Northeast Monsoon Period Research Articles

Size-speciated chemistry of aerosols during the continental to marine air-mass transition phase from tropical Western Ghats environment in peninsular India

Atmospheric aerosol characteristics from the Western Ghats (WG), a region that plays a prominent role in modulating the Indian monsoon, was evaluated to study the impacts of long-range transport, local sources, and cloud processing on their chemical properties. Size-segregated aerosols collected from Ponmudi (8.8°N, 77.1°E), a tropical high altitude location (960 m a.s.l.) in the southern part of the WG, during the continental to marine air-mass transition phase (January–April 2020–2021) were analysed for major chemical components, including carbonaceous species, water-soluble ionic species, metallic elements and aerosol liquid water (ALW). The major aerosol components during the north-east monsoon period were identified as (NH4)2SO4, organic matter, and ALW derived from long-range transported biomass emission plumes undergoing cloud processing and aqueous-phase reactions with SO2. Positive Matrix Factorization (PMF) analysis revealed the presence of aged and mixed aerosol types, with influence from local anthropogenic emissions and secondary formation processes. The source profiles for different air-masses indicate that the IGP air-mass is dominated by anthropogenic continental sources rich in sulphates, while the East Asian air-mass comprises highly aged continental emissions rich in organics and mixed with marine emissions from the Bay of Bengal. Fine mode aerosol mass was reconstructed, and organic matter to organic carbon conversion factor was estimated after mass closure, which revealed relatively high values for East-Asian air-mass, providing evidence for their oxidation during long-range transport. The hill station was also influenced by local urban valley emissions transported to the site via daytime convection and sea-breeze circulation. Consequently, the aerosol system over this region exhibited a complex mixture, with elemental carbon particles coexisting with sea-salt, sulphate, and secondary water-soluble organics. The findings highlight the need for further studies to understand the role of chemically processed and mixed aerosol system in modifying regional climate dynamics and air quality over such sensitive ecosystems.

Monitoring the Dynamics of Sedimentary Load Variations Along Coastal Regions Using UAVs After Monsoon and High Tide Events at Pantai Punggur and Pantai Perpat, Batu Pahat, Johor

This research investigates the changes in sedimentary load along the Pantai Punggur to Pantai Perpat coastline in Batu Pahat, Johor, particularly during the northeast monsoon period from October 2022 to February 2023. The study aims to produce a mapping diagram of the shoreline profile and volume changes across various locations and their association with monsoon changes. The research utilised aerial images captured by UAVs, which were analysed using Pix4D and Global Mapper software. Data was collected for six months from September 2022 to February 2023, with the observation period experiencing a high tide phenomenon on November 24, 2022, resulting in a significant change in the data for that month. Shoreline profile results did not establish a conclusive link between sediment load changes and erosion or accretion due to the lack of volumetric data. Consequently, an analysis of volume changes was conducted using the Global Mapper application. In conclusion, the northeast monsoon wind and high tide phenomena during November 2022 significantly impacted the shoreline profile and total volume of the Pantai Perpat and Pantai Punggur areas.

Lagrangian and Eulerian approach to predict the movement of radionuclides in selected potential sites in Malaysia during the monsoon period

In computing the movement of particles through the fluid, three types of dispersion models are used which are Gaussian plume models, Lagrangian puff models, and small-scale numerical models. Lagrangian particle dispersion models are increasingly used for nuclear applications. In this study, the usage of the Lagrangian model is implemented in a Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) which combines with the Eulerian model to predict the movement of radionuclides from the simulated nuclear power plant accident in selected locations in Malaysia. These include nuclear risk studies in these areas, emergency response systems, and source term analyses. This study aims to compare the risk from the dispersion of 137Cs from a simulated Nuclear Power Plant (NPP) at Mukah and Tasik Kenyir during the Northeast monsoon (8th October 2022) and Southeast monsoon (16th May 2022). The HYSPLIT model was set up based on the meteorological data during both monsoon periods and was simulated for 5 days. The outcomes revealed that the concentration of 137Cs is higher at Tasik Kenyir compared to Mukah for both during the Northeast monsoon period (3.5 x 107 Bq/m2) while for Southwest monsoon, the result is vice versa where the concentration of 137Cs at Mukah is (2.2 x 107Bq/m2). The activity concentration is then converted into rate effective dose measurement and compared with the limit suggested by ICRP which is 1 Sv per year. It is concluded that Tasik Kenyir is a more suitable location to build NPP compared to Mukah as the movement of radionuclides was dispersed to the location that contained less population.

