An accurate description of the atmospheric aerosols is needed in order to address its role in the Earth radiative balance and consequently its effect on global warming. The uncertainty on the radiative forcing due to suspended particulate matter is indeed large in magnitude if compared to the understanding of radiative forcing due to greenhouses gases such as CO2 (IPCC, 2007), and it is the dominant contributor to overall net Industrial Era forcing uncertainty (IPCC, 2018).
Compared to greenhouse gases, a great deal of these uncertainties is stemmed from the spatial and temporal inhomogeneities of the aerosols properties. This variability is mainly related to their short average life and the heterogeneous distribution of sources and their strengths, but also to complex interactions with the atmosphere and the sun radiation.
With the purpose of reducing uncertainty on aerosol characterization, several networks based on passive remote sensing techniques,using the sun as source, have been established worldwide, such as AERONET , PHOTONS , RIMA, SKYNET and WMO-GAW
According to the World Meteorological Organization (WMO) guidelines, only data provided by international networks should be used in aerosol climatology studies. These networks provide a well tracked calibration procedure, good quality standards and homogeneity on the retrievals. However many sun-sky radiometers are working out from federated network, in small independent and local networks, or even standalone. This situation implies that a large amount of data is not made available, it is difficult to reach, or it has not the quality status and homogeneity from the well established international networks. On the end the data cannot be properly used for regional climatology studies.