Located in a narrow canyon 15 km west of Boulder, Colorado, the Sunset pulsed Doppler radar was the first radar designed and constructed specifically as a VHF ST radar. The antenna system is a phased array of coaxial-colinear dopoles with computer-controlled phase shifters for each line of dipoles. It operates at a frequency of 40.475 MHz and a wavelength of 7.41M. Peak transmitter power is 100 kW. Aperture efficiency is 0.58 and resistive loss is 0.30 for its 3600 sq m area. The practical steering rate is 1 record/minute/position to any arbitrary antenna beam position. The first clear-air turbulence echoes and wind velocity measurements were obtained in 1974. Significant accomplishments are listed

Green, J. L.

English

NASA Technical Reports Server

320 
5.3A CHARACTERISTICS OF SUNSET RADAR 
J. L. Green 
NOAA, Aeronomy Laboratory 
325 Broadway 
Boulder, CO 80303 
The Sunset radar i s  a VHF, pulsed Doppler radar located i n  a narrow canyon 
near the Sunset townsite 15 lun w e s t  of Boulder, CO. T h i s  f a c i l i t y  i s  operated 
by the Aeronomy Laboratory, ERL, NOAA, exclusively for  meteorological research 
and the development of the MST and ST radar technique. 
ANTENNA 
The antenna system consis ts  of two colocated arrays,  each containing 16 
lines of coaxial-colinear dipoles. 
N-S v e r t i c a l  plane and the other i n  the E-W plane. 
necessary for  s t ee r ing  the antenna beam i s  provided by the in se r t ion  of 
remotely controlled phase s h i f t e r s  i n  the transmission l i n e  t o  each l i n e  of 
dipoles.  
hlh,....... XI256 can be summed). The p rac t i ca l  range of beam s t ee r ing  fo r  
meteorological experiments i s  345 due t o  the l o s s  of antenna gain with 
increasing zeni th  angle. The beam s t ee r ing  increment near the zeni th  i s  0.4' 
t o  take advantage of the sharp n u l l s  i n  the antenna pattern.  
s h i f t e r s  a l s o  perform the switching between the two arrays. 
i s  controlled by the on-line computer. 
One of these arrays can be steered i n  the 
The phase progression 
The phase s h i f t e r s  have binary format (i.e.,  phase increments of X/2, 
The phase 
Each phase s h i f t e r  
DATA PROCESSING 
On-line data  processing i s  performed by a Nova 800 computer. This com- 
puter provides radar control,  antenna s t ee r ing  control,  spectral  analysis  by a 
PFT algorithm, spec t r a l  averaging, on-line spectral  plot t ing,  and output t o  a 
tape recorder and a hard copy unit .  Control of the radar i s  by a 'benu" sub- 
routine t h a t  allows immediate changes i n  range gate  a l t i t u d e s ,  range ga te  
length, number of spectra averaged, and antenna beam posit ion.  
antenna posi t ions may a l so  be specified.  
Sequences of 
Coherent averaging i s  provided by analogue f i l t e r s  on each of the 16 range 
gates. The e f f ec t s  of ground c l u t t e r  are reduced by a 0 - 0.1 Hz notch i n  the 
response of these f i l t e r s .  Coherent averaging i s  especial ly  e f f ec t ive  because 
of the high pulse r e p e t i t i o n  frequency of the radar ( typical ly  6 kHz). 
Since March, 1981, ca l ib ra t ion  s ignals  from a s t a b l e  noise generator have 
been placed on each data tape for  each mode of operation used. 
brations,  along with the recorded transmitted power, are used t o  determine 
absolute radar r e f l e c t i v i t y .  
These C a l i -  
Magnetic data tapes are fu r the r  processed by a scal ing program on the 
cen t r a l  computing f a c i l i t y  of the Boulder Laboratories of NOAA. 
t h i s  program contains r a d i a l  veloci ty ,  veloci ty  width, received power, Cn , and 
the magnitude of the r e f l e c t i o n  coeff ic ient  f o r  each range gate. 
The outp t of Y 
HISTORY AND SIGNIFICANT ACCOMPLISHMENTS 
The Sunset radar was the f i r s t  radar designed and constructed spec i f i ca l ly  
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321 
Summary of Sunset radar cha rac t e r i s t i c s  
Frequency 
Wagelength 
Transmitter power 
Peak 
Average (maximum) 
( typical)  
40.475 MHz 
7.41 m 
100 kW 
16 kW 
2.5 kW 
Antenna 
Phased array of coaxial-colinear dipoles with eomputer- 
controlled phase s h i f t e r s  f o r  each l i n e  of dipoles - 
Area 
Aperture eff ic iency 
Resis t ive lo s s  
3600 mL 
0.58 
0.30 
S tee rab i l i t y  
Beam width H plane (s teerable)  4.8" 
(E-W o r  N-S v e r t i c a l  plane only) - + 60" 
E plane 4.4" 
Steering increment 0.2O 
Prac t i ca l  s t ee r ing  rate 1 record/minute/position 
t o  any a rb i t r a ry  antenna 
beam posi t ion 
as a VEF ST radar. Construction was begun i n  1973 and the f i r s t  c lear-air  
echoes and wind ve loc i ty  measurements were obtained i n  1974 (GREEN e t  a l . ,  
1975). The Sunset radar  has been used t o  demonstrate the f e a s i b i l i t y  of using 
an ST radar t o  measure wind ve loc i ty  (WARNOCK e t  al., 19781, a l l  t h ree  vectors  
of wind ve loc i ty  (GREEN e t  al., 1978a1, turbulence (VANZANDT e t  al.,  19781, 
wind v a r i a b i l i t y  (GAGE and CLARK, 19781, va r i a t ion  of c l ea r  a i r  turbulence near 
and above .thunderstorms (GREEN e t  al., 1978b), simultaneous measurement of 
hydrometeor and a i r  ve loc i ty  (GREEN e t  al., 1978b1, turbulence in t ens i ty  using 
ve loc i ty  width ( 1 9 7 8 ~ )  specular r e f l ec t ion  from s t ab le  layers  (GAGE and GREEN, 
1978), g rav i ty  (buoyancy) waves (VANZANDT e t  al., 19791, the height of the 
tropopause (GAGE and GREEN, 1979b1, turbulence parameters (GAGE e t  al., 1980) ; 
devise a p r a c t i c a l  and economical method of s t ee r ing  ST radar  antennas (GREEN 
e t  al., 1981); and estimate the gradient of temperature i n  the stratosphere 
(GAGE and GREEN, 1982). 
(References i n  t h i s  paper are included i n  the Publications l i s t e d  below.) 
PUBLICATIONS RELATED TO THE SUNSET RADAR 
Green, J. L., J. M. Warnock, R. H. Winkler and T. E. VanZandt (19751, Studies 
of winds i n  the upper troposphere with a sens i t i ve  VHF radar,  Geophvs. 
Res. Let t . ,  2, 19. 
Green, J. L., J. M. Warnock, R. H.  Winkler and T. E. VanZandt (19751, A 
s ens i t i ve  VJiF radar  fo r  the study of winds, waes, and turbulence i n  the 
troposphere, stratosphere,  and mesosphere, 16th Radar Meteorol. Conf., 
Houston, Am. Meteorol. SOC. 
VanZandt, T. E., J. L. Green, J. M. Warnock and R. W. Winkler (19751, Studies 
of winds i n  the upper troposphere with a s ens i t i ve  VEF radar,  16th Radar 
Meteorol. Con., Houston, AMS, April 22-24. 
322 
VanZandt, T. E., J. L. Green, J. M. Warnock, K. S. Gage and W. L. Clark (19771, 
Reflect ivi ty  studies with the Sunset VHF pulsed Doppler radar,  Proc. Symp. 
on Radio Prop, and Non-ionized Media, 28 April - 6 May, Centre National 
d' Etudes des Telecommunications, Par is ,  France, 519-524. 
B. B. Balsley and J. L. Green (19781, Coherent radar systems f o r  probing the 
troposphere, s t ra tosphere,  and mesosphere, Proc. 4 t h  Symp. on Meteorol. 
Observations and Instrumentation, April  10-14, 1978, Denver, CO, 227-230. 
Gage, K. S. (19781, Comparison of s ens i t i ve  Doppler radar  observations of winds 
and turbulence with i n  s i t u  observations, Proc. 4th Symp. on Meteorol., 
Observations and Instrumentation, April  10-14, Denver, CO, 231-238. 
Gage, K. S. and J. L. Green (1978), Evidence f o r  specular r e f l ec t ion  from 
monostatic VHF radar  observations of the stratosphere,  Radio Sci., 13, 
991-1001. 