An unsupervised machine learning approach for estimating missing daily rainfall data in peninsular malaysia

Rainfall data plays a vital role in various fields including agriculture, hydrology, climatology, and water resource management. Stakeholders had raised concerns over the issue of missing rainfall data as it presents a huge obstacle in achieving reliable climate forecasts. Therefore, it is necessary to perform accurate estimation for the missing daily rainfall data. Each year, the peninsular Malaysia experiences a significant rainfall event during the monsoon period due to the North-East monsoon (NEM) wind. The intricate spatial rainfall dynamics requires a computational model, capable of generating accurate estimates and deciphering hidden patterns from the missing data. An unsupervised machine learning model known as the Self-Organising Feature Map (SOFM) is developed to estimate the missing daily rainfall across 10 rainfall stations during the NEM period between 2010 and 2020. The SOFM exhibited reliable performance across the percentage of missingness between 10% to 50%. Below 50% missingness, the evaluated statistical metrics, coefficient of determination (R2) is attained above 0.5, ranging between 0.504 and 0.915; root mean square error (RMSE) between 15.9 to 22.7. The feature maps enabled the visualisation of the relationship between the rainfall intensity and studied rainfall stations. The feature maps suggested that the studied rainfall stations are inhomogeneous.

Analysis of Unidirectional Wave Spectral Characteristics in the Northeastern Waters of Taiwan

Marine energy development has been actively promoted in recent years. Analyzing wave data in the surrounding sea areas is crucial for improving wave power generator efficiency. This study collected unidirectional wave spectrum data from the northeast coastal area of Taiwan (e.g., Pengjia Islet, Fugui Cape, and NTOU). It aimed to analyze the main wave types (i.e., wind waves, swell, or mixed sea) and their proportions during the northeast and non-northeast monsoon periods. The results indicate that swell waves dominate at the NTOU buoy, while wind waves dominate at the other two stations. In addition, the analysis of wave spectra ratios revealed a low percentage of unimodal spectra (only about 0.5%), and bimodal and unformed spectra presented as predominant. Furthermore, this study also introduced a brand new JW-J wave spectrum, which combines the JW and JONSWAP spectra to describe low-frequency (swell) and high-frequency (wind wave) systems, showing superior performance compared to the Torsethaugen spectrum. Finally, this research analyzed the JW-J spectrum parameters from the Pengjia Islet and Fugui Cape stations and applied these results to the NTOU bouy for effectively describing wind/swell wave variations.

Diversity of Platygastroidea Species in Coffee Ecosystem at Thadiyankudisai, Tamil Nadu

During a one-year study from January, 2018 to January, 2019 at the Horticultural Research Station, Thadiyankudisai, Tamil Nadu, a combined count of 550 individuals of Platygastroidea species were documented under two family platygastridae (1 species) and scelionidae (9 species). Among the species diversity comprised of Telenomus sp. (52.0%) followed by Scelio sp. (11.4%), Calliscelio sp. (9.1%), Sparasion sp. (6.9%), Idris sp. (5.8%) and Baryconus sp. (4.0%). The least population was recorded in Tritelia sp. (2.2%). Researches on seasonal abundance exposed that the winter season exhibited the highest species population at 32.55%, with the South West Monsoon (SWM) following closely at 30.36%, while the North East Monsoon (NEM) period recorded the lowest species count at 16.54%. The prevalence of insect pests poses a significant challenge to achieving optimal yields in horticultural crops. Consequently, the examination of Platygastroidea species diversity assumes a pivotal role in the success of biological control strategies.

