NE Monsoon Research Articles

Investigation of climate change by analysing the rainfall pattern in kuzhithuraiyar sub-basin of India using GIS-based spatial analysis

Global climate change may have a significant effect on several environmental components in many different nations worldwide. Variations in the pattern of precipitation have an immediate impact on the management of water resources. To improve water resource management techniques, it is critical to investigate differences in the temporal and geographical rainfall patterns. The current study looks at rainfall patterns in the Kuzhithuraiyar sub-basin of the Kodayar basin, Kanyakumari District. Utilizing the mean monthly data from four distinct rain gauge locations, we have comprehensively compiled and analysed rainfall statistics over an extensive timespan of 30 years (1991–2020). For precision in temporal categorization, this data was meticulously divided into four seasonal classifications: pre-monsoon, post-monsoon, southwest monsoon (SW), and northeast monsoon (NE). Using ArcGIS 10.8, the rainfall pattern was analysed, and spatial distribution maps for the four seasons listed above were created using the inverse distance weighting (IDW) approach. The region receives an average of 1456.78 mm of precipitation each year, with the post-monsoon, pre-monsoon, SW monsoon, and NE monsoon providing 32.87 mm, 335.28 mm, 538.67 mm, and 549.97 mm, respectively. The results reveal that the model correlates mean rainfall and rainfall variability over areas of Tamil Nadu's Kuzhithuraiyar sub-basin with some accuracy in terms of the number of rainfall extremes and their spatial distribution maps.

Planktonic foraminifera fluxes and their response to the Asian Monsoon: insights from the Maldives, Indian Ocean

This study describes seasonal changes in the fluxes of planktonic foraminifera in response to changes in environmental conditions during the Asian Monsoon. Sediment trap systems were deployed for a period of 1 year at two locations in the Maldives: Kardiva Channel and Inner Sea. Twenty-six (26) planktonic foraminifera were recognized, of which six species (Trilobatus sacculifer, Globorotalia menardii, Globigerinoides ruber, Globigerina siphonifera, Neogloboquadrina dutertrei, and G. bulloides) dominated the assemblage (82%–84%) in both sites. Planktonic foraminifera fluxes and chlorophyll-a concentrations are higher in the Inner Sea. Total planktonic foraminifera fluxes show preference to high nutrient conditions during monsoon periods. Planktonic foraminifera fluxes generally follow the trend of carbonate fluxes except during October-November 2014. Species flux generally reached maximum during the NE monsoon as a response to increase in nutrient concentration brought by the movement of the North Equatorial Current over the trap sites. The expansion of nutrient-rich surface waters, occurring eastward during the SW monsoon and westward during the NE monsoon, led to an increase in the population of species dwelling in both shallow (T. sacculifer and G. ruber) and deep waters (N. dutertrei and G. bulloides). Dominance of shallow-dwelling species T. sacculifer and G. ruber throughout the sampling period suggests stable stratification of the water column. This supports the idea of wind-mixing rather than local upwelling as the driving force for enrichment of nutrients and subsequent increase in planktonic foraminifera fluxes. Lateral advection and resuspension in settling of particles to the traps is evident based on the presence of benthic foraminifera in the Inner Sea samples. These processes, however, did not significantly mask climate and surface ocean signals since there remains a clear correlation between planktonic foraminifera fluxes and environmental conditions.

Assessment of potential wave power along a coastal province, Central Vietnam

The potential wave power has been assessed based on long-term wave data along a marginal sea area offshore Phu Yen province in Central Vietnam. Based on the publicly available WaveWatch-III reanalysis wave data (NOAA), the deep-water wave climate during the period from 1989 to 2019 has been analysed and used as the boundary condition for the MIKE21 spectral wave model. The hydrodynamic module of MIKE21 is also run in coupled mode. The model has been calibrated and verified against the measured data at three wave gauges. Simulation has been performed for every month, each with 1-2 typical wave conditions. The results show that the highest wave power (~29 kW/m) occurs in December. The distribution of wave power along the 30-m depth contour has also been presented for the annual average, NE monsoon (winter) average, and S monsoon (summer) average. The distribution map shows that wave power is slightly higher in the south of this area, and the NE monsoon season comes along with much higher wave power (7.4 times compared to that of the S monsoon season). These findings may aid in planning effective exploitation of wave energy for the region.

