Status of Lightning Imager Science Team (LIST) Activities

1. Status of Lightning Imager Science Team (LIST) Activities Jochen Grandell MET division Presentation to SWG-29 (September 2010)

2. Topics • Lightning observation from space • MTG LI Product processing basics • MTG Lightning Imager Science Team (LIST) • LIST Meetings • Studies • “Generation of Artificial Proxy Data for the MTG Lightning Imager” • “Inter-comparison of LIS and Ground-Based Lightning Location System (LLS) Observations” • “Potential synergy of the global ATDnet and MTG LI measurements” • “Validation and verification strategy for MTG LI measurements”

3. Topics • Lightning observation from space • MTG LI Product processing basics • MTG Lightning Imager Science Team (LIST) • LIST Meetings • Studies • “Generation of Artificial Proxy Data for the MTG Lightning Imager” • “Inter-comparison of LIS and Ground-Based Lightning Location System (LLS) Observations” • “Potential synergy of the global ATDnet and MTG LI measurements” • “Validation and verification strategy for MTG LI measurements”

4. Lightning Detection from Space • Feasibility of lightning detection from space by optical sensors has been proven successfully by NASA instruments OTD (1995-2000) and LIS (1997-present) on low earth orbits OTD LIS • LIS – Lightning Imaging Sensor • Altitude 400 km • Orbit between ± 35o • Instantaneous field of view 550 km x 550 km, 90 seconds observation time

5. Lightning Detection from Space • Results from LIS and OTD: Global lightning distribution Annual flash density derived from NASA OTD and LIS observations (1995-2006)

6. Lightning Detection from Space • Transition from LEO to GEO: • Uniform coverage of the visible disk over land and ocean • Optical detection is sensible to total lightning (but no discrimination of ground-flashes from intra-cloud flashes possible from satellite data alone) • High temporal resolution, high detection efficiency, spatial resolution of 6-10 km – limited by scattering • Larger distance affects radiometric sensitivity and resolution capabilities • Fixed observation geometry with location dependent distortions and observation angles (northernmost member states) • Noise conditions different (external, glint, motion effects)

7. Topics • Lightning observation from space • MTG LI Product processing basics • MTG Lightning Imager Science Team (LIST) • LIST Meetings • Studies • “Generation of Artificial Proxy Data for the MTG Lightning Imager” • “Inter-comparison of LIS and Ground-Based Lightning Location System (LLS) Observations” • “Potential synergy of the global ATDnet and MTG LI measurements” • “Validation and verification strategy for MTG LI measurements”

8. MTG LI Product Processing – Spatial Pattern • Characteristics: • Size scales with cloud thickness above source • With spatial resolution 5-8 km • Mean area of lightning pulses corresponds well to a 10 km x 10 km footprint “Events” • Background scene tracking and removal • Thresholding • Event detection etc... Optical pattern of lightning on cloud surface (observed from space shuttle) Possible schema of detected lightning pulses

9. MTG LI Product Processing – L1b and L2 products • The following data/products can be identified as resulting from the L1b processing, after false event filtering: • Events with geolocation, UTC time stamp and calibrated radiance • Background images (mainly supporting navigation) • The baseline L2 products, which is a result of clustering of events in time and space, consist of: • Groups (representing lightning strokes) • Flashes(main product for most users)

10. MTG LI Product Processing – Flash Grouping Algorithm • L2 processing consists of grouping pixel-based events into groups and flashes • Temporal and spatial adjacency criteria for groups • LIS: < 350 ms and <16.5 km for flashes • Groups representing “lightning strokes” • Flashes are a collection of groups within a limited time and space (From LIS Algorithm Theoretical Baseline Document) • Lightning events detected in pixels 1…10 in a chronological order • Spatially adjacent pixels in same timeframe (LIS: 2 ms) belong to same group • Groups within < 350 ms and <16.5 km belong to same flash From LIS statistics Events : Groups : Flashes 56 : 12 : 1

11. Topics • Lightning observation from space • MTG LI Product processing basics • MTG Lightning Imager Science Team (LIST) • LIST Meetings • Studies • “Generation of Artificial Proxy Data for the MTG Lightning Imager” • “Inter-comparison of LIS and Ground-Based Lightning Location System (LLS) Observations” • “Potential synergy of the global ATDnet and MTG LI measurements” • “Validation and verification strategy for MTG LI measurements”

