The ash ejected into the atmosphere by the Eyjafjalla Icelandic volcano during its recent eruption posed such a threat to flights over much of Europe that the ensuing cancellations resulted in an unprecedented disruption of the European commercial air transportation system. Volcanic ash is not only a significant hazard to aircraft operations but also to public safety from volcanic ash fall at the surface. Given the significance of the hazards posed by volcanic ash, timely detection and tracking of the erupted ash cloud is essential to a successful warning process, particularly during and immediately following an eruptive event. In the March issue of IEEE Signal Processing Magazine, the column article written by Dr. Frank S. Marzano, discusses ground-based radar (radio detection and ranging) data processing for ash cloud remote sensing. From this article, the readers can learn more on the physical basis of retrieval algorithms and their applications on volcanic ash monitoring.