NOPR Collection:

Space-borne infrared spectro-photometer for astronomy

2016-07-20T05:46:31Z

Title: Space-borne infrared spectro-photometer for astronomy Authors: Ghosh, S K Abstract: A simple and reliable satellite-borne infrared spectro-photometer (IRSP) for astronomical applications is proposed, which can be realized in the near future using the available technological knowhow within the country. While this instrument’s demands for cryogenic and oriented platform-pointing systems are kept modest (within the anticipated reach of ISRO capabilities), it can still address a wide variety of interesting and contemporary astrophysical problems. Page(s): 191-201

Inter-annual variability and intercycle variation of major oscillations in lower and middle atmospheric temperature using radiosonde/rocket data

2016-07-20T05:37:26Z

Title: Inter-annual variability and intercycle variation of major oscillations in lower and middle atmospheric temperature using radiosonde/rocket data Authors: Kumar, K Praveen; Mohanakumar, K Abstract: Inter-annual and intercycle variations of major oscillations in lower and middle atmospheric temperature, derived from seven selected radiosonde/rocketsonde stations, have been studied. Using FFT technique and with the help of harmonic analysis, major oscillations present in temperature and their amplitude, phase and cyclic variations have been found out. Thumba exhibited an out-of-phase variation in upper stratospheric temperature compared to other tropical stations. Kwajalein recorded significant variability in annual cycle both in the upper stratosphere and lower mesosphere. Amplitudes of annual and semi-annual components in temperature exhibited an out-of-phase variation with solar cycle at a height of 35km over Wallops Island. Least inter-annual variability in temperature is observed in tropical and midlatitude troposphere. The spectrum of temperature indicated the presence of 11-yr cycle in the upper stratosphere and lower mesosphere of all tropical as well as mid latitude stations. The QBO signal in temperature is found to be weak over the southern hemispheric tropical station. The QBO in temperature is marked with a primary peak in the height range of 20-35 km and a secondary peak in the range of 57-60 km in tropics. At Thumba, the intercycle variability of QBO in temperature is relatively high at 57-60 km region. Page(s): 177-190

Characteristics of cloud drop spectra on rain and non-rain occasions

2016-07-20T05:52:59Z

Title: Characteristics of cloud drop spectra on rain and non-rain occasions Authors: Paul, S K Abstract: Measurements on drop size spectra were made in cumulus clouds over Pune (inland) region on a large number of days during the summer monsoon seasons. The measurements of the cloud drop spectra on the days with rain and with no rain in the experimental area made in 1976, 1979 and 1980 (the rain being observed within the clouds) have been studied. The average spectra were broader and concentration of drops with diameter > 50 μ m (N_L) liquid water content (LWC). Mean volume diameter (MVD) and dispersion were found to be greater on the days with rain as compared to those on the days with no rain. Total concentration (N_T) and concentration of drops < 20 μM (N_S)were lower on the occasions of rain with respect to those of no rain . The average drop size distributions were bimodal on the days with rain, while they were unimodal on the days with no rain. The variations of cloud drop spectra preceding the rain, at the initial stage of rain and following the rain are discussed. Page(s): 170-176

Estimation of meridional temperature gradient profile using Indian MST radar

2016-07-20T05:38:35Z

Title: Estimation of meridional temperature gradient profile using Indian MST radar Authors: Rao, D Narayana; Singh, H Randhir; Rao, S Vijaya Bhaskara; Raja, M K Rama Varma; Asnani, G C; Thulasiraman, S Abstract: Meridional temperature gradient profile over Gadanki (13.47°N, 79.18°E) for the height range of 4-18 km with vertical resolution of 150 m is derived, assuming geostrophic wind balance in monthly mean zonal wind and hence thermal wind relationship at this latitude. This study is carried out for the year 1996, with monthly averaged wind data obtained from the Indian MST radar common mode observations. It is observed that average meridional temperature gradient is of the order of 0.5°C/555 km in the winter season with maximum value of 1°C/555 km at around 8 km, and in the summer season it is of the order of 1°C/555 km with a maximum value of 1.75°C/555 km in the height range of 8-15 km having another peak at around 17 km. This enhancement, which is consistent with larger vertical shear in zonal wind field, is probably due to latent heat released in this region after the onset of south-west monsoon. These derived values of meridional temperature gradient are compared with the observed values obtained by using radiosonde temperature data for two stations, Visakhapatnam and Madras. These values are in good agreement,which prove the validity of the above cited approximation at this latitude. Page(s): 165-169