Vikram Sarabhai Space Centre

About: Vikram Sarabhai Space Centre is a facility organization based out in Thiruvananthapuram, India. It is known for research contribution in the topics: Aerosol & Ultimate tensile strength. The organization has 2092 authors who have published 3058 publications receiving 47975 citations. The organization is also known as: VSSC.

VHF/UHF radar observations of tropical mesoscale convective systems over southern India

Abstract: . Several campaigns have been carried out to study the convective systems over Gadanki (13.5° N, 79.2° E), a tropical station in India, using VHF and UHF radars. The height-time sections of several convective systems are investigated in detail to study reflectivity, turbulence and vertical velocity structure. Structure and dynamics of the convective systems are the main objectives of these campaigns. The observed systems are classified into single- and multi-cell systems. It has been observed that most of the convective systems at this latitude are multi-cellular in nature. Simultaneous VHF and UHF radar observations are used to classify the observed precipitating systems as convective, intermediary and stratiform regions. Composite height profiles of vertical velocities in these regions were obtained and the same were compared with the profiles obtained at other geographical locations. These composite profiles of vertical velocity in the convective regions have shown their peaks in the mid troposphere, indicating that the maximum latent heat is being released at those heights. These profiles are very important for numerical simulations of the convective systems, which vary significantly from one geographical location to the other. Keywords. Meteorology and atmospheric dynamics (Mesoscale meteorology; Convective processes) – Radio science (Remote sensing)

Global normal mode planetary wave activity: a study using TIMED/SABER observations from the stratosphere to the mesosphere-lower thermosphere

Abstract: A comprehensive study of three normal mode travelling planetary waves, namely the quasi-16, -10 and -5 day waves, is carried out globally using 5 years (2003–2007) of TIMED/SABER temperature measurements from the stratosphere to the mesosphere-lower thermosphere (MLT) by employing the two dimensional Fourier decomposition technique. From preliminary analysis, it is found that significant amplitudes of normal modes are confined to wave numbers-2 (westward propagating modes) to 2 (eastward propagating modes). The westward propagating quasi 16-day waves with zonal wave number 1 (W1; W1 refers to westward propagating wave with zonal wave number 1) peaks over winter-hemispheric high latitudes with northern hemisphere (NH) having higher amplitudes as compared to their southern hemispheric (SH) counterpart. The W1 quasi 16-day waves exhibit a double peak structure in altitude over winter hemispheric high latitudes. The eastward propagating quasi 16-day waves with wave number 1 (E1; E1 refers to eastward propagating wave with zonal wave number 1) exhibits similar features as that of W1 waves in the NH. In contrast, the E1 quasi 16-day waves in the SH show larger amplitudes as compared to the W1 waves and they do not exhibit double peak structure in altitude. Similar to the quasi 16-day waves, the quasi 10- and 5-day wave amplitudes with respect to their wavenumbers are delineated. Unlike quasi-16 and -10 day waves, quasi-5 day waves peak during vernal equinox both in the SH and NH. The peak activity of the W1 quasi-5 day wave is centered around 40°N and 40°S exhibiting symmetry with respect to the equator. A detailed discussion on the height-latitude structure, interannual variability and inter-hemispheric propagation of quasi 16-, 10- and 5-day waves are discussed. The significance of the present study lies in establishing the 5-year climatology of normal mode planetary waves from the stratosphere to the MLT region including their spatial–temporal evolution, which are very important from the middle atmospheric dynamics standpoint.

Bulk superhydrophobic materials: a facile and efficient approach to access superhydrophobicity by silane and urethane chemistries

Abstract: A promising method for constructing ‘bulk’ level superhydrophobicity on CaCO3 microparticles has been developed by employing silane and urethane chemistries in sequence. Silanol-terminated short-chain polydimethyl siloxane (PDMS) segments were grafted onto a CaCO3 surface. The particles were characterised by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and GPC analyses. By the reaction of silanol groups on the surface of CaCO3 particles with isocyanate functionalities, the crosslinking of particles was accomplished. The resultant coating exhibited a water contact angle >150° with a sliding angle approximately 5–8° on the entire material. The bulk level SH behaviour is attributed to both inter- and intraparticle hydrogen bonding, which was substantiated by FTIR. The rod-shaped morphology of the bulk material was evidenced in SEM images and resulted due to the encasing of well-connected microparticles by PDMS chains.