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Advancing Global Lightning Detection: MTG Lightning Imager Proxy Data Update

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  1. Presentation to the Convection Working Group Zagreb, Croatia 9 April 2014 MTG Lightning Imager Proxy Data Jochen Grandell

  2. Topics • Putting the MTG Lightning Imager (LI) into context • MTG LI status update • MTG LI products • Heritage products from LEO experiences • Accumulated products • Proxy data basics • LINET-based proxy data • L2 Prototype processor • L2 accumulated (proxy) product examples • Summary

  3. Lightning Imager Science Team & Mission Advisory Group • The LI activities have been supported by the Lightning Imager Science Team (LIST) in 2009-2013 • Due to program evolution, a new team (Mission Advisory Group) has been set up in early 2014. • First meeting took place on 18-19 Feb 2014

  4. Topics • Putting the MTG Lightning Imager (LI) into context • MTG LI status update • MTG LI products • Heritage products from LEO experiences • Accumulated products • Proxy data basics • LINET-based proxy data • L2 Prototype processor • L2 accumulated (proxy) product examples • Summary

  5. MTG to Secure Continuity and Evolution of EUMETSAT Services 2018/2019 and 2021 2002 1977 MOP/MTP MSG MSG MOP/MTP MTG-I and MTG-S Observation missions: - Flex.Comb. Imager: 16 channels - Infra-Red Sounder - Lightning Imager - UVN 3-axis stabilised satellites Twin Sat configuration Class 3.6-ton • Observation missions: • - SEVIRI: 12 channels • GERB • Spinning satellite • Class 2-ton • Observation mission: • MVIRI: 3channels • Spinning satellite • Class 800 kg Implementation of the EUMETSAT Mandate for the Geostationary Programme Atmospheric Chemistry Mission (UVN-S4): via GMES Sentinel 4 (Ultraviolet Visible Near-infrared spectrometer)

  6. Lightning Detection from Space – from LEO to GEO Feasibility of lightning detection from space by optical sensors has been proven by NASA instruments since 1995 on low earth orbits (LEO) OTD (1995-2000) Results from LIS/OTD: Global lightning distribution Annual flash density LIS (1997-present)

  7. Geostationary lightning imaging – objectives and benefits The LI on MTG measures Total Lightning: Cloud-to-Cloud Lightning (IC) and Cloud-to-Ground Lightning (CG) Main benefit from GEO observations: homogeneous and continuous observations delivering information on location and strength of lightning flashes to the users with a timeliness of 30 seconds • Main objectives are to detect, monitor, track and extrapolate in time: • Development of active convective areas and storm lifecycle • Lightning climatology • Chemistry (NOx production)

  8. Lightning Detection from Space – from LEO to GEO GEO lightning missions in preparation by several agencies (in USA, Europe, China) for this decade... ...all of these are building on LIS/OTD heritage Geostationary Lightning Imager (GLI) on FY-4 (China) Geostationary Lightning Mapper (GLM) on GOES-R (USA) Lightning Imager (LI) on MTG (Europe) 2015  2018  2015/2016

  9. Topics • Putting the MTG Lightning Imager (LI) into context • MTG LI status update • MTG LI products • Heritage products from LEO experiences • Accumulated products • Proxy data basics • LINET-based proxy data • L2 Prototype processor • L2 accumulated (proxy) product examples • Summary

  10. Lightning Imager (LI) main characteristics CMOS Back-thinned backside illuminated detectors with integrated ADCs The baseline for the LI is a 4-camera solution 1170 x 1000 pixels per camera. Coverage close to visible disc

  11. Lightning Imager (LI) Status Update • LI instrument and mission prime contractor is Selex ES from Italy, which includes the: • Development of the LI instrument • ...and also the L0-L1b data processing software • MTG LI Phase B2 has been kicked off in 2012 • SRR (System Requirements Review) done in two parts, finished in spring 2013 • PDR (Preliminary Design Review) started towards end of 2013 at instrument level – Mission level PDR in late spring 2014.

  12. Lightning Imager (LI) main characteristics • LI main characteristics: • Measurements at 777.4 nm • Coverage close to visible disc • Continuous measurements of (lightning) triggered events – in addition, background images typically once every minute • Ground sample distance at SSP ~4.5 km => 4.7 million pixels • Integration time per frame 1 ms (parameterised) • Background subtraction and event detection in on-board electronics • Data rate <30 Mbps; Mass < 110Kg; Power < 320W

  13. Topics • Putting the MTG Lightning Imager (LI) into context • MTG LI status update • MTG LI products • Heritage products from LEO experiences • Accumulated products • Proxy data basics • LINET-based proxy data • L2 Prototype processor • L2 accumulated (proxy) product examples • Summary

  14. L2 Flashes/Groups/Events • Product Terminology: • Events:what the instrument measures, a triggered pixel in the detector grid • Groups:collection of neighbouring triggered events in the same integration period (1-2 ms), representing roughly a lightning stroke in nature • Flashes:a collection of groups in temporal and spatial vicinity (XX km, YY ms), representing a “geophysical” flash.

