Southwest Monsoon Season Research Articles

Long-term analysis of reference evapotranspiration variations in the lower Bhavani basin

Evapotranspiration is a crucial component of the hydrological cycle and is profoundly influenced by climate change. Assessing regional evapotranspiration changes is essential for effective water resource management. The study investigated the dynamics of reference evapotranspiration in the Lower Bhavani Basin, a region with diverse landscapes increasingly vulnerable to climatic variability. Reference evapotranspiration data from the Food and Agriculture Organization using the AgERA5 dataset was analyzed to assess annual and seasonal trends from 2000 to 2022. The result showed that the mean yearly reference evapotranspiration in the basin is 1672.87 mm, with a significant decline of 3.53 mm per year. Seasonal analysis revealed a consistent decreasing trend across all seasons, with the southwest monsoon season showing the most significant reduction in evapotranspiration rates. The notable shift in the annual evapotranspiration rate was observed in 2016, highlighting the impact of climate change. Further, temperature, solar radiation and relative humidity were identified as the dominant factors influencing evapotranspiration rates in the basin. The relative moisture index indicated prevalent dry conditions, making the region susceptible to water stress. The findings provide critical insights for regional water resources management and accentuate the need for sustainable water management strategies to mitigate the impacts of climate change.

Microbial distribution in Mudbank regions off Alappuzha, South-West coast of India.

The coastal waters of Kerala, in the South Eastern Arabian Sea (SEAS), are unique during the Southwest monsoon season due to the concurrent occurrence of two physical processes, the upwelling and Mudbanks. However, little is known about the viral ecology and activity in a system where upwelling and Mudbanks coexist, though it is generally recognized that microbial assemblages play a vital role in the food web dynamics of marine systems, particularly in upwelling. Water samples were taken from monsoon and pre-monsoon period from three locations, (M1, M2, and M3) off Alappuzha, on the southwest coast of India to examine the viral activity and distribution. The dissolved oxygen levels showed the incursion of hypoxic waters in all the stations during the peak upwelling period. Upwelling signals were prominent in all the stations, but Mudbank and upwelling co-occurred at M2 alone during monsoon. The abundance of viruses ranged from 0.86 to 15.68 × 106 Viral-like Particles (VLPs mL-1) and prokaryotic abundance ranged from 2.73-16.26 × 105 cells mL-1. Viral and prokaryotic abundance was significantly higher in the monsoon compared to pre and late-monsoon. Based on Transmission electron microscopy (TEM) results, the non-tailed viruses constituted the major (43%) proportion of the total viruses in this study region. However, the viral production rates and viral-mediated bacterial mortality were high in the pre-monsoon compared to the monsoon and late-monsoon periods. There was no obvious effect of Mudbanks on viral dynamics and the observed variations in virological and hydrological features were governed mainly by coastal upwelling.

Seasonal variation of coastal currents and residual currents in the CAT BA – HA long coastal area (VIET NAM): Results of coherens model

The COHERENS model is used to investigate the temporal and spatial variation of the coastal currents in 2021 at the Cat Ba - Ha Long, northern Vietnam. The findings indicate that tidal oscillation has a notable impact on the current fields in short-term variations (hours to days). Meanwhile, the wind field and river discharge are the decisive factors affecting the seasonal variation of the current fields in Cat Ba - Ha Long coastal area. Furthermore, the characteristics of residual currents are significantly affected by river discharges and wind patterns, which vary across different months and seasons. During the southwest monsoon season (May to August), the residual currents have a prevailing direction towards the sea, from the west and south-southwest towards the east and north-northeast, reaching maximum speeds of approximately 0.1–0.15 m/s. Conversely, in the transitional and northeast monsoon seasons, the directions of residual currents are from the east-northeast to the west-southwest, with peak speed up to 0.2–0.25 m/s. Notably, the residual currents in the bottom and surface layers in the eastern-southwestern area of Cat Ba Island and the north of Ha Long Bay are in opposite directions.

