Characterization of Radiative-chemical processes at the Air/Snow Interface
Periodo: Dicembre 2020 – Novembre 2022
The air-snow interface is a critical layer that controls several processes and for this reason a deeper knowledge about driving parameters is the primary objective of this project. This goal will be approached at the Italian-French research facility at Dome-C combining different methodologies based on ground observations, proximal sensing, remote sensing and snow radiative modelling. The complexity of interconnected exchanges at the air-snow interface will be investigated considering the radiative transfer and photochemistry occurring at the surface. Both processes are strongly affected by the available snow surface area that is described by the roughness at a micro- and macro- scales. Activities will be focused on integrating already-operating observations at fixed position with spatial measurements about microphysical features of the snowed surface, the superficial roughness, the spectral/broadband albedo and the chemistry of the different involved matrices.
The optical behaviour of snow is a property that influences the processes occurring at the air-snow interface. This information synthesizes mycro-physical condition of the snow (grain size and shape) and it can varies in the space and during time. Such a behaviour can be observed measuring upwelling and downwelling rdiative fluxes as well as discriminating between direct-diffuse radiations. This activity can be supported at the BRSN facility present at Dome-C and it will be possible to define the spectral BRDF, which can represents the signal received by satellite in correspondence to different sun-surface-sensor geometries. The macroscopic behaviour of the surface will be described using digital photography in the visible and in the near-infrared spectrum and we will explore the potentiality of stereoscopic photography to define the surface roughness. The obtained information will contribute to estimate how the variability of snow types impact on two different processes: the radiative transfer and the air-snow chemical exchanges. The spatial variability will be investigated moving the experimental setup over a square kilometer that represents the pixel resolution of the MODIS sensor. Having different measurements within this pixel, we will process our data with different spatial resolution and we will compare our observations with radiative model simulations and with satellite retrievals. The impact of surface variability on air-snow chemical exchanges will be investigated by sampling snow and air, with particular attention on nitrogen and volatile organic compounds. The core of this task will be based on the estimation of nitrogen species and VOCs in the air, which is the key parameter for modelling the chemical exchanges at the interface knowing the snow microphysics, the snow chemistry and the micrometeorology. The air chemistry will be approached at the Concordia station using denuder systems, adsorbent tubes and analyzers and IC and HPLC/UV analysis in Italy. The micrometeorological characterization of the measurement site will be defined utilizing a mixed gradient-eddy covariance technique. Snow chemistry will be approached during the fieldwork collecting samples at the surface that will be conditioned and stored until the analysis that will carried out at the Italian laboratories. The TUV-snow model will be used with snow and air data to calculate fluxes of chemical species from the snowpack.
(1) Extend the knowledge about the albedo and the bidirectional reflectance factor in the solar spectral range 350-2500 nm; verify the compatibility between spectral and broadband albedo defining narrowband-to-broadband conversion site specific parameters.
(2) Assess the spatial variability of the snow cover in terms of spectral albedo and roughness under different meteo-climatic conditions.
(3) Determine implications for reactive nitrogen and carbon recycling (release, loss, oxidation, deposition) at the air-snow interface for the evaluation of photochemistry and oxidative capacity over Dome-C.
(4) Develop a database concerning surface reflectivity with accessory information about snow micro-physical features (grain size and shape, SSA, density) and surface roughness.
(5) Develop a high quality surface based reference dataset aimed to enhance CAL/VAL activities for MODIS and Sentinel-2/3 snow products over Dome-C.
(6) Develop photochemical models linking chemical and radiative exchange processes at air-snow interface to test various global change scenarios and derive the responsiveness of the chemical and physical/radiative mechanisms to photochemistry and global changes.
- Istituto Scienze Atmosfera e Clima (ISAC),
- Istituto di Ricerca sulle Acque (IRSA),
- Istituto di BioEconomia (IBE),
- Dip. Chimica – Università di Firenze (UniFI),
- Royal Holloway University of London (RHUL),
- Institute des Geosciences dè l’Environnment (CNRS),
- Agenzia Ricerca e Protezione Ambiente Veneto (ARPAV)