Gage, K. S., J. L. Green and T. E. VanZandt (19781, Application of the VHF 
pulsed Doppler radar t o  cloud physics research, Proc. Conf. on Cloud 
Physics and Atmospheric E l e c t r i c i t y ,  July 31 - August 4,  1978, Issaquah, 
Wash. 394-401. 
Gage, K. S. and B. B. Balsley (19781, Doppler radar probing of the clear 
atmosphere, Bull. h e r .  Meteorol. SOC.. 59, 1074-1093. 
Gage, K. S. and W. L. Clark (19781, Mesoscale v a r i a b i l i t y  of j e t  stream winds 
observed by t h e  Sunset VBF Doppler radar ,  J. Applied Meteorol.. 17, 1412- 
1416. 
Gage, K. S., T. E. VanZandt and J. L. Green (19781, Vert ical  p r o f i l e s  of C i n  
the f r e e  atmosphere: Comparison of model calculat ions with radar observa- 
t i ons  Proc. 18th Conf. on Radar Meteorol., March 28-31, 1978, Atlanta,  GAS 
184-189. 
Green, J. L., K. S. Gage and T. E. VanZandt (1978~1,  VHF Doppler s tudies  of CAT 
i n  the troposphere and lower s t ra tosphere,  Preprint  Vola Conf. OD. Atmos. 
Environment of Aerospace Systems and Appl. Meteorol., NOV. 14-16, New 
York, NY, 159-164. 
Green, J. L., K. S. Gage and T. E. VanZandt (1978a), Three dimensional wind 
observations of a j e t  stream using a VHF Doppler radar,  Proc. 18th Conf. on 
, Radar Meteorol., March 28-31, Atlanta, GA, 184-189. 
Green, J. L., R. H. Winkler, J. M. Warnock, W. L. Clark, K. S. Gage and 
T. E. VanZandt (1978b) , Observations of enhanced clear a i r  r e f l e c t i v i t y  
associated with convective clouds , Proc. 18th Conf . on Radar Meteorol. , 
March 28-31, Atlanta, GA, 88-93. 
VanZandt, T. E., J. L. Green, I. S. Gage and W. L. Clark, (19781, Vert ical  
p ro f i l e s  of r e f r a c t i v i t y  turbulence s t ruc tu re  constant: 
observations by the Sunset radar with a new theo re t i ca l  model, Radio 
Sci., 13, 818-829. 
comparison of 
Warnock, J. M., T. E. VanZandt, J. L. Green and R. H. Winkler (19781, Compari- 
sons between wind p ro f i l e s  measured by Doppler radar and by rawindsonde 
balloons, Geophvs. Res. Le t t . ,  5, 109-112. 
Gage, K. S., J. L: G r e e n ,  W. L. Clark and T. E. VanZandt (19791, Doppler radar 
measurement of turbulence i n  the c l ea r  atmosphere, Proc. Conf. Fourth 
Symp. on Turbulence, Diffusion and A i r  Pollution, January 15-18, Reno, 
Nevada, 522-529. 
323 
Gage, K. S. and J. L. Green (1979b), Tropopause detect ion by p a r t i a l  specular 
r e f l e c t i o n  using VHF radar,  Science. 203, 1238-1240. 
Green, J. L., K. S. Gage and T. E. VanZandt (19791, Atmospheric measurements by 
VHF pulsed Doppler radar,  IEEE Trans, on Geosci. Elec,. GE-17, 262-280. 
VanZandt, T. E., K. S. Gage and J, M. Warnock (19791, A s t a t i s t i c a l  model f o r  
the probabi l i ty  of turbulence and t h e  calculat ion of v e r t i c a l  p ro f i l e s  of 
turbulence parameters, Proc. Conf. Fourth Symp. on Turbulence, Diffusion, 
and A i r  Pollution, January 15-18, Reno, Nevada, 52-55. 
VanZandt, T. E., J. L. Green, W. L. Clark and J. R. Grant (19791, Buoyancy 
waves i n  the troposphere: 
model, Geoohvs. Res. Let t . .  6, 429-432. 
Doppler radar observations and a theo re t i ca l  
Gage, K. S., J. L. Green and T. E. VanZandt (19801, Use of Doppler radar fo r  
the measurement of atmospheric turbulence parameters from the in t ens i ty  
of c lear-air  echoes, Radio Sci., 15, 407-416. 