The impact of short-duration precipitation events over the historic Cauvery basin: a study on altered water resource patterns and associated threats

The Cauvery Delta, the ‘Rice Bowl’ of India follows a time-tested cultivation pattern over several irrigation zones. However, in this era of the Anthropocene, it is now well-established that short-duration, intense precipitation episodes will batter the flood plains year after year. The purpose of this first study is thus to quantify the impacts that such episodes may have on the floodplains of the Cauvery Delta and the concomitant threats to the historic Kallanai Dam. Precipitation events during the North-East monsoon period are driven not just by warm rain microphysics but also by large frozen hydrometeors falling from deep clouds causing undesirable flooding over the region to the extent of 66%. Additionally, from an assessment of the velocity heads and the floodwater depths, this study projects a heightened vulnerability. The total extent of submergence along riverbanks and other flow paths was estimated to be 145.98 {mathrm{km}}^{2} out of which 65.14% of the submerged area is agricultural land. The most important conceptual advance established in this paper is that sub-zones in major watersheds that are currently safe will get inundated in the RCP8.5 warming scenario in 2050.

The Role of Sulfur Emission from the Petroleum Industry on Ultrafine Particle Number Concentration in Singapore

Ultrafine particles, defined as particles with a diameter (dp) smaller than 100 nm, serve as an important component of cloud condensation nuclei, in addition to impacting human health. The dominant sources of ultrafine particles include traffic emissions and nucleation. Singapore is a tropical city that hosts petrochemical industries. To identify the sources of ultrafine particles, a year-long observation of the number size distribution was conducted in Singapore in 2018 and 2019. The concentrations of CO, CO2, CH4, and SO2 were also monitored. The particle number concentration during the southwest monsoon season was high, while that during the northeast monsoon period was relatively low. The CO concentration increased during the morning traffic rush hours, which was associated with relatively minor enhancements in ultrafine particle number concentration. The events for a high number concentration of the Aitken mode particles (dp < 50 nm) were identified during high SO2 concentration periods. The SO2 concentration was high during the afternoon because the sea breeze transported the emissions from the coastal industrial area to the observation site. The enhancements in CH4 from its background level (ΔCH4) and SO2 had a quasi-inverse relationship, as the major emission sources of these two chemical species were different. The particle number concentration (dp > 50 nm) correlated with the enhancements in CO concentration (ΔCO) for CH4-dominant air masses, suggesting that incomplete combustion processes, such as traffic emission, are important for the size range. Conversely, the number concentration of the Aitken mode particles (dp < 50 nm) increased for SO2-dominant air masses, suggesting the importance of industrial plume.

Assessing the Impact of Long-Term ENSO, SST, and IOD Dynamics on Extreme Hydrological Events (EHEs) in the Kelani River Basin (KRB), Sri Lanka

Hydrological extremes are common throughout the world and can be considered a globally significant phenomenon with severe environmental and social consequences. In recent decades, especially in the second half of the 20th century, Extreme Hydrological Events (EHEs) have attracted extensive attention. Physiological and anthropogenic factors have increased the frequency and severity of hydrological extremes worldwide in the last few decades. Recently, it has become a significant environmental issue in Sri Lanka. Both floods and droughts are widespread throughout the country, and the influence of floods is becoming more common every year. Currently, the frequency and severity of EHEs in the Kelani River Basin (KRB), Sri Lanka, are very common and have increased due to climate variations. Therefore, this study focused mainly on evaluating the EHEs and the impact of long-term El Niño Southern Oscillation (ENSO), Sea Surface Temperature (SST), and Indian Ocean Dipole (IOD) dynamics on extreme events. Rainfall Anomaly Index (RAI) and Extreme Precipitation Indices (EPIs) were calculated to examine the EHEs and their spatial variability. In addition, the relationships between EHEs and ENSO were investigated using several climate indices based on SST anomalies. Both observed and satellite-derived daily precipitation from 1951 to 2019 were used to assess the EHEs in the KRB. The trend of EHEs and the change points were evaluated using the Pettitt test, and teleconnection with global indices was examined using the correlation coefficient in the R application. The result of the study revealed that the pattern of EHEs varied spatially from 1951 to 2019. The strong La Niña years showed a high degree of teleconnection with EHEs in April (r = 0.622 at 0.05 significance level) and August (r = −0.732 at 0.05 significance level). NINO3.4 and the Southern Oscillation Index (SOI) have shown a significant positive impact on EHEs in the Northeast Monsoon (NEM) period. This research on KRB will be a popular scientific measure that can provide scientific results and solutions for the comprehensive decision-making process in the future. Investigating the global physical changes that influence EHEs is critical to taking the necessary steps to reduce the severity of hydrological extremes in Sri Lanka.

Spatial and temporal dynamics of suspended sediment concentrations in coastal waters of the South China Sea, off Sarawak, Borneo: ocean colour remote sensing observations and analysis

Abstract. High-quality ocean colour observations are increasingly accessible to support various monitoring and research activities for water quality measurements. In this paper, we present a newly developed regional total suspended solids (TSSs) empirical model using MODIS Aqua's Rrs(530) and Rrs(666) reflectance bands to investigate the spatial and temporal variation in TSS dynamics along the southwest coast of Sarawak, Borneo, with the application of the Open Data Cube (ODC) platform. The performance of this TSS retrieval model was evaluated using error metrics (bias = 1.0, MAE = 1.47, and RMSE = 0.22, in milligrams per litre) with a log10 transformation prior to calculation as well as using a k-fold cross-validation technique. The temporally averaged map of the TSS distribution, using daily MODIS Aqua satellite datasets from 2003 until 2019, revealed that large TSS plumes were detected – particularly in the Lupar and Rajang coastal areas – on a yearly basis. The average TSS concentration in these coastal waters was in the range of 15–20 mg L−1. Moreover, the spatial map of the TSS coefficient of variation (CV) indicated strong TSS variability (approximately 90 %) in the Samunsam–Sematan coastal areas, which could potentially impact nearby coral reef habitats in this region. Study of the temporal TSS variation provides further evidence that monsoonal patterns drive the TSS release in these tropical water systems, with distinct and widespread TSS plume variations observed between the northeast and southwest monsoon periods. A map of relative TSS distribution anomalies revealed strong spatial TSS variations in the Samunsam–Sematan coastal areas, while 2010 recorded a major increase (approximately 100 %) and widespread TSS distribution with respect to the long-term mean. Furthermore, study of the contribution of river discharge to the TSS distribution showed a weak correlation across time at both the Lupar and Rajang river mouth points. The variability in the TSS distribution across coastal river points was studied by investigating the variation in the TSS pixels at three transect points, stretching from the river mouth into territorial and open-water zones, for eight main rivers. The results showed a progressively decreasing pattern of nearly 50 % in relation to the distance from shore, with exceptions in the northeast regions of the study area. Essentially, our findings demonstrate that the TSS levels on the southwest coast of Sarawak are within local water quality standards, promoting various marine and socio-economic activities. This study presents the first observation of TSS distributions in Sarawak coastal systems with the application of remote sensing technologies and aims at enhancing coastal sediment management strategies for the sustainable use of coastal waters and their resources.

Impact of tropical convective conditions on solar irradiance forecasting based on cloud motion vectors

Intra-day forecasts of global horizontal solar irradiance (GHI) are widely produced by displacing existing clouds on a geo-stationary satellite image to their future locations with cloud motion vectors (CMVs) derived from preceding images. The CMV estimation methods assume rigid cloud bodies with advective motion, which performs reasonably well in mid-latitudes but can be strained for tropical and sub-tropical climatic zones during prolonged periods of seasonal convection. We study the impact of the South Asian monsoon time convection on the accuracy of CMV based forecasts by analysing 2 years of forecasts from three commonly used CMV methods—Block-match, Farnebäck (Optical flow) and TV-L1 (Optical flow). Forecasted cloud index (CI) maps of the entire image section are validated against analysis CI maps for the period 2018–2019 for forecast lead times from 0 to 5.5 h. Site-level GHI forecasts are validated against ground measured data from two Baseline Surface Radiation Network stations—Gurgaon (GUR) and Tiruvallur (TIR), located in hot semi-arid and tropical savanna climatic zones respectively. The inter-seasonal variation of forecast accuracy is prominent and a clear link is found between the increase in convection, represented by a decrease in outgoing longwave radiation (OLR), and the decrease in forecast accuracy. The GUR site shows the highest forecast error in the southwest monsoon period and exhibits a steep rise of forecast error with the increase in convection. The highest forecast error occurs in the northeast monsoon period of December in TIR. The impact of convection on the number of erroneous time blocks of predicted photovoltaic production is also studied. Our results provide insights into the contribution of convection to errors in CMV based forecasts and shows that OLR can be used as a feature in future forecasting methods to consider the impact of convection on forecast accuracy.

A study on hydogeomorphological status of kadalundi river basin in kerala using geospatial technology

Detailed hydro geomorphologic study has been carried out for Kadalundi River Basin in Kerala to understand the drainage pattern, spatial and temporal water availability using secondary data collected from different Departments. Geomorphological parameters have been estimated as a part of this study and it is found that Kadalundi river basin is a sixth order stream. The drainage pattern is complex with considerable variation in spatial arrangements, which are controlled by topography, slope, rock type and structural deformations. The basin is characterized by dendritic type of drainage pattern with variable density. The densest dendritic pattern is developed on the hard Charnockite and Gneissic rocks. In some areas, the drainage pattern is sub dendritic reflecting structural control. The existing land use pattern is derived from Indian Remote Sensing Satellite (IRS – LISS II1, P6) using ERDAS software. Using hydrological toolset of Spatial Analyst, an extension of ArcGIS software, slope map, aspect map and Digital Elevation Model (DEM) have been derived. In addition, the basic thematic map on geology and soil also been derived.. For annual period, the rainfall varies from 1800- 4100 mm, 1400- 2600 mm for South –West monsoon period and 600-1100 mm for the North-East monsoon period.

Impact of Precipitation over the Productivity of Sugarcane in Major Agro-climatic Zones of Tamil Nadu

Sugarcane is one of the traditional crops grown abundantly across the state of Tamil Nadu due to the lengthening of the period of monsoon and its diversified uses in different agro-based industries. Precipitation, a significant factor for sugarcane cultivation, has an impact on its productivity differs for different agro-climatic zones. A secondary data of district wise precipitation and sugarcane productivity of Tamil Nadu for the 30 years (1985 - 2014) were also collected. The impact of precipitation over the productivity of various crops can be explained by using the Standard Precipitation Indices (SPI) data and applying Principal Component regression (PCR) technique. Initially, SPI, A drought monitoring index, represents a Z-Score, was calculated seasonally for different agro-climatic zones. As there was a severe collinearity between the SPI values of seasons, Principal component regression analysis was used to study the impact of precipitation on the sugarcane productivity by considering the SPI values of four seasons along with time as regressor variables. The study showed that the productivity of sugarcane in Cauvery Delta zone and Western Zone mainly depended upon the precipitation during South west monsoon and North East monsoon periods. However, the productivity of sugarcane in North East zone was mostly dependent on the precipitation of Cold Weather period when compared to all other seasons. Unlikely, North west and Southern zones are not significantly influenced by the precipitation.

Distribution Patterns of Reef Fish Larvae in the Dipolog Srait, Philippines

The composition, abundance and distribution of reef fish were strongly influenced by the trends in salinity, temperature and mixing regimes of the water during the three oceanographic cruises conducted in the vicinity of the marine reserve networks of Dipolog Strait. Forty-seven families of reef fish larvae were identified. Carangidae, Labridae, Scaridae, Gobiidae and Apogonidae were the top five most abundant larvae comprising 64.7 % of the total number of reef fish larvae collected. Shifts in the dominance of the top five most abundant reef fish families occurred primarily between the northeast and southwest monsoons coinciding with the changes in the temperature profiles of the water column. Abundance of reef fish larvae showed variability across the three sampling periods due to the succession of the dominant species of reef fish larvae. Fluctuations in salinity brought about by the transition from Northeast to Southwest monsoon period could explain the variation. Density distribution of reef fish larvae significantly increased with the increasing depth of the mixed layer during northeast monsoon period. The downwelling off the coast of southern Negros in February and April cruises contributed to the high abundance of reef fish larvae in this part of the strait, while the uniform mixing of the water column in June 2010 at southwest monsoon resulted in the weakening of density gradient of reef fish larvae.The study demonstrated the variable responses of the reef fish larvae to the gradients of chlorophyll in the Dipolog Strait. A better understanding on the retention mechanism of reef fish larvae along the coast of southern Negros, where the main marine reserve networks exist, is provided by the present study.

Computation of the spatio-temporal extent of rainfall and long-term meteorological drought assessment using standardized precipitation index over Kolar and Chikkaballapura districts, Karnataka during 1951-2019

Drought is an insidious meteorological and hydrological natural phenomenon causing many adverse impacts on the environment, agriculture, and socio-economic condition, especially over a semi-arid region like Kolar and Chikkaballapura district in the state of Karnataka. When the precipitation level is inadequate to meet the demands of human activities, it leads to drought extension over a season or longer period. The present article is investigating the application of the standard precipitation index (SPI) to detect drought incidents and is widely used to understand rainfall variability. Therefore, this study attempts to analyze drought at pre-monsoon, southwest monsoon, northeast monsoon, and annual time period using SPI for Kolar and Chikkaballapur districts of Karnataka state. The outcome of this analysis demonstrates that drought occurrences are frequent in particular years and seasons with negative values of SPI along with dry, wet, and normal events. To apply any management plan with the increasing nuisance, deep knowledge is essential about meteorological, agricultural, and hydrological drought. The rainfall data for the period 1951–2019 at the eleven grid points were acquired from the India Meteorological Department with (0.25⁰ × 0.25⁰) high spatial resolution. The result revealed that a moderate dry event was observed in the pre-monsoon period at Kolar in 1993 with −0.67. Extreme drought condition was recorded during the southwest monsoon season in 1980 at Kolar with −2.22 and for the northeast monsoon, −1.67 was observed at Malur station in 1988. The seasonal crops of the southwest monsoon (June–September) are heavily dependent on this rainfall and it contributes to 58% of the annual precipitation. If there is a drop in the rainfall received during the southwest monsoon, the effect on the growing stage of agricultural crops leads to reduced crop yield.

ROTATED EMPIRICAL ORTHOGONAL FUNCTION ANALYSIS FOR SPATIO-TEMPORAL DATA ANALYSIS

Given any space-time field, Empirical orthogonal function (EOF) analysis finds a set of orthogonal spatial patterns along with a set of associated uncorrelated time series or principal components (PCs). Spatial orthogonality and temporal uncorrelation of EOFs and PCs respectively impose limits on the physical interpretability of EOF patterns. This is because physical processes are not independent, and therefore physical modes are expected in general to be non-orthogonal. Rotated empirical orthogonal functions (REOF) were introduced to generate general localized structures by compromising some of the EOF properties such as orthogonality. EOF and REOF analysis are carried out for the significant wave height (SWH) data for the Bay of Bengal (BOB) region for the period 1958 to 2001. Separate experiments were conducted for all the months together and also for July and December representing the southwest and northeast monsoon periods. The first eigenmodes account for 84%, 68%, and 59% of the total variability for the above three cases respectively. The REOF proved to be more effective than EOF for the above region.

Coastal erosion: a threat to sea turtle nesting habitat, east coast of India

Coastal erosion is a major concern and a threat to the coastal habitats, livelihood and socio-economic developments. The aims of the present research are to investigate the beach dynamics, status, and protection measures of world famous nesting habitat near Rushikulya estuary, south Odisha coast, India. Shoreline mapping and rate of changes for a period of 8 years (2005–2013) on each side of the inlet, 3-year beach profile study at six transects, and 2 years (2009 and 2010) of sediment texture studies along with coastal processes provide a clear glance of the nesting beach health. The nesting beach changes observed were significant erosion (47–126 m) with northward growth of sand spit and deposition at the beach due to deformation of spit. From 2008 to 2011, the southern part of the beach experienced high erosion, while the northern part is under erosion and deposition with seasons. Medium sand predominated along the beach, while the foreshore zone at the northern part has fine sand along with sediment accumulation during the northeast monsoon period. Annual changes in wave pattern and reversal wind and current conditions make beach cyclic at the northern part of the nesting beach, while the status of the southern part of the beach depends upon the inlet shifting and human intervention on sand spit situated at the south of Rushikulya estuary. To avoid chronic erosion at the nesting beach, the sand spit needs to be cut from the mainland through regular monitoring of beach. The present study may help to prepare a framework for proper management and conservation of nesting habitat.

