mtg lightning imager proxy data zagreb, croatia 9 april 2014 jochen grandell presentation to the...

MTG Lightning Imager Proxy Data

Zagreb, Croatia9 April 2014

Jochen Grandell

Presentation to the Convection Working

Group

Convection Workingf Group9 April 2014

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


• 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

Slide: 3

Lightning Imager Science Team & Mission Advisory Group


Topics








• Summary


MSGMOP/MTP

Observation mission:- MVIRI: 3 channels

Spinning satelliteClass 800 kg

Observation missions:- SEVIRI: 12 channels- GERB

Spinning satellite Class 2-ton

1977 2018/2019 and 20212002

Atmospheric Chemistry Mission (UVN-S4):via GMES Sentinel 4(Ultraviolet Visible Near-infrared spectrometer)

Implementation of the EUMETSAT Mandate

for the Geostationary Programme

MTG to Secure Continuity and Evolution of EUMETSAT Services

MOP/MTP MSG

MTG-I and MTG-S

Observation missions: - Flex.Comb. Imager: 16 channels - Infra-Red Sounder - Lightning Imager - UVN3-axis stabilised satellites Twin Sat configuration Class 3.6-ton

Slide: 5


Lightning Detection from Space – from LEO to GEO

OTD (1995-2000)

LIS (1997-present)

Feasibility of lightning detection from space by optical sensors has been proven by NASA instruments since 1995 on low earth

orbits (LEO)

Results from LIS/OTD: Global lightning distribution

Annual flash density


The LI on MTG measures Total Lightning: Cloud-to-Cloud Lightning (IC) and Cloud-to-Ground Lightning (CG)

Geostationary lightning imaging – objectives and benefits

Main objectives are to detect, monitor, track and extrapolate in time:• Development of active

convective areas and storm lifecycle

• Lightning climatology• Chemistry (NOx production)

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


Lightning Detection from Space – from LEO to GEO

Geostationary Lightning Imager

(GLI) on FY-4 (China)

Lightning Imager (LI) on MTG

(Europe)

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 Mapper

(GLM) on GOES-R (USA)

2015 2018 2015/2016


Topics








• Summary


Lightning Imager (LI) main characteristics

Slide: 10

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


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.

Slide: 11


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

Slide: 12


Topics








• Summary


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.


L2 Flashes/Groups/Events

Triggered event #1

Triggered event #2

Triggered event #3

Triggered event #4

Triggered event #5

Triggered event #6

Group #1.1

Group #1.2

Flash A

The “Flash tree” combining the events and the groups into one flash


Example/Conceptual representation of a L2 processing sequence:

“Flashes”“Groups”

Groups and Flashes – LIS approach followed

“Events”


Topics








• Summary


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

Slide: 18


Topics








• Summary


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”


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


Thunderstorm ElectrificationLightning and its Emissions

• VHF – Very High Frequency, (V)LF – (Very) Low Frequency


Topics








• Summary


LINET network coverage

Central Europe well covered (2008 data)

Sensor baselines

highly varying across the

network (= distance

between sensors)


Slide 25 > Eumetsat, Vienna, September 2013 > Hartmut Höller

Modeling of MTG-LI Optical SignalsStrategy for Proxy Data Generation

Transformation of LINET RF stroke data into optical groups by 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


Topics








• Summary


L2 prototype processor

Flash/group clustering

parameters easily set for each

individual run

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


Topics








• Summary


L2 Accumulated products => Proxy data examples

• Example animations shown for the Accumulated flash index product

• Proxy data pulses

LI proxy events Þ L2 processor

Þ 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)


Preparing for a user readiness study

• 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).

Slide: 30

EUM/KOEEEEIssue <No.><Date>


L2 Accumulated products

• Animations:All for 20 June 2013, different accumulation times


Full Domain: 150 s Accumulation Time


Zoom: 150 s Accumulation Time


Topics








• Summary


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


Back-up slides


Accumulated flashes, status at t = 10s

Slide: 43

EUM/Issue <No.><Date>

Event count in the 30 sec buffer (still in LI grid)

Flash count in the 30 sec buffer (still in LI grid)

2

11 1

3 12

1

11 1

1 11

= Events in Flash #1

Conceptual illustration



Slide: 44




2

11 1

4 22

1

11 1

2 21

1

1

12

1

1

11






Slide: 45







2

11 1

6 23

1

11 1

3 22

1

1

12

1

1

11

2

1 1

1

1 1



Slide: 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)

Lightning signal

Background

Time

Radiationenergy

NightDay


• Detection of events in a nutshell:

From a Lightning Optical Signal to MTG LI Events

Background scene tracking and removal

ThresholdingEvent

detection

False event filtering needed in L0-L1 processing

• True lightning events (triggered by a lightning optical signal)

• False events (not related to lightning)

From a Lightning Optical Signal to MTG LI Events

This is taking place in every 1 ms frame (1 kHz):


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


LINET operating principle

• LINET operating at the VLF/LF frequency range

Slide 49 > Eumetsat, Vienna, September 2013 > Hartmut Höller

Lightning Detection Network LINET observes sferics at VLF/LF from larger dischargesLightning Mapping Array LMA observes VHF pulses from small-scale breakdown


L2 prototype processor (2)

Screenshot of the prototype processor

Matlab GUI

-

Flash/group clustering

parameters easily set for each

individual run


L2 prototype processor (1)

• A prototype L2 processor has been developed in the EUMETSAT TCE environment using the Matlab language.

• The main objectives of the prototype processor are:

• Implementation, testing and verification of the L2 algorithms.

• Verification and validation of the various proxy data used for L2 (and L0-L1) processor development.

mtg lightning imager proxy data zagreb, croatia 9 april 2014 jochen grandell presentation to the...

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