Parameterization of sea surface drag under varying sea state and its dependence on wave age

Momentum and energy exchange at air–sea interface through wind stress is very important for air–sea interaction studies, ocean modeling, and climate studies. The accurate representation of wind stress, in terms of drag coefficient, is a key factor in estimating the momentum transfer at the interface. The drag coefficient, in general, estimated using bulk formulae does not take into account the influence of wave age. This study examines the dependence of wave age on computed surface drag coefficient obtained by combining the Toba 3/2-power law with Froude number scaling, resulting in a new drag formulation (hereafter referred as RP formulation). We demonstrate that our proposed formulation is in good conjunction with established theories for both young and mature waves. Our investigation shows the theoretical formulation advocated earlier by Guan and Xie (hereafter referred as GX) overestimated the surface drag for mature waves as wind speed tends to increase. In addition, the formulation by GX was not verified by observational data. In the present work, for validation purpose, we use time series measurement of meteorological and oceanographic data from a deep water location in the Indian Ocean which was tested with both RP and GX formulations. We find that the proposed RP formulation, which embeds the 3/2 power of wave-age, shows a better match for both young and mature waves with the results of Janssen compared to the hypothesis of conventional wave age used by GX.     

Improvements in Sensible Heat-Flux Parametrization in the High-Resolution Regional Model (HRM) Through the Modified Treatment of the Roughness Length for Heat

We discuss the impact of the differential treatment of the roughness lengths for momentum and heat ( $z_{0\mathrm{m}}$ and $z_{0\mathrm{h}}$ ) in the flux parametrization scheme of the high-resolution regional model (HRM) for a heterogeneous terrain centred around Thiruvananthapuram, India (8.5°N, 76.9°E). The magnitudes of sensible heat flux (H) obtained from HRM simulations using the original parametrization scheme differed drastically from the concurrent in situ observations. With a view to improving the performance of this parametrization scheme, two distinct modifications are incorporated: (1) In the first method, a constant value of 100 is assigned to the $z_{0\mathrm{m}}/z_{0\mathrm{h}}$ ratio; (2) and in the second approach, this ratio is treated as a function of time. Both these modifications in the HRM model showed significant improvements in the H simulations for Thiruvananthapuram and its adjoining regions. Results obtained from the present study provide a first-ever comparison of H simulations using the modified parametrization scheme in the HRM model with in situ observations for the Indian coastal region, and suggest a differential treatment of $z_{0\mathrm{m}}$ and $z_{0\mathrm{h}}$ in the flux parametrization scheme.     

Reservoir capacity estimation of Singoor reservoir,India, by per-pixel and sub-pixel processing of multi-date satellite images

Traditional approaches of image classification, such as maximum likelihood and the band thresholding method, involve the per-pixel approach to delineate the water spread area of a reservoir. One of the limitations of these approaches is that the pixels representing the reservoir border, containing a mixture of water, soil and vegetation, are classified entirely as water, thereby resulting in inaccurate estimates of the water spread area. To compute the water spread area accurately, the sub-pixel approach has been used in this study. The water spread areas extracted using per-pixel and sub-pixel approaches from IRS-1D and P6 satellite image data were in turn used to quantify the capacity of the Singoor reservoir, Andhra Pradesh, India. The estimated capacity of the reservoir using the per-pixel and sub-pixel approaches was 727.75 Mm³ and 716.11 Mm³, respectively. The validation shows that the sub-pixel approach produced much less error (1.08%) than the per-pixel based approach (3.14%).     

