Abstract. A rockfall dataset for Germany is analysed with the objective of identifying the meteorological and hydrological (pre-) conditions that change the probability for such events in Central Europe. The factors investigated in the analysis are precipitation amount and intensity, freeze-thawing cycles as well as sub-surface moisture. As there is no suitable observational dataset for all relevant sub-surface moisture types (e.g. water in rock pores and cleft water) available, simulated soil moisture and parameterised pore water are tested as substitutes. The potential triggering factors were analysed both for the day of the event as well as for the days leading up to the event. It is found that the most important factor influencing rockfall probability in the research area is precipitation amount at the day of the event but the water content of the ground on that day and freeze-thawing cycles in the days prior to the event also influence the hazard probability. Comparing results with simulated soil moisture and parameterised pore water revealed that precipitation minus potential evaporation evaluated for a weekly period performs well as a proxy for the relevant sub-surface moisture types. A logistic regression model was built, which considers individual potential triggering factors as well as their interactions. Using this model the effects of meteorological conditions on rockfall probability in the Central European low mountain ranges can be quantified. The model suggests that precipitation is most efficient, when the moisture content of the ground is high. An increase of daily precipitation from its local 50^th percentile to its 90^th percentile approximately doubles the probability for a rockfall event under median sub-surface moisture conditions. When the moisture content of the ground is at its 95^th percentile the same increase in precipitation leads to a four-fold increase in rockfall probability. The occurrence of a freeze-thaw cycle in the preceding days can further increase the rockfall hazard. The most critical combination can be expected in the winter season after a freeze-thaw transition which is followed by a day with high precipitation amounts and takes place in a region preconditioned by a high level of sub-surface moisture.

中文翻译：

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量化中欧落石触发的气象条件

摘要。分析了德国的落石数据集，目的是确定改变中欧此类事件发生概率的气象和水文（预）条件。分析中研究的因素是降水量和强度、冻融循环以及地下水分。由于没有适用于所有相关地下水分类型（例如岩石孔隙中的水和裂隙水）的合适观测数据集，因此测试模拟土壤水分和参数化孔隙水作为替代品。对事件发生当天和事件前几天的潜在触发因素进行了分析。研究发现，影响研究区落石概率最重要的因素是事发当天的降水量，但事发当天地面的含水量和事发前几天的冻融循环也对灾害性产生影响。可能性。将结果与模拟土壤水分和参数化孔隙水进行比较显示，每周评估的降水减去潜在蒸发量作为相关地下水分类型的代理表现良好。建立了一个逻辑回归模型，该模型考虑了个体潜在的触发因素及其相互作用。使用该模型，可以量化气象条件对中欧低山脉落石概率的影响。该模型表明降水最有效，当地面含水量高时。日降水量较当地增加 50^{第 1 个}百分位数到第 90^个百分位数大约使在中等地下湿度条件下发生落石事件的概率增加一倍。当地面的水分含量达到第 95^个百分位数时，同样的降水增加会导致落石概率增加四倍。前几天发生的冻融循环会进一步增加落石危险。预计最关键的组合发生在冻融转变之后的冬季，随后是降水量高的一天，并且发生在一个由高水平地下水分预处理的地区。