The Near Real Time Role of the DMSP Sensors in Monitoring Global Tropical Cyclones

The Defense Meteorological Satellite Program (DMSP) has provided multiple innovative technologies to low Earth-orbiting (LEO) satellites that benefited our ability to monitor global tropical cyclone (TC) location, structure, and intensity. The DMSP project included the first visible/infrared (Vis/IR) sensor (Operational Linescan System, OLS) designed to provide near constant instantaneous fields of view (IFOV) across the entire swath. This attribute permitted analysts to glean TC cloud structure in high resolution throughout the very large 3000 km swath and more accurately apply the Dvorak intensity method. The OLS also included a novel nighttime Vis channel whose sensitivity enables one to view nighttime cloud structure due to reflected moonlight. The early morning terminator orbit provided “first light” visible imagery crucial in defining low-level TC cloud structure for center-fixing purposes.

The Special Sensor Microwave Imager (SSM/I) became the first operational passive microwave (PMW) imager in 1987 when flown on DMSP F-8. The K, Ka and W-bands penetrate non-raining clouds, permitting TC structure views of rainbands and eyewall formation often obscured in Vis/IR imagery and a leading Dvorak technique limitation. The SSM/I enabled the retrieval of ocean surface winds, rainrate, total precipitable water (TPW), cloud liquid water (CLW), and other parameters globally. These data sets enhanced the DOD’s worldwide environmental TC characterization, including knowledge of the moisture or lack thereof in and around a TC. The SSM/I assisted in specifying the radius of gale force winds (>17 m/s) when rain permitted and the TPW/CLW mapping helped forecasters in predicting inland TC flooding.

A temperature sounding sensor (Special Sensor Microwave – Temperature (SSM/T) and then the Special Sensor Microwave – Humidity (SSM/T2) to profile atmospheric humidity were added in 1991. In 2003, the SSM/I, SSM/T and SSM/T2 sensors were combined into one sensor suite, the Special Sensor Microwave Imager Sounder (SSMIS). These profiles of temperature and moisture are crucial to mapping a TC’s warm core anomaly aloft and automated intensity algorithms were created that accurately assessed a storm’s maximum sustained winds (Vmax). Accurate objective algorithms have been created and used in NRT to detail a TC’s intensity and surface wind field using a combination of DMSP sensors both alone and in tandem with geostationary Vis/IR sensors, benefiting the trusty Dvorak method as well. Thus, due to their attributes, number of satellites in a unique orbit, and their longevity, the DMSP sensors have been linchpins on TC analyses, warnings, and forecasts benefiting millions within the vast TC global domain covered by multiple agencies.