Printer Friendly Version

WP-3D Radars


Each WP-3D aircraft has three radars: nose, lower fuselage and tail. The nose radar (a solid-state C-band radar with a 5° circular beam) is used strictly for flight safety and is not recorded for research purposes. The lower fuselage and tail radars are used for research purposes and the data are recorded on 9-track tape prior to 1993 and on Digital Audio Tape since 1993. The lower fuselage and tail radar characteristics are:

Device Parameter Units Lower Fuselage Tail
Transmitter Frequency MHz 5370 9315
Wavelength cm 5.59 3.22
PRF Hz 200 1600-3200
Pulse Length µs
(m)
6.0
(1800)
0.25-0.50
(75-150)
Peak Power kW 70.0 60.0
Minimum Detectable Signal dBm -109 -111
Antenna Hor. Beam Width deg 1.1 1.35
Vert. Beam Width deg 4.1 1.90
Gain dB 37.5 40.0
Polarization N/A linear
(horizontal)
linear
(vertical)
Stabilization deg ±5
(pitch, roll)
±25
(pitch, drift)
Radar Velocity Nyquist interval m/s N/A ±12.88 - ±25.6
Maximum unambiguous range km 750. 93.75 - 46.0
Example Olivia
(1992)

The major drawback of the Lower Fuselage radar is the large vertical beamwidth (4.1°) which causes inadequate illumination of the targets in the beam. Inadequate beam filling is a severe problem in the estimation of the reflectivity of a storm at ranges >60-90 km (see the Appendix of Marks, 1985). The critical parameters that determine the beam illumination of the target storm are the beam's vertical dimension and orientation, and the aircraft altitude. At close range there is little loss because the radar beam is narrow enough to be totally within the strong reflectivity region at lower altitudes in the storm. As range increases, the height of the center of the beam increases and more of the beam is unfilled, or filled with the less reflective portion of the storm. This problem can be solved by compositing a number of radar sweeps in time over a fixed domain (storm- or earth-relative)

The major drawback of the Tail radar is the 3.22 cm wavelength (X-band) and high PRF. X-Band radars suffer from intervening rain attenuation which limit the maximum range at which Doppler estimates are obtained. This problem is remedied by flying close to the area of interest, reducing the distance the beam has to travel through the intervening rainfall. The high PRF, coupled with the short wavelength result in a low velocity Nyquist interval and unambiguous range. The low Nyquist velocity is the hardest of the two to compensate for as intervening attenuation minimizes problems with second trip echoes. The low Nyquist velocity can be overcome through unfolding utilizing the measured component of the air velocity along the radar beam at the aircraft as a first guess. HRD has successfully unfolded velocities as high as 90 m/s using this approach in hurricanes.


References

Kollias, P., B.A. Albrecht, and F.D. Marks. 2003 "Cloud radar observations of vertical drafts and microphysics in convective rain." Journal of Geophysical Research, 108(D2) pp.4053

Black, M.L., J.F. Gamache, F.D. Marks, C.E. Samsury, and H.E. Willoughby. 2002 "Eastern Pacific Hurricanes Jimena of 1991 and Olivia of 1994 pp. The effect of vertical shear on structure and intensity." Monthly Weather Review, 130(9) pp.2291-2312

Kollias, P., B.A. Albrecht, and F.D. Marks. 2002 "Why Mie?" Bulletin of the American Meteorological Society, 83(10) pp.1471-1483

Walsh, E.J., C.W. Wright, D. Vandemark, W.B. Krabill, A.W. Garcia, S.H. Houston, S.T. Murillo, M.D. Powell, P.G. Black, and F.D. Marks. 2002 "Hurricane directional wave spectrum spatial variation at landfall." Journal of Physical Oceanography, 32(6) pp.1667-1684

Atlas, D., C.W. Ulbrich, F.D. Marks, R.A. Black, E. Amitai, P.T. Willis, and C.E. Samsury. 2000 "Partitioning tropical oceanic convective and stratiform rains by draft strength." Journal of Geophysical Research, 105(D2) pp.2259-2267

Lee, W.-C., and F.D. Marks. 2000 "Tropical cyclone kinematic structure retrieved from single Doppler radar observations, Part II: The GBVTD-simplex center finding algorithm." Monthly Weather Review, 128(6) pp.1925-1936

Lee, W.-C., B. J.-D. Jou, P.-L. Chang, and F.D. Marks. 2000 "Tropical cyclone kinematic structure retrieved from single-Doppler radar observations. Part III: Evolution and structures of Typhoon Alex (1987)." Monthly Weather Review, 128(12) pp.3982-4001

Reasor, P.D., M.T. Montgomery, F.D. Marks, and J.F. Gamache. 2000 "Low-wavenumber structure and evolution of the hurricane inner core observed by airborne dual-Doppler radar." Monthly Weather Review, 128(6) pp.1653-1680

Rogers, R.F., J.M. Fritsch, and W.C. Lambert. 2000 "A simple technique for using radar data in the dynamic initialization of a mesoscale model." Monthly Weather Review, 128(7) pp.2560-2574

Dodge, P.P., R.W. Burpee, and F.D. Marks. 1999 "The kinematic structure of a hurricane with sea-level pressure less than 900 mb." Monthly Weather Review, 127(6) pp.987-1004

Black, M.L., R.W. Burpee, and F.D. Marks. 1996 "Vertical motion characteristics of tropical cyclones determined with airborne Doppler radial velocities." Journal of the Atmospheric Sciences, 53(13) pp.1887-1909

Marks, F.D., 1985 "Evolution and structure of precipitation in Hurricane Allen (1980)." Mon. Wea. Rev., 113, 909-930.


For more information on the Radars mail to : Frank.Marks@noaa.gov

Return to aircraft page.
Return to HRD page.

Updated June 16, 2003

Employee Tools
Stay Connected