  15. L2 Flashes/Groups/Events The “Flash tree” combining the events and the groups into one flash Triggered event #1 Group #1.1 Flash A Triggered event #2 Triggered event #3 Triggered event #4 Group #1.2 Triggered event #5 Triggered event #6

  16. Groups and Flashes – LIS approach followed Example/Conceptual representation of a L2 processing sequence: “Groups” “Flashes” “Events”

  17. Topics • Putting the MTG Lightning Imager (LI) into context • MTG LI status update • MTG LI products • Heritage products from LEO experiences • Accumulated products • Proxy data basics • LINET-based proxy data • L2 Prototype processor • L2 accumulated (proxy) product examples • Summary

  18. L2 Accumulated Products • Accumulated products: • Collecting samples from a 30 second buffer • Resampled to the 2-km FCI-IR grid for simple visualising with FCI data • Events define the extent in the products • Flashes define the values in the products • For a longer temporal accumulation, the 30 second products can be stacked • Three products in all: • Accumulated flashes • Accumulated flash index • Accumulated flash radiance

  19. Topics • Putting the MTG Lightning Imager (LI) into context • MTG LI status update • MTG LI products • Heritage products from LEO experiences • Accumulated products • Proxy data basics • LINET-based proxy data • L2 Prototype processor • L2 accumulated (proxy) product examples • Summary

  20. Proxy data basics (1) • MTG LI is without heritage in GEO orbit, and the closest comparison is the Lightning Imaging Sensor (LIS) on TRMM – currently still in operation • However, LIS flying on LEO orbit can only monitor storms for less than 2 minutes at a time • In addition, coverage is limited to +/- 35 deg Lat => Europe is excluded • Use of ground-based Lightning Location System (LLS) networks as a source of proxy data is not straightforward, as they are based on RF observations of lightning and are sensitive to different parts of the lightning process • “apples and oranges”

  21. Proxy data basics (2) • The best compromise is to use ground-based lightning data, but converted to optical pulses based on case study comparisons with LIS data. • One of the networks in operation in Europe (LINET) is currently the main source of such proxy data for the LI activities. • LINET data has been compared in measurement campaigns to other ground-based systems and to LIS • As an outcome, a model for transforming the LINET stroke data into optical emission (“pulses”) has been created

  22. Thunderstorm ElectrificationLightning and its Emissions • VHF – Very High Frequency, (V)LF – (Very) Low Frequency

  23. Topics • Putting the MTG Lightning Imager (LI) into context • MTG LI status update • MTG LI products • Heritage products from LEO experiences • Accumulated products • Proxy data basics • LINET-based proxy data • L2 Prototype processor • L2 accumulated (proxy) product examples • Summary

  24. LINET network coverage Central Europe well covered (2008 data) Sensor baselines highly varying across the network (= distance between sensors)

  25. Modeling of MTG-LI Optical SignalsStrategy for Proxy Data Generation Transformation of LINET RF stroke data into optical groupsby modeling of cloud top optical emission: • Simulation of the number of optical groups per stroke (depending on LINET detection efficiency, i.e. sensor baseline, in the area) If this number is ≥ 1: • Generation of one direct coincident optical group per LINET stroke • Random generation of additional optical groups per LINET stroke according to a log-normal model for radiance, footprint and time Generation of optical events from RF stroke data

  26. Topics • Putting the MTG Lightning Imager (LI) into context • MTG LI status update • MTG LI products • Heritage products from LEO experiences • Accumulated products • Proxy data basics • LINET-based proxy data • L2 Prototype processor • L2 accumulated (proxy) product examples • Summary

  27. L2 prototype processor A prototype L2 processor in Matlab The main objectives of the prototype processor are: Implementation, testing and verification of the L2 algorithms. Verification and validation of the proxy data Flash/group clustering parameters easily set for each individual run

  28. Topics • Putting the MTG Lightning Imager (LI) into context • MTG LI status update • MTG LI products • Heritage products from LEO experiences • Accumulated products • Proxy data basics • LINET-based proxy data • L2 Prototype processor • L2 accumulated (proxy) product examples • Summary

