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Spain is one of the leading tourist destinations worldwide, but also a climate change hot-spot. Weather conditions throughout the year have enabled the implementation of alternative outdoor leisure activities to beach-based tourism, helping to alleviate the strong seasonality. Climate is currently a positive resource but it could become a limiting factor for these activities in the future. Here, we assess the present and future conditions by adopting the second generation climate index for tourism (CIT) to quantify the climate potentials for cultural, golf, sailing, hiking, cycling and football activities. Present and future potentials are derived using observed and projected daily meteorological data from the ERA-5 reanalysis and the DMI-HIRHAM5 regional climate model (RCM) included in EURO-CORDEX project, respectively. A quantile–quantile adjustment is applied to the projected CIT data to correct biases at the local scale. Present climate potentials confirm the optimal conditions of the Spanish Mediterranean coast for practicing all the activities in spring and autumn, while in summer, ideal conditions only prevail for sailing. Projections show a general future increase of excellent climate potentials in winter and a general improvement of the weather assets in the northern half of the country during the shoulder seasons, except for cycling and football. [ABSTRACT FROM AUTHOR]

In order to improve the quality of the Mediterranean high-impact weather (HIW) numerical predictions, this study proposes to modify the potential vorticity (PV) field of the model initial state, taking advantage of information provided by the water vapour (WV) channel of the METEOSAT-7 satellite. The implemented PV field modifications aim to reduce the mismatch between the upper-level PV features and the WV brightness temperatures guided by the known relation between these two fields (PV-WV technique). The PV-WV technique effectiveness is evaluated on two HIW events, and is also compared with two additional PV modification techniques from an earlier study. The chosen episodes occurred on 9-10 June 2000 and 9-10 October 2002 and produced heavy precipitation over both Spain and France. The main difference between these two episodes is found in the driving mechanism, a mesoscale cyclone for the June 2000 event and a larger low-pressure centre for the October 2002 case. The two additional PV modification techniques introduce perturbations along the zones highlighted by the MM5 adjoint model calculated sensitivity zones (PV-adjoint) and along the three-dimensional PV structure presenting the locally most intense values and gradients of the field (PV-gradient). A close examination of both case studies of the forecast rainfall fields and several objective verification indices show that the PV-WV technique performance exceeds the control (or non-perturbed) forecast skill while remaining inside the distribution obtained by both PV-gradient and PV-adjoint techniques. This PV-WV technique could be used to increase the ensemble spread introducing higher amplitude modifications. Thus, a more skilled ensemble prediction system could be built by taking advantage of the subjectivity inherent to this method (manual perturbations) and also of the uncertainty present in the initial state. [ABSTRACT FROM AUTHOR]

Abstract: A climatology of various parameters associated with severe convective storms has been constructed for Europe. This involves using the reanalysis data base from ERA-40 for the period 1971–2000 and calculating monthly means, variability range and extremes occurrence of fields such as convective available potential energy, convective inhibition energy, mid-tropospheric lapse rate, low-tropospheric moisture content and storm relative helicity for different layers. This process is a first step towards development of a synthetic climatology of European severe weather, and is publicly available at the web site http://ecss.uib.es. Preliminary results derived from these products were presented during the ECSS 2004 conference. This paper is devoted to a more detailed presentation and discussion of the main results. It is hypothesized that preferred areas for severe thunderstorms occurrence in Europe would extend along a zonal belt over the south-central regions, where high helicity associated with the extratropical storm tracks and thermodynamically-favourable profiles established over the southern Atlantic and Mediterranean Sea would most likely be concatenated. Further, this effort has been complemented with a collection of existing reports of significant (at least F2) tornadoes in Europe during the period 1971–2003. We present this data set in this paper and it also can be found at the website http://ecss.uib.es. Thus, the tornado collection can be used to test the appropriateness of the parameters selected for the synthetic climatology. In particular, it is found that the convective available potential energy, low-tropospheric moisture content and environmental shear, when related to the monthly climatology, are reasonably good descriptors of the tornadic environments. [Copyright &y& Elsevier]

A mesoscale numerical model with parameterized moist convection is applied to three cases involving heavy rainfall in the western Mediterranean region. Forecast precipitation fields, although not perfect when compared to the observations of rainfall, appear to have sufficient information to be considered useful forecasting guidance. The results illustrate that a good simulation for this type of event in a region with complex topography is strongly dependent on a good initialization and prediction of the low-level flow and water vapor distribution. For two of the cases that have a marked synoptic-scale contribution, the simulations give reasonably accurate predictions of the precipitation distribution, although the amounts are generally underestimated. The third case exhibits relatively subtle synoptic-scale forcing and is dominated by isolated convective storms (mostly over the sea) that also produced severe thunderstorms (including tornadoes), and the prediction of precipitation is not as promising. Overall, the results are encouraging in terms of potential application of mesoscale models operationally in the western Mediterranean region. Additional experiments beyond the 'control' simulations have been performed to isolate the influence of orography and water vapor flux from the Mediterranean Sea on the model simulations. This factor separation indicates that both effects can be important contributors to a successful forecast. Suggestions are offered for future efforts in pursuing the application of mesoscale models to this forecast problem. [ABSTRACT FROM AUTHOR]

