Regional Distribution of Water Vapor in the Troposphere and Excess Path Delay of Microwave in Winter in Japan

Abstract

Excess path delays due to water vapor were calculated using the data observed in February 1982 at 20 routine radio zonde stations which are given in the Aerological Data of Japan. Mean delays in the zenith direction in February are 2-3, 3-5, 5-7 and 10-15 cm in Hokkaido, northeastern Japan, south-western Japan and Bonin and Ryuku Islands, respectively. Standard deviations from these mean delays are 1, 2-3, 3-4 and 4-5 cm, respectively. The mean delays ΔLw are expressed by the surface temperature Ts at the stations as ΔLw =ΔLw0 exp (αT8) with ΔLw0=4.0 and α=0.075: This relation holds also to the seasonal variation of excess path delay at Wajima, so that the relation will hold at anytime anywhere in Japan. Simple interpolations of the present data show that excess path delays may be estimated with a precision better than 1 cm by employing the routine radio zonde observations.