Comparison of past and future Mediterranean high and low extremes of precipitation and river flow projected using different statistical downscaling methods

Abstract

Abstract. The extremes of precipitation and river flow obtained using three different statistical downscaling methods applied to the same regional climate simulation have been compared. The methods compared are the anomaly method, quantile mapping and a weather typing. The hydrological model used in the study is distributed and it is applied to the Mediterranean basins of France. The study shows that both quantile mapping and weather typing methods are able to reproduce the high and low precipitation extremes in the region of interest. The study also shows that when the hydrological model is forced with these downscaled data, there are important differences in the outputs. This shows that the model amplifies the differences and that the downscaling of other atmospheric variables might be very relevant when simulating river discharges. In terms of river flow, the method of the anomalies, which is very simple, performs better than expected. The methods produce qualitatively similar future scenarios of the extremes of river flow. However, quantitatively, there are still significant differences between them for each individual gauging station. According to these scenarios, it is expected that in the middle of the 21st century (2035-2064), the monthly low flows will have diminished almost everywhere in the region of our study by as much as 20 %. Regarding high flows, there will be important increases in the area of the Cévennes, which is already seriously affected by flash-floods. For some gauging stations in this area, the frequency of what was a 10-yr return flood at the end of the 20th century is expected to increase, with such return floods then occurring every two years in the middle Correspondence to: P. Quintana-Seguí (pquintana@obsebre.es) of the 21st century. Similarly, the 10-yr return floods at that time are expected to carry 100 % more water than the 10-yr return floods experienced at the end of the 20th century. In the northern part of the Rhône basin, these extremes will be reduced.

Functioning of the planktonic ecosystem on the Gulf of Lions shelf (NW Mediterranean) during spring and its impact on the carbon deposition: a field data and 3-D modelling combined approach

“…The zooplankton model is an adapted version of the stoichiometric model developed for heterotrophs by Anderson and Pondaven (2003) and applied in the Ligurian sea by Raick et al (2005Raick et al ( , 2006. The model developed by Raick et al (2005Raick et al ( , 2006 initially considered the cycles of carbon and nitrogen and the present work extended it to the cycles of phosphorus and silica.…”

“…During high river discharge, the effective carbon deposition would be delayed toward the south-western exit of the shelf, or even further in the open sea and the Catalan shelf, through strong horizontal advection of zooplankton communities through canyons on the slope (Kouwenberg, 1994;Qiu et al, 2010). Out of the shelf, these populations could collapse due to a lack of prey availability and then reach deep sediments under organic detritus form.…”

“…Thus, the structure of the model, and precisely the composition of PFT, has been chosen following a thorough analysis of the available experimental knowledge on the biogeochemical functioning of the NW Mediterranean Sea (e.g. Ferrier-Pagès and Rassoulzadegan, 1994;Vidussi et al, 2000;Diaz et al, 2001;Avril, 2002;Marty et al, 2002;Moutin et al, 2002;Thingstad and Rassoulzadegan, 1995;Gaudy et al, 2003;Gomez and Gorsky, 2003;Leblanc et al, 2003;Pujo-Pay and Conan, 2003;Charles et al, 2005), as well as previous modelling studies (Tusseau et al, 1997;Babin et al, 2003;Levy et al, 1998;Lacroix and Grégoire, 2002;Raick et al, 2005Raick et al, , 2006. Resulting from this analysis, the model compartments are described below.…”

“…Allen et al, 2007), the cost function score was also computed (CF, Fig. 7d) to assess the model data misfits compared with the standard deviation of the data: CF < 1 = very good, 1-2 = good, 2-3 = reasonable, >3 = poor; see Radach and Moll (2006).…”

Climate Projections of Future Extreme Events in Malaysia

“…The third type, weather typing technique is based on the concept of gathering a fixed number of discrete weather types or "states" according to their synoptic similarity. GCMs are then adopted to evaluate the change in the frequency of weather types in order to estimate climate change (Burton et al, 2010;Quintana-Segui et al, 2011).…”