Lightning activity and precipitation structure of hailstorms Guili Feng Cold and Arid Regions Environmentaland Engineering Research Institute, CAS

Xiushu Qie Institute of Atmospheric Physics, CAS

Tie Yuan Cold and Arid Regions Environmental and Engineering Research Institute, CAS

Shuzhen Niu The meteorological Observatory of Henan Province ICAE 2007 Beijing

Outline 1. Introduction 2. Data description 3. CG Lightning characteristics of hailstorms 4. The relationship between lightning activity and precipitation structure 5. Summary

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1. Introduction z MacGorman and Burgess(1994) and Stolzenburg(1994) found that severe weather generally takes place in the predominance period of positive CG lightning. z Seity et al.(2003) discovered that there is a good relationship between flash rate and updraft and echo volume with hail and graupel. Intracloud (IC) flash rate seems to be a good index of the vertical extension of graupel. z Lopez and Aubagnac(1997) noted that the number of total CG flashes is relative to graupel growth above freezing level. z Furthermore, some researchers(Lang2000, Soula2004) discovered that some severe storms produce abnormally low CG activity, contrary to the common idea that intense storms produce active CG lightning. z ……….

z Above research suggests a complex relationship between lightning activity and dynamical and microphysical processes in thunderstorms. ICAE 2007 Beijing

The Tropical Rainfall Measuring Mission (TRMM) satellite can provide not only three-dimensional cloud structure, but also lightning information as occurrence time, latitude, longitude and radiant energy. So TRMM data are helpful for studying the characteristics of lightning activity and its relationship with precipitation structure. The purpose of this work is to focus on the study of lightning activity in hailstorms and its relationship with microphysical process and precipitation structure by using TRMM orbit data and CG information. I hope it could be helpful to the application of lightning information obtained by China Lightning Detection Network to nowcasting of severe storms. ICAE 2007 Beijing

2. Data Description ¾The CG lightning data were obtained by the Henan Province Lightning Detection Network, which consists of 11 sensors and one data processing center ¾Total lightning data from TRMM Lightning Imaging Sensor(LIS) ¾Precipitation Structure from TRMM Precipitation Radar(PR) ¾Liquid and solid water content from TRMM Microwave Imager(TMI)

TRMM DATA were provided by GSFC NASA

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80% 85% 90% AnY

JiaoZ SanMX

LuoY

KaiF ShangQ

HenanBaoFProvince ZhouK NanY

Henan Province in Central China: Lat 112o—116oE Lon 32o—36oN

XinY HuangC

The distribution of 11 lightning detection stations (marked with circle) and detection efficiency (isolines) of the Henan lightning detection network ICAE 2007 Beijing

3. CG Characteristics of Hailstorms

There were 1,574,913 CG lightning flashes observed by Henan Province Lightning Detection Network in the period from 2002 to 2004. The percentage of positive CG lightning was 8.15% in the three years.

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Table 1 The statistical characteristics of 10 hailstorms that occurred in Henan during 2002-2004 Date

Location of hailfall

Weather phenomena a) b) Dmax , Vmax

Total lightning

Percentage of POP positive CG(%) (%)

Zhengzhou 5.0 cm, 19 m/s 1168 28.0 28.0 Kaifeng 3.0 cm, 21.3 m/s 858 35.1 35.1 Jiaozuo 1.2 cm, 22 m/s 672 23.6 23.6 Anyang 4.0 cm, 17.5 m/s 217 77.0 77.0 Xuchang,Jiaozuo, 2.0 cm, 20.6 m/s 1956 43.5 43.5 Luoyang,Pingdingshan 2003.06.20 Xinxiang,Kaifeng, 3.0 cm, 28 m/s 5114 25.3 25.3 Zhengzhou,Xuchang 2004.06.20 Puyang, Anyang 1.0 cm, 24 m/s 496 34.3 343.3 2004.06.24 Wuzhi 2.0 cm, 28 m/s 335 45.4 45.4 2004.06.25 Huixian 3.0 cm, 20 m/s 65 100.0 100.0 2004.07.08 Yucheng,Xiayi 2.0 cm, 18 m/s 793 42.9 42.9 a) and b): Dmax, Vmax stands for maximum diameter of hailstone and maximum instantaneous wind speed on the ground, respectively. 2002.07.19 2003.05.18 2003.06.05 2003.06.11 2003.06.19

The percentage of positive CG of ten hailstorms is high: average value of 45.5% ,ranging from 23.6% to 100% Climatological average value is 8.15%

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The evolution of CG lightning rate per 10 minutes for the hailstorm that occurred on 19 June 2003. The line below the time axis stands for hail-falling period. ICAE 2007 Beijing

a. 16:21 on 19 June 2003

b. 18:30 on 19 June 2003

Positive(+) and negative(-) CG flashes within 10mins center on ths scan time superposed on CAPPI at 2.5km from Zhengzhou Doppler radar.

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hail

The hail region seemed to correspond to the area with dense positive CG flashes. Positive CG was not active in the region with high negative CG flash density, and vice versa.