Chlorophyll-a interannual and seasonal variability in Panay Gulf: Identification of potential productive sites in the municipal waters and offshore blooms aided by water currents

Chlorophyll-a (Chl-a) is often used as a substitute for marine primary productivity measurements in fishing grounds. Panay Gulf stands as one of the Philippines’ vital fishing grounds, however, there are limited studies on its Chl-a interannual and seasonal variability. As such, this study used remotely sensed Chl-a data from 2017-2023 to assess areas with high Chl-a concentrations, and high primary productivity. The relationship of Chl-a to location, month, year, and water current variables was evaluated using a generalized additive model (GAM). Chl-a value of >10mg.m-3 was observed approximately <6.5, <2km, and <1km from the coast of Negros, Guimaras, and Panay Island respectively. During the Northeast Monsoon, short-term offshore pockets with elevated Chl-a levels were noted 13-24km from the coast of Binalbagan, Negros Occidental that function as brief feeding grounds for marine organisms. These Chl-a pockets originated from the coast of Negros Occidental and were advected by the water currents to the center of the gulf. Furthermore, 2017 and 2022 have the highest Chl-a value in Panay Gulf, coinciding with the region's seasonal high fisheries production. Major peaks were regularly observed in January and December when offshore Chl-a pockets were present. A minor peak was observed in July corresponding to the Southwest Monsoon season and attributed to summer blooms. The lowest Chl-a values were observed in September during the transition months. Furthermore, high Chl-a values were found in low current speed near the coast and water moving west and southwest during the Northeast Monsoon. This study is the first to evaluate the Chl-a dynamics in Panay Gulf, which is valuable information to understand the influence of the environment on marine productivity. This study may prompt the local government to intensify monitoring efforts and coastal protection in these valuable areas within the municipal waters.

Feeding habits of the longfin goatfish Upeneus supravittatus Uiblein and Heemstra, 2010, along Chennai coast, south India

Recognising the need to understand the feeding habits of marine fishes, a study was undertaken on the longfin goatfish Upeneus supravittatus Uiblein and Heemstra, 2010, which contributed to trawl fisheries along Chennai coast (south-east coast of India). Dataon trophic attributes such as mouth gape area, gill raker counts, stomach and intestine lengths and gut condition and contents were collected and analysed to determine condition index, index of relative importance (IRI), niche breadth and trophic level (TrL) with reference to two variables, namely, body size (small, medium and large) and season (post north-east monsoon (PNE); summer (SUM); south-west monsoon (SW); north-east monsoon (NE). The mouth gape area of U. supravittatus was 129.3 mm2. The maximum body depth-total length ratio was 1:5.0; gill rakers in lower arch was 29 and the relative intestine length was 0.48. Empty stomach contributed 56.1% of the samples. U. supravittatus fed on prey belonging to 25 Orders and &gt;40 Genera. Decapods such as shrimps and crablets were the main prey followed by fishes. The IRI of decapods was 6474 and that of fishes was only 193. The maximum prey size predated by the fish was 33.5 and 9.8% in terms of the predator’s length and weight, respectively. Higher prey diversity was noticed in small size group and during south-west monsoon season. The narrow niche breadth of 0.20 showed the selective nature of the fish to feed on decapods. The fish is a benthic carnivore with a mean trophic level of 3.58. The trophic level decreased with body size. Diet similarity was evident between north-east and post north-east monsoon and between summer and south-west monsoon seasons. Diversity indices showed marginal variation in prey diversity among size groups and among seasons. This study paves way for estimating production efficiency of U. supravittatus. Keywords: Diet composition, Index of relative importance, Trophic level, Trophic morphology, U. supravittatus

Biological and ecological determinants of Hand Foot and Mouth Disease (HFMD) in Coastal District of Northeastern Peninsular Malaysia: A 5-Year retrospective study

Hand, foot, and mouth disease (HFMD) is a common viral communicable disease in Malaysia, characterized by its self-limiting nature, yet it leads to numerous outbreaks and fatalities, particularly among young children. The current study aimed to determine the prevalence, geographic distribution, temporal patterns, and associated factors of HFMD cases within the Bachok District of Kelantan, spanning the years 2018 to 2022. A retrospective cohort study analysed extract data on independent factors and notification status from the Communicable Disease Control Information System (CDCIS). Simple and multiple logistic regression analyses were employed on a cohort of 1351 HFMD’s notifications. The retrospective analysis reveals a predominant HFMD’s notification were males (56.7%). Outpatient care was common (98.4%), with primary health care being the main choice. Logistic regression indicates higher odds for HFMD in those attending primary health care or private practitioners, daycare attendees, during the Southwest Monsoon season, and before the Movement Control Order (MCO) implementation, emphasizing key risk factors for HFMD. This study’s integrative approach recognizes that health and disease are often influenced by a combination of factors spanning the ecological, biological, and clinical domains. Thus, emphasizing the need for a comprehensive understanding when formulating public health strategies particularly in primary healthcare settings and daycare facilities during the Southwest Monsoon season.

