The need to study vertical velocity measurements from an ST radar located on the plains, far from the mountains is pointed out, as all presently available clear-air radars are located in or near mountains. The construction and operation of a VHF Doppler (ST) radar in the midwestern part of the United States to make meteorological measurements is also discussed. While primary interest is in measuring the synoptic-scale vertical velocities in the troposphere and lower stratosphere, it should be stressed, however, that the radar data set generated during the radar experiment would have many other valuable uses of interest to us and others some of whom are listed below. The required radar parameters, approximate costs, and recommended mode of operation are also detailed

Green, J. L.

Nastrom, G. D.

English

NASA Technical Reports Server

9.17A MEASUREMl3NTS OF VERTICAL VELOCITY OVER FLAT TERRAIN BY. ST RADAR 
AND OlIIER RELATED USES OF THE RADAR DATA SET 
3 .  L. Green and G. D. Nastrom* 
Aeronomy Laboratory, NOAA, Boulder, CO 80303 
*Control Data Corp., l i nneapo l i  s, MN 55440 
The f i r s t  par t  of t h i s  communication points  out the need t o  study v e r t i c a l  
ve loc i ty  measurements from an ST rada r  located  on the p la ins ,  f a r  from the 
mountains, As a l l  present ly  ava i l ab le  c lear-a i r  radars  a r e  located  i n  or  near 
mountains, the  second par t  d iscusses  the const ruct ion and opera t ion of a VIIF 
Doppler (ST) radar  i n  t h e  midwestern pa r t  of the  United S ta t e s  t o  make meteoro- 
l o g i c a l  measurements. While our primary i n t e r e s t  i s  i n  measuring the  synoptic- 
s c a l e  v e r t i c a l  v e l o c i t i e s  i n  the  troposphere and lower s t ra tosphere ,  it should 
be s t ressed,  however, t h a t  the  radar  data  s e t  generated during the  radar  ex- 
periment would have many o the r  valuable  uses of i n t e r e s t  t o  us and o the r s  some 
of whom a r e  l i s t e d  below. The required r ada r  parameters, approximate cos ts ,  
and recommended mode of opera t ion a r e  a l so  deta i led .  
SCIENTIFIC ISSUE 
The v e r t i c a l  ve loc i ty  i s  the atmospheric va r i ab le  most c lose ly  l inked with 
weather, except perhaps moisture, ye t  i t  has been almost impossible t o  measure 
d i r ec t ly .  Clear-air, or ST rada r s  o f f e r  an opportunity t o  measure the  v e r t i c a l  
ve loc i ty  d i r e c t l y  and continuously. I n  a recent study we found t h a t  the  time- 
average v e r t i c a l  motion over the P l a t t e v i l l e ,  Colorado ST rada r  compared favor- 
ably with the computed synoptic-scale v e r t i c a l  ve loci ty  under c e r t a i n  synoptic 
condit ions:  when the  prevai l ing  winds were l i g h t  or from the  eas t  and the 
synoptic-scale v e r t i c a l  ve loc i ty  was over one or two centimeters per secone . 
When the prevai l ing  winds were from the west., across  the Rocky Mountains, the  
meteorological  qoise was too l a r g e  t o  permit Computing a mean v e r t i c a l  ve loc i ty  
with s u f f i c i e n t l y  small s t a t i s t i c a l  uncer ta in ty ,  or  e l se  standing l e e  waves 
made the radar  s i t e  unrepresentative of the  l a rge  .geographical area  of the 
synoptic-scale system. I n  e i t h e r  case, it i s  a meteorological signal-to-noise 
problem induced by the  mountains. We have found a s imi lar  s i t u a t i o n  i n  the  
ALPlX da ta  from Southern France, i.e., when the  winds were off  the sea the 
measured and computed v e r t i c a l  v e l o c i t i e s  agreed favorably but when the  winds 
were across the mountains the  agreenent was poor or uncertain. Thus, we can 
conclude t h a t  a t  ST radar  s t a t i o n s  near mountains the synoptic-scale v e r t i c a l  
ve loc i ty  can be measured only under r e s t r i c t e d  conditions. These s t a t i s t i c s  
s t rongly  suggest t h a t  it may be poss ib le  t o  measure the large-scale v e r t i c a l  
