Light pollution modelling and detection in a heterogeneous environment: toward a night-time aerosol optical depth retreival method

Abstract

Tracking the Aerosol Optical Depth (AOD) is of particular importance in monitoring aerosol contributions to global radiative forcing. Until now, the two standard techniques used for retrieving AOD were; (i) sun photometry, and (ii) satellite-based approaches, such as based DDV (Dense Dark Vegetation) inversion algorithms. These methods are only available for use during daylight time since they are based on direct or indirect observation of sunlight. Few attempts have been made to measure AOD behaviour at night. One such method uses spectrally-calibrated stars as reference targets but the number of available stars is limited. This is especially true for urban sites where artificial lighting hides most of these stars. In this research, we attempt to provide an alternate method, one which exploits artificial sky glow or light pollution. This methodology links a 3D light pollution model with in situ light pollution measurements. The basic idea is to adjust an AOD value into the model in order to fit measured light pollution. This method requires an accurate model that includes spatial heterogeneity in lighting angular geometry, in lighting spectral dependence, in ground spectral reflectance and in topography. This model, named ILLUMINA, computes 1 st and 2 nd order molecular and aerosol scattering, as well as aerosol absorption. These model features represent major improvements to previous light pollution models. Therefore, new possibilities for light pollution studies will arise, many of which are of particular interest to the astronomical community. In this paper we will present a first sensitive study applied to the ILLUMINA model.

Physical behaviour of anthropogenic light propagation into the nocturnal environment

“…Moreover, the models did not account for blocking by obstacles or topography. In 2007, Aubé [27] showed that light travelling near a horizon was not as critical as previously thought. Luginbuhl et al [21] later confirmed this assertion.…”

Generación de mapas de luminancia urbana a partir de un sensor hiperespectral VNIR y una cámara fotogramétrica digital

“…donde τ(λ) es la transmisividad espectral de la atmósfera calculada para cada punto del suelo según su geometría de observación; L * (λ) corresponde a la dispersión atmosférica de la luz artificial (Aubé, 2008) y L n es un término de ruido aditivo que tiene en consideración la sensibilidad del dispositivo a las diferentes longitudes de onda.…”

Using two light-pollution models to investigate artificial sky radiances at Canary Islands observatories

“…It is, however, usually difficult to determine the range of applicability of the various algorithms. In this targeted study we compare two solution techniques: the first one is based on an enhanced single‐scattering approach originally introduced by Kocifaj (2007), and the second one implements an accurate radiative transfer model that accounts explicitly for two scattering orders (Aubé et al 2005). The numerical experiments comprise the modelling of spectral sky radiances at two observatories in the region of the Canary Islands.…”