# Rainfall Erosivity Main Features and Their Associated Synoptic Conditions in North-Eastern Romania
## 3 Results and Discussions
### The Analysis of Hourly Precipitation Amounts  
Each rain event has a mean intensity, represented by the total amount of water that falls during the entire event, as well as a maximum intensity, represented by the highest recorded intensity during the rain [54]. To assess these rainfall aspects related to intensity, we used the available data of precipitation amount at the hourly level, covering the 2013-2019 period, from two weather stations located in critical areas for soil erosion over the region (Carja in the south-east and Madarjac in the central part of the analyzed region). The March-November interval, which is particularly relevant for soil erosion, was considered in this study. Consequently, we calculated an intensity per minute for each month, based on hourly data. At the Carja weather station (Table 3), the majority of the maximum hourly precipitation amount was recorded in June. The highest value reached was 34.6 mm/h on June 24 th, 2013, followed by another 26.8 mm over the subsequent two hours. Furthermore, June reaches the highest mean rainfall intensity (0.26 mm/min) for hours recording precipitations, followed by July and September (0.15 and 0.16 mm/min, respectively), months with fewer hours with precipitations. One can also easily observe the very high variability from one year to another, with some years, such as 2014-2015, exhibiting no significant occurrences of intense rainfall. The dataset for Madarjac weather station, from the central part of the analyzed region, show the same general features. In this case, the maximum hourly intensity was reached in 2018, again in June with a maximum of 33.6 mm/h (Table 4). The critical rainfall aggressiveness season, which is defined as the period of maximum risk of severe rainfall, extends from May to July for both observation points, as is common for the entire region [50]. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Month/Year** & **2013** & **2014** & **2015** & **2016** & **2017** & **2018** & **2019** & **Average** \\ \hline March & 0.07 & 0.03 & 0.02 & 0.03 & 0.06 & 0.02 & 0.01 & 0.03 \\ April & 0.09 & 0.07 & 0.03 & 0.03 & 0.10 & - & 0.08 & 0.05 \\ May & 0.25 & **0.11** & 0.02 & 0.09 & 0.08 & 0.08 & 0.16 & 0.11 \\ June & **0.58** & 0.04 & **0.06** & **0.15** & 0.29 & **0.18** & **0.51** & **0.26** \\ July & 0.21 & 0.03 & 0.03 & 0.04 & **0.32** & 0.17 & 0.25 & 0.15 \\ August & 0.33 & 0.01 & 0.03 & 0.03 & 0.06 & 0.05 & 0.12 & 0.09 \\ September & 0.42 & - & 0.02 & 0.02 & 0.34 & 0.04 & 0.10 & 0.16 \\ October & 0.08 & 0.04 & 0.01 & 0.11 & 0.04 & 0.05 & 0.17 & 0.07 \\ November & 0.04 & 0.03 & - & 0.14 & 0.05 & - & 0.03 & 0.05 \\ Annual average & 0.23 & 0.05 & 0.03 & 0.07 & 0.15 & 0.07 & 0.16 & 0.11 \\ Maximum/hour & 34.6 & 6.60 & 3.56 & 9.10 & 20.4 & 10.7 & 30.4 & 16.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Maximum monthly precipitation intensity (mm/min) derived from hourly data during 2013–2019 at the Carja weather station (bold italic indicates the monthly maximum). As was the case with the Carja weather station, we can easily see that September records higher values of the rainfall intensity compared to August due to the intense convective processes associated with the first cold advections in early autumn. The observed differences between the two locations are primarily attributable to altitude, which can result in a slight increase in orographic uplift at the Madarjac weather station. It is important to note that the hourly precipitation levels recorded at these two locations (ranging from 30 to 35 mm/h) are notably lower when compared to long term datasets wherein maximum hourly precipitation amounts frequently surpass 40 mm/h [55]. Due to the short time interval of observations, limited to 2013-2019 for both analyzed weather stations, the maximum values of hourly rainfall amount is very likely to be underestimated, since in nearby regions like Dobrogea, similar values surpass 60 mm/h [55].