Reconciling spatial and temporal soil moisture effects on afternoon rainfall.
Soil moisture impacts on precipitation have been strongly debated. Recent observational evidence of afternoon rain falling preferentially over land parcels that are drier than the surrounding areas (negative spatial effect), contrasts with previous reports of a predominant positive temporal effect. However, whether spatial effects relating to soil moisture heterogeneity translate into similar temporal effects remains unknown. Here we show that afternoon precipitation events tend to occur during wet and heterogeneous soil moisture conditions, while being located over comparatively drier patches. Using remote-sensing data and a common analysis framework, spatial and temporal correlations with opposite signs are shown to coexist within the same region and data set. Positive temporal coupling might enhance precipitation persistence, while negative spatial coupling tends to regionally homogenize land surface conditions. Although the apparent positive temporal coupling does not necessarily imply a causal relationship, these results reconcile the notions of moisture recycling with local, spatially negative feedbacks.
Institute for Atmospheric and Climate Science, Department of Environmental Systems Science, ETH Zurich, 8092 Zurich, Switzerland.
Benoit P
BP
Guillod
Institute for Atmospheric and Climate Science, Department of Environmental Systems Science, ETH Zurich, 8092 Zurich, Switzerland.
Boris
B
Orlowsky
1] Department of Earth Sciences, VU University Amsterdam, Amsterdam 1081 HV, The Netherlands [2] Laboratory of Hydrology and Water Management, Department of Forest and Water Management, Ghent University, B-9000 Ghent, Belgium.
Diego G
DG
Miralles
Hydrology and Quantitative Water Management Group, Department of Environmental Sciences, Wageningen University, Wageningen 6708PA, The Netherlands.
Adriaan J
AJ
Teuling
Institute for Atmospheric and Climate Science, Department of Environmental Systems Science, ETH Zurich, 8092 Zurich, Switzerland.
Sonia I
SI
Seneviratne