Super Cyclone Research Articles

Satellite based analysis of rapid intensification of Super Cyclone Amphan

Tropical Cyclones (TCs) are formidable natural hazards with destructive impacts on life and property along the tropical belt. TCs are responsible for multiple hazards such as riverine and urban floods, extreme winds, and lightning, storm surge significantly amplifying the threats they pose. Rapid Intensification (RI), defined as a sudden increase in Maximum Sustained Winds (MSWs) by 30 kt or more in 24 h, has been a growing concern. These events, characterized by a swift escalation in MSW are challenging to the forecasters and remain a considerable operational challenge, amplifying risks for coastal communities. Numerical modeling also struggles to predict RI, with limitations in describing inner core convective scale processes cited as a major limitation. Monitoring and assessing TCs heavily rely on satellite-based observations due to the absence of adequate in-situ measurements over the ocean. In the present study, we examine Super Cyclonic Storm (SuCS) Amphan, the first Super Cyclone of this century, that formed over the Bay of Bengal in 2020 using satellite imagery and derived products available in near-real time to monitor and identify the early signatures for the RI. It is observed that the intensification is intricately tied to substantial expansions in both the outer and inner core sizes along with its symmetricity before the RI. Notably, no significant alterations in size are observed between the very severe cyclonic storm (VSCS) and SuCS stages. The convection characteristics of TCs are found to provide crucial markers of their intensification, with a particular emphasis on polar satellite-based passive microwave imagery for analyzing embedded convection and early eye detection. Key observations indicate that inner convective ring patterns, identified through 37Ghz microwave imagery in lower-level convection, act as precursors to rapid intensification. Concurrently, the outer ring pattern observed during the mid-life course is found to permit further intensification of the system.

Performance Assessment of 4D-VAR Microphysics Schemes in Simulating the Track and Intensity of Super Cyclonic Storm “Amphan”

Performance Assessment of 4D-VAR Microphysics Schemes in Simulating the Track and Intensity of Super Cyclonic Storm “Amphan”

VULNERABILITY OF HERITAGE SITES TO CLIMATIC EXTREME EVENTS: KHALIFATABAAD ANCIENT MOSQUE

Built heritage is the pride of human civilisation and the built environment. But nowadays, they are gradually threatened by various natural decay, deterioration, and effects of extreme climate events. Khalifatabaad (present Bagerhat) in the southwestern part of Bangladesh has a rich heritage value and was also enlisted as one of the world heritage sites by UNESCO in 1985. The Department of Archaeology Bangladesh and UNESCO are working together to conserve Khalifatabaad's heritage sites. But due to climate change and the increased number of tropical climate extreme events like sea-level rise, tropical cyclones, super cyclones, storms, tidal surges, waterlogging, salinity, dampness, etc., significant problems are arising to preserve and conserve the heritage structures of tropical regions. This paper aims to investigate and analyse the vulnerabilities of these heritage structures due to extreme climate events by following building pathology principles. The DPSIR (Driver-Pressure-State-Impact-Response) method is used as the research framework. The research data are collected and documented through a literature review, site survey, detailed observation, documentation, oral statement records, and qualitative analysis. The research outcome is focused on investigating the most responsible climate extreme events, their short-term and long-term impacts on heritage buildings, and presenting conservation strategies for the historical sites in Khalifatabaad.

Intensification mechanisms and moisture dynamics of super cyclonic storm ‘Amphan’ over the Bay of Bengal: Implications for aerosol re-distribution