Projections of CMIP5 evaporation data sets under future climate change scenarios and comparison with estimates from the observations over peninsular India

&#x0D; Present study commences from the time series analysis of evaporation data sets obtained from the Coupled Modeled Inter comparison Project of Phase 5 (CMIP5) for the study period 1979 to 2100 under the RCP 4.5 and 8.5 emission scenarios over Interior Peninsular region during the Northeast monsoon (October to December) period. Further, a comparative analysis has been carried out with the evapotranspiration (ET) estimated from the Hargreaves and Samani (1982) using the temperature data of India Meteorological Department for the period 1979 to 2005. Our results show that evaporation trends are increasing with more prominence in RCP 8.5 scenario. This increase in evaporation has been attributed to increase in air temperature which is an undisputed fact under future climate change scenario. Different climate models of CMIP5 show mixed response by displaying the positive and negative correlations with the Hargreaves ET over the study region. The results of the study will be useful in understanding the bias between the modeled data sets and the estimates of ET from the observations.&#x0D;

Moisture trajectories during heavy rainfall events using Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model

Heavy rainfall inducing other catastrophic events are frequently experienced globally. Understanding the mechanisms of moisture transport during such events will help in furthering our knowledge about such systems. In the current study, estimation of most likely moisture trajectoriesis performed using back trajectory analyses. Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model available from National Oceanic and Atmospheric Administration’s (NOAA) Air Resources Laboratory (ARL) is used for the purpose. A preliminary analysis is conducted by calculating the frequencies of back trajectories from two locations in Kerala for three heavy rainfall cases. The analysis indicates that both the locations have similar pattern of moisture trajectories during the cases occurring in south west monsoon and pre monsoon periods. However, a change in the behaviour of the trajectories for the two locations is observed for the case during the north east monsoon period. Since this study involved only individual cases, robust conclusions cannot be made based on this for the dynamics of moisture transport for these locations. More detailed analysis will follow this preliminary study in future for the purpose.

Warming of the Indian Ocean and its impact on temporal and spatial dynamics of primary production

The Indian Ocean, the third largest among the world’s oceans, is experiencing unprecedented changes in sea surface temperature (SST). We present temporal and spatial dynamics of phytoplankton and their response to warming in the Indian Ocean (∼25°N to 30°S) during 1998–2019 using remote sensing data. Our study revealed that the area of the Indian Ocean Warm Pool (IOWP), defined as waters with SST values >28 °C, is significantly expanding in most regions, particularly in the most recent decade. The increase in IOWP area was greatest (∼74%) in the south-central basin. Furthermore, SST increased significantly in most areas of the Indian Ocean (10 out of 11 regions explored) over the 22-year study period with the highest increase of 0.7 °C observed in the south-central regions. Most other regions showed an average increase in temperature of 0.4–0.5 °C. At the same time, net primary production (NPP) showed large interannual variability in northern and central regions of the Indian Ocean, with slightly decreasing trends in a few northern regions. Overall, years of the first decade (1998–2008) showed more often cooler temperatures and higher productivity, except for a few years, whereas years of the last decade (2009–2019) showed more often warmer temperature and lower productivity, except in very recent years (2017–2019) when productivity was high. Mean Chl a concentrations increased in the last decade during the northeast monsoon period in the northwestern regions, suggesting increased NPP in December to March period as a future scenario in this highly productive area of the Indian Ocean. We also observed increasing SST in several major upwelling areas during the study period, whereas Chl a showed high interannual variability with no marked significant trends in most areas. Results from this study corroborate the importance of the southwest monsoon as a key driver of seasonal patterns in Chl a in major upwelling areas of the Indian Ocean.