Search

The article presents a comparison of the trends of precipitation over Iberian Peninsula and North Atlantic Oscillation (NAO) under climate change conditions utilizing the Coupled Model Intercomparison Project phase 3. The evaluation is performed in two multi-models such as the climate in the 20th century and the 21st century. Result shows that the simulation in the 20th century underestimate the trend both in the NAO and precipitation and in the 21st century indicates a change in NAO.

The main questions motivating this study are: Can climate simulations describe the observations? To what extent can we use climate models to predict climate change? For this purpose, an analysis was made of the correspondences and/or discrepancies between observed winter precipitation data and the data from the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis project, and from two global climatic models: ECHAM4/OPYC3 and HadCM3. The data used correspond to the accumulated winter precipitation for the period 1949–2000, and comparisons of the mean and variability patterns were made. The methods used were principal components analysis, to break down variability and reduce the dimensions of the fields, and correlation and cross-spectrum analyses for comparison of the time series. For all these, we studied the suitability of their average distributions, as well as their modes of spatial and spectral variability. The results for the Iberian Peninsula show good agreement between the precipitation data of the NCEP–NCAR reanalysis and the observations, both in the average analysis and in the main modes of spatial and time variability. Therefore, the reanalysis data were proved to be a good resource for interpreting climate variations. As regards the climatic models considered, in general the results point to their suitability for describing the spatial distribution of winter precipitation, whereas the spectral association is less appropriate. The variability of the precipitation data was related to circulation patterns and teleconnection indices, such as the North Atlantic oscillation and the Arctic oscillation. The results allow us to conclude that the discrepancies between the two models and observations must be due to a weak representation of the interannual variability. Copyright © 2004 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Observational series of winter precipitation in the eastern part of the Cantabrian coast in the northern Iberian Peninsula are studied. This rather small area shows a clearly different interannual variability to the rest of the Peninsula. Series of winter precipitation for the whole area are defined using principal component (PC) analysis and they reflect the variability that can be attributed to changes in atmospheric circulation around the area. This variability is physically explained on the basis of the structure of baroclinic activity and vertically integrated moisture transports over the area derived from the NCEP/NCAR Reanalysis project. According to them, the leading PC of winter precipitation represents the overall precipitation over the area. Wet phases of this PC are associated to an increase of baroclinic activity leaving the eastern part of the Atlantic storm track and entering the Mediterranean basin. Conversely, dry phases show a strong reduction of baroclinic activity over the region. The second PC is linked to meridional water vapour transports over the area, which are affected by the topography of the region. Copyright © 2001 Royal Meteorological Society [ABSTRACT FROM AUTHOR]