Assessment and validation of evapotranspiration using SEBAL algorithm and Lysimeter data of IARI agricultural farm,India

Evapotranspiration (ET) is a vital process in land surface atmosphere research. In this study, Surface Energy Balance Algorithm for Land (SEBAL) for the assessment of ET (for 23 December 2010, 8 January 2011, 24 January 2011, 9 February 2011, 25 February 2011, 29 March 2011 and 14 April 2011) from LANDSAT7-ETM+ and validation with Lysimeter data set is illustrated. It is based on the evaporative fraction concept, and it has been applied to LANDSAT7-ETM + (30 m resolution) data acquired over the Indian Agricultural Research Institute’s agricultural farm land. The ET from SEBAL was compared with Lysimeter ET using four statistical tests (root-mean-square error (RMSE), relative root-mean-square error (R-RMSE), mean absolute error (MAE), and normalized root-mean square error (NRMSE)), and each test showed a good correlation between the predicted and observed ET values. Results from this study revealed that the RMSE of crop-growing period was 0.51 mm d^?1 for ET_SEBAL, i.e. ET_SEBAL having good accuracy with respect to observed ET_Lysimeter. Results were also validated using R-RMSE test, which also proved that ET_SEBAL data are having good accuracy with respect to observed ET_Lysimeter as R-RMSE of crop-growing period is 0.19 mm d^?1. MAE (0.19), NRMSE (0.21) and r² (0.91) tests indicated that model prediction is significant, and model can be effectively used for the estimation of ET from SEBAL as input of remote sensing data sets. Finally, the SEBAL has been useful for remote agricultural land where ground-based data (Lysimeter data) are not available for daily ET (ET_24 h) estimation. The temporal study of the ET_24 h values analysed has revealed that the highest ET_24 h values are owing to the higher development (high greenness) of crops, whereas the lower values are related to the lower development (low greenness) or null crop.     

A Single Step Acid Assisted Microwave Digestion Method for the Complete Dissolution of Bauxite and Quantitation of its Composition (Al2O3, Fe2O3, SiO2, TiO2, Cr2O3, MgO,MnO and V2O5) by ICP-AES

An acid assisted microwave-based method for the complete dissolution of bauxite using mixture of H₂SO₄, H₃PO₄ and HF acids in a single step was developed for the determination of various analytes (Al₂O₃, Fe₂O₃, SiO₂, TiO₂, Cr₂O₃, MgO, MnO and V₂O₅) using ICP-AES. The method was validated with respect to ruggedness, linearity, trueness, precision, limit of detection (LOD), limit of quantification (LOQ), working range and measurement uncertainties by analysing a bauxite reference material (Alcan BXT-12) and four certified reference materials (IPT-131, BXBA-4, NIST SRM 600, NIST SRM 697). The expanded uncertainties obtained for Al₂O₃ (40.0%), Fe₂O₃ (17.0%), SiO₂ (20.3%), TiO₂ (1.31%), Cr₂O₃ (0.024%), MgO (0.05), MnO (0.013), and V₂O₅ (0.60%), were 0.80, 0.40, 0.50, 0.033, 0.0008, 0.002, 0.0007 and 0.002 respectively, which are fit for the intended use to characterise bauxite. The developed method was also evaluated through participation in an interlaboratory comparison exercise organised by the Jawaharlal Nehru Aluminium Research Development and Design Centre (JNARDDC), Nagpur, India, using bauxite sample (BXT-JNA), with satisfactory z-scores achieved.     

Anatomy of the middle ordovician sevier shale basin,eastern Tennessee

The Sevier Shale basin in eastern Tennessee comprises one of the thickest clastic sequences (nearly 2500 m) of Middle Ordovician age in North America. The lower one-half of the sequence is composed of Lenoir, Whitesburg, Blockhouse and Sevier Formations, in ascending order. The sequence ranges in age from Whiterockian to lower Wilderness in North American stages.The Middle Ordovician sequence exhibits tidal flat (Mosheim Member of Lenoir Fm.), subtidal (main body of Lenoir Fm.), slope (Whitesburg Fm.), anoxic basin (Blockhouse Fm), turbidite and contourite (Sevier Fm.) facies. The Sevier basin evolved in five stages: First, a widespread marine transgression initiated carbonate-shelf deposition in the study area. Second, a major tectonic downwarping event caused the stable shelf to break and subside rapidly at a rate of 60–65 cm 1000 yrs^?1, and areas of shelf facies became areas of slope and basin facies. Third, global transgressions maintained the deep anoxic conditions for nearly 10 Ma. Fourth, turbidites began to fill the basin from a westward-prograding submarine fan system. Fifth, contour currents reworked the turbidites and progressively ventilated the Sevier basin. The basin-filling process terminated with shallow-water/subaerial clastics at the end of Middle Ordovician.     

