Search results for "Principal Component Analysis"

Retrieval of atmospheric CH4profiles from Fourier transform infrared data using dimension reduction and MCMC

2016

We introduce an inversion method that uses dimension reduction for the retrieval of atmospheric methane (CH4) profiles. Uncertainty analysis is performed using the Markov chain Monte Carlo (MCMC) statistical estimation. These techniques are used to retrieve CH4 profiles from the ground-based spectral measurements by the Fourier Transform Spectrometer (FTS) instrument at Sodankyla (67.4 degrees N, 26.6 degrees E), Northern Finland. The Sodankyla FTS is part of the Total Carbon Column Observing Network (TCCON), a global network that observes solar spectra in near-infrared wavelengths. The high spectral resolution of the data provides approximately 3 degrees of freedom about the vertical struc…

Landslide susceptibility mapping using precipitation data, Mazandaran Province, north of Iran

2017

Precipitation is a nonlinear and complex phenomenon and varies in time and space. It is also evident that there is a link between precipitation and shallow landslides, and precipitation is always considered as a landslide-triggering factor. This study aims to investigate the relationship between the characteristics of precipitation and the historical shallow landslides in Mazandaran Province, north of Iran. For this purpose, the spatial variability of rainfall was analyzed using monthly rainfall data collected at 15 synoptic stations distributed over the region between 1981 and 2014. Monthly precipitation and other derived parameters were used, and a hybrid model combining principal compone…

2016

Abstract. Scanning spectrometer networks using scattered solar radiation in the ultraviolet spectral region have become an increasingly important tool for monitoring volcanic sulfur dioxide (SO2) emissions. Often measured spectra are evaluated using the differential optical absorption spectroscopy (DOAS) technique. In order to obtain absolute column densities (CDs), the DOAS evaluation requires a Fraunhofer reference spectrum (FRS) that is free of absorption structures of the trace gas of interest. For measurements at volcanoes such a FRS can be readily obtained if the scan (i.e. series of measurements at different elevation angles) includes viewing directions where the plume is not seen. I…

Regional frequency analysis of extreme rainfall in Sicily (Italy)

2018

Heavy daily precipitation distribution in east-central Franceand west European meteorological patterns

2000

Principal Component Analysis is used to link the spatial distribution of Heavy Daily Precipitation (HDP) in East-Central France with meteorological patterns of the Meteo-France automatic classification, which takes into account 15 different meteorological parameters (e.g. geopotential heights at different levels, humidities, pseudo-adiabatic temperatures) over Western Europe. Every parameter is classified in 10 classes, or synoptic patterns. The annual PCA shows 3 dominant modes of HDP distribution, explaining more than 90% of the total variance. Associated atmospheric situations are obtained by using the scores of the 150 classes (10 per meteorological parameter). Other PCAs (i.e., half-an…

Detection of homogeneous precipitation regions at seasonal and annual time scales, northwest Iran

2017

Abstract Detection of homogeneous climate areas is a challenging issue, which can be affected by different criteria. One of the most prominent factors is choosing the time scale, which can lead to different spatial and temporal patterns. Total precipitation is a key factor in climatological studies, and studying its distribution is of utmost importance. The combination of principal components analysis and cluster analysis is used for homogeneous precipitation areas' detection. Hence, the spatial pattern of total precipitation was investigated in northwestern Iran during the past two decades (1991–2010) on seasonal and annual time scales. The results of clustering on each time scale were val…

Temporal variability of airborne bacterial community structure in an urban area

2006

International audience; Temporal airborne bacterial genetic community structure and meteorological factors were analysed above an urban area in the northwest of France from December 2003 to April 2004 with a sampling strategy considering different time intervals (from an hour to a month). Principal component analysis (PCA) of B-ARISA (Bacterial-Automated Ribosomal Intergenic Spacer Analysis) profiles revealed a hierarchy in the temporal variability of bacterial community: daily<weekly<seasonal. Co-inertia analysis between B-ARISA data and meteorological factors demonstrated the correlation between the seasonal variability in the bacterial community and climatic conditions such as temperatur…

REGEOTOP: New climatic data fields for East Asia based on localized relief information and geostatistical methods

2004

Climate data fields represent essential tools for climate, biogeographical and agricultural research to run models and to provide observational data for the verification of global climate models (GCM). Climate data fields are generated through interpolation of observations taken at meteorological stations. Most current interpolation procedures try to describe the influence of topography on spatial climatic variations by relating them directly to absolute elevation or by introducing simple relief variables such as exposure. In both cases this may not properly describe spatial climatic variations, particularly not those of precipitation. This paper describes a regionalization procedure (REGEO…

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.

Trends of mean temperatures and warm extremes in northern tropical Africa (1961-2014) from observed and PPCA-reconstructed time series

2016

Trends in daily maximum (TX) and minimum (TN) temperatures and indices of warm extremes are studied in tropical North Africa, west of the eastern African highlands, from 1961 to 2014. The analysis is based on the concatenation and cross-checking of two observed databases. Due to the large number of missing entries (~25%), a statistical infilling using probabilistic principal component analysis was applied. Averaged over 90 stations, the linear trends of annual mean TX and TN equal respectively +0.021 °C/yr and +0.028 °C/yr. The frequency of very hot days (TX > 35°C) and tropical nights (TN > 20°C), as well as the frequency of daily TX and TN above the 90th percentile (p90) (“warm days” and …