Sensible and latent heat flux from radiometric surface temperatures at the regional scale: methodology and validation

The CarboEurope Regional Experiment Strategy (CERES) was designed to develop and test a range of methodologies to assess regional surface energy and mass exchange of a large study area in the south-western part of France. This paper describes a methodology to estimate sensible and latent heat fluxes on the basis of net radiation, surface radiometric temperature measurements and information obtained from available products derived from the Meteosat Second Generation (MSG) geostationary meteorological satellite, weather stations and ground-based eddy covariance towers. It is based on a simplified bulk formulation of sensible heat flux that considers the degree of coupling between the vegetation and the atmosphere and estimates latent heat as the residual term of net radiation. Estimates of regional energy fluxes obtained in this way are validated at the regional scale by means of a comparison with direct flux measurements made by airborne eddy-covariance. The results show an overall good matching between airborne fluxes and estimates of sensible and latent heat flux obtained from radiometric surface temperatures that holds for different weather conditions and different land use types. The overall applicability of the proposed methodology to regional studies is discusse

The Sky Arrow ERA, an innovative airborne platform to monitor mass, momentum and energy exchange of ecosystems

Substantial worldwide efforts are underway aimed at identifying the spatial and temporal distribution of the global sources and sinks of atmospheric carbon dioxide (CO2). The sink/source strength of vegetated surfaces at ground sites can now be estimated with reasonable accuracy and micrometeorological techniques are now well established, while difficulties exist in up scaling these figures to the regional and global scales. Airborne measurement of mass, momentum, and energy fluxes for boundary layer research has been available for decades requiring the use of large aircraft to carry instruments and dedicated support facilities. The advent of compact, lowpower instruments and high speed, high-capacity digital data acquisition systems has recently allowed small research aircraft to perform such measurements with high accuracy. This paper first describes the Sky Arrow ERA (Environmental Research Aircraft), a small research aircraft that has been recently developed in Italy, in the frame of an international scientific collaboration. This aircraft can be operated to measure fluxes of mass, momentum and energy while flying at low altitude and reduced ground speed. The fluxes are computed with the airborne eddy correlation technique. The basic theory at the basis of the flux measurement technique is also described in the paper, and two application examples are discussed to illustrate the quality and the accuracy of the measurements that can be made using this research platform. Potential applications of those data to parametrize land surface schemes, validate simulation models and provide extensive and reliable ground truthing for satellite remote sensing applications are highlighted

an integrated low cost road traffic and air pollution monitoring platform to assess vehicles air quality impact in urban areas

Abstract An integrated monitoring platform (IMP) was developed for real-time monitoring of traffic flows and related air pollution in urban areas. The IMP includes: (i) an air quality monitoring unit, integrating the "Arduino" open-source technology with low-cost and high-resolution sensors, to measure air pollutant concentrations; (ii) a traffic monitoring device, equipped with a camera sensor and a video analysis software, to detect vehicles' counts, speed and category; (iii) a spatial data infrastructure, composed of a central GeoDatabase, a GIS engine, and a web interface, for data storage and management. The IMP was tested in Florence (Italy) by installing sensor devices at a road site where a 1-year measuring campaign was carried out. A reference meteorological station in the city centre was used to provide observations of wind speed and direction, air temperature, and relative humidity. In this work, a statistical analysis was performed to investigate the influence of local road traffic and meteorological conditions on CO, NO2 and CO2 concentrations. Two different methods were applied: a linear regression model and an artificial neural network. To investigate the role played by emissions from road traffic, the influence of all drivers by period of the year (cold vs. warm months) and day of the week (weekdays vs. weekends) was analysed. As a result, the contribution of local road traffic on pollutant concentrations proved to be lower than meteorological parameters

Cambiamenti nel regime pluviometrico in ecosistemi mediterranei: il progetto MIND

