global lightning observations. streamers, sprites, leaders, lightning: from micro- to macroscales...
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Global Lightning Observations
Global Lightning Observations
Streamers, sprites, leaders, lightning: from micro- to macroscalesStreamers, sprites, leaders, lightning: from micro- to macroscales
•Remote detection of lightning - information provided
•LIS and OTD - what they are and how they work
•Results from global observations
•Next generation
•Change ?
•Remote detection of lightning - information provided
•LIS and OTD - what they are and how they work
•Results from global observations
•Next generation
•Change ?
A schematic of grauple - ice crystal charge A schematic of grauple - ice crystal charge transfer in a thunderstormtransfer in a thunderstorm
Lightning production is related to microphysical and dynamic cloud processes. Lightning production is related to microphysical and dynamic cloud processes.
Ice interactions seem to play the major role in thunderstorm electrification.Ice interactions seem to play the major role in thunderstorm electrification.
Particularly rebounding collisions of graupel and ice crystals – Non-inductive Particularly rebounding collisions of graupel and ice crystals – Non-inductive charging mechanism.charging mechanism.
Necessary conditions for thunderstorm electrification: a) strNecessary conditions for thunderstorm electrification: a) strong enough enough up-draft to grow precipitation size ice. b) ice-graupel collisions in the up-draft to grow precipitation size ice. b) ice-graupel collisions in the
presence of waterpresence of water
+ + + ++ + + ++ + + ++ + + +
+ + + ++ + + ++ + + ++ + + +
- - -- - -- - -- - -
Lightning Connection to Thunderstorm Updraft,
Storm Growth and Decay
Lightning Connection to Thunderstorm Updraft,
Storm Growth and Decay
• Total Lightning —responds to updraft velocity and concentration, phase, type of hydrometeors — integrated flux of particles
• WX Radar — responds to concentration, size, phase, and type of hydrometeors- integrated over small volumes
• Microwave Radiometer — responds to concentration, size, phase, and type of hydrometeors — integrated over depth of storm (85 GHz ice scattering)
• VIS / IR — cloud top height/temperature, texture, optical depth
• Total Lightning —responds to updraft velocity and concentration, phase, type of hydrometeors — integrated flux of particles
• WX Radar — responds to concentration, size, phase, and type of hydrometeors- integrated over small volumes
• Microwave Radiometer — responds to concentration, size, phase, and type of hydrometeors — integrated over depth of storm (85 GHz ice scattering)
• VIS / IR — cloud top height/temperature, texture, optical depth
Why observe lightning?(Forecasting)
Why observe lightning?(Forecasting)
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TimeTime
Tornadotime
TornadotimeLightningLightning
RadarRadar
pp
Flux HypothesisFlux Hypothesis
Hypothesis:Hypothesis: Lightning Lightning frequency frequency ((F)F)
proportional to product proportional to product of upward non of upward non
precipitation ice mass precipitation ice mass flux flux (I) (I) and precipitation and precipitation
ice mass flux ice mass flux (p)(p)
FF = c* = c*pp**II
Supported by simple Supported by simple calculations (Blyth et al. calculations (Blyth et al.
2001) and lightning 2001) and lightning model results (Baker et model results (Baker et
al. 1995, 1999).al. 1995, 1999).
Positive chargePositive charge
Negative chargeNegative charge
Positive chargePositive charge
Positive chargePositive charge
Negative chargeNegative charge
TemperatureTemperature
Positive chargePositive charge
Charg
ing z
one
Charg
ing z
one
FF
STEPS Results – 6 June 2000
‘Garden Variety’ Single Cell Storm
Non- Precipitation ice
mass flux [g s-1 m-2] *
1011
Lig
htn
ing
p
er
rad
ar
volu
me
tim
e
Precipitation ice
mass flux [g s-1 m-2]
* 1012
How good is the apparent correlation between lightning and IWP and how does it vary
between regimes?
Method• Create land, ocean, coastal data mask
• Create scatter plot of data in previous figure (0.5 x 0.5o grid) for each partition
Result• Noisy, but clear correlations above sample noise floor in flash density
• Eyeball says best fit lines would be very similar
Clarify Signal: Ocean, Coast and Land IWP Binned by Flash Density
• When averaged, correlation is very strong, best fit lines independent of regime.
• ~95% (75%) of oceanic (coast) flash density distribution in sampling
noise (low flash density; <.007 fl/km2/day = 0.2 fl/km2/mo), low IWP
(~.01-.02 kg/m2). Sampling + DE threshold + occurrence!
• Similar functional relationships between rain (Iiquid) – lightning vary by regime.
