Signature of ENSO Signals in the Coral Growth Rate Record of Arabian Sea and Indian Monsoons

We examine here three sets of recently published data: (1) Updated Indian Rainfall (IRF) time series of the entire country covering the time span of 1826–1994, (2) coral growth rate time series for a period of 42 years spanning 1948–1990 from the Arabian Sea, and (iii) NINO3 temperature records to investigate the signature of ENSO response of the Indian monsoon. Multiple spectral techniques (e.g., multi-taper method (MTM), maximum entropy method (MEM), wavelet and cross spectra) are used to identify the coherent cyclic and nonstationary modes in these records. MTM analysis of IRF time series resolves statistically significant variability (>90% C.I) (i) at multi-decadal (66–70 years) scales related to the well-known global temperature variability of internal atmospheric-ocean origin, (ii) relatively weak signals at 13 and 22 years (solar cycles) and (iii) the 2.5 to 7.5-year cycles associated with the ENSO frequency band. The MTM spectra of the coral growth rate record also reveal statistically significant periodicities (>90% C.I.) within 1.8–4.2 ENSO frequency band, and a relatively weak signal at 12.8 years. MEM analysis confirms the stability of above spectral peaks. Wavelet spectral analyses of the above time series reveal nonstationary localized modes of ENSO evolution corresponding to 2–7 years and higher order terms. Although matching periodicities are present in these records, cross-spectral analysis of IRF and NINO3 temperature records exhibits significant coherency (>80% CI) only at periods 5.4 years and 2.7 years, suggesting the significant role of ENSO dynamics in organizing the subtle Indian monsoon at these frequencies. These results may provide significant implication for the modeling of Indian monsoon.     

Study of momentum transfers within a vegetation canopy

Two models have been developed by applying conditions of continuity between the roughness sublayer and the top of vegetation canopy having constant foliage distribution. Massman's cosh-type of wind profile and Albini's exponential wind profile have been used to derive expressions for shear stress, displacement height and roughness length in analytical forms. The computed results compared with those of Massman models (1987, 1997) show similarity with the present models.     

Use of Remote Sensing and Geospatial Technique for Pre-feasibility Analysis of Rural Water Pipeline Grids

The article outlines a procedure of pre-feasibility analysis of planned rural water supply pipeline grids in India. Usually, these type of pre feasibility studies prior to actual implementation, is carried out based on ground surveys and is time consuming. In this work, we use thematic spatial data, such as geomorphology and landuse–landcover along with digital elevation model (DEM) to carry out the pre-feasibility assessment of proposed pipeline grids. DEM generated from CartoSat-1 stereo data has been used to understand the possible topographic hindrances along the planned pipeline route and optimise the same. Further, topographic data also indicates the possible routes of gravity assisted flow. The geomorphology thematic data interpreted from Resourcesat-1 LISS III imagery is used to identify possible geomorphologic hindrances along the pipeline route. Similarly, landuse–landcover information derived from Resourcesat-2 LISS III images, was used to assess the land use/cover impact of the planed pipeline corridor. This has been demonstrated, in the current article using a hypothetical pipeline route. The activity can be carried in a specially designed geo-spatial interface in NRSC/ISRO Bhuvan geoportal. This type of assessment can prove to be time saving and cost effective at a pre-feasibility stage.     

Development of National Database on Long-term Deforestation in Sri Lanka

Sri Lanka is one of the biodiversity hotspots of the world. This study has utilized satellite remote sensing and GIS techniques to generate a nation-wide database on forests, forest types and land use/land cover of Sri Lanka. Spatial assessment of forest cover changes was carried out for the periods 1976–1985, 1985–1994, 1994–2005 and 2005–2014. The landscape fragmentation analysis has carried out to calculate the spatial and temporal patterns of forest. Land use/land cover map was prepared representing seven classes in 2014. The plantations occupy a large area (34.2%) followed by forests (33.4%) and agriculture (26.1%) in 2014. During the period of 1976–2014, the forest has been decreased by 5.5%. From 1976 to 1985 forest recorded a loss at an annual rate of 0.49%. This annual rate decreased to 0.01% during 2005–2014 indicates declining trend of deforestation and effective conservation measures. The study found deforestation hotspots in south east and northern most parts of the Sri Lanka. Total number of patches estimated has increased from 15193 in 1976 to 16136 in 2014. The study has found that main causes of deforestation in Sri Lanka were due to expansion of agriculture and plantations. The extent of change detected in the study through geospatial techniques has significance to the forest ecology and management of natural landscapes in Sri Lanka.     

