The influence of wind speed on surface layer stability and turbulent fluxes over southern Indian peninsula station

Surface to atmosphere exchange has received much attention in numerical weather prediction models. This exchange is defined by turbulent parameters such as frictional velocity, drag coefficient and heat fluxes, which have to be derived experimentally from high-frequency observations. High-frequency measurements of wind speed, air temperature and water vapour mixing ratio (eddy covariance measurements), were made during the Integrated Ground Observation Campaign (IGOC) of Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) at Mahabubnagar, India (16^°44^′N, 77^°59^′E) in the south-west monsoon season. Using these observations, an attempt was made to investigate the behaviour of the turbulent parameters, mentioned above, with respect to wind speed. We found that the surface layer stability derived from the Monin–Obukhov length scale, is well depicted by the magnitude of wind speed, i.e., the atmospheric boundary layer was under unstable regime for wind speeds >4 m s^?1; under stable regime for wind speeds <2 m s^?1 and under neutral regime for wind speeds in the range of 2–3 m s^?1. All the three stability regimes were mixed for wind speeds 3–4 m s^?1. The drag coefficient shows scatter variation with wind speed in stable as well as unstable conditions.     

Remediation of a major acid mine drainage point source discharge restores headwater connectivity for a diadromous native fish

Rivers receiving acid mine drainage (AMD) are frequently depauperate in fish and impacts may extend long distances downstream. AMD inputs may form chemical barriers for migratory species and isolate fish in unimpacted headwaters. We investigated the response of a diadromous fish, kōaro (Galaxias brevipinnis), to remediation of an AMD tributary in a 5th order river in New Zealand. A 2005 survey indicated limited recruitment of kōaro in the river likely due to the chemical barrier of AMD. By 2010, water treatment in the contaminated tributary had raised pH from a median value of 4.3 to 6 and reduced metals in the lower river, notably aluminium from a median of 2.48 to 0.41?mg/L. In 2012, kōaro density had increased by an order of magnitude relative to 2005. Furthermore, a greater proportion of juvenile fish were present. These results indicate that large-scale remediation of discharges can reverse the impacts of AMD on fish migration.     

Application of trace metal anomalies for recognition of petroleum prospects in surface sediments of Kutch and Saurashtra Basins, India

Seepage of hydrocarbons, either as macroseepage or microseepage, can set up near-surface oxidation-reduction zones that favour the development of a diverse array of chemical and mineralogic changes. In this study trace metal alterations were mapped that appear to be associated with hydrocarbon microseepages in the oil/gas fields. A total of 210 soil samples were collected from near surface sediments of Kutch and Saurashtra Basins, India. The soil samples were collected from a depth of 2–2.5 m. The paper reports the chemical alterations associated with trace metals in soils that are related to hydrocarbon microseepages above the Kutch and Saurashtra Basins, India. The soil samples for trace metals; Scandium (Sc), Vanadium (V), Chromium (Cr), Cobalt (Co), Nickel (Ni), Copper (Cu), Zinc (Zn), Barium (Ba) and Strontium (Sr) were analyzed using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The concentrations of the trace elements ranged between for Sc (12.69 to 21.91 ppm), V (109.20 to 436.05 ppm), Cr (87.15 to 481.57 ppm), Co (18.25 to 64.31 ppm), Ni (57.55 to 263.15 ppm), Cu (44.88 to 143.96 ppm), Zn (137.60 to 502.31 ppm), Ba (149.27 to 921.46 ppm) and Sr (143.93 to 425.63 ppm) were obtained. It was observed that trace elements concentrations were tremendously increased when compared with normal concentration in the soils. The adsorbed soil gas analysis showed the presence of high concentrations of ΣC₂₊ (C₂H₆, C₃H₈ and n-C₄H₁₀) ranged between 1 to 121 ppb respectively. Integrated studies of trace elements over adsorbed light gaseous hydrocarbon (ΣC₂₊) anomalies showed good correlation. The carbon isotopic composition of δ¹³C₁ of the samples ranges between — 36.6 ‰ to ?22.7‰ (Pee Dee Belemnite) suggest thermogenic source for hydrocarbon gases. The increase in trace metal concentrations near oil/gas producing areas, suggests that soil chemical change to a reducing environment, presumably due to the influence of hydrocarbon microseepage, which could be applied with other geo-scientific data to identify areas of future hydrocarbon exploration in the frontier areas.     

