Climate Detectives Projects 2018-2019

Project title: Variability and time series analysis of rainfall in Italy: a case study from a coastal area of Abruzzo region

Team: Prometeo 2018

2018-2019   Liceo Scientifico Statale   Pescara   Italy   18 Student’s age: 14-15

Over recent years the frequency of flooding or droughts seems to have increased in our territory, with considerable consequences on the society and on the natural ecosystems. In our research we studied some specific aspects of precipitation, with particular attention being paid to intense events, to understand their evolution over time and to verify their possible relationship with the frequency of drought periods. To do this we analyzed the rainfall data of the Servizio Idrografico and Mareografico of the Abruzzo region from 1951 to 2018 relevant to the weather station in Pescara, located a few kilometers south of Montesilvano where our school lies. The first step consisted in controlling the original data to ensure its completeness and its quality in order to eliminate possible persistence or outliers. Starting from the data referring to daily precipitation, we carried out a statistical analysis of the monthly and annual rainfall values and calculated a series of pluviometric indices in accordance with those of the Expert Team on Climate Change Detection and Indices (ETCCDI). Moreover we compared the results with the values of the SPI index (Standard Precipitation Index) of the European Drought Observatory (EDO) for the station in Pescara from 1975 onward one of the statistical indices most commonly used for measuring local droughts. The knowledge of the climatic extremes and their variations is particularly relevant in the definition of the strategies of adaption to climate changes and possible mitigation politics. Infact, extreme events are often the cause of significantly negative impacts on health, economy, territory, environment and society in general.

In our analysis we considered “rainy” days those with ≥ 1 mm of rainfall. For each year we calculated the following indices: a) the number of rainy days and the total amount of annual rain, so we obtained the daily intensity index (SDII, in mm/day); b) the maximum monthly rainfall value in 1 day (RX1 day, in mm); c) the RX5 index relative to the maximum monthly value of rainfall in 5 consecutive days (in mm); d) the R20 index, the annual number of days with very intense rainfall (precipitation ≥ 20 mm); e) the PCI index (Precipitation Concentration Index, De Luis et al., 1997) to evaluate how the precipitation is distributed over the years; f) the CCD index, intended as periods of the year with over or equal to 10 subsequent days of precipitation lower than 5mm. To verify a possible relationship between the periods of drought and intense rainfall events the values of the SPI-3 months from the EDO were taken into consideration. For all the indices calculated the averages for the period 1951-2018 were obtained and the trends were graphically analyzed. The results obtained for the whole time range show variations that are of no or little significance in the indicators. Nevertheless from an in-depth analysis of the graphics they show a net irregularity in the distribution of the indices in the 1990-1995 interval, marked by an inversion of the trends from negative to positive (“change point”). Therefore, subdividing the analysis into two distinct periods (1951-1995 and 1996-2018) it is possible to note significant differences both in the average values of the indices (see table) and the trend (see charts). An increase in the rainfall quantity, frequency and intensity from 1996 is also accompanied by decrease of periods of drought (SPI index), very prominent from 2003 onwards.

The “global warming” is very evident also in our region. The average daily temperature is increasing, during the period 1930-1979, equal to 0.13°C every 10 years, whilst considering the period 1950-2015, the increase shows as being equal to 0.42°C per decade, an increase which becomes even more pronounced (0.60°C per decade) considering the period 1980-2015 (ARTA Abruzzo, Report on the state of the environment 2018). In the studied area we demonstrated that in the period 1996-2018 this increase in temperature is not translated in an increase of the dry conditions but in a marked increase in the rainfall indicators (frequency and intensity of the events) and humidity in respect to the period 1951-1995. Therefore it seems likely to have been a relation between the increase in temperature and an increase in intense precipitation (length and frequency), presumably associated with the increase in the rate of evaporation given the distance from the sea. Therefore what sparks-off the intense events subject of our study appears to be the excessive warming up of the atmosphere in the city. The presence of a large quantity of cement, tarmac surfaces prevailing over green areas, car emissions, industrial plants and air conditioning systems amplify the effects of an increase in the air temperature and therefore we can act on this on a local level to lighten the effects of intense meteorological events. It consists in sensitizing public opinion and administration for a more ecological management of our territory with advantages for the whole community. Extremely heavy rainfall and flooding, long periods of drought, an increase in the air temperature, heatwaves are all events which increase security and health risks for the community and therefore it is everybody’s commitment to react so to improve the quality of the environment and our lives, also for future generations.