Scale Analysis of Spatial and Temporal Variability in Observations of Tropical Cyclones

Recent increases in computational power have allowed corresponding increases in the spatial resolution of numerical simulations of tropical cyclones. These high resolution simulations generate complex multiscale structure in the moisture and wind fields. Models typically have several physics options for PBL, microphysics or cumulus convection and they generally show a sensitivity to the choice of model physics options that is case-dependent and dependent on model resolution. The question arises as to whether there are any general statistical characteristics of the observed variability that can be used to evaluate whether the model-generated small scale variability is realistic.

To address this question, we present a comprehensive cross-platform study of scale-dependent variability in tropical cyclones based on observations from satellite, aircraft in-situ and radar, with emphasis on spatial scales below 10 km. Measures of variability are based on both one-point and two-point probability distribution functions (PDFs) of field increments over a range of scales. The PDFs are conditioned on dynamical regime or environmental forcing, and statistical signatures of the underlying dynamical processes are often revealed by considering the statistics of one variable conditioned on another. Statistical symmetries (homogeneity, stationarity and isotropy) are also investigated.