The present work describes the synthesis and characterization of pyrene derivatives, N-(1-Pyrenoylmethyl) pyridinium bromide (PM-PB) and N-(1-Pyrenoylmethyl)-N,N,N-triethylammonium bromide (PM-TAB). ...The photophysical behavior of these molecules has been studied in various protic and aprotic solvents. Using steady state fluorescence intensity, fluorescence anisotropy and dynamic fluorescence lifetime studies, the sensitivity of these molecules towards the micellization process of bile salts has been monitored. These derivatives have been effectively used in estimating critical micellar concentration (CMC) of bile salt, sodium deoxycholate (NaDC).
In the present satellite era, remote-sensing data are more useful to improve the initial condition of the model and hence the forecast of tropical cyclones (TCs) when they are in the deep oceans, ...where conventional observations are unavailable. In this study, an attempt is made to assess the impact of remotely sensed satellite-derived winds on initialization and simulation of TCs over the North Indian Ocean (NIO). For this purpose, four TCs, namely, ‘Nargis’, ‘Gonu’, ‘Sidr’ and ‘KhaiMuk’, are considered, with 13 different initial conditions. Two sets of numerical experiments, with and without satellite-derived wind data assimilation, are conducted using a high-resolution weather research and forecasting (WRF) model.The inclusion of satellite-derived winds through a three-dimensional variational (3DVAR) data assimilation system improves the initial position in 11 cases out of 13 by 34%. The 24-, 48-, 72- and 96-hour mean track forecast improves by 28%, 15%, 41% and 47%, respectively, based on 13 cases. The landfall prediction is significantly improved in 11 cases by about 37%. The intensity prediction also improves by 10–20%. Kinematic and thermodynamic structures of TCs are also better explained, as it could simulate heat and momentum exchange between sea surface and upper air. Due to better simulation of structure, intensity and track, the 24-hour accumulated rainfall intensity and distribution are also well predicted with the assimilation of satellite-derived winds.
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► A critical analysis of cation adsorption on low surface area β-MnO2 is reported. ► Detailed characterization of cation loaded β-MnO2 by XRD, FTIR, SEM and Raman spectroscopy. ► ...Red/blue shifts in Raman spectra of cation loaded β-MnO2 at 636cm−1 for Pb(II), Cu(II), Zn(II). ► Pb(II) showed an increase of ten fold loading capacity in Pb(II)–Cd(II) binary system. ► The complex behaviour of cation adsorption in binary system explained by Raman spectra.
Generally it is advocated that high surface area materials are better adsorbents due to availability of more surface active sites. In the present study, potential of a low surface area (0.81m2/g) β-MnO2 has been examined for removal of Pb(II), Cd(II), Cu(II) and Zn(II) ions from aqueous solutions. To understand the adsorption mechanism of cations the various techniques used include SEM, FTIR, XRD and Raman spectroscopy. Inner or outer sphere complex formation was envisaged due to +ve/−ve shifts in FTIR bands. Raman spectra showed shifting of band (red/blue shift) at 636cm−1 (A1g symmetric mode) for all the cations except Cd(II). Another important observation made was the decrease in scattering intensity of A1g symmetric mode after cation adsorption except for Pb(II) loaded β-MnO2. This was attributed to the breakdown of long-range translational crystal symmetry caused by the incorporated defects. Results for adsorption on β-MnO2 from binary solutions namely Pb(II)–Cd(II), Pb(II)–Cu(II), Pb(II)–Zn(II), Cd(II)–Cu(II), Cd(II)–Zn(II) and Cu(II)–Zn(II) are discussed. Pb(II) having a low adsorption capacity of only 26mg/g showed tenfold increase in presence of Cd(II). The concentration dependent selectivity of certain cations in binary system has been explained on the basis of observed changes in the Raman spectra of loaded β-MnO2.
Chromite mine overburden containing iron as oxide/hydroxide, a waste material generated in chromite mines was used as sorbent for cadmium. The iron content of material was 43.75% with a specific ...surface area of 50.8
m
2/g. Batch experiments were conducted to study the sorption behavior of Cd(II) on this material. The variable experimental parameters were: time, pH, temperature, Cd(II) and sample concentration. The point of zero charge (PZC) of the overburden sample was experimentally determined as 6.48 which shifted to a pH of 7.8 when the sample was equilibrated with 100
mg/L Cd(II) solution. Maximum loading capacity of the overburden sample was found to be ∼19
mg
Cd/g of material. It was observed that within 30
min the sorption attains equilibrium. Hence, the sorption data generated at 30
min with various initial Cd(II) concentrations and temperatures were taken to evaluate the thermodynamic parameters, i.e., Δ
G°, Δ
H° and Δ
S°. The Δ
G° values reflect the feasibility of the metal removal from aqueous solution. The negative values of Δ
H° confirmed the exothermic sorption of cadmium and the positive ΔS° values suggested the increased randomness at the solid–solution interface. The sorption data fitted well to both the Langmuir and Freundlich isotherm models indicating a monolayer sorption. The value of Freundlich parameter ‘
n’ (
n is indicative of sorption intensity) lying between 1.46 and 1.59 shows that the surface of the sorbent is heterogeneous in nature.
