NISCAIR Online Periodicals Repository Collection: IJRSP Vol.35(6) [December 2006]

Correlation of the long-term cosmic ray intensity variations with sunspot numbers and tilt angle

Title: Correlation of the long-term cosmic ray intensity variations with sunspot numbers and tilt angle

Authors: Gupta, Meera; Mishra, V K; Mishra, A P

Abstract: Based on the monthly data of sunspot numbers (SSN), tilt angle (TA) and cosmic ray intensity (CRI), a detailed correlative analysis has been performed to study the relationship of CRI (observed by the neutron monitor stations having different cut-off rigidity) with SSN and TA for the period 1976-2005, covering solar cycles 21, 22 and 23. It is an observed fact that SSN and TA are highly correlated with each other and cosmic ray intensity shows anti-correlation with them. The present analysis is found to support the earlier findings and holds good for solar cycles 21, 22 and current cycle 23. Further, the cross-correlation coefficients between CRI-SSN and between CRI-TA have been obtained considering the time-lag factor and it is found that time-lag is larger for odd solar cycles in comparison to even cycles. The odd-even behaviour in relation to time-lag is also evident from the hysteresis curve between CRI-SSN and between CRI-TA, where wider loops for odd solar cycles have been observed. Moreover, we find that correlation between CRI and SSN as well as between CRI and TA is better during negative polarity than the positive polarity of solar magnetic cycle. From the tilt angle observations, it has been noticed that the behaviour of cycle 23 in declining phase is different from that of cycle 21 and 22.

Page(s): 387-395

Studies on crop growing period and NDVI in relation to water balance components

Title: Studies on crop growing period and NDVI in relation to water balance components

Authors: Sarma, A A L N; Kumar, T V Lakshmi

Abstract: The primary water balance components such as rainfall, water need, actual evapotranspiration, water deficit and water surplus, are studied for All Andhra Pradesh for the south-west monsoon months of 1999 to 2002 on daily basis. Crop growing periods for the selected stations over Andhra Pradesh (AP) are reported to understand the climatic potentialities of the region for crop and irrigation schedule under consideration. The investigation also addresses the spatiotemporal variability of the integrated normalized difference vegetation index (INDVI) in relation to the pattern of soil moisture adequacy. Using mean daily water deficit and water need, aridity index is obtained and studied to understand drought monitoring over Andhra Pradesh in relation to INDVI. The present study shows that the crop growing periods are high to the north of 15° latitude compared to south. The relation of the rainfall with NDVI is found to be weak when the rainfall is taken for the 10-day periods compared to soil moisture adequacy. But in the case of cumulative rainfall, the results revealed better positive correlation with NDVI.

Page(s): 424-434

Vertical structure of the lower atmosphere over the Arabian Sea and West Coast Station during weak phase of the Indian summer monsoon

Title: Vertical structure of the lower atmosphere over the Arabian Sea and West Coast Station during weak phase of the Indian summer monsoon

Authors: Dharmaraj, T; Murthy, B S; Sivaramakrishnan, S

Abstract: The height of the day time mixed layer, vertical structure of the atmospheric boundary layer (ABL) and its variation over the Arabian Sea (hereafter Sea) and the West Coast Station (Goa: 15^o21' N, 73^o51' E) during the weak phase of south-west monsoon (20-24 July 2002) have been calculated using Radiosonde, the surface meteorological data collected at 12 m above mean sea level onboard ORV Sagarkanya and at Goa during ARMEX-I. It is observed that the depth of mixed layer over Goa and offshore was about 1 km during the period, while the first 200 m was showing super adiabatic lapse rate over Goa but not over the Sea. The marine atmospheric boundary layer is found to be well-mixed with its height, progressively increasing from 750 m to 1000 m during 21-24 July 2002. The vertical profiles of virtual potential temperature show an inversion above 1 km, which was very steep over both the Sea and Goa. The relative humidity (RH) in the mixed layer (0-1 km AGL) was varying from 70 to 100% over the sea, whereas over Goa it was from 70 to 90 % during 20-24 July 2002. Above 2-3 km, RH decreases from 70% to 30% over the Arabian Sea and Goa on 24 July, indicating the presence of subsiding warm and relatively dry layer.

Page(s): 418-423

Analysis of notch-loaded patch for dual-band operation

Title: Analysis of notch-loaded patch for dual-band operation

Authors: Shivnarayan; Vishvakarma, Babau R

Abstract: Analysis of notch loaded rectangular patch antenna for dual-band operation has been proposed, in which dual frequency behaviour is obtained by notch loading. The theoretical analysis is based on modal expansion cavity model. The resonance frequency changes with the variation in the length and width of the notch. Thus the input impedance, VSWR, return loss and bandwidth are calculated. The obtained resonance frequency ratio is variable from 1.17 to 1.77 with the length and width of the notch.

Page(s): 435-442