TRMM-based rainfall temporal analysis over Italy

International Journal of Climatology, 2009

Precipitation trend analysis, on different spatial and temporal scales, has been of great concern during the past century because of the attention given to global climate change by the scientific community. According to some recent studies, the Italian territory has been suffering a precipitation decrease, especially in the last 50 years, and the southern areas seem to be more affected. The aim of the present study is to analyse rainfall time series over a wide time interval and a wide area, detecting potential trends and assessing their significance. For this purpose, 211 gauged stations, mainly located within the Campania region, southern Italy, have been analysed for the period 1918-1999. An accurate database has been set up through a data quality and time series homogeneity process. Statistical analysis of the database highlight that (1) the trend appears predominantly negative, both at the annual and seasonal scale, except for the summer period when it appears to be positive; (2) over the whole reference period, positive and negative trends are significant respectively for 9 and 27% of total stations and (3) over the last 30 years, a negative trend is instead significant for 97% of the total stations.

Hydrology, 2022

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of Hydrologic Engineering, 2016

Rainfall is characterized by spatial variability, which depends on the timescale used. Experiences in analysing rainfall for different time periods have shown, in fact, that the spatial patterns of variability change depending on the time scale (from hours through days and months to seasonal and annual scales). Geostatistics offers a variety of methods for modelling spatial variability and mapping rain fields considered as realizations of random functions. The aim of this study was to analyse and quantify the spatial structure of rain fields at various timescales for climatological and water resources purposes. The data used in this study are a set of different timescales precipitation series registered in Calabria in the last years. Spatial structures of rain fields were identified over the range of timescales most often used in climatological and water resources studies varying from daily to monthly, to seasonal, to annual timescale. Results showed that spatial structure of rainfall measurements changes through the months and as the timescale increases from days to months and seasons to annual total. Orographic precipitation influences global atmospheric circulation and this could explain the different spatial patterns for short and long ranges of variation.

Atmospheric Research, 2005

Since the 18th century systematic measurements of rainfall have been collected in are examples of available long rainfall records. These data series can help analyzing the evolution of precipitation. The present paper deals with long term evolution of: (i) annual rainfall amount; (ii) annual number of rainy events; (iii) intensity of rainfall, (iv) inter-annual rainfall partitioning, i.e. the duration of wet and dry periods, and (v) maximum annual values of daily rainfall amount, duration of wet and dry periods. The evolution is studied analyzing the first two order statistics and the 30-year return period quantiles via moving window analysis. Confidence intervals are introduced to check the statistical significance of the estimated statistics and quantiles. The results are compared with those provided by the traditional Mann-Kendall test. The analysis shows how the annual precipitation exhibits a negative trend in the first half of 20th century, with a subsequent positive trend in northern Italy (Genoa, Milan and Bologna). Conversely, the dataset for Palermo (southern Italy) displays only a negative trend. Because the number of precipitation episodes is found to decrease in the investigated period, the average rain rate is significantly increasing especially in northern Italy. This is also associated with shorter duration of rain episodes with an evident effect on rainfall extremes. Dry periods tend to be longer with increasing variability. The Mann-Kendall test and its progressive form 0169-8095/$ -see front matter D (M. Cislaghi).

Natural Hazards and Earth System Sciences, 2011

This study investigates precipitation variability in five regions of Southern Italy (Campania, Apulia, Basilicata, Calabria and Sicily) using a homogeneous database of about 70 rain gauges with more than 50 years of observation. First, a statistical analysis was performed through the Mann-Kendall non-parametric test in order to determine rainfall the trend on both yearly and seasonal scales. Then, the relationship between the rainfall and some teleconnection pattern indexes was investigated using Spearman's test. The results show remarkable statistically significant negative trends for annual and winter aggregations in most part of the series. Moreover, a strong correlation has emerged between the teleconnection patterns and precipitation in Southern Italy, particularly in winter and on the Tyrrhenian side of the study area.