Distribution of total CG lightning in the hailstorm in Henan Province on 19 June 2003. + for positive CG ;

▅

for negative CG ICAE 2007 Beijing

4.Relationship between lightning activity and precipitation structure (1) Horizontal and vertical structure of precipitation (2) The relationship between lightning activity and precipitation structure (3) The relationship between lightning and microphysical structure

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(1) Horizontal and vertical structure of precipitation Hourly IR1 cloud image

Hailstorm1（HS1）： -- Occurred from 16:00 to 20:00(BST) on 19 June 2003 -- Affected jointly by the convergence aloft line, a weak cold front and the increase of lower level air temperature by solar heating. --The maximum diameter of hailstones was about 2 cm, and the maximum instantaneous surface wind speed reached 20.6 m/s. ICAE 2007 Beijing

Hourly IR1 cloud image

Hailstorm2（HS2）： -- Occurred from 19:00 to 21:00(BST) on 19 July 2002 --Affected jointly by a cold eddy aloft and a surface cold front. -- heavy rain (maximum rainfall of 57 mm within two hours) and hail (maximum hailstone diameter of 5 cm) caused serious economic loss due to ICAE 2007 Beijing the long duration of hail and damaging winds.

19:11 19 July 2002 (HS2) Orbit Number: 26660

17:03 19 June 2003 (HS1) Orbit Number: 31880

TRMM

Height /km

Height /km

Height /km

Height /km

PR

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19:11 19/07/2002 TRMM

Reflectivity dBz

2A23 of PR

Rain type

2A25 of PR ICAE 2007 Beijing

Table 2. Statistical characteristics of precipitation observed by PR in two hailstorms. Date Rain （orbit number） type

Number of pixels

2003.06.19 （31880）

stratiform convective

166 197

Rmax on pixel (mm/h) 8.8 130.3

2002.07.19 （26660）

stratiform convetive

649 391

9.0 109.5

Total Rain rate rain rate averaged by pixel (mm/h) (mm/h) 122.1 0.7 4665.1 23.8 1037.1 6026.7

1.6 15.4

--Convective

rain predominated in total rainfall in both storms, accounting for 97% and 85%, respectively.

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(2) The relationship between lightning activity and precipitation structure

19 June 2003

19 July 2002 Observed by LIS and PR ICAE 2007 Beijing

Flash count

200 150

20

100 10

50 0

0 0

10

20 30 40 50 Reflectivity (dBZ)

Percentage (%)

The histogram of variance of lightning number with reflectivity

60

•The peak flash count corresponds to the reflectivity of 35-40 dBZ at 6 km altitude, instead of the strongest reflectivity. •About 90% of lightning flashes fall into the reflectivity range from 15 to 50 dBZ, and 23% in the range of 35-40 dBZ. •83% of convective rain pixels produced lightning, whereas just 3% from the stratiform region did so. ICAE 2007 Beijing

(3) The relationship between lightning and microphysical structure C

D

There were 97 flashes during the LIS staring period, but only three positive CG flashes observed by the ground-based location network in the same period. So the ratio of IC to CG flashes was about 31:1.

+

stands for total lightning from LIS

+

-

and stands for positive and negative CG within 10 min from HLDN

lightning superposed on precipitation ice content (TMI) at 6 km altitude.

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Height /km Height /km Height /km

b: vertical profile of precipitation ice content along AB. c: vertical profile of cloud water content along AB. d: reflectivity vertical profile, the blue and red short vertical bars at bottom stands for total lightning from LIS and positive CG from groundbased location system, respectively, within ±10 km along line CD. ICAE 2007 Beijing

F=0.0164IWC+0.00335

F (fl/min/km )

F (unit in fl/km2/min): total lightning numbers are counted in each area cell of 15km×15km, then divided by staring time to get the flash rate.

2

IWC (unit in kg/m2): vertical ice water content containing all ice particles above 0oC is integrated in each pixel, and the average IWC in each cell of 15km ×15km is worked out.

IWC（kg/m2） The scatter plot of total flash rate F and ice water content IWC with the solid line as the fitted line. ICAE 2007 Beijing

5. Summary „ The percentage of positive CG lightning is high in hailstorms. „ There is an obvious jump in flash rate at the rapidly developing stage of these storms. During the hail-falling period, the positive CG lightning flashes are very active, and the negative CG flash rate generally declines with the increase of positive CG flash rate. At the dissipating stage of storms, the CG flash rate decreases remarkably. „ The total flash rates, in two analyzed typical severe hailstorms are 183 fl/min and 55 fl/min, respectively, and the corresponding ratios of IC to CG lightning are quite high. Convective rain is the overwhelming contributor to the total rainfall, and its contribution accounts for 85% and 97%, respectively.

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„ Severe weather(hailfalling,damaged wind ) often occurs in strong echo (>40dBZ) region with dense positive CG. Total lightning flashes mostly occur in the strong echo region and its surroundings, 90% of total flashes occurring in the range between 15 and 50 dBZ. Lightning activities are about 20 times more in convective region than in stratiform region. „There is a linear correlation between ice water content IWC and flash rate F, Their correlation coefficient is 0.69.

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