Search results for "Covariance"
showing 10 items of 284 documents
An Analysis of Regional and Intra-annual Precipitation Variability over Iran using Multivariate Statistical Methods
1998
The temporal and spatial precipitation regime of Iran was analysed using multivariate analyses of monthly mean precipitation records for 71 stations. A Principal Component Analysis was applied to the correlation matrix in order to describe the intra-annual variations of precipitation. The Principal Component scores were mapped to visualize the spatial structure of the three derived precipitation regimes. By applying an agglomerative clustering (WARD) of the three Principal Component scores, five homogeneous spatial clusters, representing five precipitation regions, were developed. The intra-annual types of precipitation distribution, shown by the five clusters, are described and discussed.
Alternative Diagonality Criteria for SOBI
2015
Blind source separation (BSS) is a multivariate data analysis method, whose roots are in the signal processing community. BSS is applied in diverse fields, including, for example, brain imaging and economic time series analysis. In the BSS model there are interesting latent uncorrelated variables, and the aim is to estimate the latent variables from multiple linear combinations of them. In this article we assume that these variables are weakly stationary time series, and we consider estimation methods which are based on approximate joint diagonalization of autocovariance matrices. In the popular SOBI estimator, a set of matrices is most diagonal when the sum of squares of their diagonal ele…
The role of the $\Delta(1232)$-resonance in covariant baryon chiral perturbation theory
2013
We stress, on theoretical and phenomenological grounds, the importance of the $\Delta(1232)$-resonance in a chiral effective field theory approach applied to the study of $\pi N$ scattering. We show how its inclusion as a dynamical degree of freedom allow us to obtain reliably valuable information from $\pi N$ scattering data.
Cropland and grassland management
2014
According to the latest National Inventory, the Italian agricultural sector is a source of GHGs with 34.5 Mt of CO2 eq in 2009, corresponding to 7 % of the total emissions (excluding LULUCF). In particular, more than half (19.1 Mt of CO2 eq) are N2O emissions from soils. Although the national methodology is in accordance with Tier 1 and 2 approaches proposed by the IPCC (2006), still empirical emission factors are used to assess the emission from fertilizer (e.g. 0.0125 kg N2O–N kg−1 N from synthetic fertilizers). Disaggregated data at sub-national level, including models and inventory measurement systems required by higher order methods (i.e. Tier 3), are not available in Italy so far and …
The role of vineyards in the carbon balance throughout Italy
2015
A common belief is that agricultural fields cannot be net carbon sinks, but perennial tree crops, growing a permanent woody structure with a life cycle of decades could act as carbon sink. Vineyards are good candidates to test this hypothesis, because they are often grown with limited soil cultivation and produce plenty of woody pruning material that can be left on the ground. Three Eddy Covariance sites were established in different vineyards, along a north-south transect, in Italy, to study the role of vine cultivation in the carbon balance of the Italian penisula. The year 2009 was chosen as a reference year for the three sites, in order to compare carbon budget estimates in areas charac…
Retrieval and assessment of CO2 uptake by mediterranean ecosystems using remote sensing and
2014
Photosynthesis is a process by which carbon and energy enter ecosystems. The knowledge of where,when, and how carbon dioxide (CO2) is exchanged between terrestrial ecosystems and atmosphere is crucial to close the Earth's carbon budget and predict feedbacks in a likely warming climate. Gross photosynthesis (uptake of CO2) by vegetation is responsible for the gross primary production (GPP) of the ecosystem. Normally GPP refers to the sum of the photosynthesis by all leaves measured at the ecosystem scale. John Monteith proposed in 1972 a simple approach that has become the paradigm for understanding GPP. It considers GPP as proportional to the incident short wave radiation (PAR), the fractio…
Stronger proprioceptive BOLD-responses in the somatosensory cortices reflect worse sensorimotor function in adolescents with and without cerebral pal…
2020
Graphical abstract
Diurnal and Seasonal Solar Induced Chlorophyll Fluorescence and Photosynthesis in a Boreal Scots Pine Canopy
2019
Solar induced chlorophyll fluorescence has been shown to be increasingly an useful proxy for the estimation of gross primary productivity (GPP), at a range of spatial scales. Here, we explore the seasonality in a continuous time series of canopy solar induced fluorescence (hereafter SiF) and its relation to canopy gross primary production (GPP), canopy light use efficiency (LUE), and direct estimates of leaf level photochemical efficiency in an evergreen canopy. SiF was calculated using infilling in two bands from the incoming and reflected radiance using a pair of Ocean Optics USB2000+ spectrometers operated in a dual field of view mode, sampling at a 30 min time step using custom written …
On the Use of the Eddy Covariance Latent Heat Flux and Sap Flow Transpiration for the Validation of a Surface Energy Balance Model
2018
Actual evapotranspiration is assessed via surface energy balance at an hourly rate. However, a robust estimation of daily evapotranspiration from hourly values is required. Outcomes of surface energy balance are frequently determined via measures of eddy covariance latent heat flux. Surface energy balance can be applied on images acquired at different times and spatial resolutions. In addition, hourly actual evapotranspiration needs to be integrated at a daily rate for operational uses. Questions arise whether the validation of surface energy balance models can benefit from complementary in situ measures of latent heat flux and sap flow transpiration. Here, validation was driven by image ac…
Micrometeorological and sap flow measurement of water vapour exchanges in olive: Scaling up from canopy to orchard
2009
A comparison of water consumption evaluated at tree and orchard level was carried out in a commercial olive orchard located in Sicily using up-scaled sap-flow evapotranspiration estimations and eddy covariance measurements. Sap flow probes were installed on olive trees placed in one of the four plots characterizing a heterogeneous orchard. Trees were chosen, from a preliminary footprint analysis, in correspondence to the peak of the “relative normalized contribution” to flux for the prevailing wind conditions measured by an eddy covariance station localized in the central part of the orchard. Tree-age and planting density as well as main tree and orchard characteristics (Leaf Area per tree,…