1,227 research outputs found

    Senegalese land surface change analysis and biophysical parameter estimation using NOAA AVHRR spectral data

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    Surface biophysical estimates were derived from analysis of NOAA Advanced Very High Spectral Resolution (AVHRR) spectral data of the Senegalese area of west Africa. The parameters derived were of solar albedo, spectral visible and near-infrared band reflectance, spectral vegetative index, and ground temperature. Wet and dry linked AVHRR scenes from 1981 through 1985 in Senegal were analyzed for a semi-wet southerly site near Tambacounda and a predominantly dry northerly site near Podor. Related problems were studied to convert satellite derived radiance to biophysical estimates of the land surface. Problems studied were associated with sensor miscalibration, atmospheric and aerosol spatial variability, surface anisotropy of reflected radiation, narrow satellite band reflectance to broad solar band conversion, and ground emissivity correction. The middle-infrared reflectance was approximated with a visible AVHRR reflectance for improving solar albedo estimates. In addition, the spectral composition of solar irradiance (direct and diffuse radiation) between major spectral regions (i.e., ultraviolet, visible, near-infrared, and middle-infrared) was found to be insensitive to changes in the clear sky atmospheric optical depth in the narrow band to solar band conversion procedure. Solar albedo derived estimates for both sites were not found to change markedly with significant antecedent precipitation events or correspondingly from increases in green leaf vegetation density. The bright soil/substrate contributed to a high albedo for the dry related scenes, whereas the high internal leaf reflectance in green vegetation canopies in the near-infrared contributed to high solar albedo for the wet related scenes. The relationship between solar albedo and ground temperature was poor, indicating the solar albedo has little control of the ground temperature. The normalized difference vegetation index (NDVI) and the derived visible reflectance were more sensitive to antecedent rainfall amounts and green vegetation changes than were near-infrared changes. The information in the NDVI related to green leaf density changes primarily was from the visible reflectance. The contribution of the near-infrared reflectance to explaining green vegetation is largely reduced when there is a bright substrate

    Thermal Imagery in Plant Phenotyping: Assessing Stomatal Conductance through Energy Balance Modelling

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    The importance of temperature data in plant phenotyping applications is well known as is the difficulty of correlating temperature to plant behaviours. This work investigates the emission of thermal radiation from plant leaves to validate non-contact temperature measurements as well as modelling approaches to extend the use of temperature data obtained continuously from outdoor field crops. Temperature data and weather data are combined to calculate a stomatal resistance to water loss to satisfy an energy balance. Several approaches to modelling an energy balance and their results are compared and contrasted

    Investigation related to multispectral imaging systems

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    A summary of technical progress made during a five year research program directed toward the development of operational information systems based on multispectral sensing and the use of these systems in earth-resource survey applications is presented. Efforts were undertaken during this program to: (1) improve the basic understanding of the many facets of multispectral remote sensing, (2) develop methods for improving the accuracy of information generated by remote sensing systems, (3) improve the efficiency of data processing and information extraction techniques to enhance the cost-effectiveness of remote sensing systems, (4) investigate additional problems having potential remote sensing solutions, and (5) apply the existing and developing technology for specific users and document and transfer that technology to the remote sensing community

    The HABIT (HabitAbility: Brine Irradiation and Temperature) environmental instrument for the ExoMars 2022 Surface Platform

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    Acknowledgements HABIT is an instrument of the Luleå University of Technology (LTU), led by J. Martín-Torres (PI) and M-P. Zorzano (co-PI). The international list of Co-Is and collaborators of the science team of HABIT is given in (https://atmospheres.research.ltu.se/habit/pages/team.php). HABIT engineering team: A. Soria-Salinas, M. I. Nazarious, S. Konatham, T. Mathanlal and A. Vakkada Ramachandran. HABIT IT team: J. –A. Ramirez-Luque and R. Mantas-Nakhai. ASS acknowledges the support of the LTU Graduate School of Space. M-P. Z's contribution has been partially supported by the Spanish State Research Agency (AEI) Project No. MDM-2017-0737 Unidad de Excelencia “María de Maeztu” - Centro de Astrobiología (INTA-CSIC). The HABIT FM and EQM were fabricated by Omnisys Instruments AB, based in Gothenburg, Sweden, under advice of LTU as part of the HABIT project development and funded by the Swedish National Space Agency (SNSA). We thank the ExoMars project team, European Space Agency (ESA), Roscosmos, Space Research Institute (IKI) and Omnisys Instruments AB for their hard work on the ExoMars mission. We thank Petra Rettberg and Carina Fink from DLR for their planetary protection analysis of HABIT samples. We acknowledge the Luleå University of Technology, the Wallenberg Foundation and the Kempe Foundation for support of the Mars research activities. We thank the support of the Swedish Institute for Space Physics (IRF) for the TVAC tests. The Oxia Planum environmental conditions research was partially funded by the European Research Foundation. The SpaceQ chamber has been developed together with Kurt J. Lesker Company and was funded by the Kempe Foundation. CRediT authorship contribution statement Javier Martín-Torres: Conceptualization, Methodology, Supervision, Investigation, Writing - original draft, Funding acquisition, Resources, Project administration. María-Paz Zorzano: Conceptualization, Methodology, Supervision, Investigation, Writing - original draft, Funding acquisition, Resources, Project administration. Álvaro Soria-Salinas: Formal analysis, Investigation, Visualization, Writing - review & editing. Miracle Israel Nazarious: Formal analysis, Investigation, Visualization, Writing - review & editing. Samuel Konatham: Formal analysis, Investigation, Visualization, Writing - review & editing. Thasshwin Mathanlal: Formal analysis, Investigation, Visualization, Writing - review & editing. Abhilash Vakkada Ramachandran: Formal analysis, Investigation, Visualization, Writing - review & editing. Juan-Antonio Ramírez-Luque: Software, Writing - review & editing. Roberto Mantas-Nakhai: Software, Writing - review & editing.Peer reviewedPostprin

    Influence of ground surface characteristics on the mean radiant temperature in urban areas

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    The effect of variations in land cover on mean radiant surface temperature (Tmrt) is explored through a simple scheme developed within the radiation model SOLWEIG. Outgoing longwave radiation is parameterised using surface temperature observations on a grass and an asphalt surface, whereas outgoing shortwave radiation is modelled through variations in albedo for the different surfaces. The influence of surface materials on Tmrt is small compared to the effects of shadowing. Nevertheless, altering ground surface materials could contribute to a reduction on Tmrt to reduce the radiant load during heat-wave episodes in locations where shadowing is not an option. Evaluation of the new scheme suggests that despite its simplicity it can simulate the outgoing fluxes well, especially during sunny conditions. However, it underestimates at night and in shadowed locations. One grass surface used to develop the parameterisation, with very different characteristics compared to an evaluation grass site, caused Tmrt to be underestimated. The implications of using high resolution (e.g. 15 minutes) temporal forcing data under partly cloudy conditions are demonstrated even for fairly proximal sites
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