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1

Utilizing fluctuation asymmetry to assess the effects of U-238 radioactivity on the marine ecosystem around the Madras nuclear power plant, India

AL-Sharif Sherif A., Chapara Manjulatha, El-Taher Atef, Salah-Tantawy Ahmed

Oceanological and Hydrobiological Studies

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2023

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Vol. 52, No. 4

437--445

EN

The monitoring of marine ecosystems is crucial due to the growing threat posed by nuclear power plants and other nuclear anthropogenic emissions. In our work, we used a straightforward and low-cost biomonitoring technique called fluctuation asymmetry (FA) to examine the variation between the left and right sides (developmental instability) of organisms’ traits that were influenced by genetic and environmental variables in the early stages of ontogenesis. The specimens of fish (Leiognathus sp.) and crabs (Portunus sanguinolentus) were collected seasonally and used as bioindicators to determine the effects of Uranium-238 (U-238) radioactivity around a nuclear power plant. The obtained results revealed that FA values were not considered typical values (FA = 0) in all seasons. Moreover, FA values of Leiognathus sp. exhibited insignificant fluctuation for a particular characteristic through the different seasons, while a significant fluctuation occurred amongst the characteristics themselves throughout the same season. Inversely, FA values of the four characteristics in Portunus sanguinolentus displayed seasonal variation amongst them all. Statistically, there was a strong positive correlation (r = 0.5, p < 0.05) between U-238 radioactivity in the flesh of both organisms and the fluctuation asymmetry of different traits but it is not a sign that any radioactive pollution exists.

2

Multivariate approach to evaluate the factors controlling the phytoplankton abundance and diversity along the coastal waters of Diu, northeastern Arabian Sea

Kumar Ponnusamy Sathish, Venkatnarayanan Srinivas, Pandey Vikas, Ratnam Krupa, Jha Dilip Kumar, Rajaguru S., Dharani Gopal, James Rathinam Arthur, Atmanand Malayath Aravindakshan

Oceanologia

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2022

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No. 64 (2)

267--275

EN

The present study investigated the phytoplankton assemblage and diversity with physicochemical parameters of Diu coastal waters in different seasons during 2018–19. During the study period, 61 phytoplankton species comprising diatoms (50 sp.), dinoflagellates (8 sp.), and cyanophyceae (3 sp.) were recorded. Diatom was found to be a major community and contributed 79 to 99% of total phytoplankton abundance. Reduction in dinoflagellate and dominance of pennate-diatoms were observed during the monsoon. Chlorophyll-a concentration also showed a similar trend and decreased during the monsoon. However, the phytoplankton abundance was low particularly during the monsoon which might be due to the elevated total suspended solids (TSS) load. Canonical correspondence analysis revealed that diatoms were able to survive in high TSS with the support of high nutrients; while dinoflagellates were limited due to those conditions. Overall, the reduction in phytoplankton abundance, diversity, and biomass was recorded due to the elevated TSS input along the coastal waters of Diu.

3

Inter-annual and seasonal patterns of precipitable water vapour over Malaysia from 1990-2019 based on MERRA-2 reanalysis

Makama Ezekiel K., Lim Hwee S.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2021

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Vol. 30, No. 1

208--218

EN

In this study seasonal and inter-annual patterns as well as trend in the total precipitable water vapour (TPW) over Malaysia, based on a 30-year data from MERRA-2, have been evaluated using least square regression method. Indicator TPW revealed a pair of minima in February/August and maxima in May/November with highest and lowest long-term means found in East Malaysia. Long-term seasonal variability of TPW exhibited latitudinal dependency in both the NEM and SWM seasons. Indicator TPW showed respective southeast-northwest and southwest-northeast spatial distribution in West and East Malaysia, with the highest statistically significant positive trend found in the former.

