Modification of the rainfall characteristics by the maize canopy

摘要

As rain falls on a canopy, it is redistributed and modified. While part of the rain will find a direct way through the canopy towards the ground, some will be redirected to the stem and then flow to the ground, some will accumulate on the leaves forming larger drops that will ultimately detach and fall and the remaining will eventually evaporate after the event is gone. This partitioning of rainfall into direct throughfall, stemflow and indirect throughfall modifies drop physical characteristics thatare relevant to erosion studies, such as drop size and kinetic energy, while to stored water is relevant to remote sensing of soil moisture. With that in mind, we installed two modified tipping buckets to collect and measure the throughfall, two to measure the stemflow, one regular tipping bucket to measure the incoming rainfall, two compact weather stations to measure wind and to provide us with a redundant measurement of rainfall and two optical disdrometers, one underneath the canopy, one outside ofthe canopy, to measure the modification of the drop size distribution by the plants. The instruments were operational from 8 July 2009 until 30 September 2009, when we had the opportunity to record 17 events, from which 11 had accumulation of at least 10mm. We used the data to assess the partitioning of rainfall info stemflow and throughfall and to assess the modification of drop size distribution and kinetic energy caused by the plants.