Atmospheric Research, 2009

This paper presents first exploratory results and analyses performed on a 30-year (1978-2007) homogeneous precipitation database that has been created for the Calabria peninsula, southern Italy. The database consists of complete time series of daily values of precipitation from 88 stations distributed over the region. The database temporal resolution is one day while its spatial resolution is about 10 km. Calabria offers an interesting scenario for mesoclimatic studies in spatial and temporal rainfall variability. The region is located in the Central Mediterranean Basin, which has a strong seasonal variability that mirrors in large precipitation differences among seasons. The complex orography of the region leads to different exposures of the territory to the rain-bearing air masses and large differences in rainfall can occur in few tens of kilometers. Different kinds of Mediterranean storms are important for Calabria: a) storms originating in the lee of the Alps; b) storms that enter the Basin or develop in the western Mediterranean (Gulf of Lyon, Rhone valley, Iberia, Gibraltar); c) storms from northern Africa; d) storms moving over the central Mediterranean from Balkans and eastern Europe. Again, their interaction with local orography determines complex rainfall patterns and variability. In this paper, the maps of average values of precipitation, rain frequency, rain rate, persistence of rainfall and length of dry periods are presented. Precipitation spatial structure shows that the orography and the sea have a major role, while the seasonal dependence of rainfall unequivocally reveals the influence of the synoptic scale conditions. A large number of cast-studies of heavy precipitation events have been investigated in the past and several of them refer to the east side of Calabria. The results shown here confirm this issue in a climatological sense: despite the fact that yearly precipitation is larger on the west side of the peninsula, most intense rainstorms affect mainly the east side, which is favorably exposed to these storms. The current database represents a foundation for further investigations.

Environmental Earth Sciences, 2016

The precipitation climate regime of a region is characterized by the distribution of the monthly precipitation contribution. Its temporal and spatial analysis is particularly interesting for many fields of applied sciences, such as climatology, hydrology and water resources management. With the aim to describe the climate regime, its spatial feature and relevant potential temporal shift, for a large area of southern Italy (Mediterranean basin), a database of about 559 stations has been explored through the statistical analysis of rainfall time series spanning between 1917 and 2006. After a change point analysis, aimed at the assessment of data quality, a trend analysis has been performed on both monthly precipitation, monthly percentage of annual rainfall amount and PCI-computed series. The broad extension of the area under investigation highlights a better understanding of precipitation distribution patterns over space. Results of PCI trend analysis show a significant shift, for about 40-50 % of total gauging station, over the time towards a more uniform climate regime, especially for the hilly areas. Moreover, the trend analysis on the monthly rainfall series indicates that the shift is produced by a reduction of rainfall amount during the winter season, particular consistent over the Tyrrhenian side of the peninsula, and an increase during the summer season quite widespread over the whole investigated territory.

This study presents a methodology applied for estimating monthly rainfall erosivity patterns in Campania Region, by combining sub-hourly rainfall time-series and daily rainfall time series and a geostatistical technique for representing seasonal rainfall erosivity maps.

Advances in Geosciences, 2005

The objective of the study is to assess the presence of linear and non linear trends in annual maximum rainfall series of different durations observed in Sicily. In particular, annual maximum rainfall series with at least 50 years of records starting from the 1920's are selected, and for each duration (1, 3, 6, 12 and 24 h) the Student's t test and the Mann-Kendall test, respectively, for linear and non linear trend detection, are applied also by means of bootstrap techniques. The effect of trend on the assessment of the return period of a critical event is also analysed. In particular, return periods related to a storm, recently occurred along the East Coast of Sicily, are computed by estimating parameters based on several sub-series extracted from the whole observation period. Such return period estimates are also compared with confidence intervals computed by bootstrap. Results indicate that for shorter durations, the investigated series generally exhibit increasing trends while as longer durations are considered, more and more series exhibit decreasing trends.