Search results for "Trend surface analysis"
showing 5 items of 5 documents
Northern Hemisphere extratropical cyclones: A comparison of detection and tracking methods and different reanalyses
2008
Abstract The applicability of three different cyclone detection and tracking schemes is investigated with reanalysis datasets. First, cyclone climatologies and cyclone characteristics of the 40-yr ECMWF Re-Analysis (ERA-40) are compared with the NCEP–NCAR dataset using one method. ERA-40 shows systematically more cyclones, and therefore a higher cyclone center density, than the NCEP–NCAR reanalysis dataset. Geostrophically adjusted geopotential height gradients around cyclone centers, a measure of cyclone intensity, are enhanced in ERA-40 compared with the NCEP–NCAR reanalysis dataset. The variability of the number of cyclones per season is significantly correlated between the two reanalysi…
Property loss potentials for European midlatitude storms in a changing climate
2007
[1] Winter storms of the midlatitudes are an important factor for property losses caused by natural hazards over Europe. The storm series in early 1990 and late 1999 led to enormous economic damages and insured claims. Although significant trends in North Atlantic/European storm activity have not been identified for the last few decades, recent studies provide evidence that under anthropogenic climate change the number of extreme storms could increase, whereas the total number of cyclones may be slightly reduced. In this study, loss potentials derived from an ensemble of climate models using a simple storm damage model under climate change conditions are shown. For the United Kingdom and Ge…
Global land surface phenology trends from GIMMS database
2009
A double logistic function has been used to describe global inventory mapping and monitoring studies (GIMMS) normalized difference vegetation index (NDVI) yearly evolution for the 1981 to 2003 period, in order to estimate land surface phenology parameter. A principal component analysis on the resulting time series indicates that the first components explain 36, 53 and 37% of the variance for the start, end and length of growing season, respectively, and shows generally good spatial homogeneity. Mann-Kendall trend tests have been carried out, and trends were estimated by linear regression. Maps of these trends show a global advance in spring dates of 0.38 days per year, a global delay in aut…
Strong influence of lowermost stratospheric ozone on lower tropospheric background ozone changes over Europe
2007
[1] Using ozone measurements from two sounding sites and two high-altitude stations in Central Europe, we show evidence for a dominant influence of changes in lowermost stratospheric ozone on the variability and overall upward trend of background ozone in the lower troposphere (3000–3500 m asl) during the 1992–2004 period. Numerical simulations with a stratospheric chemistry transport model suggest that changes in lower stratospheric ozone were driven by dynamics rather than by changes in stratospheric chlorine loading. In addition, Lagrangian model simulations indicate that changes in downward transport of ozone from the stratosphere into the troposphere were dominated by changes in lowerm…
Recent changes in measured wind in the NE Atlantic and variability of correlation with NAO
2010
The paper deals with wind measurements, recorded since the 1950s, at twelve meteorological stations along a transect near the westernmost European border, between 64° and 44° N. Extreme wind speed tends to decrease sharply near the northern boundary (at Reykjavick), near the middle of the study area (at Shannon and Valentia) and near the southern boundary (at Brest and Cap Ferret), to increase at Thorshavn, with less significant trends at the other stations. Average wind speeds confirm the above tendencies, with an additional increasing speed at Lerwick, Kirkwall, Malin Head, Belle-Ile and Cap Ferret. To compare changes in wind activity, the data have been subdivided into three periods: unt…