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Assessment of soil organic carbon (SOC) stock and identification of the factors influencing its spatial variation are crucial for adopting appropriate mitigation and adaptation strategies under changing climatic conditions. The present study aims to measure SOC content and stock and identify the factors contributing to SOC variation in India's sub-tropical, dry sub-humid Eastern Plateau Region (EPR). It also aims to recognize the potential land uses for enhancing the C stock in the region. Soil samples were collected from two soil depth layers—0 to 10 cm and 10 to 20 cm, from locations under different soil type, land use, and topographic conditions. The Walkley-Black method was used to determine the SOC content of the samples. Ordinary kriging based on an exponential semi-variogram model was employed to analyze the spatial variability of SOC concentration and its relationship with the sampling strata. The study shows that the topsoil variation in SOC depended mainly on the land use type and the corresponding soil properties viz. pH and texture. Cultivated areas, especially those of the lowland, recorded higher SOC than other land use classes. The findings of the present study are useful for defining agricultural management practices and carbon sequestration strategies for the region in the context of climate change. [ABSTRACT FROM AUTHOR]

This study evaluates spatial trend and distribution history of selected metals in the complex coastal environment of Odisha, India. The main objective is to analyse metal enrichment and level of contamination in sediment deposits. It is also attempted to evaluate the past depositional environment and prevailing process leading to metal enrichment and contamination. Three sediment cores up to a depth of 10 m were collected from older beach deposit of Chandbali (CB) and paleochannels of Agiviligan (AG) and Kasturikaran (KK) villages located along River Baitarani, coastal Odisha. The study area, to a large extent, is a transition zone of terrestrial and marine sediments. The assessment of metal contamination is based on spatial and down-core variability of selected metals- Al2O3, MnO, Cr, Co, Cu, Zn, and Pb against their background values. Contamination is examined using enrichment factor (EF), contamination factor (CF) and geo-accumulation index (Igeo). The study exhibits a complex pattern of metal distribution over space and time. The sediments are enriched and contaminated with MnO, Cr, and Pb not only in the surface layers but also in the deeper layers such as CBL4 (–7.3 m), CBL5 (–7.9 m), CBL6 (–10 m), AGL3 (–6 m), AGL5 (–10 m) and KKL3 (–8 m). Metal enrichment in deeper layers can be associated with the past depositional environment, prevailing processes, geology and geomorphology of the region. In the surface layers, metal contamination can result from recent anthropogenic activities like untreated industrial waste from Ferro-alloys Corporation Ltd. (FACCOR) and domestic waste. There is a decline in contamination levels as we move from inland (CB) to coast (KK). The samples are also analysed for grain size and geochemistry to differentiate between sedimentary layers deposited under distinct depositional environments in the past. The results reveal the existence of humid and dry climatic phases along with oscillating sea levels in the past, influencing metal enrichment and contamination. [ABSTRACT FROM AUTHOR]

The intensity and frequency of extreme hydrological events are on the rise due to changing climate, and it is pertinent to identify the areas which are likely to suffer from such calamities. This study examines flood and drought susceptibilities in the district with a specific focus on two urban areas—Tuting and Yingkiong. To understand susceptibility enabling conditions, the study attempts an analysis of the recent climatic trends (1991–2021) in Upper Siang district employing regression analysis, Kendall tau, and Box and Whisker plots. Results reveal a general rise in the precipitation (26.42 mm/year) as well as in the temperature (0.032 °C/year) of the study area. Susceptibility is assessed based on analytic hierarchy process and using nine physical parameters viz., absolute relief, slope, drainage density, distance from streams, soil type, topographic wetness index, normalised difference vegetation index, and land use land cover. These layers are integrated to create flood and drought susceptibility maps. About 1.82% area of the Upper Siang district is highly susceptible to floods, whereas over 27% area falls under the high risk of droughts. Even though both the towns lie on the riverbank, Tuting is more prone to floods primarily due to its location on the inner concave side of a meander bend and relatively flat terrain, whereas Yingkiong is relatively safe because it lies on an elevated river terrace. Conversely, areas of the district above 2500 m a.s.l. are highly prone to droughts because of poor accessibility to water resources. It is found that the constrained and meandering valleys are more prone to floods, while steep slopes and ridgeline areas are more prone to droughts. Appropriate region-specific management options can reduce the susceptibility to extreme events in mountainous terrains. Therefore, owing to diverse topography, a region-specific physiographic approach is required in hilly environments for efficient mitigation of the impacts of extreme events. [ABSTRACT FROM AUTHOR]

