|
|
 |
|
|
Ann. Geophys., 19, 855-861, 2001
www.ann-geophys.net/19/855/2001/
© European Geosciences Union 2001
Estimation of temperature and humidity from MST radar observations
K. Mohan1, D. Narayana Rao1, T. Narayana Rao1, and S. Raghavan2
1Department of physics, Sri Venkateswara University, Tirupati-517 502, India
2Ex-IMD, Chennai, India
Abstract. Retrieval of vertical
profiles of temperature and humidity parameters using a VHF radar is described
in this paper. For this, Indian MST radar located at Gadanki (13.5° N, 79.2°
E) has been operated in a special mode. First, vertical velocities are
collected continuously using the radar and are subjected to Fast Fourier
Transform (FFT) analysis to obtain Brunt-Väisälä oscillations. From the
measured Brunt-Väisälä oscillations, temperature profile is obtained
from the radar observations following Revathy et al. (1996). The various terms
required for the retrieval of vertical profiles of humidity are the eddy
dissipation rate, ε, the volume reflectivity, η, and
the potential refractive index gradient, M. The eddy dissipation rate,
ε, is calculated from the spectral width after removing the
effects due to non-turbulence. The volume reflectivity, η, of the
turbulence scattering is calculated using the signal-to-noise ratio as a
function of height. The potential refractive index gradient, M, is
evaluated using the measured Brunt-Väisälä oscillations, the eddy
dissipation rate and the volume reflectivity, η. Vertical profiles of
humidity are retrieved following Tsuda (1997) using the radar derived
temperature as well as the balloon measured temperature and are compared with
the humidity as measured by the radiosonde. The sign of the potential
refractive index gradient, M, is taken from the simultaneous
measurements of balloon soundings. The retrieved vertical profiles of
temperature and humidity have been compared with the radiosonde data, which are
released simultaneously with the radar observations at the radar site. A fairly
good comparison is seen between the two measurements on some days and there are
some discrepancies on some other days. The strengths and limitations in
estimating the vertical profiles of temperature and humidity from the radar
observations are discussed.
Key words. Atmospheric composition and structure
(pressure, density and temperature; enhancements and techniques)
Full Article in PDF (540 KB) |
|
|
