Interferometric measurement of tropospheric phase fluctuations at 22 GHz on antenna spacings of 27 to 540 m

Phase fluctuations at 22 GHz introduced by tropospheric events were measured by observing cosmic compact radio sources with the Nobeyama millimeter-wave array on antenna spacings of 27 to 540 m. The observed interferometer phases were used to derive Allan standard deviations
\sigma_{A}
of phase fluctuations. The standard deviations
\sigma_{A}
had good relations to antenna spacing
L
as a function,
\sigma_{A} =A \times L^{N} + B
. The exponent
N
derived from the observations in February distributed around 5/6 as expected from the Kolmogorov turbulence model, but was smaller than 5/6 from the observations in May. Time domain spectra of
\sigma_{A}
also imply that atmospheric structures (such as moist air, clouds, precipitation, etc.) have seasonal variations. Meteorological parameters monitored at the height of 20 m did not show good correlations to
\sigma_{A}
.