Spatio-Temporal Mechanisms of Rainfall in Kalaburagi District: An Analysis of Trends and Variability

The study used data from 11 taluks to analyse the changes and variability in annual and seasonal rainfall in the Kalaburagi district between 2016 and 2022. Sen Slope and Mann-Kendall analyses were used to evaluate trends, while the coefficient of variation was used to measure rainfall variability. The mean rainfall was calculated using simple mathematical formulas. The findings showed minimal seasonal and yearly variability, with the exception of the southwest monsoon season. The district as a whole as well as all 11 taluks consistently saw a rise in rainfall, according to annual Sen slope research. However, during the northeast monsoon season, negative trends were observed in Aland and Sedam Taluks. In the Mann-Kendall test, the district did not exhibit any general pattern; nevertheless, several taluks, such as Yadrami and Kamalapur, demonstrated remarkable trends in the southwest and northeast seasons, respectively. Due to geographical and climatic fluctuations, the district of Kalaburagi experienced an annual mean precipitation of 797 mm. Higher mean rainfall was recorded in Sedam, Kalagi, Chincholi, and Kamalapur, while lower mean rainfall was recorded in Jevaragi and Yadrami Taluks. In the water-scarce Kalaburagi district, this work is important for policymakers addressing climate change and water resource management.

Meteorological Sub-Divisional Scale Comparison Between Two Indian Rain Gauge-Based Rainfall Datasets for the Southwest Monsoon Season

Meteorological Sub-Divisional Scale Comparison Between Two Indian Rain Gauge-Based Rainfall Datasets for the Southwest Monsoon Season

Elucidating the bacterial communities and their hydrolytic enzyme activities during the southwest monsoon season, along the west coast of India

ABSTRACT The west coast of India (WCI) is signified by increased primary productivity during the southwest monsoon season. In this study, the bacterial counts and the cultivable communities were enumerated from water depths and sediment samples at stations, off Goa, Mangalore and Trivandrum along the WCI during the monsoon season. The results reveal that the bacterial morphotypes isolated from this study included representatives from Firmicutes (70%), Proteobacteria (20%) and Actinobacteria (5%) phylum. Phylum Firmicutes had a major representation at Trivandrum and Mangalore locations compared to those from Goa. However, the Proteobacteria phylum was more prevalent in the Goa location compared to the other two locations. The morphotypes at the genera level also showed distinct spatial variations and taxa specific to each of the three locations could also be identified through Canonical correspondence analysis (CCA). Spatial variations in hydrolytic enzyme activities were also observed, with bacterial morphotypes isolated from water samples of Trivandrum exhibiting comparatively higher activities than the Goa and Mangalore sediment samples. These findings enhance our understanding of bacterial diversity and their functional roles along the WCI, emphasizing their significance in biogeochemical cycling processes.

Insights into the population dynamics of phytophthora species associated with arecanut fruit rot disease

Phytophthora, a ubiquitous filamentous oomycete, causes huge yield losses and is fatal to arecanut palms in case of severe infection. From 2014 onwards, a severe fruit rot epidemic has been recorded during the South-West monsoon season in major arecanut-growing states of South India. We have assessed the diversity and delineated the population structure of Phytophthora isolates infecting arecanut in India using a combination of morphological traits, multi-gene profiling, haplotype analysis, and pathogenicity. Ninety-eight Phytophthora isolates were obtained from infected samples collected from disease-endemic regions of Karnataka, Kerala, and Goa states in southern India from 2014 to 2019. Morphological traits coupled with phylogenetic analysis using the loci ITS, β-tub, TEF-1α, and Cox-II identified the A2 mating type of P. meadii as the predominant species together with two isolates of homothallic P. heveae. Linkage disequilibrium analysis revealed significant diversity in the form of single nucleotide polymorphisms (SNPs) from the concatenated sequence dataset. Population structure analysis using 590 SNPs demonstrated the existence of four population groups (sub-populations at K = 4 and K = 2) and significant diversity in the geo-distant Phytophthora populations. In summary, 22 haplotypes were identified from the representative 40 isolates with higher haplotype diversity of 1.23 and relatively varying haplotype frequency. Pathogenicity assays confirmed that both the species of Phytophthora were pathogenic to arecanut, while P. meadii coastal region isolates exhibited more virulence compared to others.