Near surface manifestation of hydrocarbons in Proterozoic Bhima and Kaladgi Basins: Implications to hydrocarbon resource potential

Reconnaissance surface geochemical survey for adsorbed soil gas analysis conducted in Proterozoic Bhima and Kaladgi Basins, have revealed occurrence of anomalous concentrations of light gaseous hydrocarbons i.e. C₁ to C₄ (CH₄, C₂H₆, C₃H₈, i-C₄H₁₀ and n-C₄H₁₀) in the near surface soils. The concentrations of C₁ and ΣC₂₊(C₂H₆+C₃H₈+ i-C₄H₁₀+ n-C₄H₁₀) in Bhima and Kaladgi Basins are in the range of 1–2594 ppb and 1 to 57 ppb and 1–1142 ppb and 1–490 ppb, respectively. The carbon isotopic data of adsorbed soil gas methane in few selected samples are in the range of −29.9 to −39‰ (PDB). The evaluation of adsorbed soil gas data indicates that all the gas components are cogenetic and hydrocarbon ratios of C₁/(C₂+C₃) < 10 and C₃/C₁*1000 between 60–500 and 20–60 suggest that the adsorbed gases are derived from oil and gas-condensate zones. The carbon isotopic values of methane further support thermogenic origin of these migrated gases. The concentration distribution of C₁ and ΣC₂₊ in the study areas illustrate C₁ and ΣC₂₊ anomalies near Katamadevarhalli, Andola and Talikota in Bhima Basin and near Kaladgi, Lokapur and north of Mudhol in Kaladgi Basin. The hydrocarbon anomalies near the surface coincide with the favourable subsurface structural features and correlate with existing geochemical and geophysical data in these basins suggesting seepage related anomalies.     

Energy dependence of near-relativistic electron spectrum at geostationary orbit during the SEP events of 2005

In view of the renewed interest in the study of energetic particles in the outer radiation belt of the earth, we feel it will be helpful in looking for the energy dependence of the electron energy spectrum at geostationary orbit. This may give us some insight into how we can safeguard geostationary satellites from functional anomalies of the deep dielectric charging type, which are caused by charge accumulation and subsequent discharge of relativistic electrons. In this study we examine whether there is any energy dependence in relativistic electron enhancements at geosynchronous altitudes during solar energetic proton events of 2005.     

A study of turbulent characteristics of atmospheric boundary layer over monsoon trough region using Kytoon and Doppler sodar

As a part of the MONTBLEX-90 observational programme, Kytoon and Doppler sodar observations were taken at Kharagpur. These data are analysed to study the turbulent characteristics of the atmospheric boundary layer in terms of stability, temperature structure function (C _T ² ) and velocity structure function (C _v ² ).C _T ² follows aZ ^−4/3 law on most of the days, whereas the variation ofC _V ² is not systematic.C _V ² andC _T ² values are found to vary between 10⁻⁵−10⁻¹ m^4/3s⁻² and 10⁻⁵−10⁻²°C² m^−2/3 respectively.     

