Multi-Mission Based River Levels

Abstract

Rivers levels typically show large seasonal variations. In Arctic rivers, the water level rises rather quickly in the spring when the snow and ice are melting. This abrupt rise is challenging to capture for missions such as Sentinel-3 and SARAL/AltiKa that has a repeat period of approximately one month. However, by combining levels from several missions the temporal resolution is significantly improved. Here we use data from CryoSat-2, SARAL/AltiKa, and Sentinel-3A for a river segment to make a joint solution of the river level. We set up a model that consists of state-space model and two spline functions. The statespace model is composed of an AR1 process and an observational part, where the error follows a mixture between normal and Cauchy distributions. The spline functions account for the change in topography and a potential variation in water level amplitude along the river. We demonstrate the model for the Ob River andother selected Arctic rivers