The present research investigates the dynamics and underlying causes contributing to the exceptional intensity of Super Cyclonic Storm (SuCS) Amphan (16th to 21st May 2020) over the Bay of Bengal (BoB), as well as its impact on aerosol redistribution along the four cities of eastern coast and north-eastern India. Notably, the SuCS was formed during the first phase of the COVID-19 lockdown in India, giving it a unique aspect of study and analysis. Our analysis based on 30 years of climatology data from Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) reanalysis reveals ‘positive’ monthly anomalous winds (0.8 to 1.6 m/s) prevailed over the central BoB for May 2020. The present study further found the evolution of ‘barrier layer thickness’(BLT) leading up to landfall, noting a thickening trend from 8 to 3 days before landfall, contributing to maintaining warmer sea surface temperatures near the coast. Additionally, utilizing European Centre for Medium-Range Weather Forecasts (ECMWF), reanalysis version-5 (ERA-5) data, a mean positive sea surface temperature (SST) anomaly of 0.8 to 1 °C was observed ‘before’ cyclone period (10–15 May 2020) near the cyclogenesis point. A detailed examination of Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) vertical cross-section plots during the cyclone's intensification stage reveals the presence of high-altitude clouds composed primarily of ice crystals. Further, analysis also indicates that the cyclone transported Sea-salt PM2.5 aerosols from the ocean, dispersing them in the landfall region.The aerosol optical Depth (AOD) data obtained from the National Aeronautics and Space Administration's (NASA) ‘Clouds and the Earth's Radiant Energy System (CERES)’ mission and MERRA-2 were also analysed, revealing that the cyclone redistributed aerosols over the Bengal basin region (mainly over ‘Kolkata') and three other nearby cities along the track of the cyclone (i.e., Bhubaneswar (Odisha) Agartala (Tripura) and Shillong (Meghalaya) respectively).

Role of PBL and air-sea flux parameterization schemes in the forecast of super cyclone Amphan and ESCS Phailin in the cloud-resolving scale using WRF-ARW model

Role of PBL and air-sea flux parameterization schemes in the forecast of super cyclone Amphan and ESCS Phailin in the cloud-resolving scale using WRF-ARW model

Assessment of inundation extent due to super cyclones Amphan and Yaas using Sentinel-1 SAR imagery in Google Earth Engine

Assessment of inundation extent due to super cyclones Amphan and Yaas using Sentinel-1 SAR imagery in Google Earth Engine

Seismic Signature of the Super Cyclone Amphan in Bay of Bengal Using Coastal Observatories Operating Under National Seismological Network of India

AbstractWe examined the seismic noise data collected from coastal and inland observatories in India, affected by the super cyclonic storm Amphan in the Indian Ocean, to understand the storm dynamics. Prominent disturbances in the 0.05–0.50 Hz frequency range were observed at the seismic stations, arising due to ocean‐continent interactions. The coastal stations displayed more pronounced ground motions contrary to the inland stations, with spindle‐shaped seismic wave envelopes intensifying as Amphan approached. The maximum ground displacements and energy occurred hours after the cyclone's eye, with maximum wind speed, moved away from the stations and not when it was close to the station. We observed significant variations in primary (0.05–0.10 Hz) and secondary microseism (0.10–0.50 Hz) energy during Amphan's directional changes. Secondary microseisms in short and long periods were found at 0.20–0.50 Hz and 0.10–0.20 Hz, respectively. Primary microseisms exhibited a simple pattern and were the weakest among the three energy bands. The CAL seismic station's seismic wave envelope showed an en‐echelon feature with increasing amplitude as Amphan approached, indicating the influence of ocean resonance and coastal wave reflection. This study demonstrates monitoring of the tropical cyclone paths based on seismic signatures obtained using microseisms recorded at seismic stations, a cost‐effective tool. Integrating these seismic signals with atmospheric observations in near real‐time would probably enable an effective monitoring of cyclones and timely issuance of their alerts.

Precursors of hazard due to super cyclone AMPHAN for Kolkata, India from surface observations

The track, intensity, and associated hazards of a cyclone are mostly pre- dicted using NWP models, satellites, and radar. Though the cyclones originate and strengthen in the ocean, they cause devastation in the populated land area over which they ultimately pass. Over the years, the accuracy of cyclone prediction has improved a lot. Yet, there is some uncertainty in the accurate prediction of track, intensity and associated hazards. In this article, we have studied super cyclone AMPHAN and its hazards for Kolkata, India. Here, we have proposed a new scheme for improving the forecast accuracy for cyclone distance, associated wind, and hazard for lead time up to 12-24 hours ahead based on curve fitting techniques and extrapolation using surface observational data. For the prediction of distance of the system from the concerned station and corresponding gusty wind speed, the accuracy of the proposed scheme is found to be better than the existing operational forecast and various reputed NWP models.

