Precipitation data from the period 1961–2010 and from a dense rain-gauge network over Croatia is analysed for spatial characteristics of trends in precipitation amounts and precipitation indices. ...Besides large spatial variability, the area is characterized by large temporal (seasonal) variability. Thus, analysis is performed on annual and seasonal scales over seven predefined subregions. Ten precipitation indices are selected to assess the intensity and frequency of extreme events as well as their contribution to annual and seasonal precipitation changes. The results reveal that the changes in annual and seasonal amounts are predominantly weak. A significant trend is detected only for annual amounts (negative) in the mountainous region and for summer (negative) in the mountainous littoral, mountainous region and central hinterland. A significant positive trend for autumn appears in eastern mainland. Negative trends in summer are associated with a decrease in frequency of moderate wet days, in maximal 1- and 5-day precipitation and in an increase in light precipitation. A negative annual trend is mainly caused by a decrease in frequency of very wet days and their contribution to the total precipitation. A positive autumn trend is associated with more very wet days and an increase of their contribution to the total precipitation as well as an increase in maximal 1- and 5-day precipitation. This study complements the existing analysis of five Croatian secular data series of extreme precipitation indices by involving the whole precipitation dataset since the mid-twentieth century and fills the gap present in the trend assessment of precipitation trends in Mediterranean and Europe.
The 2m temperature (T2m) and precipitation from five regional climate models (RCMs), which participated in the ENSEMBLES project and were integrated at a 25-km horizontal resolution, are compared ...with observed climatological data from 13 stations located in the Croatian coastal zone. The twentieth century climate was simulated by forcing RCMs with identical boundary conditions from the ERA-40 reanalysis and the ECHAM5/MPI-OM global climate model (GCM); climate change in the twenty-first century is based on the A1B scenario and assessed from the GCM-forced RCMs’ integrations. When forced by ERA-40, most RCMs exhibit cold bias in winter which contributes to an overestimation of the T2m annual cycle amplitude and the errors in interannual variability are in all RCMs smaller than those in the climatological mean. All models underestimate observed warming trends in the period 1951–2010. The largest precipitation biases coincide with locations/seasons with small observed amounts but large precipitation amounts near high orography are relatively well reproduced. When forced by the same GCM all RCMs exhibit a warming in the cold half-year and a cooling (or weak warming) in the warm period, implying a strong impact of GCM boundary forcing. The future eastern Adriatic climate is characterised by a warming, up to +5 °C towards the end of the twenty-first century; for precipitation, no clear signal is evident in the first half of the twenty-first century, but a reduction in precipitation during summer prevails in the second half. It is argued that land-sea contrast and complex coastal configuration of the Croatian coast, i.e. multitude of island and well indented coastline, have a major impact on small-scale variability. Orography plays important role only at small number of coastal locations. We hypothesise that the parameterisations related to land surface processes and soil hydrology have relatively stronger impact on variability than orography at those locations that include a relatively large fraction of land (most coastal stations), but affecting less strongly locations at the Adriatic islands.
The aim of this study was to identify the main mesoscale features and mechanisms responsible for the generation of an extreme precipitation event as a contribution to improving the modelling of ...processes that produce HPEs. The event occurred during the morning hours on 22 November 2010 over the Dubrovnik coast in Croatia and the hinterland mountain range of the southern Dinaric Alps and caused severe flash floods and landslides and consequent interruption of traffic and electricity supply as well as other infrastructural damage. The analysis is geographically focused on the southern portion of the eastern Adriatic region, which is prone to relatively frequent heavy precipitation events that occur mostly in autumn. This area is one of the rainiest in Europe with expected annual amounts of precipitation greater than 5,000 mm in the mountainous hinterland. The mechanisms responsible for the formation of convection were analysed using synop measurements, satellite data and numerical experiments performed with the WRF model, which was set up at the convection-permitting resolution in the innermost domain. Satellite data were used to identify the precipitation systems and to estimate the intensity of the precipitation during the period of interest. The development of the precipitation system was connected to a strong large-scale ascent over the southern Italy and southern Adriatic due to the advection of warm air and cyclonic vorticity advection, which increases with height. The numerical simulations highlighted the essential role of a southerly low-level jet stream in the transport of warm and moist air towards the affected area. The convergence of two branches of low-level marine air favoured convection triggered over the coast and sea. Furthermore, numerical sensitivity experiments suggested that the orography of the Dinaric Alps plays an essential role in the precipitation maximum over the mountainous hinterland, but also that the orography was not the crucial factor in the heavy precipitation near Dubrovnik. This study highlights the need for a dense network of observations, especially radar measurements, to validate the simulated mechanisms and improve numerical forecasts via data assimilation.