  29. L2 Accumulated products => Proxy data examples • Example animations shown for the Accumulated flash index product • Proxy data pulses  LI proxy events • L2 processor • L2 flashes + Accumulated products • The original 30 sec product stacked into several longer periods for demonstration purposes: • 15 min (= SEVIRI Full Disk Service today) • 10 min (= FCI Full Disk Scanning Service FDC) • 5 min (= FCI Rapid Scanning Service FDC/2) • 2.5 min (= FCI Rapid Scanning Service FDC/4)

  30. Preparing for a user readiness study EUM/KOEEEE Issue <No.> <Date> • Because of no heritage in orbit or business-as-usual products, feedback and comments regarding the data usage and upcoming end-products delivered by EUMETSAT are needed. • Charting the readiness of the main data users (i.e., National Meteorological and Hydrological Services, NMHS). • Ensuring that the users are able to give valuable input already before the instrument is launched. • End-users getting a first glimpse on the data before the LI instrument itself is operational. • In addition to LINET as input data, an extension of the method is in development to have a similar approach applicable to the NORDLIS/EUCLID network as well (work in progress).

  31. L2 Accumulated products • Animations: All for 20 June 2013, different accumulation times

  32. Full Domain: 150 s Accumulation Time

  33. Zoom: 150 s Accumulation Time

  34. Full Domain: 300 s Accumulation Time

  35. Zoom: 300 s Accumulation Time

  36. Full Domain: 600 s Accumulation Time

  37. Zoom: 600 s Accumulation Time

  38. Full Domain: 900 s Accumulation Time

  39. Zoom: 900 s Accumulation Time

  40. Topics • Putting the MTG Lightning Imager (LI) into context • MTG LI status update • MTG LI products • Heritage products from LEO experiences • Accumulated products • Proxy data basics • LINET-based proxy data • L2 Prototype processor • L2 accumulated (proxy) product examples • Summary

  41. Summary • Proxy data needed for product/algorithm development, system level testing, and user readiness preparation • For the Lightning Imager, being without heritage, the creation of representative proxy data has been a top priority • LINET, a ground-based system covering much of Europe has been used as a vehicle for developing the proxy data • Based on LIS-LINET comparisons, as well as comparison to other networks’ data (CHUVA campaign) • LIST activity started in 2009 and continued since through various activities • The accumulated flash product demonstration presented • User readiness study employing the proxy data in preparation

  42. Back-up slides

  43. Accumulated flashes, status at t = 10s EUM/ Issue <No.> <Date> Event count in the 30 sec buffer (still in LI grid) = Events in Flash #1 3 2 1 1 1 1 2 Flash count in the 30 sec buffer (still in LI grid) 1 1 1 1 1 1 1 Conceptual illustration

  44. Accumulated flashes, status at t = 20s EUM/ Issue <No.> <Date> Event count in the 30 sec buffer (still in LI grid) = Events in Flash #1 = Events in Flash #2 2 1 1 4 2 2 1 1 1 1 2 Flash count in the 30 sec buffer (still in LI grid) 1 1 1 1 2 1 2 1 1 1 1 Conceptual illustration

  45. Accumulated flashes, status at t = 29s EUM/ Issue <No.> <Date> Event count in the 30 sec buffer (still in LI grid) = Events in Flash #1 = Events in Flash #2 = Events in Flash #3 2 1 1 1 2 1 6 3 2 1 1 1 1 2 Flash count in the 30 sec buffer (still in LI grid) 1 1 1 1 1 1 1 3 2 2 1 1 1 1 Conceptual illustration

  46. Detection of a Lightning Optical Signal • Lightning with a background signal changing with time: • Lightning on top of a bright background is not recognised by its bright radiance, but by its transient short pulse character • For detection of lightning, a variable adapting threshold has to be used for each pixel which takes into account the change in the background radiance • (in LIS: background calculated as a moving average) Radiation energy Background Lightning signal Night Day Time

  47. From a Lightning Optical Signal to MTG LI Events From a Lightning Optical Signal to MTG LI Events • Detection of events in a nutshell: This is taking place in every 1 ms frame (1 kHz): Event detection Background scene tracking and removal Thresholding • False event filtering needed in L0-L1 processing • True lightning events (triggered by a lightning optical signal) • False events (not related to lightning)

  48. Use of proxy data within the MTG program activities • Data is being and will be used in: • Algorithm development & testing • System level testing • User readiness activities • Proxy data also shared with other agencies • NOAA GOES-R GLM team – Steve Goodman • In talks to cooperate also with CMA on proxy data

  49. LINET operating principle • LINET operating at the VLF/LF frequency range Lightning Detection Network LINET observes sfericsat VLF/LF from larger discharges Lightning Mapping Array LMA observes VHF pulses from small-scale breakdown

  50. L2 prototype processor (2) Screenshot of the prototype processor Matlab GUI - Flash/group clustering parameters easily set for each individual run

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