Characteristic changes in the long and short spells of different rain intensities in India

In this paper, changes in the long and short spells of different rain intensities are statistically analyzed using daily gridded rainfall data prepared by the India Meteorological Department for the period 1951–2008. In order to study regional changes, analyses have been conducted over nine selected agro-meteorological (agro-met) divisions, five homogeneous zones, and also over the whole of India. Rain events of different intensities with continuous rainfall of more than or equal to 4 days are classified here as long spells. Those with less than 4 days are termed as short spells. Those results which are statistically significant at 95% confidence level are discussed in this paper. Trend analysis shows that during the summer monsoon months of June to September, short spell rain events with heavy intensity have increased over India as a whole. On the other hand, long spell rain events with moderate and low intensities have decreased in numbers. Results further show that the contributions of long spell moderate and short spell low-intensity rain events to the total rainfall have decreased whereas the contributions of short spell heavy and moderate-intensity rain events to the total seasonal rainfall have increased. Percentage changes in various categories of long and short spells in the decade 1991–2000 compared with the earlier decade 1951–1960, highlight the maximum increase in heavy-intensity short spell category and decrease in moderate-intensity long spell category in India as a whole and in most of the homogeneous zones and agro-met divisions. The changes in different types of rain events differ in the six homogeneous zones and nine selected agro-met divisions. However, in three homogeneous zones and three agro-met divisions, the short spell heavy-intensity rain events dominate as in the entire country. There are also changes observed in the monthly occurrences of above categories of rain events during the 4 months of summer monsoon. Such results with details of changes in rain categories in different parts of India have important implications in agriculture sector in the country.     

A spatially explicit scenario-driven model of adaptive capacity to global change in Europe

Traditional impact models combine exposure in the form of scenarios and sensitivity in the form of parameters, providing potential impacts of global change as model outputs. However, adaptive capacity is rarely addressed in these models. This paper presents the first spatially explicit scenario-driven model of adaptive capacity, which can be combined with impact models to support quantitative vulnerability assessment. The adaptive capacity model is based on twelve socio-economic indicators, each of which is projected into the future using four global environmental change scenarios, and then aggregated into an adaptive capacity index in a stepwise approach using fuzzy set theory. The adaptive capacity model provides insight into broad patterns of adaptive capacity across Europe, the relative importance of the various determinants of adaptive capacity, and how adaptive capacity changes over time under different social and economic assumptions. As such it provides a context for the implementation of specific adaptation measures. This could improve integrated assessment models and could be extended to other regions. However, there is a clear need for a better theoretical understanding of the adaptive capacity concept, and its relationship to the actual implementation of adaptation measures. This requires more empirical research and coordinated meta-analyses across regions and economic sectors, and the development of bottom-up modelling techniques that can incorporate human decision making.     

Spatio-temporal trend analysis of rainfall using parametric and non-parametric tests: case study in Uttarakhand,India

Theoretical and Applied Climatology - This study investigates the spatial and temporal patterns of trends and magnitude of rainfall on monthly, seasonal and annual time scales of 13 districts of...     

Merger origin for the velocity and density substructure in elliptical galaxies

We study the dynamics of mergers between two unequal elliptical systems with self-consistent numerical simulations. We present comparisons of our models to real ellipticals in a variety of properties, which include the mean central surface brightness, the shape of the surface brightness profile, and the type of rotation curve and dispersion profile. Several proofs are given that the cores of smaller, denser ellipticals sink to the remnant's centre virtually undisturbed, and create a core-within-a-core structure with definite signatures in the surface brightness profile and the velocity dispersion profile. Ellipticals with anomalous cores appear to be a natural outcome of this type of merger.     