ve loc i ty  under general  condit ions a t  a radar  s i t e  located i n  the  plains.  This 
ques t ion should be addressed by using radar  data from a s i t e  on the plains.  
The only MST radar  located i n  the cen t ra l  p l a i n s  a t  t h i s  time i s  a t  the 
Universi ty of I l l i n o i s ;  i t  does not measure the v e r t i c a l  ve loc i ty  and according 
t o  Prof. S. A. Bowhill, it could not  e a s i l y  be adapted f o r  t h a t  purpose. 
Thus we propose i n s t a l l i n g  an ST rada r  a t  a s i t e  i n  the  cen t ra l  p la ins ,  
and opera t ing continuously f o r  a t  l e a s t  a year ,  taking measurements of the 
v e r t i c a l  ve loc i ty  i n  the troposphere and lower s t ra tosphere ,  and comparing the  
r ada r  w ' s  wi th  computed values  and with proxy ind ica to r s  of the large-scale 
v e r t i c a l  motion such as  weather-radar echoes and s a t e l l i t e  p ic tures .  We 
expect these "Flatlands" d a t a  would be of i n t e r e s t  f o r  o ther  purposes a s  we l l ,  
both meteorological  and rada r  engineering, and we would; of course, make it 
ava i l ab le  t o  o ther  s c i e n t i s t s .  I f  the a b i l i t y  t o  measure the synoptic-scale 
v e r t i c a l  ve loc i ty  can be dwons t ra t ed ,  t h i s  technique~should  impact a wide 
meteorological  community. For example, research prograns such as  the  upcoming 
https://ntrs.nasa.gov/search.jsp?R=19850024237 2020-03-20T18:20:54+00:00Z
STORM project  may be enhanced by adding v e r t i c a l  ve loci ty  measurenents t o  t h e i r  
da ta  base. 
This r ada r  could be constructed t o  point  ju s t  v e r t i c a l l y  or  be made t o  
po in t  i t s  antenna bean sequent ia l ly  t o  the v e r t i c a l  and four  oblique d i r ec t ions .  
A p r a c t i c a l  da ta  r a t e  i s  one complete sequence of antenna d i r e c t i o n s  i n  500 6. 
This technique has already been t e s t ed  a t  the Sunset radar ;  it o f f e r s  the  
advantage of hor izonta l  wind measurenent t o  a i d  i n t e r p r e t a t i o n  and provides, by 
the  cont inui ty  equation, a kinematic check on the v e r t i c a l l y  pointed bean's 
measurwents.  This capab i l i ty  would permit us t o  resolve  any l inger ing 
ques t ions  regarding the  i n t e r p r e t a t i o n  of the  v e r t i c a l  ve loc i ty  measurements 
from a v e r t i c a l l y  d i r ec ted  r ada r  bean. For example, a primary r e f l e c t i n g  
mechanism f o r  the v e r t i c a l  bean i s  specular r e f l e c t i o n s  from specular layers.  
I f  the  s t a b l e  l aye r s  a r e  moving v e r t i c a l l y  a t  a r a t e  d i f f e r e n t  from the  a i r  
ve loc i ty ,  say a t  some phase ve loc i ty ,  the  r ada r  could give misleading r e s u l t s .  
By using the  s teer ing capab i l i ty  we can address t h i s  and any other  i s sues  of 
in t e rp re ta t ion .  Addit ionally,  the  s l a n t  antenna bean r e f l e c t i v i t y  would 
provide a measure of the  i n t e n s i t y  of turbulence versus  a l t i t u d e  ( the  v a r i a b l e  
Cn2). Studies of the  specular r e f l e c t i o n  phenomenon and tropopause 
de tec t ion  would be enhanced by the comparison of the v e r t i c a l  beam with the 
o f f -ve r t i ca l  beans. Spectra from the time s e r i e s  of the s l an t  a s  we l l  a s  the  
v e r t i c a l  ve loc i ty  measurements a r e  of i n t e r e s t .  The use of the u' w' from the  
va r ious  beams would allow the  computation of the v e r t i c a l  nomenturn f l u x  due t o  
g rav i ty  waves. 
The antenna con£ igu ra t ion  and design required f o r  accurate v e r t i c a l  ve- 
l o c i t i e s  w i l l  g ive  t h i s  r ada r  a useful  mesospheric capab i l i ty  and w i l l  frequent- 
ly ob ta in  echoes i n  the 65-85 km a l t i t u d e  region. Recording t h i s  add i t iona l  
da ta  w i l l  add only about 2 K/yr t o  the  cos t  of the operation. 
THE EXPERIMENT t 
( a )  S i t e  Selec t ion 
' Since we already have da ta  i n  or near mountains, the s i t e  should be a t  the  
