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Summary The aim of this paper is to analyse the potential relationship between flash flood events and convective precipitation in Catalonia, as well as any related trends. The paper starts with an overview of flash floods and their trends in the Mediterranean region, along with their associated factors, followed by the definition of, identification of, and trends in convective precipitation. After this introduction the paper focuses on the north-eastern Iberian Peninsula, for which there is a long-term precipitation series (since 1928) of 1-min precipitation from the Fabra Observatory, as well as a shorter (1996–2011) but more extensive precipitation series (43 rain gauges) of 5-min precipitation. Both series have been used to characterise the degree of convective contribution to rainfall, introducing the β parameter as the ratio between convective precipitation versus total precipitation in any period. Information about flood events was obtained from the INUNGAMA database (a flood database created by the GAMA team), with the aim of finding any potential links to convective precipitation. These flood data were gathered using information on damage where flood is treated as a multifactorial risk, and where any trend or anomaly might have been caused by one or more factors affecting hazard, vulnerability or exposure. Trend analysis has shown an increase in flash flood events. The fact that no trends were detected in terms of extreme values of precipitation on a daily scale, nor on the associated ETCCDI (Expert Team on Climate Change Detection and Indices) extreme index, could point to an increase in vulnerability, an increase in exposure, or changes in land use. However, the summer increase in convective precipitation was concentrated in less torrential events, which could partially explain this positive trend in flash flood events. The β parameter has been also used to characterise the type of flood event according to the features of the precipitation. The highest values correspond to short and local events, usually with daily β values above 0.5, while the minimum threshold of daily β for catastrophic flash floods is 0.31. [ABSTRACT FROM AUTHOR]

The present paper shows an in-depth analysis of the evolution of floods and precipitation in Catalonia for the period 1981–2010. In order to have homogeneous information, and having in mind that not gauge data was available for all the events, neither for all the rivers and stream flows, daily press from a specific newspaper has been systematically analysed for this period. Furthermore a comparison with a longer period starting in 1900 has been done. 219 flood events (mainly flash flood events) have been identified for the period of 30 years (375 starting in 1900), 79 of them were ordinary, 117 of them were extraordinary and 23 of them were catastrophic, being autumn and summer the seasons with the maxima values. 19% of the events caused a total of 110 casualties. 60% of them died when they tried to cross the street or the stream. Factors like the evolution of precipitation, population density and other socio-economical aspects have been considered. The trend analysis shows an increase of 1 flood/decade that probably has been mainly due to inter-annual and intra-annual changes in population density and in land-use and land-cover. [ABSTRACT FROM AUTHOR]

This paper aims to analyse the distribution and temporal evolution of convective precipitation in the Mediterranean region of Spain. To accomplish this goal, we used 148 sets of 5-min rainfall rate data from the 1989–2015 period. The selected regions were the Júcar Hydrographic Confederation (CHJ) and the Internal Basins of Catalonia (CIC), which cover most of the autonomous communities of Catalonia and the Valencian Community (east Spain). The average 5-min intensity threshold of 35 mm/h and the β parameter, defined as the ratio between convective precipitation versus total precipitation in any period, were used to characterise convective precipitation. Convective episodes were categorised as "very convective", "moderately convective", and "slightly convective" based on the β value. After quality control, the series of 129 stations were clustered into homogeneous precipitation zones that also include β as one of the variables of characterisation. The results show that convective precipitation can contribute to total annual precipitation by up to 16% on average, but it is generated by a very small percentage of convective events (between 3% and 6% across all the stations) in comparison with the total number of rainfall episodes. In this sense, moderately convective events are the most common, with a predominantly unimodal monthly distribution of β, with summer the most convective season. Trends show a significant increase in precipitation, convective precipitation, and convective episodes in the CHJ. On the other hand, a positive trend of convective events is predominant in the CIC region, despite an overall precipitation decrease in the analysed period. These results are relevant given that extreme daily rainfall does not show a positive or significant trend, and they are in line with the impact of climate change on increased atmospheric instability and water vapour in the atmosphere. They highlight the need to work with sub-daily precipitation series in the case of the Mediterranean, which is mainly affected by flash floods. • The contribution of convective precipitation in the East of Spain exceeds 10% annually and can reach 100% in late summer. • Convective precipitation is caused by less than 5% of annual rain episodes that are associated to heavy rains. • Orography (height, orientation, and distance to the sea) plays the major role in triggering convective precipitation. • There is a predominant increase of convective precipitation resulting from a strengthening of thermodynamic conditions. • SST has increased 0,3ºC more than air temperature in the Mediterranean region that results in increasing potential instability. [ABSTRACT FROM AUTHOR]