Search results for "term"
showing 10 items of 6745 documents
Long-term changes of the ice regime of rivers in Latvia
2016
The ice regime of rivers is considered a sensitive indicator of climate change. This paper summarises the results of research on the long-term changes in the ice regime parameters under changing climate conditions and their regional peculiarities in Latvia from 1945 to 2012. The ice cover duration on Latvian rivers has decreased during recent decades. The research results demonstrated that there is a positive trend as regards the formation of the ice cover and in 31.8% of the cases the trend is statistically significant at p < 0.05. As regards the breaking up of ice, there is a statistically significant negative trend in 93.2% of the cases at p < 0.05. This indicates an earlie…
Assessment of the Potential Evapotranspiration MODIS Product Using Ground Measurements in the Pampas
2018
Evapotranspiration is the hydrological variable of greatest relevance in the Argentina Pampas Region (APR). The estimation of potential evapotranspiration (PET) in this area becomes essential since primary productivity is directly linked to water availability. In order to evaluate the MOD16_A2 product of evapotranspiration (ET), a comparison with in situ measurements was conducted. We used ET data provided by the Oficina de Riesgo Agropecuario, corresponding to 24 stations placed in the region covering all seasons for the years 2012 to 2014. Results show an overestimation of 86% and 52% in Autumn-Winter and Spring-Summer, respectively. Mean Absolut Error (MAE) range between ±0.9 and ±2.1 mm…
Comparison and Evaluation of the TES and ANEM Algorithms for Land Surface Temperature and Emissivity Separation over the Area of Valencia, Spain
2017
Land Surface temperature (LST) is a key magnitude for numerous studies, especially for climatology and assessment of energy fluxes between surface and atmosphere. Retrieval of accurate LST requires a good characterization of surface emissivity. Both quantities are coupled in a single radiance measurement; for this reason, for N spectral bands available in a remote sensor, there will always be N + 1 unknowns. To solve the indeterminacy, temperature-emissivity separation methods have been proposed, among which the Temperature Emissivity Separation (TES) algorithm is one of the most widely used. The Adjusted Normalized Emissivity Method (ANEM) was proposed as a modification of the Normalized E…
Towards a long-term dataset of ELBARA-II measurements assisting SMOS level-3 land product and algorithm validation at the Valencia Anchor Station
2015
[EN] The Soil Moisture and Ocean Salinity (SMOS) mission was launched on 2nd November 2009 with the objective of providing global estimations of soil moisture and sea salinity. The main activity of the Valencia Anchor Station (VAS) is currently to assist in a long-term validation of SMOS land products. This study focus on a level 3 SMOS data validation with in situ measurements carried out in the period 2010-2012 over the VAS. ELBARA-II radiometer is placed in the VAS area, observing a vineyard field considered as representative of a major proportion of an area of 50×50 km, enough to cover a SMOS footprint. Brightness temperatures (TB) acquired by ELBARA-II have been compared to those obser…
NPP VIIRS land surface temperature product validation using worldwide observation networks.
2013
International audience; Thermal infrared satellite observations of the Earth's surface are key components in estimating the surface skin temperature over global land areas. This work presents validation methodologies to estimate the quantitative uncertainty in Land Surface Temperature (LST) product derived from the Visible Infrared Imager Radiometer Suite (VIIRS) onboard Suomi National Polar-orbiting Partnership (NPP) using ground-based measurements currently made operationally at many field and weather stations around the world. Over heterogeneous surfaces in terms of surface types or biophysical properties (e.g., vegetation density, emissivity), the validation protocol accounts for land s…
Landsat and Local Land Surface Temperatures in a Heterogeneous Terrain Compared to MODIS Values
2016
Land Surface Temperature (LST) as provided by remote sensing onboard satellites is a key parameter for a number of applications in Earth System studies, such as numerical modelling or regional estimation of surface energy and water fluxes. In the case of Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Terra or Aqua, pixels have resolutions near 1 km 2 , LST values being an average of the real subpixel variability of LST, which can be significant for heterogeneous terrain. Here, we use Landsat 7 LST decametre-scale fields to evaluate the temporal and spatial variability at the kilometre scale and compare the resulting average values to those provided by MODIS for the same obser…
Modified climate with long term memory in tree ring proxies
2015
ABSTRACT : A contribution to the PAGES Asia2k Working Group. ABSTRACT: Long term memory (LTM) scaling behavior in worldwide tree ring proxies and subsequent climate reconstructions is analyzed for and compared with the memory structure inherent to instrumental temperature and precipitation data. Detrended fluctuation analysis is employed to detect LTM and its scaling exponent a is used to evaluate LTM. The results show that temperature and precipitation reconstructions based on ring width measurements (mean \alpha =0.8) contain more memory than records based on maximum latewood density (mean \alpha =0.7). Both exceed the memory inherent to regional instrumental data (\alpha =0.6 for tempera…
Raindrop size distribution and terminal velocity for rainfall erosivity studies. A review
2019
Abstract The knowledge of the rainfall drop size distribution (DSD) at the land surface is essential for understanding precipitation mechanisms affecting soil erosion processes. Rainfall erosivity is defined as the potential of rain to cause erosion and it can be evaluated by rainfall kinetic power, which is determined by DSD and raindrop terminal velocity. This paper firstly deals with the raindrop terminal velocity estimate. Then the most widely used DSD are reviewed highlighting the difference between the raindrop size distribution per unit volume of air and that per unit area and time. The reliability of the available kinetic power-rainfall intensity relationships and their application …
Nitrogen broadening of SF6 transitions in the nu3 band
2001
Abstract Nitrogen induced pressure-broadened halfwidths of a number of ν3 transitions of SF6 are calculated using the complex Robert–Bonamy (CRB) formalism. The calculations are made at 200, 250, 296 and 350 K and the temperature dependence of the halfwidths are determined. The intermolecular potential is taken as a sum of the leading electrostatic and Lennard-Jones [6] , [7] , [8] , [9] , [10] , [11] , [12] atom–atom components. The dynamics of the collision process are correct to second order in time. The calculated halfwidths are used to simulate the ν3 spectrum, which is compared to a simulation made using the HITRAN96 halfwidths and measurements made at the Universite Pierre et Marie C…
Predicted temperature-increase-induced global health burden and its regional variability
2019
An increase in the global health burden of temperature was projected for 459 locations in 28 countries worldwide under four representative concentration pathway scenarios until 2099. We determined that the amount of temperature increase for each 100 ppm increase in global CO2 concentrations is nearly constant, regardless of climate scenarios. The overall average temperature increase during 2010–2099 is largest in Canada (1.16 °C/100 ppm) and Finland (1.14 °C/100 ppm), while it is smallest in Ireland (0.62 °C/100 ppm) and Argentina (0.63 °C/100 ppm). In addition, for each 1 °C temperature increase, the amount of excess mortality is increased largely in tropical countries such as Vietnam (10.…