Use of Multiple Correspondence Analysis (MCA) to Identify Interactive Meteorological Conditions Affecting Throughfall

Abstract:

Forest canopy alters rainfall reaching the surface by redistributing it as throughfall. Throughfall is critical to watershed ecological variables (soil moisture, stream water discharge/chemistry, and stormflow pathways) and controlled by canopy structural interactions with meteorological conditions across temporal scales. This work introduces and applies multiple correspondence analyses (MCAs) to a range of meteorological thresholds (median intensity, median absolute deviation (MAD) of intensity, mean wind-driven droplet inclination angle, and MAD of wind speed) for an example throughfall problem: identification of interacting storm conditions corresponding to temporal concentration in relative throughfall beyond the median observation (≥73% of rain). MCA results from the example show that equalling or exceeding rain intensity thresholds (median and MAD) corresponded with temporal concentration of relative throughfall across all storms. Under these intensity conditions, two wind mechanisms produced significant correspondences: (1) high, steady wind-driven droplet inclination angles increased surface wetting; and (2) sporadic winds shook entrained droplets from surfaces. A discussion is provided showing that these example MCA findings agree well with previous work. Meteorological threshold correspondences to temporal concentration of relative throughfall at our site may be a function of heavy T. usneoides coverage. Applications of MCA within other forests may provide useful insights to how temporal throughfall dynamics are affected for drainage pathways dependent on different structures (leaves, twigs, branches, etc.).