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11.
Summary The seasonal and diurnal variations in the vertical component of the atmospheric electric field, air temperature, relative humidity and horizontal wind speed were studied using the surface data for the two periods (1936–40) and (1962–66) recorded at the tropical urban station, Colaba, Bombay (18°51N, 72°49E, 11 m ASL), located on the west coast of India.The atmospheric electric field during the latter period (1962–66) is significantly higher (up to 42.3%) than the earlier period (1936–40). This has been attributed to the enhanced particulate concentrations in the atmosphere. The increase noticed in the atmospheric electric field is a maximum during winter and minimum during the monsoon. The atmospheric electric field exhibited a marked semi-diurnal oscillation with peaks at 0900 LST and 2200 LST during winter, premonsoon and post-monsoon seasons of both the periods. During the monsoon season the double oscillation is not marked.The variations noticed in the surface air temperature and the relative humidity are in agreement with those observed in the atmospheric electric field. The horizontal wind speed showed a decrease which has been attributed to the surface roughness resulting from urbanization.With 7 Figures 相似文献
12.
Govindasamy Vijayakumar Chang Kyoo Yoo Kuppana Gounder P. Elango Mahendiradas Dharmendirakumar 《洁净——土壤、空气、水》2010,38(2):202-209
Batch sorption experiments were carried out for the adsorption of the basic dye Rhodamine B from aqueous solution using baryte as the adsorbent. The effect of adsorbent dosage, temperature, initial dye concentration and pH were studied. Adsorption data were modeled using first and second order kinetic equations and the intra particle diffusion model. Kinetic studies showed that the adsorption process followed second order rate kinetics with an average rate constant of 0.05458 g mg–1 min–1. Dye adsorption equilibrium was attained rapidly after 30 min of contact time. The equilibrium data was fitted to the Langmuir, Freundlich and Tempkin isotherms over a dye concentration range of 50–250 mg/L. The adsorption thermodynamic parameters showed that adsorption was an exothermic, spontaneous and less ordered arrangement process. The adsorbent, baryte, was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The results showed that baryte has good potential for the removal of Rhodamine B from dilute aqueous solution. 相似文献
13.
Vijayakumar S. Nair K. Krishna Moorthy S. Suresh Babu K. Narasimhulu L. Siva Sankara Reddy R. Ramakrishna Reddy K. Rama Gopal V. Sreekanth B. L. Madhavan K. Niranjan 《Journal of Earth System Science》2008,117(1):315-323
Mass concentration and mass size distribution of total (composite) aerosols near the surface are essential inputs needed in developing aerosol models for radiative forcing estimation as well as to infer the environment and air quality. Using extensive measurements onboard the oceanographic research vessel, Sagar Kanya, during its cruise SK223B in the second phase of the ocean segment of the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB), the spatial distribution of the mass concentration and mass size distribution of near-surface aerosols are examined for the first time over the entire Arabian Sea, going as far as 58°E and 22°N, within a span of 26 days. In general, the mass concentrations (M T ) were found to be low with the mean value for the entire Arabian Sea being 16.7 ± 7 μg m?3; almost 1/2 of the values reported in some of the earlier campaigns. Coarse mode aerosols contributed, on an average, 58% to the total mass, even though at a few pockets accumulation mode contribution dominated. Spatially, significant variations were observed over central and northern Arabian Sea as well as close to the west coast of India. In central Arabian Sea, even though the M T was quite low, contribution ofs accumulation aerosols to the total mass concentration was greater than 50%. Effective radius, a parameter important in determining scattering properties of aerosol size distribution, varied between 0.07 and 0.4 μm with a mean value of 0.2 μm. Number size distributions, deduced from the mass size distributions, were approximated to inverse power-law form and the size indices (ν) were estimated. It was found to vary in the range 3.9 to 4.2 with a mean value of 4.0 for the entire oceanic region. Extinction coefficients, estimated using the number-size distributions, were well-correlated with the accumulation mode mass concentration with a correlation coefficient of 0.82. 相似文献
14.
