Page 1© Crown copyright 2004 The new Met Office ATDNET lightning detection system J. Nash, N.C....

© Crown copyright 2004

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


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


ATD Sferics Lightning Location

Whip antenna sensitive tovertical component of electromagnetic field

from lightning discharge

narrow band observationsof lightning emission

centred at 10 kHz , but new system will probably be changed to 13.6 kHz,

because of problems at 10 kHz in the Indian ocean

Frequency can be selected using software

from the operations centre


Propagation of electromagnetic waves at 10-14 kHz

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 kHz 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]


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


Arrival Time Differencefixing process

Accurate time stamping , 0.1s - rubidium oscillators, checked by GPS every second.

Waveforms are Fourier analysed and sent to the central control station within 30s (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 very much higher than with current system.


Expected disposition of out-stations in Europe


Purple lines try toimplementBefore mid- 2007

Outstation inReunion,observes at 13.6 kHz,VPN communicationsestablished and working well for several months, after initial problems


Examples from recent testing of ATDNET


Comparison of number of flashes reported by ATD and ATDNET

ATDNET much better than ATD over Europe in summer and also at long range


Extent of long range service area


ATDNET Climatology for September 2006


ATD Climatology for September 2006


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


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


Check of ATDNET output in South America


Rindat lightning detection system, southern Brazil


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


11-12 UTC

731 locations


MSG + old ATD,12 UTC for preceding 6 hours


11-12 UTC

1712 poor locations

Current ATDNET geometry not good for flashes in this area


Superimposition of lightning on MSG cloud pictures


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.


Are you interested in collaboration?

Please contact:

J. Nash

C. Gaffard

T. Oakley


ATDNET peformance over Africa, late August 2006,

0

500

1000

1500

2000

2500

3000

3500

4000

4500

10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48

Time [hours] since 00UTC on 29.08.06

Num

ber

of fl

ashe

s /5

000*

good

/tota

l

GOODATDNET

PoorATDNET

ratio good/total fixes *5000

50%(good/total)

60%

70%


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.


comparison ATD EA technology

Comparison of number of lightning reports by ATD and EATech in the area [14 W to 8 E, 48 N to 62 N ] for December to February 2003/2004

0

100

200

300

400

500

600

0 5 10 15 20 25

Time of day [ UTC]

To

tal n

um

be

r o

f fl

as

he

s in

3 m

on

ths

ATD

EATECH

ATD more sensitive than EA during day time


Questions & Answers

Page 1© Crown copyright 2004 The new Met Office ATDNET lightning detection system J. Nash, N.C....

Documents

Transcript of Page 1© Crown copyright 2004 The new Met Office ATDNET lightning detection system J. Nash, N.C....