Abstract: Title: An appraisal of rainfall estimation over India using remote sensing and in situ measurements Authors : Dwivedi, Sanjeev; Kumar Thakur, Manoj; Lakshmi Kumar, T V; Rao, B M; Kishtawal, C M; Narayanan, M S: The most important meteorological parameter Rainfall, shows high variability in space and time, particularly over
Tropics / Monsoon region. Many new observational and analysis methods to observe / analyse them by remote sensing
techniques (Satellites, Doppler Weather Radars) have emerged over the decades, besides the dense network of in situ rain
gauges, Automatic Weather Stations (AWS) etc on ground. The scales of observations being vastly different for in situ and
remote sensing methods, large discrepancies between different techniques are inherent. These problems have been brought
out through various validation studies by many groups in the country. Even on the daily all India spatial scale, basically only
the peaks and troughs from satellite estimates match reasonably well with in situ data. Results of a case study during an
intense and long-lasting rain event over Chennai, from DWR, with different satellite products and ground truth are
presented. The importance of DWR rainfall data in significantly improving the integrated products is emphasised. A simple
two-way approach to establish Z – R relationship for the DWRs in the country is also suggested. A well-coordinated
integrated programme to study the inter comparability of precipitation at various spatio- temporal scales in the context of our
water resources, model validation, extreme rainfall events, Climate change, etc., is called for. The desired accuracies from
satellite data vis a vis IMD gridded data for different applications have been summarised.Page(s): 167-177 PubDate: 2021-12-01T00:00:00Z
Abstract: Title: Spatiotemporal Distribution Of Ionospheric Irregularities Over India During St. Patrick‘s Day Storm Authors : Acharya, Rajat; Singh, Randhir; Chipade, Radhika: The irregularities formed over the equatorial ionospheric region over the Indian sector have been studied for the first time for the day of the most intense geomagnetic storm of solar cycle-24, which occurred on 17.03.2015, using Rate of TEC Index (ROTI) as the index for the study. These values have been derived using the measurements done with the TEC network receivers of the Indian SBAS system, GAGAN. Spatial and temporal variations of ROTI have been observed and compared to the same parameters on a quiet day with occurrence of nominal scintillation. The latitudinal symmetry of the irregularities for a given local time was evident. It has been found that the ionospheric irregularities formed over this region get immensely enhanced due to the storm in terms of its intensity and spatial extent, as well. The temporal spread of the irregularities has been observed and the statistical variations of the occurrences were compared with respect to those on quiet days. The results have provided few interesting observations including an understanding of the profundity and extensiveness of the irregularities and of the possibilities of consequent scintillation for the navigation signal over Indian region during space weather induced intense geomagnetic disturbances.Page(s): 178-189 PubDate: 2021-12-01T00:00:00Z
Abstract: Title: Low latitude, topside ionosphere composition and its variation with changeable solar activity Authors : Mangla, Bindu; Dwivedi, N K; Sharma, D K; Bardhan, Annana; Rajput, Anupama; Singh, S: The ions composition and their densities have been studied for different solar activity periods - along with their diurnal, seasonal and annual variations - for half of the 23rd solar cycle, covering solar minima (1995) to solar maxima (2000) over Indian sector (65–95ᵒE and 5–35ᵒN) at an average altitude of ~500 km. The study has been done by processing the data obtained from in situ measurement made by separate Retarding Potential Analyser (RPA) for electrons and ions, aboard Indian satellite SROSS C2. The plasma density has been found to be rich in O+ ion for all instances of time and showed a direct increase with solar activity. H+ has been observed to be in plenty during night time, especially from moderate to high solar activity period. The difference between H+ and O+ densities widens with increasing value of F10.7. He+ always constitutes a small part of plasma but its density exceeds H+ - during moderate to high solar activity period. O2+ has beenfound to be a minor constituent, even 3-4 folds lesser than He+ density. A positive correlation with solar activity has been found for O2+.Page(s): 190-197 PubDate: 2021-12-01T00:00:00Z
Abstract: Title: Extremely compact UWB antenna design with single Notch-Band characteristic Authors : Dalal, Kusum; Singh, Tejbir; Kumar Singh, Pawan: An extremely compact antenna design for Ultra-wideband (UWB) application has been presented in this paper that
successfully displays band-notch characteristics at the WLAN band. The design consists of a truncated radiator supplied by
a 50 Ω Coplanar Waveguide (CPW) feedline structure. The antenna has been mounted on a FR4 substrate, and its ground
plane has been etched with an inverted-L slot responsible for frequency-notch characteristics at the WLAN band (5.15-5.825 GHz). The ground plane has been defected by engraving a rectangular slot in the ground plane for improving the impedance bandwidth. The antenna has a profile size of 19×9×1.6 mm3. The performance of the antenna has also been compared with another design having twice the dimensions of the proposed structure (30×26×1.6 mm3).Page(s): 198-203 PubDate: 2021-12-01T00:00:00Z
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