8 km high with a maximum of 17 km. • The cloud is usually tall but thin with a max. echo area of about
2000 km2.
16:39:19 17:12:39 17:45:59 18:19:19 18:52:39 19:25:59Local T im e
-50
0
50E
lect
ric fi
eld
(kV
/m)
0 .00
0.10
0.20
0.30
[NO
x] (
ppm
v)
E[N O x]
0 10 20 30 40 50 600
10
20
30
40
dCLNO
x
=5.36+0.65Nl
R=0.84, N=9
dC
LN
Ox(p
pb
v)
Nl
NOx concentration and surface E-field underneath thunderstorm on July 10, 2003.
NOx increase and flash number for 9 thunderstorms in 2003.
ML9841B NOx analyzer and E-field mill
ConclusionsConclusions1. Lightning flashes are found to exhibit a continental-type behavior on the pl
ateau, but shows special characteristics under the thermal and dynamical effect of the Plateau orography.
2. The lightning activity generally peaks in June with a seasonal transition of lightning activity from east to west, showing a seasonal coincidence with the northwestward movement of Indian Monsoon.
3. The diurnal variation of lightning activity shows a single peak at 1600 LT on the plateau, but the maximum occurs earlier on the eastern and southern plateau, and earlier at prominent high mountain region and later at prominent low basins, indicating that the high elevation is conducive to the convection.
4. The surface total heat flux best accounts for the seasonal variation of lightning including the Spring anomalies. The sensible heat flux is important in modifying the efficiency of generating lightning from cloud buoyancy, at least in the Tibetan Plateau.
5. The charge structure inside the storm and lightning activity shows unique characteristics on the Plateau.
ThanksThanks
7 8 8 0 8 2 8 4 8 6 8 8 9 0 9 2 9 4 9 6 9 8 1 0 0
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Seasonal variation of lightningMaximum in June and July
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April May June
Aug.July Sept.
•The lightning activity in April mainly occurs in the south of Himalayas. •The lightning spreads out to the whole Plateau along the valleys from the southeast of the Plateau in May. •The lightning activities on the Central Plateau increases clearly in June. The most active period of lightning for the whole plateau is from late June to middle July. The maximum flash rate moves westward in July. •The maximum flash rate continues to move westward in August. The seasonal variation peaks in Aug. on the western Plateau. The activity deceases clearly in Sept.
0.3 fl·yr-1·km-2
The diurnal variations of radar echoecho top
echo top heightHeight of max. echo intensityMax. echo intensity
frequency of echoecho area
Flash rate for thunderstorms in August
Surface E filed underneath thunderstorm
20:04:08 20:37:28 21:10:48 21:44:08 22:17:28 22:50:48t
-60
-40
-20
0
20
40
E(k
v/m
)
Aug 13, 2003Hail fall: 21:00-21:09
Hail
IC: 236 +CG: 47 -CG: 1
Lightning flash on July 8, 2003
0
1
2
3
4
5
6
0 100 200 300 400 500 600 700Ti me (ms)
Rela
tive
E ch
ange
- 12
-10
-8
-6
-4
-2
0
2
Rela
tive
E ch
ange
R1
R2
R3
R4I C
16:59:22
• Most of -CG flashes follow long-duration of IC discharge with a
mean duration of about 181.4 ms.
E-field change produced by lightning flash
0
0. 4
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1. 6
2
0 100 200 300 400 500
Ti me (ms)
Rela
tive
E c
hang
e
- 9
- 7
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- 3
- 1
1
Rela
tive
E c
hang
e
Sl ow E
Fast E
I C
R1
R2
R3 R4
17:06:45July 8
• Long duration IC may suggest that -CG can only occur after
partly neutralized the lower positive charge region.