The study estimates the soil organic carbon stock under various cropping systems to assess their sequestration potential in a tropical monsoon region, namely the Chulliyar-Ikshumathi sub-watershed of Bharathapuzha in Kerala, India. The cropping systems selected are the paddy, vegetables, coconut-arecanut groves, homestead farms, and mango plantations. The standard soil analyzing procedures to collect and analyze 129 soil samples from 43 locations were followed. The carbon stock (CS) of 0–10, 10–20, and 20–30 cm depth layers at each sampling location was estimated following the Walkley-Black method. The sequestration potential of soil under each cropping system is estimated to suggest an optimal cropping system for the region. The CS decreased with depth, irrespective of cropping systems. Among the cropping systems, the mango plantations, which practiced zero/no-tillage, have stability in the distribution of CS, while paddy fields showed higher variability in the CS. Even though mango plantations have more carbon sequestration potential (CSP), the coconut-arecanut grove is a better candidate for carbon sequestration (CSeq) in this region owing to its wider areal extent and acceptability. This analysis reveals the importance of assessing CS at the watershed level for sustainable land use planning to achieve better sequestration of atmospheric carbon. [ABSTRACT FROM AUTHOR]

Glacier ice-thickness measurement and distribution is one of the essential variables to assess present status of glacier-water equivalent and its volumetric reserve as well as to model the future glacier dynamics under the climate changing scenario. Yet, substantial gaps in ice thickness information exist for the Himalayan glaciers. The present study provides a long-term assessment (1965–2016) of recessional and area change patterns, as well as the detailed field-based (2016–2017) Ground Penetrating Radar(GPR), derived ice-thickness measurement of the Menthosa Glacier, Lahaul Himalaya. Additionally, the study examines whether the modelled ice thickness from remote sensing data is consistent with the field-based GPR measurement and how can it be improved. The extensive field surveys coupled with the multi-temporal high (Corona KH-4A) to medium resolution (Landsat Enhanced Thematic Mapper+ (ETM+)/Operational Land Imager (OLI), Sentinel 2A-Multispectral Instrument (MSI)) remote sensing data and cross-sectional GPR surveyed profile measurements have been used to examine past half a century (1965–2016) glacier fluctuation and the recent ice-thickness estimations, respectively. The results show that the Menthosa Glacier receded by 301.5 ± 19.2 m during the past half a century (1965–2016) with an average annual retreat of 5.9 ± 0.4 m a−1, whereas glacier lost 0.09 km2 ice in the frontal section. Field measurement over the past one decade (2006–2017) also conforms to a continuous recessional pattern and substantial glacier degeneration particularly the extensive surface lowering and significant appearance of ice-cliffs in the ablation and lateral zones over this period. The GPR measurements (2017) show the minimum glacier ice thickness of 24 meters at 4691 m a.s.l. (in the lower part of ablation area) and maximum glacier ice thickness of 55 meters measured at 4758 m a.s.l. (in the upper left-side tributary part of ablation area). Moreover, the modelled ice thickness derived from remotely sensed data is having Root Mean Square Error (RMSE) between 38 to 72 ± 10 m as compared with GPR measured ice thickness. [ABSTRACT FROM AUTHOR]

Rainfall is time concentric in nature. The spatial and temporal distribution of rainfall is changing over the Earth with recent anthropogenic warming. The study explores various characteristics of annual and seasonal concentration of rainfall across India using the precipitation concentration index (PCI) and its trends during the period of 1986–2015, based on a high‐resolution gauge‐based rainfall data (0.25 × 0.25°), obtained from the India Meteorological Department (IMD). An intercomparison is made with 11 other gridded rainfall datasets to infer whether these datasets can reasonably reproduce the spatiotemporal distribution of PCI and its trends in various homogenous rainfall regions of India or not. These datasets are categorized into gauge‐based (APHRODITE, GPCC, CPC), satellite‐derived (CHIRPS, PERSIANN‐CDR), and reanalysis (JRA‐55, MERRA‐2, NCEP‐2, PGF, ERA‐Interim, ERA‐5). On annual scale, about 8.52, 24.1, and 67.38% of area of India are under moderate, irregular, and strongly irregular rainfall distribution, respectively. Spatial variation of PCI in India is influenced by geographical factors such as latitude, longitude, and elevation. Significant increasing and decreasing trends in annual PCI have been observed in the northeast, eastern, and western coasts of India, respectively. Gridded data intercomparison suggests that the gauge‐based APHRODITE, GPCC, and satellite‐derived CHIRPS datasets better perform in capturing the temporal and spatial variation of PCI across India when compared to the IMD gridded dataset, whereas the ERA‐5 performs better among the reanalysis datasets. However, the rainfall datasets exhibited marked differences with the IMD while estimating the annual and seasonal trend and its magnitude across various regions of India. The JRA‐55 overestimated areas of positive trend and its magnitude on annual and seasonal scale. These findings have practical implications for hydroclimatic studies. [ABSTRACT FROM AUTHOR]