(All rain certain pixels with detectable IWP included)
TRMM PR IMP
Sample “Virtual radar” retrieval
Sample “Virtual radar” retrieval
Truth
Retrieval
(radar)
(µwave + lightning)
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GPROF(cloud model)
GPROF(cloud model)
Instrument designChristian et al, J. Geophys. Res., 1989
Instrument designChristian et al, J. Geophys. Res., 1989
• Fast lens, narrowband filter at 777.4 nm
• 128 x 128 CCD array, 500 fps imaging
• Frame-to-frame subtraction isolates lightning transients against bright daytime background
• Fast lens, narrowband filter at 777.4 nm
• 128 x 128 CCD array, 500 fps imaging
• Frame-to-frame subtraction isolates lightning transients against bright daytime background
Measurement: Spatial Discrimination
Measurement: Spatial Discrimination
8 km nominal spatial resolution optimizes the lightning-to-background S/N ratio.
8 km nominal spatial resolution optimizes the lightning-to-background S/N ratio.
8 km8 km
8 km8 km
Measurement:Temporal Discrimination
Measurement:Temporal Discrimination
CCD integration interval is set to 2 ms to minimize pulse splitting between frames and minimize
integration of background signal
CCD integration interval is set to 2 ms to minimize pulse splitting between frames and minimize
integration of background signal
Measurement: Spectral FilteringMeasurement: Spectral Filtering
Narrow band interference filter passes only light from 1nm wide oxygen mutipletNarrow band interference filter passes
only light from 1nm wide oxygen mutiplet
Optical Transient Detector( launched April, 1995 )
Optical Transient Detector( launched April, 1995 )
Lightning Imaging Sensor( launched November, 1997 )Lightning Imaging Sensor( launched November, 1997 )
Lightning Detection from Low Earth OrbitLightning Detection from Low Earth Orbit
LIS on TRMMLIS on TRMM
•Lower orbit, smaller Field of View, tropical inclination
•Lower orbit, smaller Field of View, tropical inclination
History: LIS (1997-present)
History: LIS (1997-present)
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High Resolution Full Climatology Annual Flash RateHigh Resolution Full Climatology Annual Flash Rate
Global distribution of lightning from a combined nine years of observations of the NASA OTD (4/95-3/00) and LIS (1/98-12/04) instruments
Global distribution of lightning from a combined nine years of observations of the NASA OTD (4/95-3/00) and LIS (1/98-12/04) instruments
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Climatology: Diurnal cycle
Climatology: Diurnal cycle
( Local hour )( Local hour )
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Climatology: Diurnal cycle
Climatology: Diurnal cycle
( UTC Hour )( UTC Hour )
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Global lightning is modulated on annual & diurnal time scales, as well as seasonally
and interannually
Lightning Responsive to Interannual
Variability
Lightning Responsive to Interannual
Variability
Winter 1997-98 (El Niño)
Winter 1998-99 (La Niña)
Flash Rate Density-Congo
Flash Rate Density-Congo
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Flash Rate Density-IndiaFlash Rate Density-India
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LIS Ocean OverpassLIS Ocean Overpass
LIS Land OverpassLIS Land Overpass
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Major Points for Severe Weather
Major Points for Severe Weather
• Primary lightning signature is high flash rates and the “jump”
• Lightning flash rate is correlated storm intensity - higher rate implies stronger storm.
• Evolution of the lightning activity follows the updraft. Increasing activity means the storm intensifying; decreasing activity means the updraft is weakening.
• A jump in lightning activity is associated with a pulse in updraft
intensity
• These signatures, in conjunction with other NWS assets can be used to:
• Separate intensifying from weakening storms• Identify storms in process of going severe
• Quickly determine the most intense storms in a complex system
• Improved warning times
• Reduced false alarms rates
• Primary lightning signature is high flash rates and the “jump”
• Lightning flash rate is correlated storm intensity - higher rate implies stronger storm.
• Evolution of the lightning activity follows the updraft. Increasing activity means the storm intensifying; decreasing activity means the updraft is weakening.
• A jump in lightning activity is associated with a pulse in updraft
intensity
• These signatures, in conjunction with other NWS assets can be used to:
• Separate intensifying from weakening storms• Identify storms in process of going severe
• Quickly determine the most intense storms in a complex system
• Improved warning times
• Reduced false alarms rates
Lightning Sensing from GEO
Lightning Sensing from GEO
•Climate Monitoring
•Storm Development
• Ice-phase precipitation estimates
•Severe Weather Now-casting
•Data assimilation and model inputs
•Atmospheric chemistry
•Climate Monitoring
•Storm Development
• Ice-phase precipitation estimates
•Severe Weather Now-casting
•Data assimilation and model inputs
•Atmospheric chemistry
GLM : Field of View at GOES West and East
GLM : Field of View at GOES West and East
•GOES W (75ºW)•GOES W (75ºW) GOES E (135ºW)GOES E (135ºW)
• OTD climatology indicates lightning density• Range rings indicate limits of 10, 15, 20, & 50 km pixel
footprint
• OTD climatology indicates lightning density• Range rings indicate limits of 10, 15, 20, & 50 km pixel
footprint
GEO -EastGEO -East
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•Questions ?•Questions ?