Changes in rainfall patterns in Mediterranean ecosystems: the MIND project. Will Mediterranean terrestrial ecosystems be affected by the expected changes in precipitation regimes? If so, by how much and in which direction? These questions are at the basis of the research performed in context of the EU MIND project, whose key objectives were: i) to investigate the potential effects of increasing drought on Mediterranean terrestrial ecosystems at the process, ecosystem and regional scales and ii) to assess ecosystem vulnerability to changes in rainfall patterns. A network of experimental study sites has been created in Portugal, Spain, France and Italy, where field manipulations alter the amount of water available to the ecosystem. The most up-to-date methods of ecophysiology, micrometeorology, soil ecology and remote sensing have been used to elucidate the mechanisms that regulate the response of vegetation and soil to changes in water availability. This information is providing the basis for the implementation and validation of simulation models capable of predicting the drought response of Mediterranean terrestrial ecosystems, and their vulnerability to future climate change, on a larger scale. The out-coming results are elucidating how water availability affects plant ecophysiological processes, the dynamics of soil carbon and the overall exchange of mass and energy between the land and the atmosphere. This paper focuses on some of the important, yet preliminary, results on C and energy fluxes that have been obtained at the large scale troughfall manipulation experiment (Tolfa, Italy), in a forest dominated by Arbutus unedo L

CEFLES2: the remote sensing component to quantify photosynthetic efficiency from the leaf to the region by measuring sun-induced fluorescence in the oxygen absorption bands

The CEFLES2 campaign during the Carbo Europe Regional Experiment Strategy was designed to provide simultaneous airborne measurements of solar induced fluorescence and CO2 fluxes. It was combined with extensive ground-based quantification of leaf- and canopy-level processes in support of ESA's Candidate Earth Explorer Mission of the "Fluorescence Explorer" (FLEX). The aim of this campaign was to test if fluorescence signal detected from an airborne platform can be used to improve estimates of plant mediated exchange on the mesoscale. Canopy fluorescence was quantified from four airborne platforms using a combination of novel sensors: (i) the prototype airborne sensor AirFLEX quantified fluorescence in the oxygen A and B bands, (ii) a hyperspectral spectrometer (ASD) measured reflectance along transects during 12 day courses, (iii) spatially high resolution georeferenced hyperspectral data cubes containing the whole optical spectrum and the thermal region were gathered with an AHS sensor, and (iv) the first employment of the high performance imaging spectrometer HYPER delivered spatially explicit and multi-temporal transects across the whole region. During three measurement periods in April, June and September 2007 structural, functional and radiometric characteristics of more than 20 different vegetation types in the Les Landes region, Southwest France, were extensively characterized on the ground. The campaign concept focussed especially on quantifying plant mediated exchange processes (photosynthetic electron transport, CO2 uptake, evapotranspiration) and fluorescence emission. The comparison between passive sun-induced fluorescence and active laser-induced fluorescence was performed on a corn canopy in the daily cycle and under desiccation stress. Both techniques show good agreement in detecting stress induced fluorescence change at the 760 nm band. On the large scale, airborne and ground-level measurements of fluorescence were compared on several vegetation types supporting the scaling of this novel remote sensing signal. The multi-scale design of the four airborne radiometric measurements along with extensive ground activities fosters a nested approach to quantify photosynthetic efficiency and gross primary productivity (GPP) from passive fluorescence

The BLLAST field experiment: Boundary-Layer late afternoon and sunset turbulence

Due to the major role of the sun in heating the earth's surface, the atmospheric planetary boundary layer over land is inherently marked by a diurnal cycle. The afternoon transition, the period of the day that connects the daytime dry convective boundary layer to the night-time stable boundary layer, still has a number of unanswered scientific questions. This phase of the diurnal cycle is challenging from both modelling and observational perspectives: it is transitory, most of the forcings are small or null and the turbulence regime changes from fully convective, close to homogeneous and isotropic, toward a more heterogeneous and intermittent state. These issues motivated the BLLAST (Boundary-Layer Late Afternoon and Sunset Turbulence) field campaign that was conducted from 14 June to 8 July 2011 in southern France, in an area of complex and heterogeneous terrain. A wide range of instrumented platforms including full-size aircraft, remotely piloted aircraft systems, remote-sensing instruments, radiosoundings, tethered balloons, surface flux stations and various meteorological towers were deployed over different surface types. The boundary layer, from the earth's surface to the free troposphere, was probed during the entire day, with a focus and intense observation periods that were conducted from midday until sunset. The BLLAST field campaign also provided an opportunity to test innovative measurement systems, such as new miniaturized sensors, and a new technique for frequent radiosoundings of the low troposphere. Twelve fair weather days displaying various meteorological conditions were extensively documented during the field experiment. The boundary-layer growth varied from one day to another depending on many contributions including stability, advection, subsidence, the state of the previous day's residual layer, as well as local, meso- or synoptic scale conditions. Ground-based measurements combined with tethered-balloon and airborne observations captured the turbulence decay from the surface throughout the whole boundary layer and documented the evolution of the turbulence characteristic length scales during the transition period. Closely integrated with the field experiment, numerical studies are now underway with a complete hierarchy of models to support the data interpretation and improve the model representations.publishedVersio

