0000000000117338
AUTHOR
José A. Valiente
An Autonomous System to Take Angular Thermal-Infrared Measurements for Validating Satellite Products
An autonomous system for field land surface temperature (LST) measurements taken at different observation angles was developed to be deployed easily at any conventional meteorological tower station. The system permits ground-truth data to be acquired on a continuous basis, and angularly scans land and sky hemispheres with a single thermal-infrared (TIR) radiometer. This paper describes the autonomous angular system and the methodology to assess ground-truth LST and relative-to-nadir emissivity data from system measurements. Ground-truth LSTs were used to validate satellite-retrieved LST products at two experimental sites (rice crop and shrubland areas). The relative-to-nadir emissivity valu…
Influences of synoptic situation and teleconnections on fog-water collection in the Mediterranean Iberian Peninsula, 2003-2012
Fog-water collection has been widely analysed for its quantification and potential uses; however, there are few studies assessing the synoptic conditions and large-scale teleconnection patterns that affect its occurrence. Focusing on the Mediterranean Iberian Peninsula, this work aims to analyse the synoptic patterns, both at surface level and 850 hPa geopotential height, that most likely to favour fog-water collection, and to quantify the relationship between fog-water collection and the NAOi (North Atlantic Oscillation index), MOi (Mediterranean Oscillation index) as well as WeMOi (Western Mediterranean Oscillation index) teleconnection patterns. For this purpose, daily fog-water observat…
Proposal and Validation of an Emissivity-Dependent Algorithm to Retrieve Sea-Surface Temperature From MSG-SEVIRI Data
A frequent and accurate determination of sea-surface temperature (SST) would permit an improvement in both the forecasting of natural hazards and the monitoring of the effects of climate change. The Meteosat Second Generation (MSG) spinning enhanced visible and infrared imager (SEVIRI) (MSG-SEVIRI) offers this possibility, since it has a temporal resolution of 15 min. Current algorithms for SST retrieval from MSG-SEVIRI data use angular-dependent coefficients, but they do not use sea-surface emissivity (SSE) as an explicit input. This letter proposes a both angular- and emissivity-dependent split-window equation, together with simple equations to estimate SSE and atmospheric water-vapor con…
Evaluation of Landsat-8 TIRS data recalibrations and land surface temperature split-window algorithms over a homogeneous crop area with different phenological land covers
Abstract Successive re-calibrations were implemented in Landsat-8 TIRS data since launch. This paper evaluates the performances of both: (1) these re-calibrations, up to the last calibration update announced for TIRS data in the next Landsat Collection 2; and (2) single-channel (SC) corrections and split-window (SW) algorithms to retrieve land surface temperature (LST) from TIRS data. A robust and accurate multi-year (2014–2019) set of reference ground data were used, which included thermal infrared (TIR) radiance measurements taken along transects in a uniform and thermally homogeneous rice paddy area, but also emissivity measurements for the different ground covers at the site through the…
Land surface air temperature retrieval from EOS-MODIS images
The knowledge of the spatial and temporal patterns of surface air temperature (SAT) is essential to monitor a region's climate and meteorology, to quantify surface exchange processes, to improve climatic and meteorological model results, and to study health and economic impacts. This letter analyzed correlations between SAT and geophysical land surface variables, mainly land surface temperature (LST), to establish operative techniques to obtain spatially continuous land SAT maps from satellite data, unlike data provided by meteorological station networks. The correlations were analyzed by using EOS-MODIS images, meteorological station network data, and geographical variables. Linear regress…
Sea surface temperature and torrential rains in the Valencia region: modelling the role of recharge areas
Abstract. Heavy rain events are frequently recorded in the Western Mediterranean causing economic losses and even human casualties. The Western Mediterranean is a deep and almost closed sea surrounded by high mountain ranges and with little exchange of water with the Atlantic ocean. A main factor in the development of torrential rains is ocean-atmosphere exchanges of heat and moisture that can potentially destabilize air masses travelling over the sea. The study of air mass trajectories previous to the rain event permits the identification of sea areas that could probably contribute to the development or intensification of rainfall. From a previous Mediterranean sea surface temperature clim…
Narrow-band to broad-band conversion for Meteosat-visiible channel and broad-band albedo using both AVHRR-1 and -2 channels
Abstract Satellite-derived broad-band albedo offers a useful tool for monitoring surface conditions. Given the limited wavelength window of most satellite radiometers, satellite albedo studies need to define narrow-band to a broad-band transformations. Signals from the AVHRR channels on board the NOAA-11 satellite, the Meteosat visible channel and a rectangular spectral band from 0-3 to 2.5 μm were simulated for a set of 20 representative land surfaces. The radiative transfer code described in Tanre et al. (1990) was used to obtain top of the atmosphere radiances. The derived signals were then correlated to predict broadband albedo and the Meteosal response via the two AVHRR signals. The re…