New towns in India: 1971

This paper deals with the mode of emergence, population size, functional nature and distributional pattern of new towns in India as recorded at the 1971 Census. It was discovered that (i) an overwhelming majority of new towns were not new settlements but expanded villages. The rest owed their status to one of four situations: an independent town is carved out of an existing urban place; neighbouring towns are merged into a new unit; a declassified town in 1961 gets reclassified in 1971; and a new town is built, usually on planned lines; (ii) mode of emergence was the most vital factor in determining demographic attributes; (iii) new towns represented two contrasting tendencies in Indian urbanisation: concentrated urbanisation around metropolitan nodes and dispersed urbanisation in recently developing backward regions.     

Spatial and temporal aspects of phytoplankton blooms in complex ecosystems off the korean coast from satellite ocean color observations

Complex physical, chemical and biological interactions off the Korean coast created several striking patterns in the phytoplankton blooms, which became conspicuous during the measurements of ocean color from space. This study concentrated on analyzing the spatial and temporal aspects of phytoplankton chlorophyll variability in these areas using an integrated dataset from a Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Advanced Very High Resolution (AVHRR) sensor, and Conductivity Temperature Depth (CTD) sensor. The results showed that chlorophyll concentrations were elevated in coastal and open ocean regions, with strong summer and fall blooms, which appeared to spread out in most of the enclosed bays and neighboring waters due to certain oceanographic processes. The chlorophyll concentration was observed to range between 3 and 54 mg m^-3 inside Jin-hae Bay and adjacent coastal bays and 0.5 and 8 mg m^-3 in the southeast sea offshore waters, this gradual decrease towards oceanic waters suggested physical transports of phytoplankton blooms from the shallow shelves to slope waters through the influence of the Tsushima Warm Current (TWC) along the Tsushima Strait. Horizontal distribution of potential temperature (θ) and salinity (S) of water off the southeastern coast exhibited cold and low saline surface water (θ<19°C; S<32.4) and warm and high saline subsurface water (θ>12°C; S>34.4) at 75dBar, corroborating TWC intrusion along the Tsushima Strait. An eastward branch of this current was called the East Korean Warm Current (EKWC), tracked with the help of CTD data and satellite-derived sea surface temperature, which often influenced the dynamics of mesoscale anticyclonic eddy fields off the Korean east coast during the summer season. The process of such mesoscale anticyclonic eddy features might have produced interior upwelling that could have shoaled and steepened the nutricline, enhancing phytoplankton population by advection or diffusion of nutrients in the vicinity of Ulleungdo in the East Sea.     

Impact of Annular Solar Eclipse of 15 January 2010 on the Atmospheric Boundary Layer Characteristics Over Thumba: A Case Study

On 15 January 2010, Thumba (8.5°N, 76.9°E) witnessed one of the longest known noontime annular solar eclipses (ASEs) spanning a period of about 7 min, centered at 1314 hours local time. In this research article, we present a case study on the behaviour of the atmospheric boundary layer characteristics and its vertical structure in response to this rare celestial event by making use of a suite of different in-situ instruments. During the peak period of the ASE, the incoming solar irradiance was dimmed by about 87% of its normal values, resulting in a significant reduction in the magnitudes of turbulent kinetic energy and surface-layer turbulent fluxes of heat and momentum. The intensity and vertical thickness of the sea/land breeze circulation cell over the study domain also weakened. However, the mixed layer heights determined from balloon-borne GPS Radiosonde did not show any appreciable changes. Analysis of vertical profiles of thermodynamic parameters in association with the wind direction during ASE indicated the formation of a double mixed layer between 700 and 1500 m and is attributed to horizontal advection of a different airmass at those altitudes.