Improving forecasts of tropical cyclogenesis and intensity change: the role of spaceborne Doppler radar

Tropical cyclones, particularly those far out at sea beyond the range of aircraft reconnaissance and land-based radar, have long posed challenges to modelers and forecasters alike. More daunting still is the process of tropical cyclogenesis, which numerical weather prediction models (NWPs) have to date shown little skill in capturing. Clearly, more data in these poorly observed regions would go a long way toward meeting these challenges. Indeed, spaceborne radar, such as that aboard the Tropical Rainfall Measuring Mission (TRMM) satellite, has already helped fill the data void to some degree, but the poor temporal resolution of the observations is a problem, as is the inability of the TRMM precipitation radar (PR) to resolve the vertical mass flux field.

To address these shortcomings, a new generation of satellites (both polar-orbiting and geosynchronous) have been proposed which would bring Doppler radar to space, making it possible to observe both the precipitation and vertical motion fields of cloud systems in the tropics with increasing frequency, resolution and, it is anticipated, to greater effect. Using the University of Wisconsin Nonhydrostatic Modeling System (UW-NMS), an Ensemble Square-Root Filter (EnSRF) is employed to gauge the impact these new observations have on simulations of both developing and mature Tropical Cyclones. It is shown that the new data have the potential to significantly improve forecasts of tropical cyclogenesis and intensity change, as well as provide greater insight into the physical mechanisms at work in these processes.