A low grade siliceous limestone sample from the Jayantipuram mine of Andhra Pradesh, India, has been investigated for its suitability for cement making. Petrological as well as X-ray diffraction pattern studies indicated that the limestone sample was crystalline and dominantly composed of calcite and quartz. They are simple in mineralogy, and yet they have variable silica and lime contents. Geochemical analysis results of twenty five hand picked samples indicated that the limestone from the Jayantipuram mine shows a wide range of variations in LOI (29.94% to 40.64%), SiO2 (6.14% to 27.18%), CaO (37.93% to 50.78%), Al2O3 (0.49% to 2.27%) and Fe2O3 (0.28% to 2.4%). MgO, K2O, Na2O, TiO2 and MnO2 are present in traces. CaO with LOI shows a strong positive correlation where as CaO with SiO2 shows a strong negative correlation because of mineralogical factors. The chemical composition of the limestone reflects its mineralogical composition. The distribution of various elements in the acid-soluble fraction has been studied by the factor analysis method in order to interpret in terms of their mineralogy, sedimentary environment and diagenesis. Mineralogy, recrystallization and other diagenetic changes are the main factors affecting the distribution of the elements and their mutual relationships in the limestone. The aim of this paper is also to analyze how significantly the two parameters, silica modulus and lime saturation factor, influence this low grade siliceous limestone sample from the Jayantipuram mine of Andhra Pradesh, India, for the cement making process from the geochemical data. 相似文献
15.
Climate Dynamics - Regional climate model (RegCM-4.6.0) coupled with Community Land Model (CLM4.5), which includes SNow, ICe and Aerosol Radiation (SNICAR) model was used to investigate the effect... 相似文献
16.
The total ozone content in the atmosphere was determined from the multichannel photometer observations of direct solar radiation made in the urban environment at Pune (18° 32 N, 73° 51E, 559 m ASL) and Sinhagad hill station (18° 22N, 73° 45E, 1305 m ASL) during March 1980-February 1982. The total ozone content of the atmosphere was computed making use of the differential absorption of solar radiation due to ozone at 0.4 and 0.6 m wavelengths in the Chappuis band. The values of the ozone data obtained from the photometer observations at Pune and Sinhagad were compared with the corresponding ozone data obtained from the Dobson spectrophotometer located at Pune. Values of ozone obtained by the photometric method were found to be smaller by 8–18% than the Dobson values when Vigroux's absorption coefficients were used. Similarly, when the absorption coefficients of Inn and Tanaka (1953) were used, the ozone values obtained by the photometric method were smaller by 4–14% than the Dobson values. The ozone values at the hill station obtained from the photometric method were in better agreement (5%) with the Dobson values. 相似文献
17.
A new method of analysis namely, Singular Spectrum Analysis (SSA) is applied to the Indian Summer Monsoon (June-September) Rainfall (ISMR) series. The method is efficient in extracting the statistically significant oscillations with periods 2.8 and 2.3 year from the white noise of the ISMR series. The study shows that 2.8 / 2.3 year cycle captures the variability of the ISMR related to Southern Oscillation / Quasi Biennial Oscillation. The temporal structure of these oscillations show that these are in phase in extreme (excess and drought) monsoon conditions as well as in El Nino Southern Oscillation (ENSO) years. Both these oscillations show minimum variability during the period 1920-1940 and there is an increasing trend in the variability of these oscillations in the recent decades. The study enables to obtain pure signal consisting of reconstructed time series using these two Oscillations, from the original white noise series. 相似文献
18.
Ponnusamy Senthil Kumar Subramaniam Ramalingam Ramasundaram Vijayakumar Abhinaya Selvaraj Dinesh Kirupha Arukkani Murugesan Subramanian Sivanesan 《洁净——土壤、空气、水》2012,40(2):188-197
This paper discusses about the adsorption of metal ions such as Cu(II), Cd(II), Zn(II), and Ni(II) from aqueous solution by sulfuric acid treated cashew nut shell (STCNS). The adsorption process depends on the solution pH, adsorbent dose, contact time, initial metal ions concentration, and temperature. The adsorption kinetics was relatively fast and equilibrium was reached at 30 min. The adsorption equilibrium follows Langmuir adsorption isotherm model. The maximum adsorption capacity values of the modified cashew nut shell (CNS) for metal ions were 406.6 mg/g for Cu(II), 436.7 mg/g for Cd(II), 455.7 mg/g for Zn(II), and 456.3 mg/g for Ni(II). The thermodynamic study shows the adsorption of metal ions onto the STCNS was spontaneous and exothermic in nature. The kinetics of metal ions adsorption onto the STCNS followed a pseudo‐second‐order kinetic model. The external mass transfer controlled metal ions removal at the earlier stages and intraparticle diffusion at the later stages of adsorption. A Boyd kinetic plot confirms that the external mass transfer was the slowest step involved in the adsorption of metal ions onto the STCNS. A single‐stage batch adsorber was designed using the Langmuir adsorption isotherm equation. 相似文献
19.
