The new Met Office ATDNET lightning detection system

ATDNet/ATD § The flash location process in ATDNET is similar to the existing ATD

ATD Sferics Lightning Location Whip antenna sensitive to vertical component of electromagnetic field from

Propagation of electromagnetic waves at 10 -14 k. Hz § The strong emissions from

New outstation allows much higher throughput than old outstations, essential to meet user requirements

Arrival Time Difference fixing process § Accurate time stamping , 0. 1 s -

Expected disposition of out-stations in Europe © Crown copyright 2004 Page 7

Purple lines try to implement Before mid- 2007 Outstation in Reunion, observes at 13.

Examples from recent testing of ATDNET © Crown copyright 2004 Page 9

Existing ATD depends on NOS since October 2004 © Crown copyright 2004 Page 10

Comparison of number of flashes reported by ATD and ATDNET much better than ATD

Extent of long range service area © Crown copyright 2004 Page 12

ATDNET Climatology for September 2006 © Crown copyright 2004 Page 13

ATD Climatology for September 2006 © Crown copyright 2004 Page 14

Completion of operational link from flash location processor to logical data store and then

Operational computers now all configured , and NOS feeding directly to Flash Location processor

Check of ATDNET output in South America © Crown copyright 2004 Page 19

Rindat lightning detection system, southern Brazil © Crown copyright 2004 Page 21

Limitations in Africa requiring better communications to Mediterranean sensors and new sensors located south

11 -12 UTC 731 locations © Crown copyright 2004 Page 23

MSG + old ATD, 12 UTC for preceding 6 hours © Crown copyright 2004

Current ATDNET geometry not good for flashes in this area 11 -12 UTC 1712

Superimposition of lightning on MSG cloud pictures © Crown copyright 2004 Page 26

For the future § Various countries have indicated willingness to collaborate further in extending

Are you interested in collaboration? § Please contact: § J. Nash § C. Gaffard

70% 60% 50%(good/ total) © Crown copyright 2004 Page 29

future work § compare efficiency/ accuracy with meteo france § investigate why poor ratio

comparison ATD EA technology ATD more sensitive than EA during day time © Crown

Questions & Answers © Crown copyright 2004 Page 33

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The new Met Office ATDNET lightning detection system J. Nash, N. C. Atkinson, E. Hibbett, G. Callaghan, P. L. Taylor, M. Turp, P. Odams, D. Jenkins, S. Keogh, C. Gaffard, E. Walker Met Office, Exeter/Reading TECO-2006, 4 -6 December 2006, Geneva © Crown copyright 2004 Page 1

ATDNet/ATD § The flash location process in ATDNET is similar to the existing ATD in principle, but ATDNET uses updated technology throughout. § The system is designed and operated entirely by Met Office staff and does not rely on support from any other commercial lightning detection manufacturer. § ATDNET is designed to run autonomously under the supervision of a network manager, with much less intervention expected from Met Office network and Engineering than with the current ATD § Data acquisition is PC based § Communications will be transitioned to Internet systems § ATDNET will have more outstations than the current ATD to cope with situations where severe local storms reduce the sensitivity of some outstations § In the immediate future , the Met Office is committed to extending the main service area from Europe to the whole of Africa and Arabia and the western Indian Ocean © Crown copyright 2004 Page 2

ATD Sferics Lightning Location Whip antenna sensitive to vertical component of electromagnetic field from lightning discharge narrow band observations of lightning emission centred at 10 k. Hz , but new system will probably be changed to 13. 6 k. Hz, because of problems at 10 k. Hz in the Indian ocean Frequency can be selected using software from the operations centre © Crown copyright 2004 Page 3

Propagation of electromagnetic waves at 10 -14 k. Hz § The strong emissions from lightning at these frequencies are caused by rapid neutralisation of charge in the lowest few hundred meters of cloud-to ground strokes. § Atmospheric attenuation at 10 to 14 k. Hz is very low and the electromagnetic discharge (SFERIC) can propagate over thousands of kilometres along the earth-atmosphere waveguide. § Propagation is best over the sea or moist surfaces, and differs between day and night because of the different height of the reflecting layers in the ionosphere between day and night. § ATDNET outstations Fourier analyse the SFERIC wave. § The waves from the different outstations are correlated in the central Flash Location Processor to obtain time differences between the stations. § A minimum of 3 pairs of time differences are required for a location, but it is preferable to have at least 4 if possible to guard against error in an individual time difference [ possibly 110 µs] © Crown copyright 2004 Page 4

Arrival Time Difference fixing process § Accurate time stamping , 0. 1 s - rubidium oscillators, checked by GPS every second. § Waveforms are Fourier analysed and sent to the central control station within 30 s (will use cheap internet based communication, transition for all outstations should be achieved during 2007 ) § Waveforms from different outstations are correlated to estimate time differences § Arrival Time Differences are then used to calculate lightning position by iterative method § Distribution of data messages every five minutes, but potential to extract messages within 2 minutes for new products. § Speed of data delivery much higher than with current system. © Crown copyright 2004 Page 6

Purple lines try to implement Before mid- 2007 Outstation in Reunion, observes at 13. 6 k. Hz, VPN communications established and working well for several months, after initial problems © Crown copyright 2004 Page 8

For the future § Various countries have indicated willingness to collaborate further in extending ATDNET towards a global system § Met Office is currently setting up the infrastructure to deal with the interested parties , so that suitable arrangements can be made § The extension of the system across Africa and Arabia will be primarily funded by the Met Office, with suitable memoranda of understanding agreed with countries hosting sensors. § Individual negotiations will be pursued with countries in other regions, as policy for expansion is agreed with Met Office board. § The main limitation on speed of expanding the network is setting up the communications. Here the main difficulties have now been overcome, but the complexity of dealing with various network operators often limits the rate of expected progress. © Crown copyright 2004 Page 27

future work § compare efficiency/ accuracy with meteo france § investigate why poor ratio good/total fixes § introduce a wave propagation model § evaluate more accurately the accuracy § simulate different design. © Crown copyright 2004 Page 30