Five indices of extreme precipitation are analysed over the Croatian Adriatic region on a seasonal and annual basis from 19 meteorological stations and a 3-member ensemble of the Regional Climate ...Model (RegCM3) simulations in the reference (1961−1990) and the near-future (2011−2040) climate. Future climate integrations are performed under the IPCC A2 emission scenario. Uncertainty of projected changes is assessed by comparing RegCM3 results with those from a subset of the ENSEMBLES regional climate models. Observed wet extremes exhibit large values in the areas close to the coastal mountains. Interannual variability in the number of very wet days (R95) and the fraction of precipitation associated with very wet days (R95T) is relatively large in all seasons, indicating a variable synoptic activity over the Adriatic region from one year to the next, as well as variable intense showers in the summer. The most prominent feature is a statistically significant decrease in the observed maximum number of consecutive dry days (CDD) during the autumn. When compared against the observations, RegCM3 overestimates observed precipitation and maximum 5 d precipitation amounts (Rx5d) in all seasons except the summer with statistically significant differences. Simulated number of dry days (DD) is generally underestimated and, consequently, R95 is mostly overestimated. Of all indices considered, R95T is best simulated by the model. The interannual variability of precipitation and indices is generally well reproduced. The projected changes in the mean and indices of extreme precipitation in the near future are weak overall, except in the autumn, in both the RegCM3 ensemble and selected ENSEMBLES models. Although the Mediterranean region is characterised as one of the regions most responsive to climate change, our results indicate that over the eastern Adriatic region, significant changes may not occur in the near future.
Daily maximum and minimum temperatures from 29 low-lying and mountain stations of 7 countries in Central Europe were analyzed. The analysis of the annual variation of diurnal temperature range helps ...to distinguish unique climatic characteristics of high and low altitude stations. A comparison of the time series of extreme daily temperatures as well as mean temperature shows a good agreement between the low-lying stations and the mountain stations. Many of the pronounced warm and cold periods are present in all time series and are therefore representative for the whole region. A linear trend analysis of the station data for the period 1901-1990 (19 stations) and 1951-1990 (all 29 stations) shows spatial patterns of similar changes in maximum and minimum daily temperatures and diurnal temperature range. Mountain stations show only small changes of the diurnal temperature range over the 1901-1990 period, whereas the low-lying stations in the western part of the Alps show a significant decrease of diurnal temperature range, caused by strong increase of the minimum temperature. For the shorter period 1951-1990, the diurnal temperature range decreases at the western low-lying stations, mainly in spring, whereas it remains roughly constant at the mountain stations. The decrease of diurnal temperature range is stronger in the western part than in the eastern part of the Alps.
Five indices of extreme precipitation are analyzed over the Croatian Adriatic region on a seasonal and annual basis from 19 meteorological stations and a 3-member ensemble of the Regional Climate ...Model (RegCM3) simulations in the reference and the near-future climate. Observed wet extremes exhibit large values in the areas close to the coastal mountains. Inter-annual variability in the number of very wet days (R95) and the fraction of precipitation associated with very wet days (R9ST) is relatively large in all seasons, indicating a variable synoptic activity over the Adriatic region from one year to the next, as well as variable intense showers in the summer. The projected changes in the mean and indices of extreme precipitation in the near future are weak overall, except in the autumn, in both the RegCM3 ensemble and selected ENSEMBLES models. Although the Mediterranean region is characterized as one of the regions most responsive to climate change, our results indicate that over the eastern Adriatic region, significant changes may not occur in the near future.
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