Minakshi Devi

The role of solar activity in the growth of an earthquake (EQ) is the topic of study here, focussing on the correlation & distribution function between global EQ events of M ≥ 4.5 and solar parameters covering seven cycles from 18 to 24. The analysis modes are in two steps: (i) EQ events in a total of all cycles taken under study and solar role on their growth; and (ii) EQ events filtered for a High Solar Active (HSA) and a Low Solar Active (LSA) years for each individual cycle & the respective contribution of solar strength to their occurrences. The paper presents the observation by drawing a relation between EQ event ratio during LSA and HSA year, i.e., EQ_LSA/EQ_HSA with the corresponding Rz ratio of the years, an approach adopted to reduce any bias/errors that arise on availability of more EQ data as year advances. The analysis offers a negative cum complex distribution with more EQ cases at 60–70% below the peak Rz when strong solar ambiances are observed to inhibit the growth of severe EQ events. The overall correlation analyses between Rz, geomagnetic indices like Kp/DST, and EQ-events of different magnitudes also provided a conclusion that solar ambiances play a complicated role in the growth process of an EQ. These observations are discussed by invoking the Forbush effect along with the possible contribution of atmospheric variabilities like global temperature, lithosphere heat content, and anthropogenic components.

The Amphan a Tropical super Cyclone (TC) had grown in the background of high Sea Surface Temperature of 32⁰C-34⁰ C, over the Bay of Bengal and in an artificially controlled pollution-free status of the Indian zone during the COVID-19 lockdown; thus providing an opportunity in examining the cyclone effects on the atmospheric dynamics in this special background. The paper presents the contributions of the Amphan wind to the atmosphere/environment of the North Eastern (NE) part of India along its track-path, after its landfall at 24.65⁰N, 88.30⁰E on May 20, 2020. The analysis supported by the troposphere temperature, relative humidity, precipitation, and suspended particles along with respective temporal and spatial profiles, finally offered that the Amphan-wind had brought down the temperature for a weeklong period, reduced the pollution level by 20% to 30% for more than a week but produced short-lived changes in humidity and precipitation over the NE-zone. The contribution of pollution is brought in to ambit of discussion to the weeklong sustenance of low temperature and in reducing the precipitation intensity when the growth environment of the CCN was artificially curtailed. The data sources are ground-based sensors, AWS, model profiles, and satellite observations.

The paper presents atmospheric coupling physics through identifying a few significant features imprinted on the ionosphere by certain unique seismic environments when a number of successive cluster of earthquakes ranging from 7.1 to 8.2 magnitudes occurred within about two weeks period, over the East-West Pacific zone covering 150° E to 70° W. Amongst the cases considered here are earthquakes of Chile Apr. 1, 2014 (M = 8.2) and Apr. 3, 2014 (M = 7.7), New Guinea Apr. 11, 2014 (M = 7.1) and Solomon Islands 13.04.2014 (M = 7.6). The main data source for the study is Global TEC with supplementary inputs from GPS observations taken at Guwahati (26° N, 92° E), an Appleton anomaly crest region. A few EQ events with epicenters in and around this anomaly zone are also taken in the study to focus on the seismic induced density features like Earthquake time Equatorial Anomaly (EEA) and Earthquake time Equatorial Anomaly Crest (EEAC) developed over the belt. Such anomalous modifications in TEC resulting to growths of EEA and EEAC covering Solomon Islands—New Guinea extending up to Chile along the fault lines for more than a month, are significant observations brought out in the paper. The GPS TEC data from Gauhati University are utilized in identifying the epicentre position through anomalous appearance of satellites beyond the Line Of Sight (LOS) observation. Finally, the seasonal role on enhancing the seismic induced E-field coupled by mutual interactive EQ preparatory effects of the three major events as well as in enhancement of EQ time radon emission through fault is invoked in explanation to the anomalous density features.

Geomagnetic storm is one of the major disturbances in Earth’s magnetosphere and its effect on ionosphere is a well studied area, yet there are a few aspects still require attention for...

The Varsha, a spectral hydrostatic general circulation model, is run regularly at an eight-processor Flosolver machine at Gauhati University (26°10′ N, 91°45′ E), with the aims to predicting track of cyclones generated in the Bay of Bengal and forecasting precipitation occurrence and intensity over the north-eastern part (NE) of India, induced by such events. The initial conditions of the model are prepared from FNL dataset of National Centre for Environmental Prediction (NCEP), available at 1°×1° resolutions. The predicted tracks of a few cyclonic events as SIDR (Nov, 2007), Aila (May, 2009) and Laila (May, 2010) are presented along with their contribution to precipitation in the NE. Each prediction, when assessed through observations obtained from satellite-based measurements of Tropical Rainfall Measuring Mission (TRMM) and National Oceanic and Atmospheric Administration (NOAA), and also from India Meteorological Department (IMD), shows that the model-generated zonal wind is a good precursor parameter in track determination of a cyclone. The reliability of the model-projected precipitation features over the NE, contributed by such storms, is also highlighted.

Total electron content (TEC) data, obtained from satellites, are used in the search for imprints for identifying the probability factor of an impending earthquake. Extraction of earthquake induced signature is done mainly from day-to-day variations in TEC peak (TEC_peak.). The use of a single parameter such as TEC_peak is not always enough to formulate such a pointer. The paper therefore focuses on the need to introduce other markers such as the shape of TEC profile and to utilize any modification in the profile shape caused by an impending earthquake to identify precursors. An automatic pattern matching approach for processing global positioning system (GPS) generated TEC records is introduced to achieve this aim and TEC profiles are passed through a template framed from the time series of quiet day data. The Dynamic Time Warping (DTW) algorithm is adopted to look for deviations in the entire TEC profile of days prior to the earthquake with respect to the template. Variation, if any, would be used as an index of earthquake induced signature. A few case studies using this algorithm are presented in the paper. Work is based on TEC data collected from the GPS receiver at Guwahati (26° 10′ N, 91° 45′ E), an equatorial anomaly crest station.

The article discusses the development and operational details of Differential Absorption LiDAR (DIAL) for the measurement of methane concentration in the semi-urban environment of Gauhati University. The system comprises two specifically selected wavelengths in 3 μm range: one is an absorbing wavelength (λ_on) and the other is non-absorbed (λ_off) by methane molecules. Pulses of 10 ns for the two wavelengths are transmitted alternately for interleaved sampling of differential absorption. The pulse repetition rate is variable between 1 and 20 Hz. The slope and integrated target approaches are adopted to calculate the methane concentration, and observed figures are compared with globally reported values.