The present study aims to analyse the effect of climate and land cover changes on the discharge of the Upper Beas River basin. The study used climate, soil, land use/land cover, and elevation data in the Soil and Water Assessment Tool (SWAT) model to estimate the discharge that is calibrated and validated using the observed discharge data of the Thalout gauge site. The findings suggest that basin hydrology is more sensitive to climate change than land cover changes. Mean annual discharge shows a rise between 0.31 and 9.65% under climate change scenarios, but it may decline by 9% under land cover change scenarios by the mid-21st century. Under all the climate change and land cover scenarios, seasonal variations in discharge are more prominent than annual changes. Water availability would be more in pre-monsoon season because of warming in the future. These changes would be beneficial in the short run, but may adversely affect the water availability in the long run. [ABSTRACT FROM AUTHOR]

The subsurface sediment archives provide clues to the past climate of the Earth. To reconstruct the paleoclimate of Lower Baitarani Basin, a 1000 cm deep sediment core (JP) was collected from the flood plain located in Jhumpuri village of Jajpur, Odisha. A total number of eleven distinct layers were identified based on variations in the sediment colour and textural at varying depths. From each layer, a representative sample was collected and carried to the laboratory for further assessment. Each of these sub-samples was examined for particle size analysis, availability of total organic carbon (TOC), and elemental concentration. The physical and geochemical proxies as paleoproductivity, terrestrial flux, weathering, level of salinity, colour, and texture variations were utilised to examine the paleoclimate of the area. The colour variations of the subsurface sequences suggest that the deposition has occurred under both freshwater and stagnated/marshy conditions. The texture variations—clay, silty clay, and loamy fine sand—also indicate deviations in sediment supply and rate of sediment aggradation during climatic shift between warm-humid and cold-arid episodes. With the help of geochemical proxies to illustrate the terrestrial flux: Fe2O3, Al2O3, TiO2, MgO, CaO, Cu, Co, Ba, and Zn; paleoproductivity: TOC,CaO/Al2O3, Zn/Al2O3,Sr/Al2O3, Cu/Al2O3, and Ba/Al2O3; weathering: Fe2O3/Al2O3, TiO2/Al2O3, and MgO/Al2O3; and the salinity index, a relatively cold-dry climate is inferred during the sedimentation of basal layers. Subsequently, a shift to the relatively warm-humid phase is suggested which again was followed by a cold-dry, and warm-humid phases. In the recent deposits, the proxies have not shown any considerable variation indicating prolongation of the existing warm-humid phase. However, some indications of a climatic shift to colder climate is also marked in the surface layer (JPL1). [ABSTRACT FROM AUTHOR]

Appraisal of potential evapotranspiration (PET) is needed for estimating the agricultural water requirement and understanding hydrological processes in an arena. Therefore, aim of the paper was to estimate the PET in the upper Beas basin, situated in the Western Indian Himalaya, under future climate change scenarios (by mid-21st century). Climate data (1969–2010) of Manali, Bhuntar and Katrain were obtained from India Meteorological Department (IMD) and the Indian Agricultural Research Institute (IARI). Landsat data were used for mapping land use/land cover (LULC) conditions of the basin through decision tree technique. Elevation detail of the catchment area is derived from the Cartosat-1 digital elevation model (DEM). Simulations of PET were done by the Soil and Water Assessment Tool (SWAT) model. The model was calibrated using the average monthly discharge data from Thalout station. The study found fluctuations in PET under different climate change scenarios. It is likely to increase in near future owing to the rise in temperature. The higher water demand can be met from the excess snowmelt water reaching the lower basin area during the cropping seasons. This study will be helpful to understand water availability conditions in the upper Beas basin in the near future. [ABSTRACT FROM AUTHOR]

