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Assessing the local hemispheric spectral sky artificial radiances contribution and sensitivity from different parts of a territory

Earth Science 2013
by

Martin Aube

on 16 July 2013

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Transcript of Assessing the local hemispheric spectral sky artificial radiances contribution and sensitivity from different parts of a territory

Assessing the local hemispheric spectral sky artificial radiances contribution and sensitivity from different parts of a territory
Model
validation / calibration

Martin Aubé
Cégep de Sherbrooke

Earth Science 2013, Las Vegas
OMM
Satellite Suomi NPP
Québec
Montréal
Clear with moon
Clear without moon
OI (557nm)
OI (557 nm)
OI (630 nm)
Na
Hg
OH
Sc & Na
Summary of
lamp conversion

Maps
before/after
Hg 546 nm - clear summer
Na 569 nm - clear summer
Hg 546 nm - turbid summer
Hg 546 nm - clear winter
NPS night sky team - 2007
Sky radiance Model
Ray traycing algorithm
Statistical method to optimize ground level source selection and for 2nd order scattering volume
Wavelength dependant (reflectance, atmospheric optics, lamp SPD)
Calculation of shadowing effects from topography
Explicit calculation of 1st and 2nd order of scattering
Calculation of lambertian ground reflectance
Calculation of subgrid obstacles (trees, buildings)
Calculation of atmospheric extinction
Users can define their light distributions (horizontally averaged IES files)
Calculation for any observer position and viewing angle
Aerosol types (rural, urban, maritime) and loading
Account for relative humidity, ground level atm. pressure
Typical
model inputs

Upward radiance from DMSP-OLS satellite (stable light)
Ground spectral reflectance (3 bands) from MODIS satellite
Ground elevation from Shuttle Radar Topography Mission
Land/water map from MODIS satellite
Aerosol models from Shettle and Fenn 1979 (rural, urban, maritime)
Aerosol optical depth
Relative humidity
Ground level air pressure
Typical angular light distribution patterns per source types and per geographical zones
Typical ratio of lamp spectra (Hg vs Na) per source types and/or zones
Lamp pole height per source types
Typical obstacle height and mean free path toward ground
Standard
parameters
Typical model outputs
2-Radiance contribution map
Online portal
Some interesting model results
Computing infrastructure
Privileged access to Mammouth-Serie-II
super computer at Université de Sherbrooke, Canada
Managed by Calcul Québec and Calcul Canada
2464 cores (21,6 Tflop/s)
Typically 1000 cores can be assigned to our experiments
One calculation for ~100 000 km2 takes between 12h - 3 days
SRTM (topography)
Light distribution patterns
Hg lines
Na lines
Light inventory
radiant power maps
Canary sky law
La Palma
Tenerife West
Canary sky law
La Palma
Tenerife West
Spatial resolution: 1 km
Relative humidity: 70%
Aerosol optical depth (5 values): 0.05, 0.1, 0.2, 0.5, 1.0
Zenith angles (6 values): 0, 30, 50, 60, 70, 75
Azimuth angles (24 values): 0, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, 180, 195, 210, 225, 240, 255, 270, 285, 300, 315, 330, 345
Wavelength (5 values): 436nm, 498nm, 546nm, 569nm, 616nm
1-Radiance
3-Radiance sensitivity map
This map is showing from where comes the radiance and in what proportion (units % per sq km)
Zenith before midnight, AOD=0.1, wavelength=569nm (Na)
Southward 20 deg. above horizon, AOD=0.1, wavelength=569nm (Na)
Radiance contribution maps for Tenerife Observatory (OT)
Crédits: J.C. Casado
This map is showing from where comes the radiance (recorded in OT toward zenith (left) and south z=70deg (right)) and in what proportion (% per sq km)
This map is showing the radiance contribution of a single "standard" light fixture at each sq km.
Zenith before midnight, AOD=0.1, wavelength=569nm (Na)
Southward 20 deg. above horizon, AOD=0.1, wavelength=569nm (Na)
Radiance sensitivity maps for Tenerife Observatory (OT)
Mont-Mégantic Obs
Results
Natl park cabin
Astrolab pub. outreach center
Nearest house
2009
Toward Sherbrooke the largest nearby city (60 km)
Contribution maps @ 569 nm
3 different base layers
{
modeling zone
zooming
capabilities
This map is showing the radiance contribution of a single "standard" light fixture at each sq km.
Zenith before midnight, AOD=0.1, wavelength=569nm (Na)
Contribution
Sensitivity
Conclusion
Add a pin for observer position
Add the radiance value
Add a table for calibration constants
Add a web access to the original data
Add maps for cloudy skies
Add more sites
Madrid area
Mount Palomar Observatory
Cherenkov Telescope Array (Argentina)
Berlin area
The portal is a powerful tool to help authorities to reduce sky brightness and allow an easy access to the data for the scientific community and for the public.
Future work:
Thank you!
Possibility to locate a specific source
Origin of Sherbrooke city center zenith radiance @ 569 nm
In cities, sky brightness is coming from an average of nearby sources so that sky brightness is almost constant inside a large city. Sky btightness is falling down when exiting the city
Low turbidity
High turbidity
Low turbidity
High turbidity
r~15 km
r~50 km
Obs.
Obs.
Under hazy atm. the contribution of nearby sources to the near horizon sky brightness is very important.
r<2 km
r<6 km
Sherbrooke
Sherbrooke
Observatorie del Teide
Funding for this research was provided by the fond québécois pour la recherche sur la nature et les technologie (FQRNT), by Éducation, loisirs et sports Québec, by Cégep de Sherbrooke, and by Compute Canada.
Montréal
Sherbrooke
2012 Night lights from space, satellite Suomi NPP
Montréal
Québec
Sherbrooke
Micoua, Canada
Fred Lawrence Whipple Obs
Huntington beach
Lowell Obs.
Anderson Mesa Obs.
Discovery Channel Telescope
Astrolab, Mont-Mégantic
Tucson
Phoenix
Flagstaff
Los Angeles
Saint-Camille
Baie-Comeau
Tenerife Obs.
Madrid *
Hefei, China
Fudan University
Shanghai
Lin'an
Las Vegas
Canary Islands
Marrakech
Casablanca
Barcelona *
Pic du Midi *
CTA *
Mendoza
Santiago
Buenos Aires
Mt Palomar Observatory
Organ pipe cactus N.M.
La Palma Obs. (ORM)
2010
SAND-3
2007
NPS sky team 2007
Kitt Peak Ntl Obs.
US Naval Obs.
Effect of
snow cover

Mont-Mégantic observatory: a success story
1st international dark sky reserve
Effect of aerosol content
Effect of the variability of lighting practices
Effect of distance to a source
Effect of viewing angle
SAND-2
Spectrometer

Moon
Future Experiments
Summer 2013
Winter 2014
Winter zenith
contrib.
Summer zenith
contrib.
1.6x
Larger sky radiance in winter but coming from nearer sources
2005 @ 569 nm
2006
Canary sky law
Light pollution
Orion constellation seen from different light pollution levels
Stars
Full transcript