4

Satellite estimates of the long-term trend in phytoplankton size classes in the coastal waters of north-western Bay of Bengal

Miranda Joereen, Lotliker Aneesh Anandrao, Baliarsingh Sanjiba Kumar, Jena Amit Kumar, Samanta Alakes, Sahu Kali Charan, Kumar Tummala Srinivasa

Oceanologia

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2021

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No. 63 (1)

40--50

EN

The study presents long-term variability in satellite retrieved phytoplankton size classes (PSC) at two coastal sites, off Gopalpur and Visakhapatnam, in the north-western Bay of Bengal. The abundance-based models by Brewin et al. (2010) (B10) and Sahay et al. (2017) (S17), for retrieval of PSC (micro, nano, and picophytoplankton), from satellite data, were validated. Both the models performed well in the retrieval of nano and microphytoplankton. However, B10 performed poorly in retrieving picophytoplankton. The statistical analysis indicated better performance of the S17 model and hence was applied to Moderate Resolution Imaging Spectroradiometer onboard Aqua satellite (MODISA) data to understand the temporal (at monthly climatology) and spatial variability (from nearshore to offshore). The spatial distribution indicated nearshore dominance of micro and offshore dominance of picophytoplankton. In nearshore waters off Gopalpur, microphytoplankton dominated throughout the year except for months of south-west monsoon (June and July) where the dominance of picophytoplankton was observed. All PSC exhibited similar distribution at an annual scale with a primary peak during pre-monsoon (March and April) and a secondary peak during post-monsoon (September-November). However, microphytoplankton concentration during post-monsoon was higher off Gopalpur in comparison to Visakhapatnam. The higher microphytoplankton concentration during pre-monsoon was attributed to recurrent phytoplankton blooms. Whereas, post-monsoon increment could be attributed to enhanced phytoplankton growth by availing nutrients sourced from monsoonal precipitation induced terrigenous influx. The outcome of the present study recommends the use of the S17 model for satellite retrieval of PSC from the north-western Bay of Bengal.

5

Study of statistical estimated parameters using ERA5 reanalysis data over Khulna region during monsoon season

Koutavarapu Ravindranadh, Umakanth N., Satyanarayana T., Kumar M. Seshu, Rao M. C., Lee Dong‑Yeon, Shim Jaesool

Acta Geophysica

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2021

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Vol. 69, no. 5

1963--1978

EN

Thunderstorms are extreme localized weather phenomena that form primarily as a result of intense atmospheric convection. These are characterized by heavy rainfall, lightning and thunder. Thunderstorms occur in monsoon season over some parts of the world, and they can be found in the rain bands of many convective systems. Thunderstorms are a natural weather occurrence that results in significant damage to property and people all over the world. Lifted index, K index, total totals index, humidity index (HI), total precipitable water (TPW), convective available potential energy, deep convective index, S index, maximum temperature and rainfall parameters are investigated over Khulna region in Bangladesh during the monsoon season. We have measured all the above parameters using daily ERA5 reanalysis data for the monsoon season from 2011 to 2020. High TPW values (~>60 mm) and low HI values (~<20 K) are observed during July and August months over Khulna region. DCI values greater than 30 °C are observed which indicates highly favorable for severe convection-related thunderstorms. We have experimented ARMA model to estimate four parameters. The major motive behind this is to compare the accuracy of the ARMA model data to ERA5 data. For obtaining reliable statistical estimates of thunderstorm parameters, the ARMA model proved to be extremely useful.

6

Indian Ocean wind speed variability and global teleconnection patterns

Sinha Mourani, Jha Somnath, Chakraborty Paromita

Oceanologia

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2020

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No. 62 (2)