Public Relations New Trends on Disaster Management: Special Reference of Bihar

India has been historically prone to natural disasters on account of its distinctive geo-climatic conditions. Floods, droughts, cyclones, earthquakes and landslides are perennial phenomena. The vulnerability in India is a lot compared to developed countries. this can be leading to vast losses in terms of human, financial, environmental and resource. At the worldwide level, there has been appreciable concern over natural disasters. when the state super cyclone and also the Bhuj earthquake, we tend to complete the necessity to adopt a multi-disciplinary and multi-sectoral approach and incorporate risk reduction within the development plans and methods. The new approach of the Government of India takes from the conviction that development cannot be done properly unless disaster mitigation is constructed into the event method. Disaster Management occupies a crucial place in this country's policy framework. This paper is to spotlight the disaster profile of Bihar and Disaster Management in Bihar.

Impact assessment of COSMIC-2 bending angle in the GSI 4D-EnVar analysis scheme operational at NCMRWF

ABSTRACT This paper highlights the quality and impact of the COSMIC-2 bending angle through an Observation System Experiment, using a hybrid Gridpoint Statistical Interpolation – 4 Dimensional Ensemble Variational analysis scheme. The data quality is assessed by comparing it with the model’s background field. Analysis and background field that fit to temperature, humidity and wind components from radiosondes are verified, and the impact over model forecasts is evaluated using various metrics. There is an overall improvement, especially over the tropical region, where consistent and statistically significant positive impact is observed over the troposphere extending up through the lower to the middle stratosphere. A case study of the Super Cyclonic Storm AMPHAN showed minor improvement in central pressure and maximum 10 m wind speed. Reduction in the direct positional error of the cyclone track showed improvement in the analysis.

A study of upper ocean characteristics in response to the three intense re-curving tropical cyclones from the Arabian Sea using satellite and in situ measurements

We present the sea surface temperature (SST), latent heat flux (LHF), and sensible heat flux (SHF) studies of three tropical cyclones in the Indian subcontinent region. These three tropical cyclones were scrutinized based on their intensity scale ranging from Category 2 (Very Severe Cyclonic Storm, VSCS) to Category 5 (Super Cyclonic Storm, SuCS) on a hurricane scale (IMD scale). VSCS Vayu, SuCS Kyarr, and ESCS (Extremely Severe Cyclonic Storm) Maha formed over the Arabian Sea in June, October, and November 2019, respectively. There is a 2∘C to 4∘C difference in the SST during the pre- and post-cyclone period along the best track. The maximum reductions in SST up to 8∘C have occurred in the region from where the cyclones have re-curved. The enthalpy fluxes (LHF and SHF) are highest at 280 W/m2 around the cyclone’s best track and follow the same direction of the cyclone development. Prior flux changes in the cyclone region may have a role in directing the cyclone’s best track. Argo floats within 1∘ from the best track revealed that pre-cyclone SST was warmer at the surface than post-cyclone SST. The sub-surface SST at a depth of 100–150 m suggests a warming of the ocean in the post-cyclone period near and adjacent to cyclone intensification regions due to the upwelling of the warm subsurface waters. The upper ocean response is crucial to studying the increasing intensity of TCs and the re-curvature of its best track over the Arabian Sea.

Vertical structure of North Indian Ocean tropical cyclones: A composite analysis using TRMM and GPM

The present study deals with the vertical structure of Tropical Cyclones (TC) from 2010 to 2020 over the North Indian Ocean (NIO) using the Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement Mission (GPM). We analyzed 31 TC which were characterized as severe cyclonic storms, very severe cyclonic storms, and super cyclones out of which 18 occurred over the Bay of Bengal and 13 over the Arabian Sea. The normalized intensity difference method of brightness temperature is used to distinguish the regions of the TC into eyewall, inner rainband, outer rainband, and outer region after identifying the eye. The eye radius (Re) of the cyclone is used to define the annular regions. The vertical structure is explored using the reflectivity in each region of the cyclone and also with respect to convective precipitation, stratiform precipitation, and sea surface temperature. The intensity of the convection in the eyewall and the rainbands is strong and reaches up to an altitude of 14 km. The outer rainbands were more of stratiform nature and a distinct bimodal distribution is observed with a peak below and above the bright band. The outermost region exhibited the characteristics of both the convective and stratiform, however, the intensity is observed to be less. The convection is observed to be strong in the eyewall for high SST compared to the marginal, however, the vertical extent is large in the marginal SST. The vertical structure of the TC over the NIO contained a wider distribution of reflectivity and vertically extended compared to that of the cyclones in the other oceanic basins.

