[From NOAA HRD]
On September 14, 1982, while NOAA42 was flying the first Synoptic Flow experiment, NOAA43 was taking the first Doppler radar readings from an aircraft in a tropical cyclone. The flight into Hurricane Debby was designed to fly several legs into and out of the eye, forming triangular areas where the radar scans would overlap from different segments of the flight track. This allowed researchers to calculate (post-flight) the wind vectors within the overlap area. Prior to this, the only wind measurements taken within tropical cyclones were just along the flight track of the aircraft. Now the entire wind field of the core of a hurricane could be calculated from a single flight.
[Detail of the track of flight into Hurricane Debby. From NOAA]
Using the Debby measurements, Frank Marks and Bob 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 (see figure at top). This allowed for the first description of mesocyclones associated with potentially destructive local wind speed maxima superimposed on the basic flow.
Prior to the 1982 Hurricane Field Program, the tail radar of the NOAA43 aircraft had been modified to take Doppler measurements. Named for Christian Doppler, such radars read not only the strength of the return signal but also the shift in frequency of the return. This shift is proportional to the speed of the target toward or away from the radar antenna. If an area of precipitation is measured by two Doppler radars or by one Doppler radar from two locations (such as from a moving aircraft) then the vectors of the rain particles’ motions can be calculated.
Edited for WeatherNation by Meteorologist Mace Michaels