Compact EDDY: a compact, low consumption eddy covariance logging system

Compact_Eddy is a handheld computer-based logging system developed for eddy covariance installations. It is flexible to support different types of sonic anemometers, it has storing capability on internal memory, and data processing capability. The software is written in the Visual Basic .NET platform, entirely based on standard Windows operating systems thus allowing easy installation and configuration for a wide range of handheld PCs. The software computes half hourly statistics and fluxes with a simplified procedure, stores binary data with efficient memory usage and can be configured to send periodically, to a remote control station, system status information and basic computations using a GSM modem. The use of a handheld computer resulted in an average real conditions power consumption of 2.9 W, very low if compared with other standard logging devices, allowing important savings especially when systems are powered with solar panels in remote areas. Compact_Eddy has been installed and tested in three locations, with very different environmental conditions ranging from eastern European mountain forests to African semi-desertic areas. The field results demonstrated that the system operated reliably, resulting to be a good low-cost alternative to laptop computers and dataloggers. \ua9 2008 Elsevier B.V. All rights reserved

A new tower-based hyperspectral system for the estimation of CO2 fluxes and biophysical parameters in a subalpine grassland ecosystem

Linking optical remote sensing with carbon fluxes and biophysical parameters is critical to exploit spatial and temporal extensive information useful for validating model simulations at different scales. Proximal sensing is fundamental to quantify and understand the seasonal dynamics of ecosystems and to upscale the observations carried out at the ground level. In this study, we present the results from an ongoing research project at the FLUXNET eddy covariance site of Monte Bondone (Italy). The site is located at 1550 m a.s.l. on a mountain plateau in the Italian Alps (Viote del Monte Bondone). The area is managed as an extensively-managed meadow, cut once a year, and dominated by Nardus stricta and Festuca nigrescens. The climate of this area is sub-continental (warm and wet summer), with precipitation peaks in spring and autumn. A new hyperspectral system (WhiteRef Box, developed by Fondazione Edmund Mach in collaboration with the Institute of Biometeorology, CNR, Italy) based on the ASD FieldSpec spectrometer (spectral range 350-2500 nm, resolution ~3 nm at 700 nm) was designed to acquire continuous radiometric measurements. The system was installed on the eddy covariance tower at a height of 6 m, with a field of view of 25°. To obtain reflectance values, white panel radiance spectra and canopy radiance spectra were collected every 5 minutes between 10:00 a.m. and 1:00 p.m. (solar time) during the growing season of 2013. In addition, measurements of biophysical parameters such as above-ground biomass, fraction of Absorbed Photosynthetically Active Radiation (fAPAR), Plant Area Index, Canopy Chlorophyll Content, Canopy Water Content and Green Herbage Ratio were performed at weekly intervals within the spectrometer footprint (~5 m2). In this work, we present some preliminary results regarding the potential of spectral vegetation indices - based on VNIR and SWIR spectral bands- for capturing seasonal trends of CO2 fluxes as well as vegetation biophysical parameters dynamics. Spectral vegetation indices sensitive to chlorophyll content (such as Meris Terrestrial ChIorophyll Index, Vogelmann Indices) showed a good linear correlation with fAPAR, daily Gross Primary Production and chlorophyll content (R2> 0.8 for all the three variables). The SWIR-based Vegetation Indices (e.g. Normalised Difference Infrared Index, Moisture Stress Index) confirmed their ability to estimate Canopy Water Content. Most of the analyzed indices showed to be linearly related with Green Herbage Ratio (explaining more than 80% of variance). The Near Infrared Difference Index (Vescovo et al., 2012) confirmed his potential in predicting canopy structural parameters such as Plant Area Index and biomass (R2> 0.90)