Observed oceanic response to Tropical Cyclone Amphan (2020) from a subsurface mooring in the Bay of Bengal

Upper ocean responses to the super Tropical Cyclone (TC) Amphan and modulation of energy dissipation by internal tides were investigated using in situ observations from a subsurface mooring in Bay of Bengal (BoB). The observations showed that the entire observed water column (150–800 m) cooled significantly, up to a maximum of 2 ℃, and salinity increased significantly at 150–200 m within one week after the TC, mainly due to the TC-induced upwelling. Dynamic response was characterized by strong near-inertial oscillation above 120 m. The near inertial waves (NIWs) had a maximum velocity and kinetic energy at 112.6 m, about 0.34 m/s and 59.5 J/m3, respectively. The energy spectrum and bicoherence analysis indicated that, the nonlinear wave-wave interaction between NIWs (f) and semi-diurnal tide (D2), as well as the self-interaction of NIWs were enhanced after the passage of TC. The nonlinear wave-wave interaction processes were able to transfer energy to higher mode internal waves, thus accelerating energy attenuation. Hence, the observed e-folding time for near-inertial kinetic energy (6.2 days) was only 41 % of the theoretical e-folding time. This study provided a new evidence for the mechanism of energy dissipation of NIWs and semi-diurnal tide during a TC condition in the southern BoB.

Simulation of the tide–surge: super cyclone Sidr

Simulation of the tide–surge: super cyclone Sidr

Low latitude atmospheric-ionospheric dynamical response to Prior, During, and Post stages of Super Cyclonic Storm “AMPHAN”

We present the most intensified Super Cyclonic Storm (SuCS) “AMPHAN” impacts on the low latitude atmospheric–ionospheric system from Ionosonde Observations over Chiang Mai (CMU) located at 18.76°N and 98.93°E. Extensive analysis has been carried out using ionospheric parameters foF2 and hmF2, wind components, and Outgoing Longwave Radiation (OLR). The dynamical response of atmosphere-ionosphere to SuCS AMPHAN (16–21 May 2020) has been studied in depth, and the effect of the cyclone is classified as non-cyclonic or Prior (9–15 May 2020 taken as reference), During (16–21 May 2020) and Post (22–28 May 2020) stages. We found a significant reduction in foF2 and modulated hmF2 during SuCS AMPHAN. Peak variation in ionospheric foF2 and hmF2 is seen during the ESCS (19 May 2020) and landfalling conditions. The appearance of low OLR and strong negative vertical velocity indicates deep convection during the cyclone. Evidence of 2–6 h gravity wave activity has strongly appeared in precipitation, and the ionospheric foF2 and hmF2 confirm the tropical cyclone – ionosphere dynamical coupling.

Assessment of input and dissipation source terms in the spectral wave model during tropical cyclones of varying intensity in Bay of Bengal

The vulnerability of the tropical cyclonic activities in the Bay of Bengal (BoB) domain are analyzed in terms of its destructive potential. The wave characteristics due to cyclones of varying intensities: Vardah, a Very Severe Cyclonic Storm (VSCS); Phethai, a Severe Cyclonic Storm (SCS); and Amphan, the Super Cyclonic Storm (SuCS) in BoB during 2016, 2018, and 2020 causing loss to human life and wealth, are investigated. The input-dissipation source term packages in the spectral wave models under tropical cyclones are studied through (i) integrated parameter, significant wave height, and (ii) individual source term analysis. In addition to the default linear drag coefficient in the wind input source term of van der Westhuysen et al. (2007), two nonlinear formulations of the drag coefficient are included to understand its influence on the source terms. The integrated parameters such as significant wave height are compared with buoy measurements, and the performance of the packages is ascertained through statistical error estimates. Energy contribution from the different source terms under various packages to generate the extreme significant wave height over the domain during the cyclonic period is established. The influence of the drag coefficient on the input source term is found to be pronounced.