Conversion of nadir, narrowband reflectance in red and near-infrared channels to hemispherical surface albedo
Abstract Measured nadir-viewed narrow-band reflectanees in red and near infrared channels simulating AVHRR Channels 1 and 2 are compared with measured integrated solar spectrum hemispherical albedos. Reflectanees and albedos were measured from an aircraft over four widely different vegetation surfaces in southeastern Tasmania (Australia). A linear function is used to simultaneously correct for narrow band to broad band conversion errors and to convert nadir viewed reflectances to hemispherical albedos. While the application of the conversion equation presented is limited to the vegetation types of the study, the equation is independent of vegetation type. Results indicate that the reflectan…
Spatio-temporal variability of fog-water collection in the eastern Iberian Peninsula: 2003-2012
Abstract Among the different inputs involved in the hydrological system, fog water measured by man-made passive devices is one of the most unknown components, although it could be an additional water resource for specific environmental applications (forest restoration, forest firefighting, etc.). Focusing on the Mediterranean Iberian Peninsula, the aim of this work is to quantify fog-water collected by a 24-fog-stations network spread across three latitudinal sectors with different locations (coastal, pre-littoral and inland), and to determine the most productive sites. Measurements from the network show that distance-to-sea, latitude or elevation differences between stations are factors af…
Evaluation of the S-NPP VIIRS land surface temperature product using ground data acquired by an autonomous system at a rice paddy
Abstract The S-NPP VIIRS Land Surface Temperature (LST) product attained the stage V1 of validation maturity (provisional validated) at the end of 2014. This paper evaluates the current VIIRS V1 LST product versus concurrent ground data acquired at a rice paddy site from December 2014 to August 2016. The experimental site has three different seasonal and homogeneous land covers through the year, which makes the site interesting for validation activities. An autonomous and multiangular system was used to record continuous ground data at the site. The data acquired at zenith angles similar to the VIIRS viewing angles were used for the validation to avoid possible differences between satellite…
Chemical characterization in coastal fog and rain at Mount Monduver fog-collection station, Mediterranean Iberian Peninsula
Abstract An experimental site was selected for fog- and rain-water quality analyses. The selected location corresponds to Mount Monduver of 843 m elevation, being geographically centered in the Mediterranean Iberian Peninsula. Single fog- and rain-water samples were taken manually with a dedicated fog and rain collectors, to prevent any contamination with dry-deposition. Besides, a permanently exposed fog collector and a rain gauge were also used for the collection of water samples affected by dry deposition. Results indicated that all chemical analyses complied with Spanish drinking water regulations, except for the particular case of the dry-deposition contaminated water samples. A furthe…
Prospective use of collected fog water in the restoration of degraded burned areas under dry Mediterranean conditions
Abstract A mountainous plot located in the interior of the Valencia region (east coast of the Iberian Peninsula) was identified for reforestation using the fog-water collection potential prevailing in the area. Fog data were obtained by means of an instrument ensemble consisting of a passive cylindrical fog-water collector, a rain gauge, a wind direction and velocity sensor and a temperature and humidity probe. Preliminary results gave rise to the additional deployment of a low-cost 18-m 2 flat-panel collector connected to three 1000-l tanks for larger scale fog-water collection and storage. The 2007 annual rate of fog water that could be derived from the instrument ensemble amounted to 3.3…
Accuracy assessment of land surface temperature retrievals from MSG2-SEVIRI data
The accuracy of the Land Surface Temperature (LST) product generated operationally by the EUMETSAT Land Surface Analysis Satellite Applications Facility (LSA SAF) from the data registered by the Spinning Enhanced Visible and Infrared Imager (SEVIRI) on board the geostationary METEOSAT Second Generation 2 (MSG2, Meteosat 9) satellite was assessed on two test sites in Eastern Spain: a homogeneous, fully vegetated rice field and a high-plain, homogeneous area of shrubland. The LSA SAF LSTs were compared with ground LST measurements in the conventional temperature-based (T-based) method. We also validated the LSA SAF LST product by using an alternative radiance-based (R-based) method, with grou…
Climatology of the stability and humidity terms in the Haines Index to improve the estimate of forest fire risk in the Western Mediterranean Basin (Valencia region, Spain)
The stability and moisture content of the different atmospheric levels are commonly used to assess the risk index in the propagation and evolution of a hypothetical forest fire. The Haines Index (HI) combines these terms to determine the environmental potential for wildfire growth. In this paper the environmental stability and humidity associated with the lower atmospheric layers in the Western Mediterranean Basin are investigated by analysing HI calculations over a 29-year period. The HI climatology can be applied to the study of plume-dominated forest fires. These fires tend to present very erratic propagation behaviour and create highly dangerous situations for fire brigades. Thus the kn…