Advancing Tropical Cyclone Forecasts Using Aircraft Observations - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 177

5. Airborne Doppler Radar
Radar played an important role in studies of tropical cyclones since it was
developed in the 1940s. In the last 15 years, technological improvements such
as the P-3 tail airborne Doppler radar on the P-3s, the operational Weather
Service Radar 1988-Doppler (WSR-88D) radar network, and portable Doppler
radars produced a new generation of TC data which have given scientists an
unprecedented opportunity to document the dynamics of tropical cyclones and
hence led to improved understanding of these devastating storms. Airborne
Doppler radar data sets collected in the 1980s represented our best information
on the kinematic structure of TCs (e.g., Marks and Houze, 1984, 1987; Marks
et al., 1992; Houze et al., 1992; Gamache et al., 1993), while airborne and
ground-based Doppler radars were instrumental in determining the kinematic
structure of the outer rainbands (e.g., Ishihara et al., 1986; Powell, 1990a,b;
Barnes et al., 1991; Tabata et al., 1992; Ryan et al., 1992; Barnes and Powell,
1995). These data sets revolutionized our perception of the kinematic structure
of a mature tropical cyclone from an axisymmetric vortex to one that recognizes
the significance of asymmetric motions to track and intensity changes.
The NOAA P-3 airborne Doppler datasets were used for improved
understanding of symmetric vortex and major asymmetries. The addition of a
second airborne Doppler radar on the other P-3 enabled true dual-Doppler
analyses and the ability to study the temporal evolution of the kinematic structure
over 3-6 h. The advent of the WSR-88D Doppler radar network, and
construction of portable Doppler radars that can be moved to a location near
tropical cyclone landfall have also generated new and unique datasets enabling
improved understanding of (1) severe weather events associated with landfalling
tropical cyclones, (2) boundary layer wind structure as the storm moves from
over the sea to over land, and (3) spatial and temporal changes in the storm
rain distribution. The P-3 airborne Doppler and WSR-88D data have also been
instrumental in developing a suite of operational single Doppler radar algorithms
to objectively analyze a tropical cyclone's wind field by determining the storm
location and defining the primary, secondary, and major asymmetric circulations.
These algorithms are used operationally on the P-3 aircraft and on the ground
at NOAA's National Hurricane Center.
Using the first Doppler radar measurements obtained in a TC, Marks and
Houze (1984) described for the first time important asymmetric TC structure
characteristics. Data from orthogonal flight legs from one aircraft were
combined into a three-dimensional pseudo-dual-Doppler horizontal wind
analysis assuming that features were stationary during the observation time
(e.g., Fig. 7). This allowed for the first description of mesocyclones associated
with potentially destructive local wind speed maxima superimposed on the
basic flow. Marks and Houze (1987) first documented the three-dimensional
kinematic asymmetric eyewall structure with another pseudo-dual-Doppler
analysis. They extended the composite structure of Jorgensen (1984b) in