The deficiency in rainfall leads to meteorological droughts. Its manifestations are visible both in the vegetation cover and soil moisture. The present study assessed the characteristics of agricultural drought following meteorological droughts. The study also assessed the severity of meteorological droughts and their manifestation on the agriculture and soil moisture in a semi-arid area. The study has been carried out for the Malaprabha sub-basin which partly covers three districts of North Interior Karnataka, India. India Meteorological Department's (IMD) criteria have been used to identify the drought years, and its severity has been assessed through the Standard Precipitation Index (SPI). The IMD's monthly rainfall data were used to identify the drought years and periods for the region. Among the drought years, the mild, moderate, and severe drought along with deficit and excess rainfall years were considered to assess and characterize the soil moisture conditions and the agricultural drought. The satellite image based indices for these selected years were constructed to determine the soil moisture conditions and the agricultural drought severity. The Temperature-Vegetation Dryness Index (TVDI) was used to determine the soil moisture conditions. The indices employed to determine the agriculture drought are NDVI, Thermal Condition Index (TCI), Vegetation Condition Index (VCI), and Vegetation Health Index (VHI). These satellite-based indices were calculated using the Landsat images of the selected drought and non-drought years. The results showed that the seasonal and annual drought are frequent in the study area. There are spatial and temporal variations in the drought years and their severity. The satellite-based indices clearly indicate the spatial variation in the agriculture droughts and its intensity. It has been found that the impact of drought on agriculture has significantly reduced due to the development of well-irrigation in the sub-basin. VHI is more appropriate in determining the agricultural drought and its characteristics. [ABSTRACT FROM AUTHOR]

Sea Level Rise (SLR) is considered as one of the effects of climate change that leads to Salt Water Intrusion (SWI) into the coastal areas around the world, thereby contaminating the groundwater and making it unusable for household and irrigation purposes along the coastal areas. Therefore, this paper is an attempt to analyze the change in sea level and shoreline and the consequent changes on the quality of groundwater in lowland and midland areas of Ernakulam district, Kerala. The tidal gauge data were sourced from the Permanent Service for Mean Sea Level (PSML) to assess the changes in sea level during 1971-2007. Remote sensing data was utilized for estimating the shoreline changes along the coast of the district using Digital Shoreline Analysis System (DSAS). The physical and chemical properties of groundwater were sourced for 27 locations from Central Ground Water Board (CGWB). Ionic ratios were computed to assess the salinity levels in the sampling locations. Sodium percentage (Na %) and potential salinity were computed for determining SWI and the suitability of the groundwater usage for domestic and irrigation purpose. Spatial variation of pH, EC, TDS and ionic ratios were assessed in the GIS environment through IDW interpolation. Findings indicate a rising trend in sea level at the rate of 1.8 mm/yr along the coast of the study area. Shoreline accretion and erosion was also observed at different locations along the coast during 2002-2012, though the rate of change varied across the shoreline. In general, water has shown slight alkaline nature, with pH varying from 7.2 to 8.2 at some locations, particularly along the coast. Higher values of EC and TDS were also observed along the coastal aquifer and may be ascribed to SWI. Sodium percentage (Na %) and potential salinity suggest presence of salt water. However, groundwater in majority of the areas especially away from the coast is good for domestic and irrigation uses. This study showed the groundwater quality deterioration, mainly due to the intrusion of sea water, particularly along the coastal areas of the Ernakulam district. [ABSTRACT FROM AUTHOR]