High‐intensity rainfall over northeast India: Spatial pattern, short‐term fluctuations and associated multiscale oscillations

AbstractNortheast India (NEI) receives most of its rainfall in the southwest monsoon (SWM) season. The region is known to have frequent and persistent rainfall events of high intensities and the region is vulnerable to potential high‐impact meteorological events. This study analyses observed daily rainfall data for the SWM months (JJAS) during 1991–2020 to better understand the climatology of high‐intensity rainfall (HIR) occurrences and their persistence. The agglomerative hierarchical cluster analysis has delineated four distinct clusters and Cramer's t test indicates no significant fluctuations at 5% significant level in the HIR events in these clusters. ERA‐5 reanalysis data have been used to find the moisture transport for synoptic‐scale (3–7 days), quasi‐bi‐weekly oscillations (10–20 days) and intraseasonal oscillations (30–60 days) for each cluster. Under positive synoptic‐scale phases, HIR in the clusters on southern latitudes of NEI occurs due to moisture incursion from the Bay of Bengal from southwesterlies at 850 hPa, and in the clusters on the northern latitudes, it is primarily due to westerlies. For, quasi‐bi‐weekly oscillations, westerlies at 850 hPa are favourable for moisture transport in most of the clusters during its positive phase. On the other hand, for positive phase of intraseasonal oscillations, westerlies at 850 hPa dominate the moisture transport in all the clusters. Also, most of the HIR events occur whenever Madden–Julian Oscillation (MJO) is in phase 1 and 2 with higher amplitude (RMM ≥1).

Precipitation Trend Analysis of Highland, India

Highland regions often rely heavily on agriculture for livelihoods. Rainfall (including snowfall) trends can directly impact crop yields and agricultural productivity. Monitoring rainfall trends aid in assessing the impacts of climate change on biodiversity, habitat suitability, and ecosystem services. Highland regions are particularly vulnerable to climate change impacts. Analyzing long-term rainfall trends provides valuable insights into climate change patterns and helps in formulating adaptation strategies to cope with changing environmental conditions. This study is based on the long-term rainfall analysis using a novel method called the 5-year lag method. The analysis has been carried out annually and the four seasons- January and February (winter/cold weather season), March, April, and May (Pre-monsoon/summer/hot weather/thunderstorm season), June, July, August and September (South-west monsoon/summer monsoon season), October, November and December (Post-monsoon/north-east monsoon/retreating south-west monsoon season).

A study on surface air Beryllium-7 concentration at radionuclide station in Tanah Rata, Cameron Highlands (MYP42) during southwest monsoon seasons in Malaysia

A study on surface air Beryllium-7 concentration at radionuclide station in Tanah Rata, Cameron Highlands (MYP42) during southwest monsoon seasons in Malaysia

Modelling Wind Speed, Humidity, and Temperature in Butterworth and Melaka during Southwest Monsoon in 2020 with a Simultaneous Linear Functional Relationship

The extension of parameter estimation from a bivariate linear functional relationship model (LFRM) to simultaneous LFRM for linear variables using the maximum likelihood estimation (MLE) method is explored in this paper. The covariance matrix of the parameter estimates is derived through the Fisher information matrix. A simulation study was done to investigate the performance of the parameter estimation. According to the simulation study, the estimated parameters have a small bias. The beauty of simultaneous LFRM lies in developing the model to study the relationship between more than two linear variables while considering error terms for all variables. The applicability of the proposed simultaneous model is demonstrated using wind speed, humidity, and temperature data from Butterworth and Melaka during the southwest monsoon season of 2020.

