This animation shows daily snowpack estimates from Biome-BGC for one year out of a fourteen-year sequence (1983-1996). Snowpack is an important variable controlling soil temperature, which in turn is an important control on heterotrophic respiration (HR). Interannual variation in HR is a strong determinant of the net exchange of carbon in terrestrial ecosystems. These results help us to interpret the predictions of net ecosystem carbon exchange from Biome-BGC, and aid in the comparison of those predictions to observed interannual variations in the atmospheric CO2 concentration.