Seasonality in groundwater recharge in Coastal Southwestern India and its hydrological implications based on stable isotopes (δ18O, δD)

This study observes and interprets the spatio-temporal variation in the oxygen and hydrogen isotopic composition (δ18O, δD) of shallow groundwater in the Southwestern Coastal state of India, Kerala, in terms of seasonally varying rainfall, physiography, and hydrogeological settings of this region. This study identifies effective groundwater recharge sources and their relative contributions and provides first-order estimates of submarine groundwater discharge by interpreting the spatio-temporal variations in the stable isotopes of oxygen and hydrogen in groundwater, collected from 225 locations for pre-monsoon and post-monsoon seasons in conjunction with the isotopic composition of rainfall. Spatio-temporal variations in the δ18O and d-excess, with other hydrogeological data, reveals that: (1) ∼4.9 Billion Cubic Meter (BCM) of fresh water from rainfall during May to October mixes with ∼5.9 BCM of residual pre-monsoon groundwater across Kerala. (2) ∼ 11% area of Kerala is additionally recharged by the NE monsoon rainfall. (3) The annual groundwater recharge varies physiographically from ∼2.2 BCM in the lowland to ∼1.5 BCM in the midland and ∼1.2 BCM in highland regions. (4) On an annual basis, 41% of replenishable groundwater is drained as SGD into the Arabian Sea.

Sea Level Variability in the Equatorial Malacca Strait: The Influence of Climatic–Oceanographic Factors and Its Implications for Tidal Properties in the Estuarine Zone

The sea level trend in the equatorial Malacca Strait is a significant issue that needs to be reviewed since it is an area of interest. Assessing its future impact on estuarine tidal characteristics is worth studying because it relates to the potency of coastal damages. This study aimed to discuss the relationship between sea level variations and anomalies and their possible triggering factors and to estimate the future impacts on the tidal properties in the estuarine zone. Tide gauge and altimetry data in the Tanjong Pagar site were used to assess the sea level trends over 27 years of observation (from 1992 to 2019). Both altimetry and tide gauge data showed an upward trend, with 0.24 cm/year and 0.39 cm/year, respectively. Due to the near-equatorial area of interest, sea level variability is more synchronized with ENSO rather than IOD. At some points, ENSO shapes the sea level fluctuation, with an R2 of less than 10%. For specific periods, the coupling effects between MJO and La Niña may trigger higher evaporation in the maritime continent, triggering increasing sea levels. Of particular concern, among the other assessed factors, the zonal currents and winds (wind-driven currents) are strongly correlated with sea level variations, primarily during the NE monsoon and the second transitional periods, with a determination coefficient of about 18–36%. As a result of sea level rises, it is estimated that tidal constituent amplitudes will increase by about 8.9% and 18.3% in 2050 and 2100, respectively. The increase in tidal range will possibly relate to the tidal bore passage in the Kampar estuary. Therefore, more advanced hydrodynamic modeling is necessary to determine the impact of sea level rises on tidal bore generation.

Assessment of Wet and Dry Spells Over North Western Zone of Tamil Nadu Using WASP

Rainfall is the most dependent weather factor that decides the success or failure of a crop in a location. The behaviour of rainfall plays a major role in the selection of crop, cropping system and cropping pattern. It is also essential for planning of water resource management structures. Hence it is essential to study the anomaly in rainfall over a long period of time to identify the deviation in rainfall pattern over the region. Weighted Anomaly of Standardized Precipitation Index (WASP) is an index that can help in identifying the occurrence of dry or wet spells over different time scales (tri, hexa, nona and dodeca-monthly). The analysis was carried out for Salem district of Tamil Nadu over a period of 30 years (1991-2020) which has an average rainfall of 990 mm per year with bimodal distribution. The analysis shows an increase in near normal events, decrease in wet as well as dry events with 3 m, 6 m, 9 m and 12 m WASP. The 3 m-WASP indicates the north east monsoon have more variability in rainfall since more number of wet as well as dry events have occurred during this season. With 6 m WASP During, in all the 3 decades, the consecutive wet as well as dry events have been occurred during the winter and NE monsoon seasons. This shows the risk in crop cultivation during NEM season because of higher instability in rainfall. Considering the longer time scale of 9 m and 12 m WASP indicates the occurrence of prolonged extreme dry or extreme wet events to be very minimal. The negative effects of these events can be handled easily by adopting proper drainage, water harvesting and storage structure within the farms. These structures can also help in recharging the ground water table in addition to supplementing water needs for the crops.

Role of Ocean-Atmosphere Interface in Annual and Semiannual SST Cycles in the Indian Ocean

A long-term analysis of temperature can be used to describe the main mechanisms that operate at the surface of the ocean. The average sea surface temperature (SST) contour plots for the Indian Ocean are produced based on the World Ocean Atlas Data Set (1994). SST, together with the independent variables wind (Wx, zonal component of pseudo-stress wind and Wy, meridional component of pseudo-stress wind), net-down-fresh-water-flow (NDFF), and Ekman pumping, are included in a multiple regression analysis to define the relative importance of each one of these variables in the physical processes at the surface of the Indian Ocean. The NDFF data set is based on COADS (Comprehensive Ocean-Atmosphere Data Set). The wind data is obtained from the Florida State University (FSU). The harmonic terms of the variables are calculated, which is considered to be stationary and expressed by a Fourier series as a cosine function. The harmonic terms are multiplied by the maximum amplitude of the variables and then added to their mean annual values. The isotherms are mainly meridional along the western boundary, but zonal in the southern Indian Ocean. The annual component is seen to have a maximum in July, Summer Monsoon (SW Monsoon) and a minimum in January, during the Winter Monsoon (NE Monsoon). The amplitude of the semiannual component is smaller, with two maxima in May and October and two minima in February and August. The small magnitude of these residuals errors is an indication that the temperature variability during this period and for this area can be explained reasonably well by the two harmonic terms. In the Arabian Sea, the final regression equations for SST variability show that it is mainly affected by the Wx, Ekman pumping and NDFF. For most of the areas of the Bay of Bengal, as well as for most of the locations in the southern tropical Indian Ocean, the entered independent variables can explain SST. Two components fit to observation can be used to predict SST together with the regression equations. Although harmonic analysis can be used to study SST variability, a multiple regression analysis is required to identify and quantify the variables related to areas of large annual and semiannual variability. Different techniques are therefore used together to provide more reliable results in SST configuration in the Indian Ocean.

The effect of environmental factors on spatial-temporal variation of heterobranch sea slug community in northern Taiwan

Sea slug (Subclass Heterobranchia) biodiversity is an important element of marine coral reef communities. However, due to their small size and cryptic behavior, few studies have examined their spatiotemporal variation. Taiwan is in the middle of East Asia Island Arcs, where it is one of the hotspots of sea slug diversity. Meanwhile, the northeast coast of this island lies within the subtropical monsoon region, where the climate shifts from a warm southwest monsoon (SW: May to Sep) to a cold northeast monsoon (NE: Oct to Apr). Between the monsoons, distinct temperatures and currents result in different community structures. To understand how those environmental factors (i.e., monsoon season, diel period and water depth) influence sea slug species richness and assemblages, we surveyed these invertebrates monthly at both night and day by diving in a marine protection area (CJ) and at a nearby non-protected site (MR) from May 2020 to Apr 2021. We showed that the species composition in our sampling area was highly consistent with what was found in Okinawa and Pescadores island, but less similar to those in southern Taiwan or Hong Kong. On the northeast coast of Taiwan, sea slug number and abundance were both higher in CJ than MR, but biodiversity (H’) and the species evenness indexJ’ was lower in CJ than MR. Additionally, cluster analysis indicated that the sea slug assemblages differed between the two sites. Monsoon season significantly influenced both species richness and species assemblages, with species richness during SW being significantly higher than in the NE monsoon and species assemblages also being distinct between these two seasons. Moreover, species richness increased with water depth (within the surveyed range of 0-25 m). Diel period did not exert a strong impact on sea slug biodiversity, except for species richness at CJ, where it was higher during the day than at night. Our study suggested that changing currents between the monsoon seasons could transport individuals originating from either the north or south of these island arcs. Furthermore, temperature and food sources may differ between seasons and depths, thereby influencing sea slug assemblages in this region.