Most of the nature‐related economic costs and human losses in many regions of Europe are due to extreme weather events such as heat waves, cold spells, persistent droughts, heavy precipitation and intense cyclonic wind‐storms. Extreme precipitation events are projected by climatic models to become more intense over the continent while droughts might last longer by the end of the century. In dry regions as Southern Europe, soils are predicted to dry out as temperatures and evapotranspiration rise and rain‐bearing atmospheric circulations become less frequent. Prospects on the future of climate indices linked to extreme phenomena are herein derived by using observed and model projected daily meteorological data. Specifically, E‐OBS high resolution gridded datasets of observed precipitation and surface minimum and maximum temperatures have been used as the regional observed baseline. For projections, the same meteorological variables have been obtained from a set of regional climate models integrated in the European EURO‐CORDEX project, considering the RCP8.5 future emissions scenario. A quantile–quantile adjustment has been applied to the simulated regional scenarios to reduce biases in modelled extreme regimes. Results suggest that warm days will substantially increase across Europe, consistently with a decrease of cold nights. An increase in heat wave amplitude is expected across the continent, with South Eastern Europe and the Mediterranean as the most affected regions. In contrast, Northern Europe will undergo the largest decrease in cold spell magnitude. An overall rise in the frequency and volume of heavy precipitations is projected in all seasons, even if the number of dry days is also expected to increase, except in the Baltic countries. Regarding abnormally long dry periods (extreme droughts), we find that the occurrence of episodes would reduce over Europe as consequence of projected increases in length. [ABSTRACT FROM AUTHOR]

Predictability of high-impact weather constitutes a major challenge. In this study, we contribute to this relevant topic by analyzing the characteristics of multiple ensemble prediction systems aimed at sampling initial and/or model uncertainties for three exemplary heavy precipitation systems that occurred over the western Mediterranean. In particular, initial condition perturbations are generated by (i) directly downscaling the ensemble members from a global ensemble and (ii) creating perturbations by sampling a wide range of scales using an adaptation of the breeding methodology. Model error is sampled by applying stochastic perturbations to physical parameterizations and to microphysics parameters. A positive impact in terms of ensemble diversity is obtained when initial condition perturbations across a broad range of scales are applied, especially at low levels and for cases in which local factors are more relevant. Regarding stochastic model perturbations, they display very localized perturbations with low amplitude, which are insufficient to capture extreme scenarios, except when local factors play a dominant role. However, when combined with initial condition perturbations, they generally increase diversity and perturbation amplitude over areas characterized by deep moist convection. This outcome exhibits the positive impact of sampling both uncertainty sources, even in the extremely nonlinear regime that defines convective-scale phenomena. • Initial condition perturbations sampling multiple scales increase the ensemble diversity and skill obtained with downscaling. • Stochastic perturbations are insufficient to produce skillful forecasts, except when scattered convection is dominant. • The combination of multiple perturbations is effective to improve ensemble performance at the nonlinear convective-scale. • Ensemble sizes larger than 50 members are required to capture extreme scenarios appropriately. [ABSTRACT FROM AUTHOR]

Despite the relatively successful long-lead-time forecasts of the storms during the 3 May 1999 tornadic outbreak in Oklahoma and Kansas, forecasters were unable to predict with confidence details concerning convective initiation and convective mode. The forecasters identified three synoptic processes they were monitoring for clues as to how the event would unfold. These elements were (a) the absence of strong surface convergence along a dryline in western Oklahoma and the Texas Panhandle, (b) the presence of a cirrus shield that was hypothesized to limit surface heating, and (c) the arrival into Oklahoma of an upper-level wind speed maximum [associated with the so-called southern potential vorticity (PV) anomaly] that was responsible for favorable synoptic-scale ascent and the cirrus shield. The Pennsylvania State University-National Center for Atmospheric Research Fifth-Generation Mesoscale Model (MM5), nested down to 2-km horizontal grid spacing, is used in forecast mode [using the data from the National Centers for Environmental Prediction Aviation (AVN) run of the Global Spectral Model to provide initial and lateral boundary conditions] to explore the sensitivity of the outbreak to these features. A 30-h control simulation is compared with the available observations and captures important qualitative characteristics of the event, including convective initiation east of the dryline and organization of mesoscale convective systems into long-lived, long-track supercells. Additional simulations in which the initial strength of the southern PV anomaly is altered suggest that synoptic regulation of the 3 May 1999 event was imposed by the effects of the southern PV anomaly. The model results indicate that 1) convective initiation in the weakly forced environment was achieved through modification of the existing cap through both surface heating and synoptic-scale ascent associated with the southern PV anomaly; 2) supercellular organization was supported regardless... [ABSTRACT FROM AUTHOR]

