NISCAIR Online Periodicals Repository Community: IJRSP Vol.35 [2006]

Supercell storm at Kolkata, India and neighbourhood-Analysis of thermodynamic conditions, evolution, structure & movement

Sat, 29 Jul 2006 22:58:59 GMT

Title: Supercell storm at Kolkata, India and neighbourhood-Analysis of thermodynamic conditions, evolution, structure & movement

Authors: Sinha, Vivek; Pradhan, Devendra

Abstract: On 12^th March 2003 a very severe thunderstorm traversed across the Gangetic West Bengal in India and adjoining areas of Bangladesh. Documentation and analysis of the thermodynamic condition of the atmosphere and evolution, structure and movement of the storm as tracked by the Doppler radar is presented in this paper. One particular cell of the system lasted for over 12 h. Based on the internal structure, reflectivity, duration and weather pattern on the ground, it has been concluded that the particular cell was a supercell.

Page(s): 270-279

Study of amplitude spectrum of VLF sferics and vertical electric field at Kolkata

Mon, 29 May 2006 22:58:59 GMT

Title: Study of amplitude spectrum of VLF sferics and vertical electric field at Kolkata

Authors: De, S S; De, B K; Adhikari, S K; Sarkar, B K; Guha, A

Abstract: From the measurements of atmospheric electric field and VLF sferics at Kolkata (22^o34´ N, 88^o30´ E), some correlation studies have been made. It is observed that the diurnal variation of vertical electric field averaged for 20 fair weather days maintains good connectivity with diurnal variation of VLF sferics activity. The variations are in contrast with the accepted unitary diurnal changes of vertical electric field and thunderstorm occurrence frequency curve with a maximum around 1900 hrs UT and a minimum around 0400 hrs UT. Some results in this context are presented in this paper.

Page(s): 187-192

Wind profiler radar for understanding the tropical convective boundary layer during different seasons

Wed, 29 Mar 2006 22:58:59 GMT

Title: Wind profiler radar for understanding the tropical convective boundary layer during different seasons

Authors: Reddy, K Krishna; Kozu, Toshiaki; Rao, D Narayana

Abstract: This paper elucidates tropical continental boundary layer structures and their evolutions during different seasons over Gadanki, Southern India. Gadanki-LAWP (Lower Atmospheric Wind Profiler Radar) has proved to be an excellent tool for studying convective structures and boundary layer depth with good temporal (~ 10 min) and vertical resolution (150 m). We used LAWP reflectivity, Doppler velocity and spectral width data in time versus altitude to characterize general behaviour of convective boundary layer based on the “morning” and “evening” transition. From a wide variety of observed patterns, three categories are identified: (i) Descent, (ii) Ascent, and (iii) Inversion Layer (IL). Long-term Gadanki-LAWP observational results show the Ascent cases occur on relatively warm and moist days with strong turbulence and weak capping inversion [maximum occurrence in monsoon], descent days occur [pre-monsoon] on warm dry convection days and IL days occur [winter] on dew/fog and drier days with subsidence inversion and/or advection of warm air from the Bay of Bengal.

Page(s): 105-115

Radiometric scene correction of temporal multi-spectral satellite data for crop discrimination

Wed, 29 Mar 2006 22:58:59 GMT

Title: Radiometric scene correction of temporal multi-spectral satellite data for crop discrimination

Authors: Sahoo, R N; Tomar, R K; Rao, C S; Sehgal, V K; Charchi, Nirupa; Abrol, I P; Tiwari, M K; Wadhawani, M K

Abstract: Multi-date satellite images under different conditions of the same area are difficult to compare because of change in atmospheric propagation, sensor response and illuminations. To overcome this problem, a radiometric normalization technique, which is based on the statistical invariance of the reflectance of man-made in-scene elements (pseudo invariant features) was attempted. The LISS-III data of IRS-1D of three dates were taken for discrimination of crops and retrieval of crop statistics. To develop temporal NDVI profile of the various crop types, relative image-to-image radiometric scene normalization of each band was done using linear transformation. Water body, orchard and other less dynamic features were excluded and multidate-NDVI image having only agricultural crops was obtained for identification and classification of various crops. Nine classes were identified and discriminated as different crops by analyzing temporal NDVI profile pattern based on ground truth, crop calendar and information on crop sowing and harvesting time. Spatial distribution of different crops was analyzed and crop area statistics was computed.

Page(s): 116-121