o the r  orographic extreme -- smooth t e r r a in .  Midwestern s t a t e s ,  especia l ly  
Indiana and I l l i n o i s ,  a r e  f l a t  and r e l a t i v e l y  f a r  from mountains. We have al-  
ready contacted the  Base Commanders a t  Grissom Air Force Base, I N ,  Whitenan Air  
Force Base, MO, and Chanute Air Force Base, IL, and f ind  t h a t  they have space 
ava i l ab le  and technic ians  (who would change tapes and check d i a l s )  on duty even 
during holiday periods. Purdue Universi ty,  Lafayette,  I N ,  has space ava i l ab le  
and has expressed i n t e r e s t  i n  a cooperative experiment. We have arranged t o  
personally inspect  these and perhaps other.  prospective s i t e s  i n  l a t e  May of 
t h i s  year. 
(b )  Frequency 
Although a frequency a l l o c a t i o n  must be obtained when the  s i t e  i s  se lec ted ,  
a frequency near 49 MIIz i s  l i k e l y  (wavelength = 5 m). We have had experience. 
with the proposed measurement i n  t h i s  frequency band. 
( c )  Equipment 
A phased dipole  antenna would be purchased or  b u i l t  a t  the Aeronomy Labo- 
ra tory .  A 100-kW t ransmi t t e r  and the  necessary data-processing equipment would 
be purchased. The individual  komponents would be checked out a t  the Sunset 
Radar i n  combination with an ex i s t ing  radar  before shipment and assembly a t  the  
new radar  s i t e .  I t  should be noted t h a t  the checkout of the  new radar  a t  Sun- 
s e t  would provide a unique comparison of operation a t  7.4 m and 6 m wavelengths. 
The mul t iposi t ion antenna configuration would require  a second antenna 
colocated with the f i r s t  but a t  a r i g h t  angle t o  it. Steering would be by re- 
mote control led  phase s h i f t e r s  developed f o r  use a t  the Sunset Radar. 
( d l  Operation 
The proposed "Flatland" radar  would operate continuously a t  a range reso- 
l u t i o n  of 1 km with a minimum of in terrupt ion.  I f  the  s t ee rab le  option i s  im- 
plemented with i t s  wide range of experimental p o s s i b i l i t i e s ,  the mode of opera- 
f i o n  would be optimized f o r  the v e r t i c a l  veloci ty  measurement. It i s  proposed 
t h a t  t h i s  mode of operation 'be changed infrequently,  i f  a t  a l l ,  during the  
f i r s t  year of operation. As i t  turns  out, t h i s  i s  a l s o  the optimm measurement 
technique f o r  most of the addi t ional  s c i e n t i f i c  uses of data l i s t e d  above, 
s ince  they require  a consis tent  data  s e t  of long duration. 
( e l  On-Line Procesing and Data Collection 
A v a r i e t y  of methods a r e  avai lable :  One mode i s  t o  h i r e  a technician t o  
change the  tapes a t  the radar s i t e  (estimated a t  $30 K per year)  or asking an 
A i r  Force Base t o  ass ign someone t o  do it. The mode of co l l ec t ion  t h a t  we 
favor i s  t o  bring the  radar output back t o  Boulder, CO, by a leased telephone 
l ine .  A s  shown t h i s  would cost  about $15,000 per year and would allow ex- 
perienced people a t  the Aeronomy Laboratory t o  monitor the qua l i ty  of the data.  
The cost  of changing tapes would of course be eliminated. I n  pr inciple ,  te le-  
phone access could be provided f o r  those experimenters requir ing real-time 
data  . 
CHARACTERISTICS OF "FLATLAND" RADAR t 
Location 
Wavelength 
Antenna 
S P e  
Feed 
Size 
S t e e r a b i l i t y  
Transmitter 
Peak power 
Average power 
Range reso lu t ion  
Operation 
Somewhere in  Missouri, I l l i n o i s  or 
Indiana 
probably 6 m 
Ruo colocated a r rays  of coaxial- 
col inear  dipoles 
Tapered t o  reduce sidelobes 
50 - 100 m square 
Five preset  posi t ions  
Vert, 15' (E, W, N, S) 
100 kW 
3 - 5 k W  
1 km ( w i l l  have c a p a b i l i t i e s  fo r  
150 m - 2.4 km) 
Fixed mode 
(continuously sequenced through 
5 antenna posi t ions)  


Measurements of vertical velocity over flat terrain by ST radar and other related uses of the radar data set

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