A diagnostic evaluation of three project ANOMALIA case studies involving heavy precipitation in the western Mediterranean region has been carried out. The evaluation shows the unique characteristics of each event, as well as some limited similarities. Heavy precipitation events in the western Mediterranean region typically occur downstream of a significant cyclone aloft (often, but not always, exhibiting "cutoff" cyclone characteristics), but important structural and evolutionary differences are found among these cases. At low levels, a long fetch of flow over the Mediterranean Sea frequently interacts with terrain features to produce persistent heavy precipitation. Although most heavy precipitation events occur during the fall season, they can develop at other times. In the first case, the synoptic-scale environment produced low static stability and substantial storm-relative environmental helicity, thereby supporting both heavy rain in the vicinity of Valencia on mainland Spain and on Ibiza in the Balearic Islands, as well as a tornado at Menorca in the Balearic Islands on 7-9 October 1992. The second case involved a slow-moving cyclone that destabilized the stratification and produced several days of heavy precipitation over the period 31 January-6 February 1993. In the third case, in the Italian Piedmont region on 5-6 November 1994, the heavy precipitation included a nonconvective component, with moist but relatively stable air impinging on steep terrain gradients. A set of basic diagnostic tools is applied to the cases, and it is shown that anything but a superficial diagnosis of each case requires flexibility in selecting diagnostic tools. The ways by which heavy precipitation is created can vary substantially from case to case and in different parts of the world; however, there is a common thread. Heavy precipitation is the result of moist, low-level air ascending rapidly, so any diagnosis aimed at forecasting heavy precipitation needs to address the... [ABSTRACT FROM AUTHOR]

The Maritime Continent is a major active convective area and one of the most challenging regions in terms of atmospheric modelling. Rainfall in the Maritime Continent is driven by both large-scale phenomena such as the Madden-Julian Oscillation and ENSO, and fine-scale processes such as land-sea breeze and tropical convection. In combination, they produce very particular precipitation regimes that models consistently fail to reproduce across spatial resolutions, regardless of their dynamic formulation. Climate simulations at convection-permitting scales are now becoming possible. Rather than simply increasing spatial resolution, these experiments constitute a conceptual advance since they no longer rely on many of the assumptions of convective schemes. Here, we use the Weather Research and Forecasting model operating at multiple resolutions (32, 16, 8, 4 and 2km) to determine the role of the spatial resolution and the representation of convection on the realism of precipitation in the Maritime Continent. We show that the key aspect to better simulate precipitation in the region is the explicit representation of deep convection, while the benefit of increasing spatial resolution is limited. Both explicit convection and parameterized shallow convection produce precipitation at the right time of the day because they do not transform CAPE as readily as the deep convection scheme. Thus, not only precipitation but also other processes linked to convective circulation such as land-sea breeze are better represented when deep convection is explicitly resolved. In spite of generating a diurnal cycle that better matches the observations, there are features that remain a challenge even at the kilometre scale, such as the land/ocean distribution of total precipitation amounts. Explicitly resolving deep convection has implications for the lower atmosphere mixing, specially over the ocean, where the model does not generate enough energy to trigger convection and produce rainfall. As such, the microphysics and the planetary boundary layer take on particular importance in the challenge of simulating tropical convective precipitation in very high-resolution experiments. [ABSTRACT FROM AUTHOR]

The Mediterranean region is a unique area characterized by a large spectrum of atmospheric phenomena, some of which have a high impact on many aspects of human activities, safety and wellbeing. The area is long considered as a hot spot of such atmospheric phenomena deserving multidisciplinary scientific attention. The scientific research that has been carried out on these high impact atmospheric processes that occur in the Mediterranean area is indeed widespread and the available international literature is very extensive. The paper touches initially the temperature and precipitation regimes, followed by a discussion of floods and droughts. The exciting cyclogenetic patterns of explosive cyclones and medicanes are presented in separate sections. The lightning activity and the presence of dust and other pollutants are also presented herein. The atmospheric chemistry of the region which is increasingly becoming of utmost importance for the area under study is distinctly discussed. Attempts to modify the weather (the precipitation, in particular) are outlined too. The effects of climatic change on various atmospheric processes are considered throughout this paper, in addition to a dedicated section on temperature and precipitation. [ABSTRACT FROM AUTHOR]