Assessment of Ecological Disturbance on Indian Sundarbans with Special Reference to Amphan Cyclone by Using Geospatial Technology

The mangrove ecosystem of Sundarbans region plays a significant ecological and socio-economic role in both India and Bangladesh. An increase in coastal human settlements makes the area more vulnerable to natural disasters such as tsunamis and cyclones. Mangroves, as an exclusive group of plants, provide many ecological services such as reducing the impacts of cyclonic storms and gales and minimizing the sea level rise due to global warming. Sundarbans were facing immense destruction due to super cyclones during the past years. The present study investigated the ecological disturbance caused by the cyclone Amphan in Indian Sundarbans using remote sensing multispectral imagery. The pre and post-cyclonic Landsat data were analyzed to quantify the damaged area in Sundarbans due to the effect of the cyclone, Amphan. Normalized Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) were used to estimate the vegetative changes or losses that occurred due to the cyclone. Normalized Difference Water Index (NDWI), Normalized Difference Bareness Index (NDBaI) and Normalized Difference Salinity Index (NDSI)) were the other indices used to study the effects of cyclone. The study found that from pre to post-cyclonic period, mangroves reduced from 1,851.88 km2 to 1,643.74 km2 and about 50.18 km2 of vegetation becomes sparse. High salinity values were observed during the post-cyclonic period which indicated that the super cyclone resulted in saltwater intrusion. From pre to post cyclone, NDBaI results showed an increase in barren land from 908.13 km2 to 1,365.57 km2.

Modeling of impact assessment of super cyclone Amphan with machine learning algorithms in Sundarban Biosphere Reserve, India

Modeling of impact assessment of super cyclone Amphan with machine learning algorithms in Sundarban Biosphere Reserve, India

Impact Assessment of Tropical Cyclones Amphan and Nisarga in 2020 in the Northern Indian Ocean

The Northern Indian Ocean (NIO) is one of the most vulnerable coasts to tropical cyclones (TCs) and is frequently threatened by global climate change. In the year 2020, two severe cyclones formed in the NIO and devastated the Indian subcontinent. Super cyclone Amphan, which formed in the Bay of Bengal (BOB) on 15 May 2020, made landfall along the West Bengal coast with a wind speed of above 85 knots (155 km/h). The severe cyclone Nisarga formed in the Arabian Sea (ARS) on 1 June 2020 and made landfall along the Maharashtra coast with a wind speed above 60 knots (115 km/h). The present study has characterized both TCs by employing past cyclonic events (1982–2020), satellite-derived sea surface temperature (SST), wind speed and direction, rainfall dataset, and regional elevation. Long-term cyclonic occurrences revealed that the Bay of Bengal encountered a higher number of cyclones each year than the ARS. Both cyclones had different intensities when making landfall; however, the regional elevation played a significant role in controlling the cyclonic wind and associated hazards. The mountain topography on the east coast weakened the wind, while the deltas on the west coast had no control over the wind. Nisarga weakened to 30 knots (56 km/h) within 6 h from making landfall, while Amphan took 24 h to weaken to 30 knots (56 km/h). We analyzed precipitation patterns during the cyclones and concluded that Amphan had much more (1563 mm) precipitation than Nisarga (684 mm). Furthermore, the impact on land use land cover (LULC) was examined in relation to the wind field. The Amphan wind field damaged 363,837 km2 of land, whereas the Nisarga wind field affected 167,230 km2 of land. This research can aid in the development of effective preparedness strategies for disaster risk reduction during cyclone impacts along the coast of India.

Assessing the Impact of Super Cyclone Amphan on Indian Sundarban Biosphere Reserve

Assessing the Impact of Super Cyclone Amphan on Indian Sundarban Biosphere Reserve