Tropical cyclone activity in global warming scenario

Research efforts focused on assessing the potential for changes in tropical cyclone activity in the greenhouse-warmed climate have progressed since the IPCC assessment in 1996. Vulnerability to tropical cyclones becoming more pronounced due to the fastest population growth in tropical coastal regions makes it practically important to explore possible changes in tropical cyclone activity due to global warming. This paper investigates the tropical cyclone activity over whole globe and also individually over six different ocean basins. The parameters like storm frequency, storm duration, maximum intensity attained and location of formation of storm have been examined over the past 30-year period from 1977 to 2006. Of all, the north Atlantic Ocean shows a significant increasing trend in storm frequency and storm days, especially for intense cyclones. Lifetime of intense tropical cyclones over south Indian Ocean has been increased. The intense cyclonic activity over north Atlantic, south-west Pacific, north and south Indian Ocean has been increased in recent 15 years as compared to previous 15 years, whereas in the east and west-north Pacific it is decreased, instead weak cyclone activity has been increased there. Examination of maximum intensity shows that cyclones are becoming more and more intense over the south Indian Ocean with the highest rate. The study of the change in the cyclogenesis events in the recent 15 years shows more increase in the north Atlantic. The Arabian Sea experiences increase in the cyclogenesis in general, whereas Bay of Bengal witnesses decrease in these events. Shrinking of cyclogenesis region occurs in the east-north Pacific and south-west Pacific, whereas expansion occurs in west-north Pacific. The change in cyclogenesis events and their spatial distribution in association with the meteorological parameters like sea surface temperature (SST), vertical wind shear has been studied for Indian Ocean. The increase in SST and decrease in wind shear correspond to increase in the cyclogenesis events and vice versa for north Indian Ocean; however, for south Indian Ocean, it is not one to one.     

CLASS B 1359 + 154: Modelling lensing by a group of galaxies

The recently discovered gravitationally lensed system CLASS B1359 +154 appears to have six detectable images of a single background source at a redshift of 3.235. A group of galaxies acts as the lens, at a redshift of ∼ 1. The present work identifies two distinct, physically plausible image configurations, a 7-image one and a 9-image one. Mass models are constructed corresponding to realizations of these two configurations. Both models call for, in addition to non-singular galaxy-type lenses, a larger scale mass component that resembles the extended dark matter distributions seen in relatively low-redshift galaxy groups. It is presently observationally impossible to study the extended X-ray emission from a group at such a high redshift, hence lensing studies are of some interest. A lensed system with a high image multiplicity does not necessarily admit of a unique lensing interpretation; discrimination is possible with additional observable details (e.g., the image parities, which are uncommon among even the simpler systems).     

An assessment of the merits of remote sensing techniques for environmental mapping: A case study from Kerala

For a proper analysis of any ecosystem and the assessment of environment impact on it, the bearing of data on distribution properties and characteristics of land-form, water, vegetation, soil and rock and even of the typology of cultural pattern are to be evaluated on the basis of the everchanging anthropogenic involvement. The extent to which the techniques of Remote Sensing alone could attain this is yet to be ascertained. The direct method for this would be to conduct the resource surveys of specific regions exclusively and separately by remote sensing as well as by field-studies and then compare the results. An extract of a major study pursued in this line in the Coastal Zone of Kerala, India has indicated an authenticity of about seventy percent through remote sensing. Weighing on the comparative time factor involved, the procedure of mapping through remore sensing alone may be advocated.     

Waves off Puducherry, Bay of Bengal, during cyclone THANE

We studied the wave characteristics during the very severe cyclonic storm THANE which crossed the east coast of India between Puducherry and Cuddalore based on waves measured at a location in Bay of Bengal at 14 m water depth. Objective of the paper is to document the highest wave height measured in the nearshore waters of east coast of India. On 29 December 2011, cyclone passed within 77–315 km of the wave measurement location with maximum wind speed of 46.3 m/s (90 knots) and resulted in maximum wave height of 8.1 m. Maximum wave height recorded is 0.54 times the water depth, and the ratio of crest height to wave height of the highest wave recorded is 0.65. Maximum value of significant wave height estimated using the parametric wave model for deep-water conditions is 6.4 m, whereas the measured value is 6 m indicating that parametric wave model estimates the wave height reasonably well (within 8 % error) during the cyclone period.     

