Although soil moisture strongly affects plant growth and the evolution of both weather and climate, there is no global network to measure it. When accurate readings of soil moisture are fed into weather and climate models, the forecast quality improves and longer lead times become possible. Soil moisture is one of the leading factors in flood and landslide risk, and it also plays an important role in the global carbon cycle through its effects on plant growth.
Many field studies have shown that microwave radars provide useful data on soil moisture. SMAP combines an active radar with passive radiometer, allowing soil moisture to be measured and analyzed globally at a resolution of 3 to 10 kilometers every 2 to 3 days. The results help Earth scientists to better represent the water, energy, and carbon cycles in global models of weather and climate. Significant advances in long-range weather and seasonal forecasting become possible, and the data help build a new generation of hydrologic models for predicting and studying floods and droughts.