Spatial distribution and trends of different precipitation variability indices based on daily data in Northern Chile between 1966 and 2015

Abstract. Northern Chile is one of the most arid regions in the world, as includes the Atacama Desert, but in high altitudes, precipitation is recorded in a very constricted season every year. This makes that water availability is one of the main concerns for policymakers. Accumulated rainfall presents very high differences from one year to another, and this makes that climate projections have a very low degree of confidence in this area. So to this region it is more interesting to study the irregularity of precipitation itself instead of the accumulated rainfall values. According to daily data of 161 meteorological stations, 4 irregularity indices of precipitation were calculated: concentration index, entropy, persistence index and fractal dimension. These indices were determined according to observed values, and then determined their spatial distribution by interpolating following multivariate regression models that consider different geographical variables such as latitude, distance to the Amazon basin, elevation, orientation and curvature. The temporal trends of each index and for each meteorological station were also calculated, and showed different results depending on the latitude and the elevation. These changes agree with the observed modifications on the intertropical atmospheric circulation and with the changes in the precipitation diurnal cycle. These results will help to improve climate projections for these region and to inform the development of water management policies.