Preface 



This atlas has been prepared for the radio engineer who wants an estimate of the 

 behavior of the radio refractive index at any point on the earth. It has many limitations, 

 which the authors have tried to point out in the text, but should provide useful informa- 

 tion for engineering design and predictions of tropospheric radio circuits. 



The work upon which this atlas is based has been in progress for several years in 

 the Radio Meteorology Section of the Central Radio Propagation Laboratory, National 

 Bureau of Standards, Boulder, Colo.* Many people have contributed to this research effort 

 through the years, and it is not feasible to acknowledge them all individually. Those most 

 directly involved with the preparation of material for this atlas include W. B. Sweezy and 

 W. A. Williams, who were responsible for most of the computer programming; Mrs. B. J. 

 Weddle, who assisted in processing and cataloging of the data; T. D. Stevens, who did 

 most of the compiling, checking, and plotting of the maps, graphs, and tables; and 

 L. P. Riggs, J. D. Horn, and Mrs. G. E. Richmond (deceased), who contributed to the 

 atlas project in its early stages. 



The National Weather Records Center of the U. S. Weather Bureau in Asheville, 

 N. C, supplied the meteorological data upon which this atlas is based, and also performed 

 the preliminary conversions of these data to refractivity parameters. 



Finally, we thank the personnel of the U. S. Navy Weather Research Facility at 

 Norfolk, Va., who foresaw a need for such an atlas and have arranged for support of the 

 project over a period of years. 



'Now the Institute for Telecommunication Sciences and Aeronomy (ITSA), Environmental Science Services Administration. 



Ill 



