Dataset associated with "A nonmonotonic precipitation response to changes in soil moisture in the presence of vegetation"

In many parts of the world, humans rely on afternoon rainfall for their water supply. However, it is not fully understood how land surface properties influence afternoon precipitation. In fact, disagreement remains regarding the relative prevalence of “wet-soil advantage” regimes, in which wet soils receive more precipitation than do dry soils, and “dry-soil advantage” regimes, in which the opposite occurs. Recent studies have proposed that the permanent wilting point (PWP) soil moisture threshold influences the location and organization of convective clouds. Motivated by this work, we investigate how changes in soil moisture relative to the PWP affect the timing and amount of surface rainfall, as well as how this response depends on the presence or absence of vegetation. This investigation is carried out by conducting several series of high-resolution, idealized numerical experiments using a fully coupled, interactive soil-vegetation-atmosphere modeling system. From these experiments, a new soil moisture-precipitation relationship emerges: in the presence of vegetation, simulations with moderately dry soils, whose initial liquid water content slightly exceeds the PWP, generate significantly less surface precipitation than do those with the driest or wettest soils. This result suggests that simulated “wet-soil advantage” and “dry-soil advantage” regimes may not necessarily be mutually exclusive, insofar as extremely wet and extremely dry soils can both exhibit an “advantage” over moderately dry soils. This non-monotonic soil moisture-precipitation relationship is found to result from the PWP’s modulation of transpiration of water vapor by plants. In the absence of vegetation, a wet-soil advantage occurs instead in these idealized simulations.

全球诸多地区，人类的供水依赖午后降雨。然而，学界尚未完全明晰地表属性如何影响午后降水。事实上，关于“湿土优势（wet-soil advantage）”与“干土优势（dry-soil advantage）”两种情景的相对普遍程度，学界仍存在分歧：前者指湿润土壤较干燥土壤获得更多降水，后者则反之。近期研究指出，永久萎蔫点（permanent wilting point, PWP）这一土壤湿度阈值会影响对流云的分布与组织形态。受此研究启发，本研究探讨了相对于永久萎蔫点的土壤湿度变化如何影响地表降雨的发生时间与降雨量，同时分析该响应如何受植被存在与否的调控。本研究借助完全耦合的交互式土壤-植被-大气模拟系统，开展多组高分辨率理想化数值实验以完成上述探究。实验结果揭示了全新的土壤湿度-降水关联规律：在植被存在的场景下，初始液态水含量略高于永久萎蔫点的中度干燥土壤模拟组，其产生的地表降水量显著低于最干燥或最湿润的土壤模拟组。该结果表明，模拟得到的“湿土优势”与“干土优势”情景未必互斥——因为极端湿润与极端干燥的土壤，均较中度干燥土壤呈现出“优势”。这种非单调的土壤湿度-降水关联，源于永久萎蔫点对植物水汽蒸腾过程的调控。而在无植被存在的理想化模拟场景中，则呈现出湿土优势情景。