Effect of Microbial Siderophore DFOB on Pb, Zn, and Cd Sorption Onto Zeolite

Recent studies suggest that siderophores form stable complexes with divalent metals and affect their mobility. In this work, effects of trihydroxamate microbial siderophores and desferrioxamine-B (DFOB) on Pb(II), Zn(II), and Cd(II) sorption by two kinds of synthesized zeolites (13X and Na?CY) as a function of pH were investigated. Results showed that 13X zeolite has a higher sorption affinity for studied metals than Na?CY. DFOB strongly affected metal sorption on both zeolites. Under slightly acidic to neutral condition, DFOB increased the metal sorption on zeolites due to the sorption of positively charged heavy metal?CDFOB complexes. Whereas by increasing pH (>7), the mobilizing effect of DFOB was observed for Pb, Zn, and Cd. DFOB drastically decreased (80?%) Zn sorption in alkaline condition. As a result, siderophores can weaken the treatment efficiency of zeolites and increase the bioavailability of metals in soils. Surface complexation modeling revealed that the effects of DFOB on metal sorption by 13X and Na?CY zeolites can be explained by the differences in their surface charge. In general, the result shows the influence of DFOB on metal sorption by zeolites over the pH range 4?C9 and decreasing in the sequence Zn?>?Pb?>?Cd.     

Spectral wave characteristics off Gangavaram,Bay of Bengal

Spectral wave characteristics were studied based on waves measured for 1 year during 2010 off Gangavaram, Bay of Bengal. Maximum wave height of 5.2 m was observed on 19 May 2010 due to the influence of cyclonic storm LAILA. The wave spectrum was single-peaked during 57 % of the time and the double-peaked spectrum observed was mainly swell-dominated. Low-frequency waves (0.05–0.15 Hz) were predominantly from 150° to 180°, whereas high-frequency waves (>0.15 Hz) during November–January were mainly from 90° to 120°, and during July and August from 180° to 210°. Annual average significant wave height was similar to the value (1 m) observed in the eastern Arabian Sea.     

On the Predictability of Northeast Monsoon Rainfall over South Peninsular India in General Circulation Models

In this study the predictability of northeast monsoon (Oct–Nov–Dec) rainfall over peninsular India by eight general circulation model (GCM) outputs was analyzed. These GCM outputs (forecasts for the whole season issued in September) were compared with high-resolution observed gridded rainfall data obtained from the India Meteorological Department for the period 1982–2010. Rainfall, interannual variability (IAV), correlation coefficients, and index of agreement were examined for the outputs of eight GCMs and compared with observation. It was found that the models are able to reproduce rainfall and IAV to different extents. The predictive power of GCMs was also judged by determining the signal-to-noise ratio and the external error variance; it was noted that the predictive power of the models was usually very low. To examine dominant modes of interannual variability, empirical orthogonal function (EOF) analysis was also conducted. EOF analysis of the models revealed they were capable of representing the observed precipitation variability to some extent. The teleconnection between the sea surface temperature (SST) and northeast monsoon rainfall was also investigated and results suggest that during OND the SST over the equatorial Indian Ocean, the Bay of Bengal, the central Pacific Ocean (over Nino3 region), and the north and south Atlantic Ocean enhances northeast monsoon rainfall. This observed phenomenon is only predicted by the CCM3v6 model.     

Micro pulse lidar observations of mineral dust layer in the lower troposphere over the southwest coast of Peninsular India during the Asian summer monsoon season

A large aerosol plume with optical depth exceeding 0.7 engulfs most parts of the Arabian Sea during the Asian summer monsoon season. Based on Micro Pulse Lidar observations during the June–September period of 2008 and 2009, the present study depicts, for the first time, the existence of an elevated dust layer occurring very frequently in the altitude band of 1–3.5 km over the west coast of peninsular India with relatively large values of linear depolarization ratio (δ_L). Large values of δ_L indicate the dominance of significantly non-spherical aerosols. The aerosol optical depth of this layer (0.2) is comparable to that of the entire atmospheric column during dust-free days. Back-trajectory analysis clearly shows the advection of airmass from the arid regions of Arabia and the west Arabian Sea, through the altitude region centered around 3 km. This is in contrast to the airmass below 1 km originating from the pristine Indian Ocean region which contains relatively spherical aerosols of marine origin with δ_L generally <0.05.     

Development of fragility functions as a damage classification/prediction method for steel moment‐resisting frames using a wavelet‐based damage sensitive feature

Fragility functions are commonly used in performance‐based earthquake engineering for predicting the damage state of a structure subjected to an earthquake. This process often involves estimating the structural damage as a function of structural response, such as the story drift ratio and the peak floor absolute acceleration. In this paper, a new framework is proposed to develop fragility functions to be used as a damage classification/prediction method for steel structures based on a wavelet‐based damage sensitive feature (DSF). DSFs are often used in structural health monitoring as an indicator of the damage state of the structure, and they are easily estimated from recorded structural responses. The proposed framework for damage classification of steel structures subjected to earthquakes is demonstrated and validated with a set of numerically simulated data for a four‐story steel moment‐resisting frame designed based on current seismic provisions. It is shown that the damage state of the frame is predicted with less variance using the fragility functions derived from the wavelet‐based DSF than it is with fragility functions derived from an alternate acceleration‐based measure, the spectral acceleration at the first mode period of the structure. Therefore, the fragility functions derived from the wavelet‐based DSF can be used as a probabilistic damage classification model in the field of structural health monitoring and an alternative damage prediction model in the field of performance‐based earthquake engineering. Copyright © 2011 John Wiley & Sons, Ltd.