Storm extreme levels and coastal flood hazards: A parametric approach on the French coast of Languedoc (district of Leucate)

Coastal flooding is a significant risk on the shores of Languedoc-Roussillon. The storms that periodically hit the coast can generate strong swells and storm surges. Most beach resorts, built on a low elevation dune ridge, are periodically flooded during major storms. Although risks zoning regulations take into consideration coastal flood hazards, the delineation of vulnerable areas is still insufficient and the commonly accepted threshold is regularly exceeded during most severe storms. This paper presents a method to improve the assessment of extreme storm-related water levels. It relies on fieldwork carried out in the Leucate commune (Aude), which is particularly exposed to the risk of sea level rise. It considers both storm surges and wave phenomena that occur within the surf zone (set-up and swash), calculated from the Simulating WAves Nearshore (SWAN^®) numerical wave model and the Stockdon formula. Water levels reached during several recent storm events have been reconstructed and simulations of submerged areas were carried out by numerical modelling.     

Spectroscopic investigation and theoretical modeling of kaolinite-group minerals and other low-temperature phases

This article summarizes some recent results obtained on the physical properties of environmental minerals, mostly kaolinite-group minerals and Fe- and Al-(hydr)oxides occurring in lateritic soils. The defective structure of these minerals, including impurities, stacking faults and radiation-induced defects, is probed using infrared spectroscopy and electron paramagnetic resonance. Resulting information bears on models of soil formation and transformation mechanisms of minerals in low-temperature environments. We underline the increasing impact of quantum chemical modeling in this field, providing straightforward interpretations of spectroscopic signals and overcoming the limits of fingerprint approaches. Importantly, the first-principles modeling of isotopic fractionation factors provides new links between mineralogical and geochemical investigations of secondary minerals.     

The relationship between volatile halocarbons and phytoplankton pigments during a Trichodesmium bloom in the coastal eastern Arabian Sea

Eukaryotic phytoplankton such as diatoms and prymnesiophytes produce biogenic halocarbons in the ocean that serve as important sources of chlorine and bromine to the atmosphere, but the role of cyanobacteria in halocarbon production is not well established. We studied distributions of chloroform (CHCl₃), carbon tetrachloride (CCl₄), methylene bromide (CH₂Br₂) and bromoform (CHBr₃) in relation to phytoplankton composition, determined from pigment analysis complemented by microscopic examination, for one month in coastal waters of the eastern Arabian that experienced a Trichodesmium bloom that typically occurs during the Spring Intermonsoon season. High concentrations of zeaxanthin (23 μg l⁻¹), alpha beta betacarotene (6 μg l⁻¹) and chlorophyll a (67 μg l⁻¹) were found within the bloom whereas the marker pigment concentrations were low outside the bloom. CHCl₃ and CCl₄ occurred in relatively high concentrations in surface waters whereas CH₂Br₂ and CHBr₃ were restricted to the subsurface layer. Chlorinated halocarbons were positively inter-correlated and with CHBr₃. The observed spatial and temporal trends in brominated compounds appear to be related to the abundance of Trichodesmium although correlations between concentrations of brominated compounds with various marker pigments were poor and statistically non-significant. The results support the existence of multiple sources and sinks of halogenated compounds, which might obscure the relationship between halocarbons and phytoplankton composition.     

Do abyssal scavengers use phytodetritus as a food resource? Video and biochemical evidence from the Atlantic and Mediterranean

