Accession Number : AD0716774

Title :   Tropospheric Effect on Electromagnetically Measured Range: Prediction from Surface Weather Data.

Descriptive Note : Technical memo.,

Corporate Author : JOHNS HOPKINS UNIV SILVER SPRING MD APPLIED PHYSICS LAB

Personal Author(s) : Hopfield,Helen S.

Report Date : JUL 1970

Pagination or Media Count : 41

Abstract : The height integral of tropospheric refractivity (n-1), where n is refractive index, measures the range error in a vertically arriving electromagnetic signal. Such height integrals were studied, using meteorological balloon data from widely separated locations. Although the 'dry' part of (n-1) at any point in the troposphere depends on both pressure and temperature (P/T), its height integral was found to be a linear function of surface pressure only, both theoretically and from observed data. The equivalent height for the quartic model of (n-1)dry must therefore vary as surface temperature. Height parameters were computed from balloon data and were closely the same for all stations: a 'dry' height of 40.1 km at 0C, decreasing to zero near 0K. Using these, the model predicts vertical range error (dry part) within a few millimeters rms. Study of the very much smaller but more variable 'wet' contribution is continuing. (Author)

Descriptors :   (*TROPOSPHERE, REFRACTIVE INDEX), (*RADIO WAVES, RANGE FINDING), RANGE(DISTANCE), MATHEMATICAL PREDICTION, METEOROLOGICAL BALLOONS, SATELLITES(ARTIFICIAL), INTEGRALS, SURFACE TEMPERATURE, REFRACTION, TABLES(DATA), BAROMETRIC PRESSURE

Subject Categories : Atmospheric Physics
      Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE