Multiscale observations of tropical cyclone structure using airborne Doppler composites

Advances in the prediction of tropical cyclone (TC) structure, intensity, and rainfall have lagged behind advances in track prediction. A primary reason for this lag is the challenge required to properly represent the multiple spatial and temporal scales that play a key role in these processes, where spatial scales range from 1000's of km to mm and temporal scales range from days to seconds. A better understanding and modeling of these processes is necessary before significant forecast improvements can be realized. Observations across these scales therefore play an important role in this task, both in improving our understanding of the relevant physical processes and the modeling of them through rigorous data assimilation and detailed model evaluation.

The NOAA Hurricane Research Division has been collecting airborne Doppler radar data in tropical cyclones for the past 30 years. These data has been used to identify many basic aspects of the vortex- and convective-scale structure and evolution, primarily by analyzing data from individual cases. In this work, composites of tropical cyclone structure derived from a database of Doppler observations from many tropical cyclones will be presented for the first time. These composites will present information across multiple scales: the vortex-scale structure in three dimensions, convective-scale features and how they vary within the vortex, and structures in the tropical cyclone boundary layer. The use of a compositing technique produces robust measurements that can be applied in a variety of situations. For example, they can be used to identify possible differences in vortex- and convective-scale structures in tropical cyclones that undergo rapid intensification vs. those that do not, and they can be used to evaluate model-generated tropical cyclone structures for a multitude of simulations in a variety of scenarios. Some examples of this utility will be presented.