Wednesday, 1 August 2001
Initialization of a hurricane vortex with single-Doppler radar data
A method for hurricane vortex initialization has been developed that
utilizes the bounded derivative initialization (BDI) in conjunction with
the vorticity method to accurately determine the hurricane vortex dynamic
structure based on the single Doppler radar wind fields retrieved from the
ground-based velocity track display (GBVTD) technique. The GBVTD
technique retrieves the reliable rotational wind and vorticity of a
tropical cyclone (TC) from single Doppler radar data. Based on the
momentum conservation, the vorticity method derives the hurricane
divergent wind/vertical velocity from the high temporal and spatial
vorticity variations retrieved by GBVTD. The divergent wind field,
inferred dynamically, is used in conjunction with the rotational wind
observed from single Doppler radar data to determine the total wind field,
including the vertical velocity in a hurricane vortex. BDI derives smooth
initial fields that evolve smoothly on the advective timescale by
requiring a number of time derivatives in the initial data order of unity.
In this study, BDI is used to smoothly insert the three-dimensional
hurricane wind fields into the environmental flow defined by the
analysis/forecast fields output from larger scale models such as the Eta
model. BDI provides an effective way to reduce the amplitude of fast waves
generated by the inconsistent initial states between the derived
three-dimensional vortex wind and the environmental Eta fields.
Supplementary URL: