The dataset of the first observatory from the French network of critical zone observatories (OZCAR) located in an insular tropical and volcanic context, integrating a “Tropical Montane Cloud Forest”: The ERORUN-STAFOR observatory. This collaborative observatory is located in the northern part of La Réunion island (Indian Ocean) within the watershed of Rivière des Pluies (45.0 km²) which hosts the TMCF of Plaines des Fougères, one of the best preserved natural habitats in La Réunion Island. Since 2015, the ERORUN-STAFOR monitoring in collaboration with local partners collected a multidisciplinary dataset with a constant improvement of the instrumentation over time. At the watershed scale and in its vicinity, the ERORUN-STAFOR observatory includes 10 measurement stations covering the upstream, midstream and downstream part of the watershed. The stations record a total of 48 different variables through continuous (sensors) or periodic (sampling) monitoring. The dataset consists of continuous time series variables related to (i) meteorology, including precipitation, air temperature, relative humidity, wind speed and direction, net radiation, atmospheric pressure, cloud water flux, irradiance, leaf wetness and soil temperature (ii) hydrology, including water level and temperature, discharge and electrical conductivity (EC) of stream, (iii) hydrogeology, including groundwater level, water temperature and EC in two piezometers and one groundwater gallery completed by soil moisture measurements under the canopy. The dataset is completed by periodic time series variables related to (iv) hydrogeochemistry, including field parameters and water analysis results. The periodic sampling survey provides chemical and isotopic compositions of rainfall, groundwater, and stream water at different locations of this watershed. The ERORUN-STAFOR monitoring dataset extends from 2014 to 2022 with an acquisition frequency from 10 min to hourly for the sensor variables and from weekly to monthly frequency for the sampling. Despite the frequent maintenance of the monitoring sites, several data gaps exist due to the remote location of some sites and instrument destruction by cyclones. This observatory is a unique research site in an insular volcanic tropical environment offering three windows of observation for the study of critical zone processes through upstream-midstream-downstream measurements sites. This high-resolution dataset is valuable to assess the response of volcanic tropical watersheds and aquifers at both event and long-term scales (i.e. global change). It will also allow various progress in understanding the significant role of the TMCFs in the recharge processes, the hydrogeological conceptual model of volcanic islands, the watershed hydrosedimentary responses to extreme climatic events and their respective evolution under changing climatic conditions.

Les ondes VLF émisent par des transmetteurs sur Terre, se propagent dans le guide d'onde formé par l'ionosphère et la Terre. En cas de changement de conductivité des limites de ce guide d'onde, les signaux reçus sont modifiés. C'est ce qu'il peut arriver par un forçage d'origine solaire (éruptions) ou liés à des zones orageuses (TLE). L'analyse de ces signaux en amplitude et phase permet de remonter à la perturbation de la densité électronique. Celle-ci induit notamment une augmentation de l'absorption HF. Outre les études sur la réponse de l'ionosphère à un forçcage (solaire ou TLE), le projet a une dimension sociétal en fournissant des alertes temps réel sur l'occurrence d'une éruption solaire. L'instrument est composé de deux "boucles" (plutôt des triangles) magnétiques orientées NS et EW. La base de l'antenne mesure 4.57m, la hauteur 2.80m, soit une surface totale de 5.22m2. Avec 11 tours de fil de cuivre on obtient une sensibilité de 3.57E-13 T/rt-Hz; Les "boucles" sont connectées à un pré-ampli situé au pied du mât. Ce pré-amp contient également le système de calibration. Un câble apportant l'électricité et ramenant les signaux part du pré-amp, courre dans les chemins de câble et arrive au "line Receiver", un boite électronique jaune située près du PC de contrôle. Cette électronique contient un ADC et reçoit le timing du GPS. L'ensemble des signaux est ensuite conduit vers le PC de contrôle qui effectue la démodulation des signaux MSK (méthode de transmission des données VLF) et produit les données NarrowBand et BroadBand. L'instrument fonctionne en continue 24/365. Le PC redémarre seul en cas de coupure d'électricité. Pour vérifier que l'instrument est bien en fonctionnement, il suffit de regarder la date et l'heure du spectrogramme affiché (rafraichissement toutes les minutes).

The beach profile is a sectional representation of its topography. The beach topography and its dynamics (by beach profile or transect approach) is illustrated by the acquisition of altimetry data along a fixed profile. 42 profiles are regularly monitored on the reef coast of Reunion Island: 2 profiles per year before the swell seasons of summer and austral winter; the impact of the events of strong swells (cyclones, southern swells) is systematically measured on the labeled Dynalit sites and more sporadically on the other sites. The methodology deployed locally since 2012.