Investigation of X-ray cavities in the cooling flow system Abell 1991

We present results based on the systematic analysis of Chandra archive data on the X-ray bright Abell Richness class-I type cluster Abell 1991 with an objective to investigate properties of the X-ray cavities hosted by this system. The unsharp masked image as well as 2-d β model subtracted residual image of Abell 1991 reveals a pair of X-ray cavities and a region of excess emission in the central ～12 kpc region. Both the cavities are of ellipsoidal shape and exhibit an order of magnitude deficiency in the X-ray surface brightness compared to that in the undisturbed regions. Spectral analysis of X-ray photons extracted from the cavities lead to the temperature values equal to $1.77_{-0.12}^{+0.19}~\mathrm{keV}$ for N-cavity and $1.53_{-0.06}^{+0.05}~\mathrm{keV}$ for S-cavity, while that for the excess X-ray emission region is found to be equal to $2.06_{-0.07}^{+0.12}~\mathrm{keV}$ . Radial temperature profile derived for Abell 1991 reveals a positive temperature gradient, reaching to a maximum of 2.63 keV at ～76 kpc and then declines in outward direction. 0.5–2.0 keV soft band image of the central 15′′ region of Abell 1991 reveals relatively cooler three different knot like features that are about 10′′ off the X-ray peak of the cluster. Total power of the cavities is found to be equal to ${\sim}8.64\times10^{43}~\mathrm{erg\,s}^{-1}$ , while the X-ray luminosity within the cooling radius is found to be $6.04 \times10^{43}~\mathrm{erg\,s}^{-1}$ , comparison of which imply that the mechanical energy released by the central AGN outburst is sufficient to balance the radative loss.     

A multiwavelength view of the ISM in the merger remnant galaxy Fornax A

We present multi-wavelength imagery of the merger remnant galaxy NGC 1316 with an objective to study the dust content and its association with the other phases of the interstellar medium. Color-index maps as well as extinction maps derived for this galaxy reveal an intricate and complex dust morphology in NGC 1316, i.e. there is a prominent lane in the inner part, while at about 6-7 kpc it apparently takes the form of an arc-like pattern extending along the northeast direction. In addition to this, several other dust clumps and knots are also evident in this galaxy. The dust emission mapped using Spitzer data at 8 μm indicates even more complex morphological structures of the dust in NGC 1316. The extinction curve derived over the optical to near-IR bands closely follows the standard Galactic curve, suggesting similar properties of the dust grains. The dust content of NGC 1316, estimated from optical extinction, is ～ 2.13 105M⊙ . This is a lower limit compared to that estimated using the IRAS flux densities of ～5.17×106M⊙ and the flux densities at 24, 70 and 160 μm from MIPS ～3.2×107M⊙ . High resolution Chandra observations of this merger remnant system have provided an unprecedented view of the complex nature exhibited by the distribution of hot gas in NGC 1316, which closely matches the morphology of ionized gas and to some extent also the dust. X-ray color-color plots for the resolved sources within the optical D 25 extent of NGC 1316 have enabled us to separate them into different classes.     

Spatial Variability and Precision Nutrient Management in Sugarcane

Investigations were carried out to develop precision nutrient management techniques for sugarcane. The study area (800 ha) comprised of Bijapur, Bilgi and Jamakhandi talukas that lie between 16° 34′–28° 10′ N latitudes and 75° 33′–75° 37′ E longitudes and located around Nandi Sahakari Sakkare Karkhane (NSSK) Niyamit, Galagali. The soils are medium to deep black with pH and EC ranging from 7.32 to 8.36 and 0.17 to 1.13 dS/m, respectively. The soils are low to medium in available nitrogen, medium in available phosphorus and high in available potassium content. Crop condition assessment was made through analysis of LISS-III satellite images using Erdas Imagine software. Fertigation with 300 kg N and 195 kg K per ha at fortnightly interval and soil application of 32 kg P per ha as basal, recorded higher sugarcane yield (167 Mg ha^?1) as compared to 124 Mg ha^?1 obtained with soil application of 250 kg N, 32 kg P and 156 kg K per ha and flood irrigation as per the package recommended by the University(POP). Fertigation of N and K at weekly interval recorded highest NDVI value (0.354) and soil application of nutrients as per POP resulted in the lowest NDVI of 0.219.