Deep-sea benthic communities derive their energetic requirements from overlying surface water production, which is deposited at the seafloor as phytodetritus. Benthic invertebrates are the primary consumers of this food source, with deep-sea fish at the top of the trophic hierarchy. Recently, we demonstrated with the use of baited cameras that macrourid fish rapidly respond to and feed vigorously on large plant food falls mimicked by spinach (Jeffreys et al., 2010). Since higher plant remains are scarce in the deep-sea, with the exception of canyons, where terrestrial material has been observed, these results led us to ask if a more commonly documented plant material i.e. phytodetritus might form a food source for deep-sea fish and mobile scavenging megafauna. We simulated a phytodetritus dump at the seafloor in two contrasting environments (1) the NE Atlantic where carpets of phytodetritus have been previously observed and (2) the oligotrophic western Mediterranean, where the deposition of phytodetritus at the seafloor is a rare occurrence. We recorded the response of the scavenging fauna using an in situ benthic lander equipped with baited time-lapse cameras. In the NE Atlantic at 3000 m, abyssal macrourids and cusk-eels were observed ingesting the phytodetritus. The phytodetrital patch was significantly diminished within 2 h. Abundance estimates calculated from first arrival times of macrourids at the phytodetrital patch in the Atlantic corresponded with abundance estimates from video-transect indicating that fish were attracted to the scent of phytodetrital bait. In contrast to this, in the western Mediterranean at 2800 m a single macrourid was observed investigating the phytodetrital patch but did not feed from it. The phytodetrital patch was significantly diminished within 6.5 h as a result of mainly invertebrate activity. At 1900 m, Lepidion lepidion was observed near the lander and the bait, but did not feed. The phytodetrital patch remained intact until the end of the experiment. In the deployments in the Mediterranean abundance estimates from first arrival times at the bait, corrected for their body size, were lower than estimates obtained from video-transects and trawl catches. This suggests that the Mediterranean fish were not readily attracted to this food source. In contrast, invertebrates in the Balearic Sea were observed ingesting the phytodetritus bait despite the rare occurrence of phytodetritus dumps in the Mediterranean. Stable isotope values of the fish at both study sites, set within the context of the benthic food web, did not demonstrate a strong trophic link to phytodetritus. Fatty acid profiles of these fish indicated a strong link between their lipid pool and primary producers i.e. phytoplankton, which may be attributed to trophic transfer. The usefulness of fatty acid biomarkers in ascertaining deep-sea fish diets is discussed. Our study suggests that the abyssal grenadier C. armatus on the Atlantic Iberian margin is attracted to phytodetritus. However the exact contribution of this food source to the diet of macrourids in this area remains unresolved.     

An analytic investigation of oscillations within a harbor of constant slope

Longitudinal and transverse oscillations within a harbor of constant slope are analyzed. Based on the linear shallow water approximation, longitudinal oscillations are described with Bessel equations. Ignoring friction, oscillations are forced using the period of the incident perpendicular wave field by the method of matched asymptotics. The analytic results show that the varying depth shifts the resonant wave numbers to lower values than those for the same geometric harbor with constant depth. Furthermore, we extend the shallow water equations to a linear, weakly dispersive, Boussinesq-type equation by modifying the offshore velocity component, and then use it to investigate possible existing transverse oscillations in the harbor of constant slope. These oscillations are types of standing edge waves. Their character is quite sensitive to the boundary condition at the backwall of the harbor.     

Primary description of surface water phytoplankton pigment patterns in the Bay of Bengal

Spatial and temporal variations in surface water phytoplankton pigment distribution in the Bay of Bengal were studied during the spring intermonsoon (SpIM, February–April) and the commencement of the summer monsoon (CSM, May–June), using pigment and diagnostic indices. The Prokaryotic pigment index (Prok_DP) was dominant at all the oceanic stations whereas the Flagellate pigment index (Flag_DP) was dominant at the near coastal stations. However, during the commencement of summer monsoon, an oscillation in the dominance of Prok_DP and Flag_DP was observed in the central oceanic bay, whereas flagellates and diatoms were dominant at the near coastal stations. This change in pigment pattern is possibly related to the influence of rainfall. Comparison of pigment data with microscopic cell counts indicated a significant relationship between the diatom pigment index (Diat_DP) and diatom abundance. However, the relationship between the dinoflagellate pigment index (Dino_DP) and dinoflagellate abundance was not significant. Studies coupling pigment composition analysis with microscopic analysis of phytoplankton in natural conditions should thus be a prerequisite in establishing valid biogeochemical and ecosystem models.