12. MTG Lightning Imager Science Team (LIST) • In order to support activities for establishing a scientific baseline for the operational LI L2 processor, a MTG LI Science Team has been established. • The main objectives of the team is to: • Assist EUMETSAT with the implementation of the MTG LI L2 scientific baseline processor. • Prepare an Algorithm Theoretical Baseline Document (ATBD). It includes also a description of the proxy dataset, to be used for algorithm development and processor development. • The ATBD will be subject for review at the Preliminary Design Review (PDR) concluding the MTG system Phase B activities

13. The MTG LI Science Team currently consists of the following members: Alec Bennett (MetOffice – UK) Daniele Biron (USAM – Italy) Eric Defer (LERMA – France) Ullrich Finke (U. Hannover – Germany) Hartmut Höller (DLR – Germany) Philippe Lopez (ECMWF) Douglas Mach (NASA – USA) Antti Mäkelä (FMI – Finland) Serge Soula (Laboratoire d'Aerologie – France) MTG Lightning Imager Science Team (LIST)

14. Topics • Lightning observation from space • MTG LI Product processing basics • MTG Lightning Imager Science Team (LIST) • LIST Meetings • Studies • “Generation of Artificial Proxy Data for the MTG Lightning Imager” • “Inter-comparison of LIS and Ground-Based Lightning Location System (LLS) Observations” • “Potential synergy of the global ATDnet and MTG LI measurements” • “Validation and verification strategy for MTG LI measurements”

15. The following meetings have taken place until now: A 4th meeting is being planned for 16-17 Nov 2010 Meetings

16. LIST has identified the lack of suitable proxy data as the critical item limiting progress. Proxy data could be generated from several means, each with its relative merits. In addition, LIST identified the need to: Explore potential synergies between ground-based and space based observations Identify validation and verification strategies for the LI observations. In response, the Secretariat initiated four studies as summarized in the following. Meetings – roadmap for studies established

17. Topics • Lightning observation from space • MTG LI Product processing basics • MTG Lightning Imager Science Team (LIST) • LIST Meetings • Studies • “Generation of Artificial Proxy Data for the MTG Lightning Imager” • “Inter-comparison of LIS and Ground-Based Lightning Location System (LLS) Observations” • “Potential synergy of the global ATDnet and MTG LI measurements” • “Validation and verification strategy for MTG LI measurements”

18. Studies and deliverables

19. Studies and deliverables

20. Topics • Lightning observation from space • MTG LI Product processing basics • MTG Lightning Imager Science Team (LIST) • LIST Meetings • Studies • “Generation of Artificial Proxy Data for the MTG Lightning Imager” • “Inter-comparison of LIS and Ground-Based Lightning Location System (LLS) Observations” • “Potential synergy of the global ATDnet and MTG LI measurements” • “Validation and verification strategy for MTG LI measurements”

21. In the study a tool has been developed which enables the generation of artificial lightning data on pulse, storm and global scales. Basic concept of the artificial data generation is that lightning is represented by “energy samples” which are generated randomly in accordance with the empirically found distributions. Natural distribution of lightning shows many scales. As an idealisation, three basic scales of lightning distribution can be distinguished: global, storm, and pulse scales. Study: “Generation of Artificial Proxy Data for the MTG Lightning Imager”

22. LIProxy - Software for generation of artificial lightning proxy data SW is written in the Matlab programming language. Dedicated for use in simulation of the detection process of optical pulses from lightning and in the development of algorithms for the detected lightning events. Current status: The version 1.0 of the software with its Graphical User Interface (GUI) has been released to LIST during the 3rd LIST meeting (29-30 June 2010) for extensive testing in order to evaluate the tool and its feasibility for LIST usage. Study: “Generation of Artificial Proxy Data for the MTG Lightning Imager”

23. Topics • Lightning observation from space • MTG LI Product processing basics • MTG Lightning Imager Science Team (LIST) • LIST Meetings • Studies • “Generation of Artificial Proxy Data for the MTG Lightning Imager” • “Inter-comparison of LIS and Ground-Based Lightning Location System (LLS) Observations” • “Potential synergy of the global ATDnet and MTG LI measurements” • “Validation and verification strategy for MTG LI measurements”

