Thursday, 13 February 2003
Initialization of a hurricane vortex based on single-doppler radar observation
An initialization scheme for tropical storms has been developed and
used to initialize hurricane Danny (1997) for a high resolution
numerical simulation with MM5/WRF mesoscale models.
The newly developed initialization scheme
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.
BDI combines
the divergent wind field inferred dynamically and the rotational wind
observed from single Doppler radar data to determine the total wind field,
including the vertical velocity in a hurricane vortex.
BDI is also used to smoothly insert the derived hurricane vortex intoenvironmental flows defined by forecast fields from larger scale models.
The MM5 four-dimensional data assimilation system (FDDA) is used to nudge to thederived smooth kinematic wind fields in order to retrieve unobserved fields
such as temperature and moisture fields. The balanced hurricane vortex with
thermodynamic and moisture fields is used as the initial condition for the
simulation of hurricane Danny with high resolution MM5/WRF models.
Supplementary URL: