Showing papers by "Animesh Maitra published in 2021"

Non-Rainy Attenuation Over Earth-Space Paths at Tropical and Temperate Sites Using Meteorological Data and NWP Products

Abstract: A long-term investigation of the attenuation in non-rainy conditions has been carried out, for a tropical and a temperate location, using meteorological data and NWP (Numerical Weather Prediction) products during the period 2011-2015. The results show that ERA-5 full profiles are appropriate to estimate non-rainy attenuation in lieu of radiometric or radiosonde observations. Simpler regression-based methods are established. A new formulation for oxygen attenuation is introduced, which only requires surface temperature and pressure. Mass absorption coefficients are used for water vapour and cloud attenuation. Simpler regression-based approaches are then validated. The non-rainy attenuation at K, Ka and Q bands has been found noticeably higher in the tropics than in the temperate region. This study would facilitate the planning of global mobile satellite communication systems.

Rain drop size distribution analysis at a tropical location near land-sea boundary

Abstract: Rain events can be characterized by rain drop size distribution (DSD) that denotes the number of drops as a function of diameter per unit size interval and per unit volume of space. DSD (at ground level) describes the microstructure of precipitation during different phases of rain varying both spatially and temporally. DSD can be influenced by the nature and origin of rain. The present study investigates the role of continental and maritime airflow in influencing the precipitation features near the land-sea boundary. The data of the rain DSD used in the present analysis are collected from a ground-based disdrometer located at Kolkata, India, near land-sea boundary during the year of 2011–2017. The dataset is divided into two categories, namely, maritime and continental rainfall, based on the airflow trajectories associated with rain events exclusively from Bay of Bengal or land region in the west of Kolkata as derived from TRAJSTAT software. The events with trajectories extending both over land and sea region are excluded for the present study. Variations of the DSD parameters using the gamma model are presented showing the abundance of smaller drops during maritime rain events whereas dominance of larger rain drops in the case of the continental rain events. The Z-R relations are also found to be significantly different for these two types of rain. The present study reveals the microstructures of rain at a location where the influences of both land and sea climatic features prevail.

Five Years Change of Land Use Land Cover Concerning Covid 19 Lockdown and Amphan Cyclone using GIS Technique over a Location in Sundarban

Abstract: The Sundarban is the world’s biggest mangrove forest, located on Bangladesh’s and India’s southern coasts. The forest protects biodiversity and the local population from various natural disasters. This paper has primarily focused on the change in land use land cover (LULC) of a location in Sundarban delta (21°56’ N, 89°10’ E) using two LANDSAT satellite images for the year 2015 and the lockdown period of 2020, with the help of Geographical Information System (GIS) and supervised machine learning technique. With the reduction of upstream water and sediment supplies, the water body in the Bay of Bengal has increased. The extent of vegetation and agricultural land has decreased due to urbanization and erosion by the Bay of Bengal. The difference between the LULC before and after the Amphan cyclone indicates that land area has been reduced over this area.

Study of Propagation Channel Modeling and Comparison of Rain Cell Models over a Tropical Location using Ground based Observations

Abstract: This paper presents some important results of propagation channel modeling at a tropical location, Kolkata. Propagation impairments, namely, rain attenuation, cloud attenuation and water vapor attenuation has been investigated using ground based measurements. Though rain attenuation shows high values at high frequencies and low elevation angles, however the effect of cloud attenuation at earth-space path is also significant. It has been observed that rain has significant impact on bit error probability. Site diversity is a useful fade mitigation technique which is based on the concept of horizontal extent of rain cells. Performance of Different rain cell models have been compared in connection to calculate diversity gain over this location. The ITU-R model shows the best performance.