revisiting estimation of tc winds from ir imagery
TRANSCRIPT
Revisiting estimation of TC winds from IR Imagery
Making sense of the data
Data and documentation• Flight-level data (1995-2012)• Estimates of tangential wind
at the 500km radius (GFS)• IR images (3-hourly here)• Best track (intensity, motion)• Methods to estimate surface
inflow angles• Methods to reduce winds
from flight-level to the surface
Analyses• Analyze aircraft data on a
polar grid, motion relative– Apply surface reduction– Decompose into wavenumber
0, 1, and 2
• Analyze IR images on a polar grid, motion relative– Decompose into 2-D principle
components
Method• Single-field principle component analysis (SFPCA; Bretherton
et al. 1992) applied to the amplitude and phase of the wind field– This relates intensity, latitude, translation speed, and the IR principle
components to the surface wind speeds
• Extrapolate the Amplitudes of wavenumbers through the 166km to 500km region of the vortex
• Apply inflow angles that are a function of translation speed, intensity, radius, and the radius of maximum wind (Zhang and Uhlhorn 2012)
Example Hurricane Ike 10 Sep 2008 18UTC
3-hourly wind estimates Ike 2008