An important component of ionospheric plasma irregularity studies in the Indian low latitudes involves the study of the plasma bubbles which produce intense scintillations of the transionospheric satellite signals. Many such plasma bubble induced (FBI) scintillation events were identified while recording 244 MHz signal from the geostationary satellite Fleetsat (73°E) at Delhi (28.6°N, 77.2°E) during March-April 1991. This type of scintillations represents changes in plasma processes. These scintillations are spectrally analyzed using an autoregressive (AR) scheme, which is equivalent to maximum entropy method of spectrum analysis, amenable to extracting optimum spectral content from short data lengths (20–40 s). Each spectrum is assigned a level of detectability using the final prediction error (FPE) derived from the optimum filter order required to resolve the spectrum. Lower detectability together with a higher order filter indicate a higher level of coherence for the plasma irregularities (discrete structures). Consistent patterns for these scintillations emerge from the present analysis as follows: (1) the initial and final phases of a scintillation patch display quasiperiodic oscillations. Their corresponding spectra show dominant (Gaussian shaped) spectral features with detectability levels of –6 dB to –12 dB and requiring a higher order (>6) AR filter for their spectral resolution. These are most likely associated with discrete filament-like or sheet-like plasma structures that exist near the bubble walls. (2) Two main features of the scintillation spectra could be positively associated with the well-developed plasma bubble stage: (a) spectra displaying a power-law process with a single component spectral slope between 1.6 to 3.0. Generally such spectra are resolved with a 2nd order filter and have a 1 dB to 6 dB of detectability. (b) Spectra displaying a double slope, indicating an inner and an outer scale regime for the power-law irregularities. These spectra are resolved with higher order filters (>3 but <7) and possess detectability levels of –1 dB to 3 dB. These spectra display finer spectral changes, perhaps indicative of the nature of continuously evolving plasma irregularities. As an example, an analysis of a single scintillation patch is presented to highlight the geophysical significance of the present approach. Some important parameters used in the AR scheme of spectral analysis are given in the Appendix. 相似文献
20.
The physical characteristics of the summer monsoon clouds were investigated. The results of a simple cloud mod-el were compared with the aircraft cloud physical observations collected during the summer monsoon seasons of 1973,1974,1976 and 1981 in the Deccan Plateau region.The model predicted profiles of cloud liquid water content (LWC) are in agreement with the observed profiles. There is reasonable agreement between the model predicted cloud vertical thickness and observed rainfall.The observed cloud-drop spectra were found to be narrow and the concentration of drops with diameter >20μm is either low or absent on many occasions. In such clouds the rain-formation cannot take place under natural atmos-pheric conditions due to the absence of collision-coalescence process. A comparison of the model predicted and ob-served rainfall suggested that the precipitation efficiency in cumulus clouds of small vertical thickness could be as low as 20 per cent.The clouds forming in the Deccan Plateau region during the summer monsoon are, by and large, cumulus and strato-cumulus type. The vertical thickness of the cumulus clouds is in the range of 1.0-2.0 km. The LWC is found to be more in the region between 1.6-1.9 km A. S. L., which corresponds to the level at almost 3 / 4 th of the total verti-cal thickness of the cloud and thereafter the LWC sharply decreased. Nearly 98 per cent of the tops of the low clouds in the region are below freezing level and the most frequent range of occurrence of these cloud-tops is in the range of 2.0-3.0 km A. S. L.. The dominant physical mechanism of rain-formation in these summer monsoon clouds it the col-lision-coalescence process. 相似文献