Comparison of common air pollutants, meteorological parameters, and cardio-respiratory hospitalization between urbanized areas in Kelantan

A high concentration of air pollution is relational to meteorological conditions and the consequences can lead to health problems which are cardiovascular and respiratory-related diseases. This study aimed to compare air pollution, meteorological reading, and hospitalization in urbanized areas in Kelantan. The secondary data for this study were obtained from DOE and MOH for descriptive and trend analysis from the year 2000 until 2015 at three different locations: Tanah Merah, Pengkalan Chepa, and Kota Bharu Kelantan. The mean concentration for SO2, O3, CO, NO2, and PM10 were 0.001 ± 0.001 μg/m3, 0.014 ± 0.004 μg/m3, 0.657 ± 0.145 mg/m3, 0.007 ± 0.002 μg/m3 and 45.195 ± 11.229 μg/m3 respectively. Overall, the concentration of all the criteria air pollutants was lower than the MAAQS except for PM10. The trend analysis shows the concentration of air pollutants, and the meteorological parameter were fluctuating and influenced by the monsoon. High wind speed and temperature were observed during the NE and SW monsoon, respectively. Tanah Merah showed a higher concentration of PM10 compared to the other two locations. In contrast, Kota Bharu and Pengkalan Chepa has higher gasses concentration than Tanah Merah. The gasses result in consistent with cardio and respiratory-related hospitalization which showed higher hospitalization recorded in Kota Bharu than Tanah Merah. In conclusion, the urbanized areas have different dominant air pollutants due to the potential major sources that exist differently.

Validation of Cloud Burst over Chennai in 2015 using Radar data

In 2015, three synoptic-scale weather systems affected Tamil Nadu and Pondicherry during the NE Monsoon season, causing extensive rainfall activity. Extremely heavy rains occurred over Chennai and surrounding districts, due to which Chennai was fully inundated. Rain rate of the order of 100-200 mm/hour led to cloudburst over Chennai. In this paper, we have used radar data to examine and substantiate the cloud burst that led to these torrential rains over Chennai during 8-9 November and 30 Nov-2 December 2015

Distribution features of the weather conditions in Nha Trang Bay (The South China Sea)

Nha Trang Bay is a semi-envelop coastal basin. It is located on the west coast of the South China Sea as well as in the south of the central part of the Vietnamese coast. The climate of the bay belongs to the sub-equatorial zone or to the zone of equatorial-tropical monsoons. Determination of the meteorological characteristics of an ocean region, especially for nearshore bay waters, plays a very important role in the sustainable development of the social-economical system of Vietnam. This paper presents a spatial and temporal long-term analysis of several meteorological characteristics in Nha Trang Bay, such as wind, tropical cyclones, air temperature, air humidity, and rainfall. The meteorological data were collected from the Nha Trang meteorological station during 1977–2015 (wind data until 2020).
 The data for typhoons were extracted from the National Weather Service (USA) and the Japan Meteorological Agency during 1945–2015. Statistical methods for collecting and analyzing data to estimate the statistical parameters of meteorological characteristics were used in the study.
 A study of results shows that the meteorological characteristics in the Nha Trang Bay are a seasonal variation of the East Asian monsoon (northeastern-NE and southwestern-SW monsoons).
 The winds in Nha Trang Bay are the seasonal change, influenced by the NE monsoon from October to April and the SW monsoon from June to August. May and September are the transition periods.
 Nha Trang Bay has a temperate tropical climate because the temperature regime of the bay ranges from less than 25°C in the winter and more than 28°C in the summer.
 Extreme conditions, including typhoon activity and heavy rainfall (coinciding with high humidity), occurred in October, November, and December.