Designing and Modelling of Wind Turbine Simulation Using MATLAB / SIMULINK

Abstract: The renewable energy, Malaysia hopes to lessen its reliance on oil and gas. Wind energy is one of the more promising renewable sources of electricity. Malaysia is situated in an area with low wind speeds, with an annual mean wind speed of 1.2- 4.1 m/s, close to the equator. The northeast monsoon and the southwest monsoon are the two monsoonseasons that Malaysia experiences. While wind speeds during the northeast monsoon can approach 15 m/s, they can only reach 7 m/s during the southwest monsoon season. The potential for wind energy in Sarawak, Malaysia, has only receiveda limited amount of research and study. In this article, MATLAB/SIMULINK will be used for modelling and simulation of numerous wind energy conversion systems (WESC) utilizing different generators operating under the same conditionsin order to analysis the generators' efficiency. Although ultimately all of them are equally efficient, PMSG has shown tobe more efficient than SCIG and DFIG at lower wind speeds. SCIG, DFIG, and PMSG efficiency are, respectively, 66.25%, 69.38%, and 71.88% at the rated wind speed.

Recent Precipitation Trends in Six Districts of the Ken River Basin of Bundelkhand Region, India

The future development and sustainable management of water resources will be greatly influenced by the trend analysis of precipitation. This paper focuses on the analysis of rainfall trends in the Bundelkhand region, particularly in six districts covering the Ken basin. Mann-Kendall test was employed to identify potential trends, and the Sen’s slope estimator was utilized to quantify the magnitude of change during 1990 to 2020. Given that a significant portion of rainfall occurs during the southwest monsoon season, the study included both seasonal (monsoon) and annual analyses. The findings indicated a decreasing trend in precipitation for both the monsoon season and the annual scale, although many districts exhibited insignificant trends. The outcomes of this study offer valuable insights for agriculture, related sectors, and contribute to the food and energy security considerations for the six districts in the Bundelkhand region and regions with similar physiography.

A particle tracking model approach to determine the dispersal of riverine plastic debris released into the Indian Ocean

Although the Indian Ocean receives a large amount of land-based plastic waste, the studies on pathways of riverine plastic debris are limited to date. Therefore, a particle tracking model that included ocean surface currents, horizontal diffusion, Stokes drift, windage, and beaching/re-drifting processes was developed to reproduce the behavior of riverine plastic debris in the Indian Ocean. The modeled particles were released in the model domain based on riverine plastic debris database. The maximum abundance of beached particles occurred during the southwesterly monsoon season, particularly in the Bay of Bengal. The particles released from the rivers were trapped in the northern Indian Ocean unless both Stokes drift and windage were excluded from transportation velocity. These results suggest that the riverine plastic debris was trapped in the northern Indian Ocean until it fragmented into less buoyant small microplastics drifting in the subsurface layer, free from windage and Stokes drift at increasing depths.

Assessment of spatiotemporal variability of ultraviolet index (UVI) over Kerala, India, using satellite remote sensing (OMI/AURA) data.

The spatial and temporal dynamics of daily ultraviolet index (UVI) for a period of 18 years (2004-2022) over the Indian state of Kerala were statistically characterised in the study. The UVI measurements used for the study were derived from the ultraviolet-B (UVB) irradiance measured by the Ozone Monitoring Instrument (OMI) of the AURA satellite and classified into different severity levels for analysis. Basic statistics of daily, monthly and seasonal UVI as well as Mann-Kendall (MK) statistical trend characteristics and the rate of change of daily UVI using Theil-Sen's slope test were also evaluated. A higher variability of UVI characteristics was observed in the Kerala region, and more than 79% of the measurements fell into the categories of very high and extreme UVI values, which suggests the need of implementation of appropriate measures to reduce health risks. Although the UVI measured during the study period shows a slight decrease, most of the data show a seasonal variation with undulating low and peak values. Higher UVI are observed during the months of March, April and September. The region also has higher UVI during the southwest monsoon (SWM) and summer seasons. Although Kerala region as a single whole unit, UVI show a non-significant decreasing trend (-0.83), the MK test revealed the increasing and decreasing trends of UVI ranging from -1.96 to 0.41 facilitated the delineation of areas (domains) where UVI are increasing or decreasing. The domain of UVI increase occupies the central and southern (S) parts, and the domains of decrease cover the northern (N) and S parts of the Kerala region. The rate of change of daily UVI in domain of increase and decrease shows an average rate of 0.34 × 10-5 day-1 and -2 × 10-5 day-1, respectively. The parameters (rainfall, air temperature, cloud optical depth (COD) and solar zenith angle (SZA)) that affect the strength of UV rays reaching the surface indicate that a cloud-free atmosphere or low thickness clouds prevails in the Kerala region. Overall, the study results indicate the need for regular monitoring of UVI in the study area and also suggest appropriate campaigns to disseminate information and precautions for prolonged UVI exposure to reduce the adverse health effects, since the study area has a high population density.

