Desarrollo y evaluación de técnicas radiométricas de observación de aerosoles y vapor de agua en la atmósfera desde plataformas terrestres

Abstract

The present doctoral thesis aims to introduce tools that allow us to increase the observational capacity of aerosols and water vapour in the atmosphere, in order to contribute to the improvement of the spatio-temporal representation of these atmospheric components at a global/regional level and the estimation of its tendencies. This work will be developed by making use of multi-platform observations capable of increasing the coverage and availability of relevant information on atmospheric aerosols and water vapour from a scientific point of view. This work analyzes, firstly, the intercomparison and consistency of the two main groundbased networks of observation of atmospheric aerosols established at a global level, GAW-PFR (Global Atmosphere Watch - Precision Filter Radiometer) and NASAAERONET (National Aeronautics and Space Administration - AErosol RObotic NETwork). These two networks have been implemented in order to obtain the spatio-temporal distribution of the aerosol optical depth (AOD) and an estimate of its size using the ˚Angstr¨om Exponent (AE). The intercomparison and consistency was carried out at the Iza˜na Atmospheric Observatory, which is an absolute calibration centre for both networks and a test bed for the Commission for Instruments and Methods of Observation (CIMO) of the World Meteorological Organization (WMO) for aerosol and water vapour remote sensing instruments. In this analysis it was possible to verify that, despite the marked technical differences between both networks, the AOD, in the spectral bands of 440, 500 and 870 nm, retrieved with the Cimel CE318 photometer used by AERONET, met the traceability requirements with the GAW-PFR reference established by the WMO. Next, and as a second part of this doctoral thesis, two instrumental devices were developed: the ZEN-R radiometers that measure the zenith sky radiance (ZSR), which are characterized by their simplicity and robustness as they lack mobile parts. The first of these developments, the ZEN-R41, was the first prototype intended only for the measurement of atmospheric aerosols in the atmospheric column, while the second development, the ZEN-R52, is an improved version that also allows remote sensing of precipitable water vapour (PWV) thanks to the inclusion of an additional optical channel in the spectral band centred at 940 nm. In order to make this relatively simple observation system possible, the necessary methodology had to be developed to obtain the AOD (ZEN-AOD-LUT) and the PWV (ZEN-PWV-LUT), from the ZSR measurements. This procedure based on look-up-table (LUT) was pre-evaluated from ZSR measurements of the Cimel CE318 photometer at three stations characterized by the presence of atmospheric dust, but with very different atmospheric characteristics (Iza˜na, Tamanrasset and Santa Cruz de Tenerife), obtaining very satisfactory results. In a second step, the ZEN system, made up of the ZEN-R radiometer and the aforementioned associated LUT methodology, was evaluated at the Iza˜na Atmospheric Observatory, showing its viability as a sufficiently precise aerosol and water vapour remote sensing tool to be used in networks deployed in remote areas and sparsely covered by current ground-based remote sensing networks. The latter application can provide key complementary information to understand desert dust emission processes, and to improve current early warning networks, in which we can find the SDS-WAS (Sand and Dust Warning Advisory and Assessment System) of the WMO.