Environmental Regulation of Photosynthetically Produced Dissolved Organic Carbon by Phytoplankton Along a Subtropical Estuarine Bay

Photosynthetically produced dissolved organic carbon (PDOC) released by marine phytoplankton has an important significance on the marine carbon cycle and on the growth of heterotopic bacteria (HB). However, PDOC is often neglected in the estimation of global marine primary productivity and carbon sequestration capacity. This work studied the issue of PDOC and its environmental regulation mechanism through field investigation and lab experiments in an estuarine bay during southwest and northeast monsoon. We used the percentage of extracellular release (PER) as a key indicator to evaluate the contribution of PDOC to total primary productivity (TPP). We also compared PER among different seasons and sectors and then analyzed the inter-relationship between PDOC and bacterial carbon demand (BCD), size-fractionated phytoplankton, bacterial production (BP), and TPP. We finally discussed the impact factors of PDOC productivity. The results showed that the average contribution of PDOC to TPP in Qinzhou bay could reach 15% during two seasons, which satisfies about 25% of the carbon requirement by HB in the bay. Multiple factors contribute to the seasonal (SW monsoon 13% < NE monsoon 18%) and sectoral variation (outer bay 26% > middle bay 17% > inner bay 7%) in PER, the most significant of which are salinity and nitrogen to phosphorus ratios. PER is also related to phytoplankton community structure and nutrient limitation, the higher PER in the outer bay is attributed to the dual effect of picophytoplankton being the predominant species and a severe imbalance in the nitrogen to phosphorus ratio, both of which lead to increased phytoplankton PDOC release. On the other hand, the lower PER in the inner bay was mainly due to the dominance of microphytoplankton and nitrogen to phosphorus ratio which is close to the redfield ratio. There is still a non-uniform conclusion on the relationship between PER and TPP, suggesting that this relationship needs to be evaluated not only in a horizontal-independent way but also through seasonal and vertical dimensions. The non-linear relationship between PDOC and BCD found in this study potentially indicated weak coupling between phytoplankton exudation and bacterial metabolism. In addition to phytoplankton exudate, HB is still dependent on other sources of DOC to meet their carbon requirements.

Remote forcing of winter cooling in the Arabian Sea: Implications for the NE monsoon

The regional climate in the Asian subcontinent is highly influenced by the Southwest Monsoon (SWM) and Northeast Monsoon (NEM) during boreal summer and winter, respectively. Although the response of the SWM to the abrupt climatic changes recorded in the Greenland ice core records is well documented, the response of the NEM to the high latitude climate shifts is less well-understood due to the lack of winter monsoon records in the region. Here for the first time, we report the variability of winter cooling in the Arabian Sea and the associated NEM strength over the last ~37 kyr BP using seasonal sea surface temperatures (SST) derived by artificial neural network technique (ANN), based on planktonic foraminiferal species abundance data. Low winter SST anomalies in the northeastern Arabian Sea, a proxy for NEM strength, coincide with cold stadials (YD, H1, H2, H3) in the Greenland record and weakened SWM, implying that the cold conditions in Greenland strengthen the NEM and weaken the SWM on the Asian Subcontinent. Asynchrony between the NEM and SWM variability between ~37 and 9 kyr BP was driven by the southward shift of the Intertropical Convergence Zone (ITCZ) during colder phases of the Greenland stadials strengthening the NEM and weakening the SWM. This study implies that the migration of the ITCZ in the tropical Indian Ocean is controlled by the meridional atmospheric temperature gradient resulting from Atlantic Meridional Overturning Circulation (AMOC) changes. • Close link between NEM and winter cooling in the Arabian Sea was documented. • Strong coupling between AMOC and ITCZ migration • Distinct asynchrony between strengths of NEM & SWM during YD, H1, H2, H3 • NEM variability shows a clear contrast between MIS 2 and MIS 1.

Crop planning based on rainfall variability for Bastar region of Chhattisgarh, India


 Analysis of long-term rainfall data (1986-2018) of Bastar region revealed decreasing trend in total quantum of annual rainfall with varying frequency and distribution. The quantity of winter and summer rains decreased drastically during 2008-18 as compared to earlier two decades (1986-96 and 1997-2007). SW monsoon rain of 2008-18 was more than past two decades, whereas NE monsoon rain changed much in quantity except during 1997-2007. During 1986-96, the pre-monsoon shower was received in April, but later two decades the shower was received in May, which supports for summer ploughing and dry aerobic seeding. The cropping period almost synchronized between 22-43 standard meteorological week (SMW) reaching 93.11 mm per week as maximum rainfall. As the probability of 20 mm rainfall decreased from 75 to 50%, the crop yield got reduced by 30%. The mid-land rice with a probability of 13.47 to 16.07 mm rain per week supported growth phase during 17-21SMW. Whereas, upland rice maturing in 90-100 days could avoid dry spells, if the rice is managed by conservation furrows at the time of sowing. The summer ploughing is preferred with more than 40 mm rain in single day during March to April for mitigating dry spells. On the other hand, preparatory tillage and sowing were performed together in support of ripening niger and horsegram under probability of 75, 50 and 25% rain through crop planning. Maize and small millets reduced yield significantly when rainfall reached 75% deficit, whereas 25% deficit rain did not affect the yields.

Calculation and analysis of cloud attenuation and other cloud parameters in India for earth-space links

• The cloud attenuation is higher during the SW monsoon season followed by NE monsoon, pre-monsoon and winter seasons at the places considered. • The maximum cloud attenuation of 1.67 dB/km is measured in Hyderabad by WVP-NTU cloud detection model at 24 GHz. • The WVP-NTU cloud detection model is more suitable for the five places considered as compared to the SU model. An effort is made to examine the cloud parameters over few stations in India for one year from October 2016 to September 2017. This study includes the investigation of cloud base height, cloud top height, zero degree isotherm height, number of cloud layers, cloud thickness, number of days cloud detected, cloud liquid water content and cloud attenuation at 6 GHz, 12.5 GHz and 24 GHz. Salonen Uppala (SU) model and Water Vapor Pressure-Nanyang Technological University (WVP-NTU) model are used for cloud detection using the radiosonde data at Bangalore, Hyderabad, Mumbai, Thiruvananthapuram and Chennai. The cloud parameters found using both the models are compared. WVP-NTU model shows enhanced values for most of the cloud parameters over SU model. Cloud base height calculated using these models are compared with METAR data and found that Cloud base height from WVP-NTU model matches well with METAR data. Cloud liquid water content and cloud attenuation values are calculated using the ITU-R model. The cumulative distributions (CDF) of cloud attenuation for one year are compared for the places considered. The seasonal CDFs of cloud attenuation using the WVP model are compared with the rain statistics. In this study, the maximum cloud attenuation of 1.67 dB/km is measured in Hyderabad by WVP-NTU combined ITU-R model at 24 GHz.

Trends and patterns of SST and associated frontal frequency in the Vietnamese upwelling center

Ocean fronts are areas of increased primary productivity susceptible to climate induced ocean warming. Quantifying the spatial and temporal variability of thermal fronts in rapidly warming parts of the ocean is needed. Frontal frequency (FF) in SST imagery was examined in the coastal upwelling region of South-Central Vietnam, a known marine hotspot. Level-1 daily MODIS data between 2003 and 2018 was used to generate level-3 mapped SST products. The Cayula and Cornillon single image edge detection (SIED) algorithm was used to extract fronts from the SST imagery. Two types of fronts were found in the area, both strongly influenced by seasonal monsoons. Upwelling fronts were found along the southeast coast of Vietnam and extending eastward from the upwelling center during the SW monsoon. Shelf fronts, running along the 100 m – 200 m isobath, separate the cold-water current from the north with the open ocean during the NE monsoon. An upward trend of SST was recorded at approximately 0.05 °C/year throughout the 16-year period (p < 0.05), with rates of increase being higher during the Southwest (SW) monsoon period (May-September). The two longest marine heatwaves (MHW) occurred during El Niño years, nine days in 2010 and 16 days in 2016 with highest maximum intensity of 2.95 °C. The results show that FF trend is increasing significantly in region with shelf fronts and that this increase is associated with a positive SST trend. Additionally, El Niño/La Niña is associated with variability of fronts in this small-scale marine hotspot over the last 16 years.

Seasonal Diversity and Distribution of Butterflies in G.Venkataswamy Naidu College Campus, Kovilpatti, Tuticorin District, Tamil Nadu

This study was conducted to prepare a baseline inventory, seasonal population trends and status of butterfly inhabiting the campus of G. Venkataswamy Naidu College, Kovilpatti, Tuticorin. The survey yielded 309 individuals of 48 butterfly species, belonging to the families Nymphalidae, Pieridae, Lycaenidae, Papilionidae and Hesperiidae. Nymphalidae were found to be the dominant family during all seasons. Species abundance was highest during the northeast monsoon and winter periods. The maximum number of 163 individuals was sampled during the NE monsoons followed by winter 109 individuals and SW Monsoon showed 23 individuals. The summer showed least skewed 15 individuals were recorded. The butterfly species composition and relative abundance belonged to the families Namphalidae (17 Species; 35.42%), Pieridae (11 species; 25.00%), Lycaenidae (7 Species; 14.58%), Papilionidae (8 Species; 16.67%) and Hisperiidae (4 Species; 8.33%). The maximum number of butterfly species and maximum number of individuals were sampled during the monsoons, indicating that, the southern plains area of India butterflies prefer cool seasons for breeding and emergence. Three endemic species like Cepora nerissa, Troides minos and Atrophaneura hector and seven protected species like Euploea core, Cepora nerissa, Appias albino, Castalius rosimon, Euchrysops cnejus, Troides minos and Atrophaneura hector were listed under the Wildlife Protection Act 19720. These species highlighted greater importance of conservation in college campus. A checklist of butterfly species is also provided. The observation will support the detailed study of ecologically important local butterfly fauna of the college campus in Kovilpatti which provide a valuable resource to nature.

Boron Isotopic Analysis of Representative Atmospheric Aerosols Derived From Long-Range Transported/Local Emission on an Islet Offshore NE Taiwan

To identify pollutant origins and their potential sources from either long-range transported (LRT) or local emissions, the Boron (B) concentrations and the B isotopic compositions (δ11B) in the water-soluble fraction of aerosols were determined. These aerosols were collected from an islet offshore in northeastern Taiwan, Peng Chia Yu (PCY), a non-residential islet, from January 1998 to March 2000. This islet may be influenced by various pollutants or chemical transport during monsoon periods, but suffers minimal human perturbation locally. The B in the specimens falls to 0.3–1.63 ng m−3 during the SW monsoon seasons when compared to 0.46–2.56 ng m−3 in the NE monsoon. However, the δ11B results show no clear variations in both monsoon seasons (10.7–24.3‰), regardless of differences in air mass origin. A two end-member mixing scenario is proposed to explain our observations using the obtained δ11B and 1/[B] results. The ocean endmember is characterized by high 1/[B] and high δ11B; while other endmember is from continental endmember or anthropogenic contributions that are characterized by of 1/[B] and lowδ11B (δ11B &amp;lt; 10‰). Based on these chemical and isotopic results, we found aerosol emissions in northern Taiwan are characterized as low B with nearly constant δ11B, when compared with long-range transported continental endmembers derived from nearby regions. This study provides preliminary B and δ11B levels in aerosols derived from LRT/local emissions and discusses potential monsoonal effects on aerosols offshore of NE Taiwan.