The Impact of Climate change on Water Resources in Northern Sri Lanka: Stakeholder Perspectives

Climate change is a global phenomenon affecting the entire planet, including Sri Lanka. The Northern Province of Sri Lanka is particularly vulnerable to the impacts of climate change, especially regarding water resources. Public awareness of climate change and its impact on water resources is crucial for sustainable water management practices in the study area. In this context, this study attempted to analyze public perception of the climate change impact on the water resources of Northern Sri Lanka. There are different groups of water users in the study area. They were stratified as agriculture water users, industrial water users, fishing water users and domestic and drinking water users. Accordingly, a questionnaire survey was conducted using a stratified sampling method to identify consumer perceptions, and the collected data were analyzed using the SPSS tool. 87% of the consumers believe that climate change has a significant impact on water resources, and 50% of the people expressed vulnerability of the agriculture sector to the climate change impact on water resources. Water scarcity during the yala season became a crucial threat to paddy cultivation in the study area. Other kind of water users such as industrial water users, fishing water users and drinking and domestic water users face difficulties in obtaining water resources for their needs during the SWMS and FIMS. Furthermore, drinking and domestic water users mentioned that they face water quality issues especially during July, August and September. During the southwest monsoon season, water users face difficulties in obtaining water for their domestic needs due to water scarcity. Majority of the water users know about climate change, but many of them don’t know how climate change affects their water sources. Water suppliers should implement special projects regarding climate change impacts on water resources in the study area. This will lead the water users to use water efficiently and protect the water sources sustainably.

Development of Synoptic Analogue Model for Quantitative Precipitation Forecast over Cauvery basin, India

Daily Average Areal Precipitation (AAP) data of South West Monsoon Season for 2012 to 2020 in respect of sub-basins of Cauvery river basin were collected alongwith synoptic systems causing rainfall in the sub-basins. Five synoptic systems namely Depression/Deep Depression, low/well marked low(WML) pressure area, Upper air cyclonic circulations(UAC), off-shore trough(OST)/OST with embedded cyclonic circulations, east-west shear zone are considered in the study. Rainfall(AAP) caused by these systems considered are 11-25mm, 26-50mm, 51-100mm and &gt; 100mm. Number of days for which these systems caused rainfall under each range was computed. The rainfall range with highest frequency for the particular system is taken as Synoptic Analogue Model. OST/OST with embedded cyclonic circulation has contributed significantly to rainfall in all the sub-basins. Depression/Deep Depression over Rayalaseema, Tamil Nadu and Pondicherry, South Interior Karnataka or North Interior Karnataka provides &gt; 50mm rainfall in Harangi basin. Depression/Deep Depression over Rayalaseema, Tamil Nadu and Pondicherry, South Interior Karnataka or North Interior Karnataka provides &gt; 50mm rainfall in Harangi basin. Low/Well Marked Low over Telangana provides &gt; 50mm rainfall in Hemavathy basin. Upper Air Cyclonic circulation(UAC) over Rayalaseema provides &gt; 50mm rainfall in Kabini basin. UAC over Rayalaseema, South East Bay of Bengal or West Central Bay of Bengal off Coastal Andhra Pradesh leads to &gt;100 mm rain in Harangi. UAC over Coastal Karnataka and North Interior Karnataka or OST from Konkan Goa/Maharashtra to Karnataka leads to &gt;100 mm rain in Upper Vaigai.&#x0D; &#x0D; Key words- Aerial Average Precipitation, QPF, Cauvery river basin, Synoptic Analogue Model