126--138

EN

The influence of the local sea surface temperature (SST) and remote ENSO (El Niño-Southern Oscillation) indices on the wind speed (WS) data were explored for the Indian Ocean region. Relationships among the parameters were studied using spatial correlation plots and significant correlation ranges. Two months (July and January) representing opposite monsoon phases were selected for analysis for the period 1950-2016. There was a significant negative correlation between WS and SST over the Bay of Bengal (BOB) during July. Although different ENSO indices correlated differently in different areas of the Indian Ocean, the region off the coast of Sri Lanka was most significantly teleconnected. The southwest monsoon locally impacted the WS and SST relationship and the WS parameter was remotely teleconnected in both the monsoon seasons. Further empirical orthogonal function (EOF) analysis was applied on the 67 years WS data of the BOB region to extract the dominant mode representing maximum variability of the total variance. The temporal pattern of the first principal component (PC1) of WS data was linked to the North Atlantic Oscillations in January and the Atlantic Multidecadal Oscillation in July respectively. The continuous wavelet power spectra of the PC1 of WS showed significant regions in the 2-4-year band resembling the ENSO variability. Wavelet coherence applied between PC1 of WS and the ENSO indices showed greatest values for January in the 8-16-year band and for July in the 0-4-year band. A close relationship was established between the WS variability in BOB and the ENSO indices.

7

The interaction between local factors and the Convectively Coupled Equatorial Waves over Indonesia during the Western North Pacific and Australian monsoon phase

Pramuwardani Ida, Sunarto Hartono, Sopaheluwakan Ardhasena

Meteorology Hydrology and Water Management. Research and Operational Applications

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2020

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Vol. 8, Iss. 1

84--89

EN

A large scale perturbation by the Convectively Coupled Equatorial Waves (CCEW) is often observed in the tropics as a precursor to influence weather condition, for example over the Indonesian archipelago (Maritime Continent (MC)). This study examines the interaction between local factors and CCEW with regard to convection and vertical interferences on a local scale over Indonesia during extreme Western North Pacific (WNP) and Australian (AU) monsoon phases. Through space-time spectra analysis of a 15 year (2001-2015) Tropical Rainfall Measuring Mission (TRMM) 3B42 dataset, the propagation of CCEW, i.e. Kelvin, Equatorial Rossby (ER) and Mixing Rossby-Gravity (MRG) waves was assessed. An Empirical Orthogonal Function (EOF) 1 and 2 for each wave evolution across the region of Indonesia, was then compared with daily precipitation anomalies and multilevel wind observations from seven locations in Indonesia to assess the interaction between local factors and CCEW. Results suggest there is evidence of local convection associated with Kelvin waves in the afternoon through to the evening in Tangerang, Surabaya and Makassar during WNP monsoon phases. Local convection associated with MRG waves only occurred in Makassar at the last evolution day during the same period, while there is no clear evidence for an interaction between local factors for ER waves. Low-level westerly winds appear to be significantly coupled with convection from Kelvin waves in Tangerang, Surabaya, and Makassar during the WNP monsoon phase, while the interaction is less significant for MRG-coupled convections (except in Makassar during the same monsoon phase) and absent for ER waves. This study suggests that the global scale phenomena of the Kelvin wave is associated with local scale factors in controlling convection, particularly during an extreme WNP phase in Indonesia.

8

Palaeoflood records from Upper Kaveri River, Southern India: evidence for discrete floods during Holocene

Kale V. S., Achyuthan H., Jaiswal M. K., Sengupta S.

Geochronometria

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2010

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Vol. 37

49-55

EN

A record of six discrete middle Holocene floods has been established based on sedimentological and stratigraphical studies in the upper Kaveri catchment at Siddapur. The flood events are represented by six discrete, sharp-bounded, sand-silt couplets. Texturally and geochemically the suite of couplets is quite distinct from the overlying and underlying structureless fluvial deposits. Based on OSL ages the suite of couplets cover the Holocene from ~8 to ~2 ka. Such evidence is not present or reported from any other river originating in the Western Ghat in the Indian Peninsula. We argue that the six couplets represent short-term, high discharge events or flash floods. The initiation of this phase of flash floods broadly corresponds with the southward migration of ITCZ and a gradual decline in Indian summer monsoon precipitation starting at ~7.8 ka. Comparison of the elevation of the highest couplet with the high flood level (HFL) of the 1961 extraordinary flood on Kaveri demonstrates that the 20th century flood was higher than the mid-Holocene palaeofloods.