Evolution of radar and lightning parameters in summer thunderstorms

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1 Evolution of radar and lightning parameters in summer thunderstorms rms Rigo,, T., Argemí,, O., Bech,, J., and Pineda, N. Servei Meteorològic de Catalunya, c/berlín Barcelona 08029, SPAIN

2 INDEX Introduction The systems: radar and lightning detector networks The product and the real-time tool Spatial analysis Life cycle: radar and lightning parameters Conclusions

combining lightning and radar data To obtain models and features of

3 Introduction The objectives: To develop a real-time product capable to identify, track and generate alerts for severe weather events, combining lightning and radar data To obtain models and features of thunderstorms that affect the area: life-cycle and geographical distribution

Introduction Principles: It exists a good correlation between lightning and reflectivity values in most of thunderstorms that are observed in

4 Introduction Principles: It exists a good correlation between lightning and reflectivity values in most of thunderstorms that are observed in Catalonia The operational time of both systems (lightning detectors and radars) is compatible in order to work in near real-time (delay of 10 minutes)

5 The systems The XRAD network is composed by 4 radars, which are of Doppler type and operate on C-band. The short range product (which has the better spatial resolution) covers the whole area of Catalonia

The arrangement of the antennas in the country is designed to provide good

6 The systems The XDDE system is formed by 4 sensors, and a processing system in SMC headquarters. The arrangement of the antennas in the country is designed to provide good coverage to all of Catalonia, with precision in pinpointing lightning at 500 meters throughout a large part of Catalonian territory.

7 The product and real-time The methodology combines 4 type of objects: - precipitation observed with radar (>12 dbz) - well-developed convection - regions with IC activity - regions with CG activity An structure is the sum of all the objects present in the same area. These structures are identified and tracked in the past time, in order to know the phase of development

8 The product and real-time Lightning flashes (IC or CG) are grouped in pixels considering the same spatial resolution of the radar product. Objects obtained from rainfall estimated by radar (2D) and lightning activity (IC and CG) are determined using threshold methodologies. Radar convection (3D) is considered when values of reflectivity exceed some thresholds in more than one vertical level and for an area that has more than 16 km2 All the objects are integrated in a unique grid, with the purpose of obtaining the structures, for which are calculated some geometric features, as electrical and radar parameters.

which affect the area of analysis, and the surroundings.

9 The product and real-time The combination of both systems helps to complete the information of the thunderstorms which affect the area of analysis, and the surroundings. The product is helpful in the cases that one sensor is not working

Spatial analysis: summer of 2008 For radar

In the Pyrenees area (topographical influence) 2.

10 Spatial analysis: summer of 2008 For radar structures (2D and 3D), areas with higher activity are concentrated in two different geographical zones: 1. In the Pyrenees area (topographical influence) 2. In the Mediterranean Sea, in front of the central and southern coast (sea influence) 3D radar 2D radar

the region, it is necessary to difference

11 Spatial analysis: summer of 2008 In the case of CG and IC structures, the distribution is quite similar. Considering the geographical features of the region, it is necessary to difference between two type of cases: depending on the mechanism of forcing. CG IC

12 Life cycle of thunderstorms The diurnal cycle has been detected, observing the maximums of generation and dissipation of the structures

13 Life cycle of thunderstorms The life cycle of the thunderstorms has been divided in three stages: - development: growing of the different radar and lightning parameters - maturity: phase when the parameters reach and maintain the maximum values - dissipation: decrease of the tendency for all the parameters. Thunderstorms have been divided in three types, considering their severity (~number of CG/minute): weak, moderate, or strong

Life cycle of thunderstorms The longer stage for all types is maturity, existing a bigger difference with the other phases when more severe is the thunderstorm.

14 Life cycle of thunderstorms The longer stage for all types is maturity, existing a bigger difference with the other phases when more severe is the thunderstorm. Also the major part of the electrical activity of thunderstorms is registered in the maturity stage. However, it must be considered that at all stages is possible to detect flashes.

15 Life cycle of thunderstorms The distribution of duration of thunderstorms shows two peaks of maxima at 140 and 220 minutes. In general, as longer is the duration of the structure, more severe is it.

16 Life cycle of thunderstorms The maximum reflectivity and the precipitation estimated by the radar for the thunderstorms present a similar pattern, with higher values during maturity stage and for the strong cases.

area, number of IC and CG flashes, Zmax) allows to generate a model of life cycle

17 Life cycle of thunderstorms The normalization in time and frequency of different parameters (e.g. area, number of IC and CG flashes, Zmax) allows to generate a model of life cycle for thunderstorms using 25, 50 and 75 percentiles. Future objective consists in the implementation in real time, for nowcasting purposes. #CG Area #IC #ZMax

18 Life cycle of thunderstorms 120 Develop. Maturity Dissipation Top Isotherm - 40ºC: between and m Zmax Area 20 Flash: IC, CG <2 CG/min = 80 min CG/min = 110 min min >10 CG/min = 180 min min

19 Life cycle of thunderstorms Is it possible to due the same analysis for multicell systems

20 Life cycle of thunderstorms Is it possible to due the same analysis for multicell systems (This is not a joke, it's a real case!!!)

21 Life cycle of thunderstorms In multicellular structures, different stages of the forming cells are involved in the general live cycle This is a problem for the application of the presented methodology to these systems Then, the stages (development, maturity, and dissipation) must be redefined in order to consider other aspects Top (km) Zmx (dbz/10) #IC/6min Log(area) #CG/6min Closed maximums of lightning activity (~15 min)

22 Conclusions Thunderstorms features: two natures of development: due to topographic forcing (Pyrenees) or maritime influence (Mediterranean sea) diurnal cycle has been observed, with a maximum of birth at 12 UTC, and for death at 19 UTC major number of IC/CG flashes are produced during maturity stage. However, the number of flashes in the other phases aren t underestimated as more severe is the thunderstorm, higher is the maximum reflectivity observed and more longer is the duration

Conclusions Others aspects: the normalization of the parameters in duration and frequency allows to determine the life cycle of thunderstorms however, the application in real time is not easy,

23 Conclusions Others aspects: the normalization of the parameters in duration and frequency allows to determine the life cycle of thunderstorms however, the application in real time is not easy, because we don t know the duration of the thunderstorm for the cases of multicells, the application of this methodology must be modified, considering other parameters to determine the frontier between the different stages

A COMPARISON OF THE LIGHTNING JUMP ALGORITHM USING TOTAL LIGHTNING VERSUS CLOUD-TO-GROUND FLASHES.

A COMPARISON OF THE LIGHTNING JUMP ALGORITHM USING TOTAL LIGHTNING VERSUS CLOUD-TO-GROUND FLASHES. Rigo, T. (1), C. Farnell (1, 2) (1) Servei Meteorologic de Catalunya (2) University of Barcelona. Faculty