Response of Sandy Lake in Schirmacher Oasis,East Antarctica to the glacial-interglacial climate shift

Freshwater lakes in Antarctica fluctuate from ice-free state (during austral summer) to ice-cover state (during austral winter). Hence the lakes respond instantly to the seasonal climate of the region. The Antarctic seasons respond sharply to the glacial and interglacial climates and these signatures are archived in the lake sediments. A sediment core from Sandy Lake, a periglacial lake located in Schirmacher Oasis of East Antarctica records distinct changes in grain-size, C, N, C/N ratios (atomic), δ¹³C_OM and δ¹⁵N_OM contents during the last 36 ky. The contents of the sedimentary organic matter (OM) proxies (C_org ~ 0.3 ± 0.2%, C/N ratios ~9 ± 5 and δ¹³C_OM ~?18 ± 6‰) indicate that the OM in this lake sediment is a product of mixing of terrestrial and lacustrine biomass. Distinctly lower contents of C_org (~0.2%) and sand (~50%), low C/N ratios (~8) and depleted δ¹³C_OM (~?20‰) during the Last Glacial Maximum (LGM: 32–17 ky BP based on Vostok Temperatures) suggest greater internal (autochthonous) provenance of organic matter and limited terrestrial (allochthonous) inputs probably due to long and intense winters in the Antarctic. Such intense winters might have resulted the lake surface to be ice-covered for most part of the year when the temperatures remained consistently colder than the Holocene temperatures. The denitrification within the lake evident by enriched δ¹⁵N_OM (>10‰) during Antarctic LGM might have resulted from oxygen-limitation within the lake environment caused by insulated lake surface. The gradual increases in δ¹³C_OM, C/N and sand content starting at ~11 ky BP and attaining high values (~?11‰, ~10 and ~80% respectively) at ~6 ky BP together suggest a subtle change in the balance of sources of organic matter between algal and macrophyte/bryophyte nearly 8–9 ky later to the beginning of the deglaciation. Thus the seasonal opening-up of the Sandy Lake similar to the modern pattern started with the establishment of the optimum temperature conditions (i.e., 0 °C anomaly) in the Antarctic, prior to which the lake environment might have remained mostly insulated or closed.     

Geo-hydrological database modeling for integrated multiple hazards and risk assessment in Lesser Himalaya: a GIS-based case study

The main objective of the study was to assess the integrated multiple hydrological hazards and their environmental and socio-economic risks in Himalaya through geographical information system (GIS) and database management system (DBMS). The Dabka Watershed constitutes a part of the Kosi Basin in the Kumaun Lesser Himalaya has been selected for the case illustration. The Dabka DBMS is constituted of three GIS modules, that is, geo-informatics, hydro-informatics and hazard-informatics. Through the integration and superimposing of these modules prepared Hydrological Hazard Index to identify the level of vulnerability for existing hydrological hazards and their socio-economic and environmental risks. The results suggested that geo-environmentally most stressed barren land areas have high rate of runoff, flood magnitude, erosion sediment load and denudation during rainy season particularly in the month of August (i.e., respectively, 84.56 l/s/km², 871.80 l/s/km², 78.60 t/km² and 1.21 mm/year), which accelerates high hazards and their socio-economic and environmental risks, whereas geo-environmentally least stressed dense forest areas experience low rate of stream runoff, flood magnitude, erosion sediment load and denudation in the same season and month (i.e., respectively, 20.67 l/s/km², 58.12 l/s/km², 19.50 t/km² and 0.20 mm/year) comparatively have low hazards and their socio-economic and environmental risks. The other frazzled geo-environment that also found highly vulnerable for natural hazards and their risks is agricultural land due to high stream runoff, flood magnitude, erosion sediment load and denudation rates (i.e., respectively, 53.15 l/s/km², 217.95 l/s/km², 90.00 t/km² and .92 mm/year). This makes it necessary to take up an integrated and comprehensive sustainable land use policy for the entire Himalaya region based on the scientific interpretation of the crucial linkages between land use and hydrological hazards, that is, floods, erosion, landslides during rainy season and drought due to dry-up of natural springs and streams during summer season. The study would help the village, district and state development authority to formulate decision support system for alternate planning and management for the Himalaya region.     

Effects of density, temperature and velocity gradients on inertial Alfven wave in cusp region

The kinetic approach is used to evaluate the dispersion relation and growth/damping rate of inertial Alfven wave (IAW) with density, temperature and velocity gradients in an inhomogeneous plasma. The effects of gradient terms are studied for both the regions k_⊥ρ_i<1 and k_⊥ρ_i>1, where k_⊥ is the perpendicular wave number and ρ_i is the ion gyroradius. The relevance of theoretical results so obtained is predicted in accordance to the FAST observations in the cusp region. The results are interpreted for the space plasma parameters appropriate to the cusp region. This study elucidates a possible scenario to account for the particle acceleration and the wave dissipation in inhomogeneous plasmas. This model is also able to explain many features observed in plasma sheet boundary layer as well as to evaluate the dispersion relation, growth/damping rate and growth/damping length of inertial Alfven wave. It is found that density, temperature and velocity gradients control the wave frequency and effectively enhance the growth rate of inertial Alfven wave.     

Rodent fossils from Dharmsala Group in Himachal Pradesh: Addition to pre-Siwalik Himalayan Miocene fauna

While constraining Cenozoic evolution of the Himalaya through enlightening fossils we find that Dharmsala Group (intervening Subathu Group and Siwalik Group) in Kangra Valley and adjoining coevals yield sporadic fossils. Hence, this first record of fossil rodents from Dharmsala Group is an important addition to an earlier report of dinothere from these horizons. The rodent material from grey facies of the Dharmsala Group comprises of an isolated premolar and fragments of a tooth and an incisor. Available crown details in conjunction with distinctive dimensions of the premolar lead to its assignment to Hodsahibia, a baluchimyine taxon; this taxon of Eocene lineage of south Asian-African distribution is already on record from early Oligocene horizons in Bugti area, Pakistan.