The Use of Satellite Information for Precomputing the Snowmelt Runoff Hydrograph L. S. Kuchment a , A. N. Gel’fan a , V. N. Demidov a , and P. Yu. Romanov b a Water Problems Institute, Russian Academy of Sciences, ul. Gubkina 3, Moscow, 119333 Russia b Cooperative Institute for Climate Studies, University of Maryland, 5825 University Research Court, College Park, MD 20740-3823 Received December 1, 2009 Abstract—A technique is proposed of precomputing the snowmelt runoff hydrograph on the basis of physical and mathematical models of river runoff formation, available standard data of surface hydro- meteorological measurements, and satellite measurements of Earth’s surface conditions. The computa- tions were carried out for two regions including the basins of the Vyatka and Don rivers. It is demon- strated that, in spite of the possible errors and gaps depending on meteorological conditions, the satellite snow cover measurements can be an important addition to the surface measurements for simulating a spatial picture of the runoff formation. The use of physical and mathematical models of the runoff formation enables to reduce the errors of satellite snow cover data and to ensure the spatiotemporal continuity of its monitoring. DOI: 10.3103/S1068373911090093 INTRODUCTION The snowmelt runoff hydrograph shape is predetermined by the spatial distribution of the snow cover during the snow melting and the predictability of characteristics of spring and summer floods depends greatly on the quality of information on this distribution. The surface measurements of snow cover characteristics require significant material expenditures and have been considerably reduced in Russia in recent 15–20 years. At the same time, an evident progress has been made in the world during these years in developing the methods of measuring the snow cover characteristics from space. First of all, the determination of snow water equivalent and snow coverage of the territory should be marked out. However, the errors of satellite measurements of snow cover characteristics depend greatly on meteorological conditions; therefore, the gaps often take place in these data and the accuracy of satellite information turns out to be insufficient to compute the runoff hydrograph, especially for the forest-covered catchments. The maps of the snow coverage of the territory for the globe have been plotted by NASA (the United States) since 2000 with the maximum spatial resolution of 500 m and maximum temporal resolution of once a day. When plotting the maps of snow coverage of the territory, the data of reflectivity of the Earth’s surface measured by MODIS radiometer within two wavelength bands are used. The accuracy of such measu- rements for the open territory at the cloudless weather is rather high (93% from the data of [11]) and, in a number of papers, these measurements are used for computing the recession part of the runoff hydrograph as the basic input information (for example, [8, 9, 12]). However, for the forest areas or at greater cloudiness, this information is not reliable. Since 2002, NASA has produced the daily AE-DySno maps of snow water equivalent for the whole globe with the resolution of 25 km. These maps are plotted on the basis of the difference in the brightness temperature in two frequency ranges measured with the AMSR-E radiometer installed on Aqua satellite of the Global Observing System. The error of snow water equivalent determination using this method is esti- mated by its authors as 25% [7] and it can be significantly larger for the forest-covered areas and when the snow becomes saturated with the snowmelt waters [10]. Comparison of the snow water equivalents ob- tained from the daily AE-DySno maps and those from the data of surface measurements in several areas of the European territory of Russia revealed that the errors of satellite measurements of snow water equivalent can reach 200% [6]. 630 ISSN 1068-3739, Russian Meteorology and Hydrology, 2011, Vol. 36, No. 9, pp. 630–637. Ó Allerton Press, Inc., 2011. Original Russian Text Ó L.S. Kuchment, A.N. Gel’fan, V.N. Demidov, P.Yu. Romanov, 2011, published in Meteorologiya i Gidrologiya, 2011, No. 9, pp. 86–96.