Coastal upwelling along the west coast of Sabah and its impact on coastal aquaculture management

The aquaculture industry in Malaysia is currently growing at nearly 9 percent per year and is generating more than 250,000 tons of production per annum. However, little commercial scale aquaculture is present along the west coast of the state of Sabah. Few if any studies have been conducted to investigate aquaculture site suitability along the west coast of Sabah and the wider west coast of Borneo from an environmental or coastal management perspective. To determine the site suitability for marine aquaculture and other coastal resource users there needs to be an improved understanding of the physical, chemical, and biological characteristics of the coastal environment. One year of data collection including the long-term deployment of Conductivity, Temperature and Depth (CTD) sensors, and bi-monthly water column and seabed sediment sampling was undertaken to provide an indication if the coastal waters between Kota Belud and Kudat are suitable for marine aquaculture purposes. The site provided an analogy for much of the west coast of Borneo, especially the west coast of Sabah, due to similar oceanographic drivers in the region. Results indicated that during the NE monsoon period there is dramatic decrease in water temperature due to the upwelling of cold dense nutrient rich water onto the west coast of Sabah's continental shelf from deeper offshore areas of the South China Sea. This large change in temperature will likely rule out the potential commercial marine grow out of such species as Asian Seabass and perhaps Tropical Spiny Lobsters. Other species such as Cobia, Grouper and Snapper which have a wider tolerance for temperature change will likely be suitable but at times will be stressed due to magnitude of the observed changes. Such observations have ramifications in regard to site suitability for future resource consent applications for open ocean and coastal aquaculture along the west coast of Borneo. In summary the study highlights how physical processes can impact on resource use and development in a coastal setting.

Satellite-based observation of ocean productivity in southeast Arabian Sea using chlorophyll, sea surface temperature and wind datasets

The phytoplankton variability and ocean productivity have been studied with the retrieval of chlorophyll concentration (CC) from various satellite ocean colour missions. The phytoplankton distribution is related to ocean processes and physical parameters such as temperature, wind speed, currents, etc., at regional and global scales. In the current study, the phytoplankton productivity has been observed in the southeast Arabian Sea during southwest (SW, June–September) and northeast (NE, October–December) monsoon seasons using merged chlorophyll product datasets during the years 2017 and 2018. There has been an observation of high chlorophyll concentration (~5.0 mg m−3) in the southeast Arabian Sea (southern tip of India) during SW monsoon and less in NE monsoons (~1.0 mg m−3). The spread in CC has been observed maximum during July–September. High anomaly of CC was observed along north-eastern Arabian Sea during northeast monsoon months of 2017 due to the very severe cyclonic storm Ockhi. Similarly, during August 2018, high chlorophyll concentration was observed (18.8 mg m−3) in south-eastern tip as a result of heavy rainfall and discharge of nutrient rich riverine water. The sea surface temperature (Modis-Aqua SST) has been observed to be cooler (26–27°C) in the SE Arabian Sea coastal waters during July–August as compared to warmer (28–30°C) surrounding waters. During the SW monsoon (June–August), the wind speed has been observed to be of high magnitude (~10 m/s), which was not evident during September. The alongshore (north-westerly) wind has been observed during July–September in the near coastal water that causes coastal to offshore moving Ekman mass transport (EMT). Similarly, the alongshore (north-easterly) wind has been observed during December in the southern tip of India and off Sri Lankan west coast. The strong zonal EMT (–1500 to –500 kg/m/s) has been observed in the southeast Arabian Sea during July–September 2017 and 2018 which is weak to moderate (> –500 kg/m/s) in NE monsoon months. Statistical analysis has been made between SST, wind speed and CC which shows significant correlation coefficient (r > 0.6, p < 0.001). Hence, the present study confers that the alongshore wind and high wind speed regions are favourable to upwelling events and have been responsible for cooling of SST resulting in high productivity zones in the southeast Arabian Sea, which is important from the point of view of marine fishery and ecosystem assessment.