24. The study was to compare optical lightning observations from LIS and ground-based LINET measurements in the VLF/LF frequency band. Primary objective: to get information on the relation of VLF/LF and optical measurements. Secondary objective: to enable the creation of proxy data from the LINET data. LINET is a time-of-arrival system enabling the identification of both Cloud-to-Cloud and Cloud-to-Ground lightning with comparable detection efficiency (in 3D). At present, the LINET network consists of more than 100 sensors sites in 20 European countries and is owned and operated by Nowcast GmbH. Study: “Inter-comparison of LIS and Ground-Based Lightning Location System (LLS) Observations”

25. A statistical analysis of the relations between the LIS and LINET data sets led to model distribution functions suitable for generating random proxy optical data from a given set of observed LINET strokes. The main objective of the proxy data generation is to get data which is directly usable for processor development/testing (MTG LI view data) Several days of observations have up to now been converted into MTG LI proxy data over the area covered by the LINET system. Study: “Inter-comparison of LIS and Ground-Based Lightning Location System (LLS) Observations”

26. Topics • Lightning observation from space • MTG LI Product processing basics • MTG Lightning Imager Science Team (LIST) • LIST Meetings • Studies • “Generation of Artificial Proxy Data for the MTG Lightning Imager” • “Inter-comparison of LIS and Ground-Based Lightning Location System (LLS) Observations” • “Potential synergy of the global ATDnet and MTG LI measurements” • “Validation and verification strategy for MTG LI measurements”

27. The Met Office study provided a first look into the feasibility of using global or at least LI-coverage ground-based lightning location systems in conjunction with MTG LI data in providing added value as synergetic products. The study summarises the main requirements for lightning data users based on Met Office surveys, which form a useful baseline from which to assess the suitability of systems and products used. Of the long-range ground-based VLF lightning location networks considered likely to cover the MTG footprint, the Met Office ATDnet system demonstrates suitability for most of the user criteria (especially over Europe) Several advantages of combining ATDnet lightning location data with the MTG LI have been identified with suggestions for synergetic products. No specific technical detail on their implementation could be provided yet. Study: “Potential synergy of the global ATDnet and MTG LI measurements”

28. Topics • Lightning observation from space • MTG LI Product processing basics • MTG Lightning Imager Science Team (LIST) • LIST Meetings • Studies • “Generation of Artificial Proxy Data for the MTG Lightning Imager” • “Inter-comparison of LIS and Ground-Based Lightning Location System (LLS) Observations” • “Potential synergy of the global ATDnet and MTG LI measurements” • “Validation and verification strategy for MTG LI measurements”

29. The study provides an overview, not concentrating on specific elements The study highlights the need to perform calibration, verification and validation in various levels. L1b: detection efficiency, false alarm rate and location accuracy. L2: performance of the algorithms used to associate optical pulses in flashes. The L2 validation activities should be performed based on simultaneous concurrent observations of MTG LI, ground-, air- and space-based lightning locating systems: Ground-based: ATDnet, LINET, Vaisala GLD360, VHF systems... Space-based: inter-comparison of MTG LI and GOES GLM, and comparison with possible low-earth orbit missions in the MTG LI timeframe Validation campaigns Study: “Validation and verification strategy for MTG LI measurements”

30. Back-up slides

31. Lightning Detection from Space • Geostationary fields of view of • Meteosat Third Generation Lightning Imager (MTG LI) • GOES-R East and West Geostationary Lightning Mapper (GLM) MTG LI GOES-R West GOES-R East

32. Lightning Detection from Space • Altitude, FOV and observation angle for LEO and GEO • Challenges: • Sensitivity to weak lightning: important for early lightning detection • Geometric distortions for larger nadir angles – lowers resolution • Side view of clouds for large satellite zenith angles

33. MTG LI Product Processing – Lightning Signal • Characteristics of the lightning signal (pulse shape): • Pulse delay and broadening due to scattering • Fast rise within 250 µs, followed by fast (but slower>) decay • Total width between 300-800 µs • Result of scattering is: • Broadening and delay of the pulse in time • Spatial widening up to several km • Partitioning of energy between upper and lower cloud surface

34. (full table from report) Study: “Potential synergy of the global ATDnet and MTG LI measurements”