EGU25-13674, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-13674
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
 A decade-long analysis of rainfall in Rome based on disdrometer: Rain patterns and Intermittency 
Ravi Shankar Pandey1, Natale Alberto Carrassi1, Federico Porcù1, and Elisa Adirosi2
Ravi Shankar Pandey et al.
  • 1University of Bologna, Department of Physics and Astronomy, Bologna, Italy (ravishankar.pandey@unibo.it; alberto.carrassi@unibo.it; federico.porcu@unibo.it)
  • 2Istituto di Scienze dell'Atmosfera e del Clima, Roma, Italy (elisa.adirosi@artov.isac.cnr.it)

The study presents the first analysis of the rain structure based on 11 years (2013-2023) of continuous 1-min disdrometer data collected by the TC-Clima disdrometer located nearby Rome (Italy). The investigation employs various techniques, including delineating rainfall events based on different minimum inter-event times (MITs), calculating rain rate, mass-weighted mean diameter (Dm), as well as stratiform and convective precipitation classification. The dataset has been pre-processed to filter/remove missing/erroneous information and to ensure unbiased measurements. Seasonal variations showed that autumn had the highest rainfall accumulation (38.8%, 3126.8 mm), despite shorter rain durations (1116.5 hours) compared to winter (1446.5 hours). Winter contributed 28.2% (1986.65 mm) with prolonged rain events of smaller droplets (Dm = 0.98), while summer had the lowest total rainfall (10%, 1329.6 mm) but the highest average rain rate (3.4 mm/h) and largest drops (Dm = 1.39). The difference in drop sizes and rain types across seasons is important, as stratiform clouds, linked to steady rain, were more common in autumn and winter, while convective clouds, associated with intense, short-duration rain, dominated summer. We then focus on rainfall intermittency: the abrupt onset or interruptions of rainfall events. We quantify intermittency by using the intermittency fraction (IFr), i.e., the proportion of time with no rain during an event. Diurnal analysis of IFr revealed significant seasonal differences. Intermittency Fraction peaked between 9am and 2pm, with summer seeing sharp peaks before noon, followed by a rapid decrease in the afternoon. Winter maintained more consistent IFr throughout the day. Rain interruptions have been more frequent in winter, but these breaks were generally short, indicating long-duration, low-intensity rainfall. In contrast, summer had fewer interruptions, but they lasted longer due to intense, short-lived rain. These seasonal differences are robust and appear also by varying the fixed-time averages of the rainfall intermittency. Overall, the longest continuous rain event lasted 19.4hrs, while the longest dry spell was 534.4hrs. The rainfall is an intermittent natural phenomenon whose start and end are defined by rainless intervals referred to as minimum inter-event time, MIT. Intra event rainfall intermittency across various MITs shows higher IFrs at shorter MITs, particularly during summer. Our research also shows that disdrometer measures higher rain amount than conventional rain gauge with highest contrast in summer season. This further underscores the importance of high-resolution rainfall data for accurate predictions. Disdrometers confirmed to be a unique source of reliable and detailed rainfall measurements, which are essential for enhancing resilience against hydro-meteorological challenges such as flooding.

How to cite: Pandey, R. S., Carrassi, N. A., Porcù, F., and Adirosi, E.:  A decade-long analysis of rainfall in Rome based on disdrometer: Rain patterns and Intermittency , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13674, https://doi.org/10.5194/egusphere-egu25-13674, 2025.

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