Emission of smoke and aerosol from open field burning of crop residue is a long-standing subject matter of atmospheric pollution. In this study, we proposed a new approach of estimating fuel load in the fire pixels and corresponding emissions of selected GHGs and aerosols i.e. CO2, CO, NO2, SO2, and total particulate matter (TPM) due to burning of crop residue under rice and wheat cropping systems in Punjab in north-west India from 2002 to 2012. In contrasts to the conventional method that uses RPR ratio to estimate the biomass, fuel load in the fire pixels was estimated as a function of enhanced vegetation index (EVI). MODIS fire products were used to detect the fire pixels during harvesting seasons of rice and wheat. Based on the field measurements, fuel load in the fire pixels were modelled as a function of average EVI using second order polynomial regression. Average EVI for rice and wheat crops that were extracted through Fourier transformation were computed from MODIS time series 16 day EVI composites. About 23% of net shown area (NSA) during rice and 11% during wheat harvesting seasons are affected by field burning. The computed average fuel loads are 11.32 t/ha (±17.4) during rice and 10.89 t/ha (±8.7) during wheat harvesting seasons. Calculated average total emissions of CO2, CO, NO2, SO2 and TPM were 8108.41, 657.85, 8.10, 4.10, and 133.21 Gg during rice straw burning and 6896.85, 625.09, 1.42, 1.77, and 57.55 Gg during wheat burning. Comparison of estimated values shows better agreement with the previous concurrent estimations. The method, however, shows its efficiency parallel to the conventional method of estimation of fuel load and related pollutant emissions. [ABSTRACT FROM AUTHOR]

Emission of smoke and aerosol from open field burning of crop residue is a long-standing subject matter of atmospheric pollution. In this study, we proposed a new approach of estimating fuel load in the fire pixels and corresponding emissions of selected GHGs and aerosols i.e. CO2, CO, NO2, SO2, and total particulate matter (TPM) due to burning of crop residue under rice and wheat cropping systems in Punjab in north-west India from 2002 to 2012. In contrasts to the conventional method that uses RPR ratio to estimate the biomass, fuel load in the fire pixels was estimated as a function of enhanced vegetation index (EVI). MODIS fire products were used to detect the fire pixels during harvesting seasons of rice and wheat. Based on the field measurements, fuel load in the fire pixels were modelled as a function of average EVI using second order polynomial regression. Average EVI for rice and wheat crops that were extracted through Fourier transformation were computed from MODIS time series 16 day EVI composites. About 23% of net shown area (NSA) during rice and 11% during wheat harvesting seasons are affected by field burning. The computed average fuel loads are 11.32 t/ha (±17.4) during rice and 10.89 t/ha (±8.7) during wheat harvesting seasons. Calculated average total emissions of CO2, CO, NO2, SO2 and TPM were 8108.41, 657.85, 8.10, 4.10, and 133.21 Gg during rice straw burning and 6896.85, 625.09, 1.42, 1.77, and 57.55 Gg during wheat burning. Comparison of estimated values shows better agreement with the previous concurrent estimations. The method, however, shows its efficiency parallel to the conventional method of estimation of fuel load and related pollutant emissions. [ABSTRACT FROM AUTHOR]

Aerosols are one of the key components of climate systems. They absorb and scatter both solar and terrestrial radiation and produce strong surface as well as atmospheric radiative forcing effects. Aerosol climatology includes the measurement of light extinction by aerosol scattering and absorption, by procedures such as aerosol optical depth (AOD), angstrom exponent (α), single-scattering albedo (ω), and size distribution. This article analyses the dynamics of seasonal AOD over the Indian subcontinent from 2001 to 2009 using the MODIS level 2 data set. The analysis carried out for winter, pre-monsoon, monsoon, and post-monsoon seasons is based on 8 days' composite AOD data for selected months representative of each season. The spatial variability of AOD has been shown to be 0.47 μm and 0.66 μm for fine- and coarse-mode aerosols, respectively, which illustrates the principle of relative difference. The dynamics of seasonally averaged AOD over the period under study represent an increasing tendency from 0.20 to 0.37 at 0.47 μm and from 0.16 to 0.26 at 0.66 μm during winter (2003–2009), whereas AOD in the pre-monsoon season ranged from 0.24 to 0.16 at 0.47 μm and from 0.24 to 0.16 at 0.66 μm (2005–2009). The monsoon season yielded an AOD of less than 0.15 throughout the study period, and the post-monsoon season recorded an increasing tendency from 0.18 to 0.29 at 0.47 μm and from 0.16 to 0.19 at 0.66 μm (2005–2009), reflecting a similar trend to that of the winter AOD curve. The spatial distribution of AOD shows that the northern part of India – especially the Indo-Gangetic plain – remains most affected by high AOD throughout the year. Such high AOD can be attributed to increasing anthropogenic emission due to an ever-increasing population, and urban, industrial, and other economic activities causing high concentrations of fine-mode organic and inorganic aerosol particles, along with coarse soil and mineral dust over the Indo-Gangetic plain. [ABSTRACT FROM PUBLISHER]