RADAR PROPAGATION FORECASTING 



109 



the top of the water modification zone, and from 

 there to 1,000 ft a gradual decrease was forecast on 

 the basis of the conclusions regarding the advectiou 

 of a little dry air indicated by the midnight Albany 

 sounding. 



The verification shown by the broken line in Fig- 

 ure 1 turned out rather well in this instance. The 

 computed and verified M curve proved to possess 

 almost identical slopes throughout with the top of 



VERIFICATION 



JULY 26,1944 lOOOE WEATHER BUREAU FORECAST 27 

 SMILES SOUTHEAST OF EASTERN POINT, MASS. C77 



17 19 21 23 



TEMPERATURE 

 IN C 



VAPOR PRESSURE 

 IN MILLIBARS 



Figure 1. Space forecast of M curves. 



the M inversion in both very close to 150 ft. This was 

 one of the better forecasts. It can be seen that actual 

 values of temperature and vapor pressure between 

 forecast and verification might vary by several de- 

 grees, but as long as they have the same slopes at the 

 same elevation they will produce M curves reason- 

 ably close to one another. 



Conclusions. It is felt that the method of forecast- 

 ing used was a marked improvement over the tech- 

 nique employed previously. It is potentially capable 

 of dealing with the low-level modification problem 

 in the case where the intial air is stratified as well as 

 the one in which the initial air is homogeneous before 

 it passes out to sea. 



8 2 RADAR PROPAGATION FORECASTING" 



This is a report of results obtained by an AAF 

 board project investigating radar propagation fore- 

 casting, which was started as two distinct j)rograms in 

 September 1944. The first part of the project was 

 carried out at the Radiation Laboratory with facili- 

 ties used by Group 43 during over-water transmission 

 measurements in the summer of that year. During 

 that time, with the invaluable assistance of Group 42, 

 a forecasting system was developed for the over-water 

 case, the results of which are presented in Section 



"By Lt. J. R, Gerhardt and Lt. W. E. Gordon, AAF Board. 



S.l."^ These reports gave preliminary results of the 

 MIT program and the recommended forecasting pro- 

 cedures. The second part of the propagation forecast- 

 ing program was set up at Orlando, Florida, to study 

 particularly the over-land forecasting phase and to 

 investigate some of the operational uses of such fore- 

 casts. 



With this in mind, AAF Board Project HS'TG'T, 

 "The Determination of the Practicability of Forecast- 

 ing Meteorological Effects on Radar Propagation," 

 was initiated late in 1945 with the following specific 

 objectives : 



1. To determine the practicability of forecasting 

 those low-level meteorological conditions which affect 

 radar propagation. 



2. To determine the accuracy with which radar 

 propagation forecasts can be made from the corre- 

 sponding meteorological conditions. 



3. To determine the operational uses of such fore- 

 casts. 



4. To determine the optinnim meteorological ob- 

 servation site with relation to the site of the radar 

 employing the forecasts. 



5. To determine the suitability of available low- 

 le^■el sounding equipment. 



It was originally planned to study the over-land 

 and over-water problems simultaneously, but because 

 of the lack of a coastal radar site until the last month 

 of the program the project was divided into two 

 phases: (1) the general study of the over-land prop- 

 agation variations in an attempt to devise a suitable 

 forecasting procedure and (2) an evaluation of the 

 results obtained from both the over-water and over-land 

 methods, with possible tactical applications under field 

 conditions at the site of a powerful coastal radar. 



Figure 3 is a map of central Florida giving in de- 

 tail specific facilities used throughout the project. 

 Headquarters was established at the Weather Central, 

 Orlando, where complete weather information, fore- 

 casts, and analyses were available. The meteorological 

 data used throughout the project consisted of surface 

 and upper air observations for the general central 

 Florida area. 



Detailed synoptic maps of Florida were drawn cov- 

 ering periods of 6 hours each to determine wind 

 patterns and representative land temperatures and 

 dew points ; piballs'' for Orlando, Sebring, and Tampa 

 were plotted up to 2,000 ft to determine trajectories and 



'Elaborated in references 1 to 3. 



■"A small balloon with standard rate of rise released for 

 tracking by a theodolite for estimation of upper-air winds. 



