An automated method for the documentation of cloud-top characteristics of mesoscale convective systems

Measurements of cloud-top area, centroid, and eccentricity for mesoscale convective systems (MCS's) have been automated. The algorithm resides on the PROFS-2 VAX 11/780 computer and utilizes digital infrared imagery received at the local satellite ground station. The software is user-activated and processes one image per run. All operations are performed within the bounds of a user-defined image subsector. Cloud tops are isolated at a threshold of -52°C; if the area at this threshold exceeds 10,000 km2, the storm is documented. Documentation includes area and centroid measurements at -52°C, -58°C, -64°C, -70°C, and -76°C. Also, the eccentricity of the storm is estimated by fitting an ellipse to the -52°C envelope and computing the ratio of the minor to major axis. Results are written to file for later printing, and to a RAMTEK monitor. On the monitor, the processed sector is displayed with a geographical map background, cloud tops are color-coded according to the five threshold temperatures, and the major and minor axes' endpoints of best-fit ellipses to documented storms are highlighted. Tests have shown that the algorithm provides acceptable results as long as storm cloud tops are isolated from one another and are well defined. However, on occasions when storms are merged at the cloud definition threshold (-52°C), the algorithm has no way to objectively separate them, and thus erroneously documents the merged storms as one large MCS.