NISCAIR Online Periodicals Repository Community: IJRSP Vol.37 [2008]

Measurement of complex dielectric constant of soils of Gujarat at X- and C-band microwave frequencies

Title: Measurement of complex dielectric constant of soils of Gujarat at X- and C-band microwave frequencies

Authors: Gadani, D H; Vyas, A D

Abstract: Dielectric constant and dielectric loss of soils collected from different districts of Gujarat state for various moisture contents have been measured at X- and C-band microwave frequencies. It has been observed that the dielectric constant of soils depend on the moisture content in the soils and frequency of measurement. Dielectric constant of soils increases slowly with increase in the moisture content in the soil up to the transition moisture, after which it increases rapidly with moisture content. The measured values of complex permittivity of dry and wet soils are compared with the values calculated from the empirical models and are found to be in agreement. The observed complex permittivity is used to calculate emissivity of soils for various moisture contents. It has been found that emissivity of soils decreases with increase in moisture content in the soil.

Page(s): 221-229

Measurement of CO and SO₂ trace gases in southern India during ISRO-GBP Land Campaign – I

Title: Measurement of CO and SO₂ trace gases in southern India during ISRO-GBP Land Campaign – I

Authors: Reddy, R R; Gopal, K Rama; Narasimhulu, K; Reddy, L Siva Sankara; Kumar, K Raghavendra; Ahammed, Y Nazeer; Vinoj, V; Satheesh, S K

Abstract: Under ISRO-GBP land campaign-I, the concentrations of CO and SO₂ gases were simultaneously measured during 1-29 Feb. 2004 over southern India. These measurements were made onboard instrument vehicle along the road network during the dry, winter season of 2004. The study region covered coastal, industrial, urban, rural, remote, semi-arid and vegetated forest lands in the central part of the southern India. Average CO concentration at Nellore, an urban and coastal site is comparatively high (1300 ppbv) and the same is low (620 ppbv) at Sri Perumbuthur, a semi-urban site. These maximum levels of CO at Nellore may be due to traffic emissions and shallow surface layer. Average SO₂ concentrations at Sri Perumbuthur and Shadnagar (5 ppbv) are significantly higher than those at other locations. Fairly good correlation has been established between CO, SO₂ and meteorological parameters over the study region.

Page(s): 216-220

Retrieval of raindrop size distributions from the L-band and VHF wind profilers during convective and stratiform rain

Title: Retrieval of raindrop size distributions from the L-band and VHF wind profilers during convective and stratiform rain

Authors: Sharma, Sanjay; Sarma, Diganta Kumar; Konwar, Mahen; Das, J; Jain, A R

Abstract: A new approach is proposed to retrieve the rain drop size distribution (RDSD) by the combined use of velocity spectra of L–band and VHF wind profilers by taking into account of updrafts/downdrafts. The corrected velocity spectra during rain are fitted with the lognormal functional form by using the Marquerdt-Levenberg algorithm. The corrected velocity spectrum of the L-band profiler is converted to RDSD spectrum. On 22-23 June 2000, for convective and stratiform rain, the retrieved rain integral parameters from the wind profilers are compared with Joss-Waldovegel Disdrometer (JWD) measurements. Reasonably good agreement is found between the observations from these two systems, when the updrafts/downdrafts corrections are applied. During the convective rain, for rain rate, the root mean square (rmse) and correlation coefficients are found to be 5.0 mm/h and 0.74, respectively and for mean rain drop diameter (D_m) the rmse and correlation coefficient are 0.66 mm and 0.58. Similarly during stratiform rain, rmse and correlation coefficients for rain rate are found to be 1.01 mm/h and 0.71. For D_m, the rmse and correlation coefficient are 0.67 mm and 0.65, respectively. An inverse relationship is observed between profiler derived total number of drops (N_t) and D_m.

Page(s): 185-196

Monitoring tropical cyclone evolution with NOAA satellites microwave observations

Title: Monitoring tropical cyclone evolution with NOAA satellites microwave observations

Authors: Singh, Devendra

Abstract: An attempt has been made in this paper to demonstrate the potential use of observations from Advanced Microwave Sounding Unit (AMSU) onboard NOAA 15, 16, 17 and 18 satellites series for the monitoring of tropical cyclones. Geophysical parameters derived from AMSU measurements like surface pressure, upper tropospheric warm core, gradient winds and cloud liquid water are demonstrated for the monitoring of the intensity of recently formed tropical cyclone in the Bay of Bengal on 28 Nov. 2005. The AMSU soundings, which penetrate high clouds, delineate the development and dissipation of the upper tropospheric warm core associated with a tropical cyclone. Vertical cross-sections reveal the intensification of the upper tropospheric warm core as the storm develops, and the downward propagation of the warm core as the storm dissipates.

Page(s): 179-184

NISCAIR Online Periodicals Repository Community: IJRSP Vol.37 [2008]

Measurement of complex dielectric constant of soils of Gujarat at X- and C-band microwave frequencies

Measurement of CO and SO2 trace gases in southern India during ISRO-GBP Land Campaign – I

Retrieval of raindrop size distributions from the L-band and VHF wind profilers during convective and stratiform rain

Monitoring tropical cyclone evolution with NOAA satellites microwave observations

Measurement of CO and SO₂ trace gases in southern India during ISRO-GBP Land Campaign – I