Green, J. L. and K, S. Gage (19801, Observations of s t a b l e  layers  i n  the tropo- 
sphere and s t ra tosphere using VHF radar,  Radio Sci., 15, 395-405. 
VanZandt, T. E., K. S. Gage, and J. M. Warnock (19801, Progress i n  modelling 
turbulence parameters from pro f i l e s  of background winds, temperature, and 
humidity, Proc. AMS 19th Conf. on Radar Meteorol., April  15-18, 613-615. 
Gage, K, S. and J. L. Green (19801, Prospects f o r  a quantative measurement of 
atmospheric s t a b i l i t y  using VHF radar,  Proc. AMs 19th Conf. on Radar 
Meteorol., April 15-18, M i a m i  Beach, FL, 605-612. 
Green, J. L., J. M. Warnock, W. L. Clark and F. J. Eggert (19801, Modifications 
t o  the Sunset radar t o  provide beam steer ing,  Proc. AMs 19th Conf. on Radar 
Meteorol., April 15-18, Miami Beach, FL, 575-576. 
Green, J. L., K. S. Gage, W. L. Clark, T. E. VanZandt and P. H. Hildebrand 
(19801, J o i n t  instrumented a i r c r a f t  and VHF Doppler radar  measurements of 
wind near Boulder, CO, Proc. AMs 19th Conf. on Radar Meteorol., 
April  15-18, M i a m i  Beach, FL, 624-628. 
VanZandt, T. E., K. S. Gage and J. L. Green (19791, The use of Doppler radar  
measurement of atmospheric turbulence parameters i n  t h e  c l ea r  atmosphere, 
Collection of Extended Abstracts Presented a t  ICMUA Sessions and IUGG 
Symp. 18, XVII IUGG Gen. Assemb., Canberra, Australia,  285-292. 
Gage, K. S. and J. L. Green (1979a), Observations of s t a b l e  layers  i n  the middle . 
atmosphere using VHF radar,  Collection of Extended Abstracts Presented a t  
ICMUA Sessions and IUGG Symp. 18, WII IUGG Gen. Assemb., Canberra, 
Austral ia ,  325-332. 
Gage, K. S., B. B. Balsley and J. L. Green (19811, Fresnel s ca t t e r ing  model fo r  
the specular echoes observed by VHF radar,  Radio Sci.. 16, 1447-1453. 
Gage, K. S. and J. L. Green (19821, A technique fo r  determining the  temperature 
p r o f i l e  from VHF radar observations, J. A D P ~ .  Meteorol.. 21, 1155-1158. 
Balsley, B. B., J. L. Green, W. L. Ecklund, W. L. Clark, R. G. Strauch and 
A. C. Riddle (19811, Jo in t  observations of gravi ty  w a v e  a c t i v i t y  i n  v e r t i -  
cal winds i n  the troposphere and lower stratosphere Over a 63 km baseline 
obtained with clear-air  VHF radars  a t  P l a t t w i l l e  and Sunset, Colorado, 
Preprint  Vola 20th Conf. on Radar Meteorol., Boston, Nov 30 - Dec 3, AMS, 
110-115. 
324 
G r e e n ,  3. L., J. M. Warnock, W. L. Clark, F. J. Eggert and K. J. Ruth (19811, 
Modifications t o  the Sunset radar t o  provide antenna beam steer ing,  Pre- 
p r i n t  Vol., 20th Conf. on Radar Meteorol., Boston, Nov 30 - Dec 3, AMs, 
7-10. 
VanZandt, T. E.,, K, S. Gage and J. M. Warnock (19811, An improved model for  the 
c s l cu la t ion  of p r o f i l e s  of C 
p r o f i l e s  of wind, temperature and humidity, Preprint  Vol., 20th Conf. on 
Radar Meteorol., Boston, MA, N w  30 - Dec 3, AMs, 129-135. 
and i n  the f r e e  atmosphere from background 
Ecklund, W. L., K. S. Gage, B. B. Balsley, R. G. Strauch and J. L. Green 
(19821, Vert ical  wind v a r i a b i l i t y  observed by VHF radar  i n  the l e e  of the 
Colorado Rockies, Mon. Wea. Rev.. 110, 1451-1457. 


Characteristics of Sunset radar

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