Search results for "Sensing"
showing 10 items of 1698 documents
Relationship between the effective cloud optical depth and different atmospheric transmission factors
2015
This study examines the sensitivity of cloud optical depth (COD) for overcast conditions to radiation transmission using data collected in Valencia, Spain. These relationships are provided as simple empirical functions, therefore avoiding the need to apply complex model minimisation schemes to obtain COD. Comparisons are presented between COD obtained by a minimization method and several radiation transmission factors comprising a clearness index (kt), a modified version (kt'), a cloud modification factor (CMF) and its modified version (CMF'). Additionally, a statistical model of COD proposed by J.C. Barnard and C.N. Long (2004) is tested with our data. Statistical relationships between COD…
Evaluation of the MOZAIC Capacitive Hygrometer during the airborne field study CIRRUS-III
2018
The MOZAIC Capacitive Hygrometer (MCH) is usually operated aboard passenger aircraft in the framework of MOZAIC (Measurement of Ozone by Airbus In-Service Aircraft) for measuring atmospheric relative humidity (RH). In order to evaluate the performance of the MCH, the instrument was operated aboard a Learjet 35A research aircraft as part of the CIRRUS-III field study together with a closed-cell Lyman-α fluorescence hygrometer (Fast in situ Stratospheric Hygrometer, or FISH) and an open-path tunable diode laser system (Open-path Jülich Stratospheric TDL ExpeRiment, or OJSTER) for water vapour measurement. After reducing the CIRRUS-III data set to data corresponding to MOZAIC aircraft operatio…
Reproducing cloud microphysical and irradiance measurements using three 3D cloud generators
2007
Using three cloud generators, three-dimensional (3D) cloud fields are reproduced from microphysical cloud data measured in situ by aircraft. The generated cloud fields are used as input to a 3D radiative transfer model to calculate the corresponding fields of downward and upward irradiance, which are then compared with airborne and ground-based radiation measurements. One overcast stratocumulus scene and one broken cumulus scene were selected from the European INSPECTRO field experiment, which was held in Norwich, UK, in September 2002. With these data, the characteristics of the three different cloud reproduction techniques are assessed. Besides vertical profiles and histograms of measured…
Evaluation and comparison of satellite precipitation estimates with reference to a local area in the Mediterranean Sea
2014
Precipitation measurement is a key activity for the analysis of storm processes as well as every hydrological process. Satellite retrieval systems, rain-gauge network and radar systems are complement to each other in terms of their coverage and capability of monitoring precipitation. Satellite rainfall estimates systems produce data with global coverage that can provide information in areas for which data from other sources are unavailable. Without referring to ground measurement, satellite-based estimates can be bias. Although some gauged adjusted satellite precipitation products are developed, an effective way of integrating multi-sources of precipitation information is still a challenge.…
Column-integrated aerosol optical properties from ground-based spectroradiometer measurements at Barrax (Spain) during the Digital Airborne Spectrome…
2003
[1] The Digital Airborne Imaging Spectrometer Experiment (DAISEX) was carried out for the European Space Agency (ESA) in order to develop the potential of spaceborne imaging spectroscopy for a range of different scientific applications. DAISEX involved simultaneous data acquisitions using different airborne imaging spectrometers over test sites in southeast Spain (Barrax) and the Upper Rhine valley (Colmar, France, and Hartheim, Germany). This paper presents the results corresponding to the columnintegrated aerosol optical properties from ground-based spectroradiometer measurements over the Barrax area during the DAISEX campaign days in the years 1998, 1999, and 2000. The instruments used f…
Characterization of the atmosphere during SEN2FLEX 2005 field campaign
2008
The European Space Agency carried out the Sentinel-2 and Fluorescence Experiment (SEN2FLEX) campaign in Barrax (Spain) during the summer of 2005, with the main objective of observe solar induced fluorescence signal using the AirFLEX airborne instrument over different vegetation targets in order to verify signal suitability for observations from space as proposed in the FLEX mission. A highly precise atmospheric correction is mandatory for adequate measurements of the AirFLEX instrument; thus a complete characterization of the atmosphere was programmed in SEN2FLEX in order to document the presence of atmospheric aerosols above the experimental area, as their effects represent the major sourc…
Radiative Flux Estimation from a Broadband Radiometer Using Synthetic Angular Models in the EarthCARE Mission Framework. Part II: Evaluation
2012
AbstractThe instantaneous top-of-atmosphere (TOA) radiance-to-flux conversion for the broadband radiometer (BBR) on board the Earth Clouds, Aerosols, and Radiation Explorer (EarthCARE) was assessed in Part I of this paper, by developing theoretical angular distribution models (ADMs) specifically designed for the instrument viewing configuration. This paper validates the BBR ADMs by comparing derived flux estimates with flux retrievals obtained from the Clouds and the Earth’s Radiant Energy System (CERES) Terra models. A CERES BBR-like database is employed in the assessment, which is an optimum dataset to validate the BBR algorithms and to determine the benefits of the multiangular conversio…
Autonomous marine hyperspectral radiometers for determining solar irradiances and aerosol optical properties
2017
We have developed two hyperspectral radiometer systems which require no moving parts, shade rings or motorised tracking, making them ideally suited for autonomous use in the inhospitable remote marine environment. Both systems are able to measure direct and diffuse hyperspectral irradiance in the wavelength range 350–1050 nm at 6 nm (Spectrometer 1) or 3.5 nm (Spectrometer 2) resolution. Marine field trials along a 100° transect (between 50° N and 50° S) of the Atlantic Ocean resulted in close agreement with existing commercially available instruments in measuring (1) photosynthetically available radiation (PAR), with both spectrometers giving regression slopes close to unity (Spectrometer …
Surface temperature retrieval from Along Track Scanning Radiometer 2 data: Algorithms and validation
2004
[1] A study has been carried out using MODTRAN 3.5 simulations of the Along Track Scanning Radiometer 2 (ATSR-2) data at 3.7, 11, and 12 μm wavelengths to give a range of algorithms for estimating surface. Making use of the dual-angle feature of the ATSR-2, algorithms based on dual-angle, split-window, and mixed structure have been considered. The coefficients of the algorithms are derived by regression analysis using the MATLAB code. The evaluation of the sensitivity of each algorithm shows that in general, dual-angle algorithms provide smaller errors in the estimation of surface temperature than the split-window algorithms and that the algorithms with water vapor dependence give an improv…
Flux retrieval optimization with a nonscanner along-track broadband radiometer
2003
[1] The theoretical behavior of broadband flux retrieval is analyzed with the aid of a radiance field database. Several angular inversion models are developed for different viewing configurations, with special emphasis in a nonscanner along-track design concept. Results show that the performance of these angular models depends on the viewing zenith angle (VZA). When cloud cover is predominant within the observed scene, VZAs around 55° (shortwave) and 50° (longwave) minimize the error when deriving fluxes. These results might help in the design of future missions where the main idea is to obtain accurate instantaneous measurements of top of atmosphere reflected and emitted fluxes. Such measu…