Do atmospheric teleconnection patterns influence rainfall erosivity? A study of NAO, MO and WeMO in NE Spain, 1955-2006

Abstract

Rainfall erosivity is the ability of precipitation to erode soil. Raindrops impact on the surface—rainsplash—represents an important mechanism of soil particles detachment. If the soil is not perfectly flat rainsplash will also produce the movement of soil particles down the slope due to diffusion. But even in the case of flat soils the detached particles will be available for transport by other erosion agents such as surface runoff. Despite its importance as fundamental erosion process very few studies have addressed the climatology of rainfall erosivity. It is known fact rainfall erosivity in long term (e.g., cumulative annual values) is determined by a few number of heavy events. This study analyses the interannual variability of daily rainfall erosivity in NE Spain during the period 1955–2006, and its connection with atmospheric circulation patterns influencing rainfall in the region, namely the North Atlantic Oscillation (NAO), the Mediterranean Oscillation (MO) and the Western Mediterranean Oscillation (WeMO). It is found that the erosive power of rainfall is stronger during negative phases of the three atmospheric circulation indices, and weaker during positive conditions. Daily rainfall erosivity series were adjusted to a Generalized Pareto probability distribution for positive and negative days of the atmospheric circulation indices, for assessing their effects on rainfall erosivity extreme events. Results showed higher values expected for a given return period in most of the area under negative conditions of all indices, especially at the Mediterranean coast. Overall, MO and WeMO showed the strongest influence on daily rainfall erosivity extremes. These findings would be useful in the implementation of soil conservation strategies.