The convection and planetary boundary layer (PBL) processes play significant role in the genesis and intensification of tropical cyclones (TCs). Several convection and PBL parameterization schemes ...incorporate these processes in the numerical weather prediction models. Therefore, a systematic intercomparison of performance of parameterization schemes is essential to customize a model. In this context, six combinations of physical parameterization schemes (2 PBL Schemes, YSU and MYJ, and 3 convection schemes, KF, BM, and GD) of WRF-ARW model are employed to obtain the optimum combination for the prediction of TCs over North Indian Ocean. Five cyclones are studied for sensitivity experiments and the out-coming combination is tested on real-time prediction of TCs during 2008. The tracks are also compared with those provided by the operational centers like NCEP, ECMWF, UKMO, NCMRWF, and IMD. It is found that the combination of YSU PBL scheme with KF convection scheme (YKF) provides a better prediction of intensity, track, and rainfall consistently. The average RMSE of intensity (13 hPa in CSLP and 11 m s
−1
in 10-m wind), mean track, and landfall errors is found to be least with YKF combination. The equitable threat score (ETS) of YKF combination is more than 0.2 for the prediction of 24-h accumulated rainfall up to 125 mm. The vertical structural characteristics of cyclone inner core also recommend the YKF combination for Indian seas cyclones. In the real-time prediction of 2008 TCs, the 72-, 48-, and 24-h mean track errors are 172, 129, and 155 km and the mean landfall errors are 125, 73, and 66 km, respectively. Compared with the track of leading operational agencies, the WRF model is competing in 24 h (116 km error) and 72 h (166 km) but superior in 48-h (119 km) track forecast.
The tropical cyclone (TC) forecast verification procedure followed by India Meteorological Department (IMD) is reviewed herewith as compared to the standard prescribed by World Meteorological ...Organisation. The limitations in the present procedure and the future scope are presented and analysed.The IMD has considerably increased its efforts in recent years in the areas of TC forecasting and verification. Many facilities have been developed to enable a detailed assessment of the global model’s performance in the forecasting of TCs as well as operational TC forecast performance. Further development of these facilities is being undertaken by IMD. There are grey areas in TC forecast verification of IMD in the field of calculation of forecast error in surface wind radii in geographical quadrants, which is yet to start. Also there is need for improvement in verification of storm surge, wave height, coastal inundation forecasts and heavy rainfall forecasts by calculating the skill parameters and also by improving the analysis data required for verification of forecasts. Similarly there is need for verification of strike probability as well as dynamical cone of uncertainty as given by ensemble prediction system. Keywords: tropical cyclone, forecast verification, error, skill
Over the North Indian Ocean (NIO) and particularly over the Bay of Bengal (BoB), the post-monsoon season from October to December (OND) are known to produce tropical cyclones, which cause damage to ...life and property over India and many neighbouring countries. The variability of frequency of cyclonic disturbances (CDs) during OND season is found to be associated with variability of previous large-scale features during monsoon season from June to September, which is used to develop seasonal forecast model of CDs frequency over the BoB and NIO based on principal component regression (PCR). Six dynamical/thermodynamical parameters during previous June–August, viz., (i) sea surface temperature (SST) over the equatorial central Pacific, (ii) sea level pressure (SLP) over the southeastern equatorial Indian Ocean, (iii) meridional wind over the eastern equatorial Indian Ocean at 850 hPa, (iv) strength of upper level easterly, (v) strength of monsoon westerly over North Indian Ocean at 850 hPa, and (vi) SST over the northwest Pacific having significant and stable relationship with CDs over BoB in subsequent OND season are used in PCR model for a training period of 40 years (1971–2010) and the latest four years (2011–2014) are used for validation. The PCR model indicates highly significant correlation coefficient of 0.77 (0.76) between forecast and observed frequency of CD over the BoB (NIO) for the whole period of 44 years and is associated with the root mean square error and mean absolute error ≤ 1 CD. With respect to the category forecast of CD frequency over BoB and NIO, the Hit score is found to be about 63% and the Relative Operating Curves (ROC) for above and below normal forecast is found to be having much better forecast skill than the climatology. The PCR model performs very well, particularly for the above and below normal CD year over the BoB and the NIO, during the test period from 2011 to 2014.
India Meteorological Department (IMD) introduced the objective tropical cyclone (TC) track forecast valid for next 24 hr over the north Indian Ocean (NIO) in 2003. It further extended the validity ...period up to 72 hr in 2009. Here an attempt is made to evaluate the TC track forecast issued by IMD during 2003–2011 (9 years) by calculating the direct position error (DPE) and skill in track forecast. The accuracy of TC track forecast has been analysed with respect to basin of formation (Bay of Bengal, Arabian Sea and NIO as whole), season of formation (pre-monsoon and post-monsoon seasons), intensity of TCs (cyclonic storm and severe cyclonic storm or higher intensities) and type of track of TCs (climatological/straight moving and recurving/looping type). The average DPE is about 140, 262 and 386 km and skill is about 27%, 39% and 50%, respectively for 24, 48 and 72 hr forecasts over the NIO as a whole during 2009–2011. Though the DPE is higher and skill is less as compared to those in northwest Pacific and north Atlantic Ocean, the rate of decrease (increase) in DPE (skill) is higher over the NIO in recent years. The DPE (skill) over the NIO has decreased (increased) at the rate of about 7.3 km (3%) per year during 2003–2011 for 24 hr forecasts.
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