Aircraft observations of electrical conductivity in warm clouds

Aircraft observations of electrical conductivity and cloud microphsical, dynamical and other electrical parameters were made in warm stratocumulus and cumulus clouds forming during the summer monsoon seasons (June-September) of 1983 and 1985 in the Deccan Plateau region, India. A Gerdien type cylindrical condenser was used for the measurement of electrical conductivity. The variations in the electrical conductivity are observed to be closely associated with the updrafts and downdrafts in the cloud, liquid water content, cloud droplet charge and coro-na discharge current. The value of electrical conductivity in warm clouds is found to be in the order of 10-12 ohm-1 m-1 which is two orders higher than that observed in clear-air at cloud-base levels in some regions by other investigators.Classical static electricity concepts predict reduced conductivity values inside clouds. Cloud electrical conductivi-ty measurements, particularly in warm clouds are few and the results are contradictory. The recently identified mech-anism of vertical mixing in clouds lends support to coovective charge separation mechanism with inherent larger than clear-air values for cloud electrical conductivity and therefore consistent with the measurements reported herein.     

Changes in daily maximum temperature extremes across India over 1951–2014 and their relation with cereal crop productivity

This study used gridded daily maximum temperature data (1°?×?1°) for 1951–2014 period to analyze the trend in monthly extreme warm days (ExWD) and changes in its probability distribution in each grid. It also analyzed the trend in spatial spread of annual ExWD over the study period at four exceedance levels and further related the number of ExWDs with cereal crop productivity of India. Extreme warm days have increased throughout India but were statistically significant in 42% grids. The increase was consistent over all the months in north-eastern region, southern plateau and both the coastal plains. It also increased significantly over north-western and central India during April to June summer period. The probability distribution of ExWD also changed significantly in many grids, especially in southern plateau and both the coastal plains. The changes indicated increased frequency in the existing levels of extremes and new occurrences of higher frequency of extremes. The analysis of land area affected by different levels of extremes indicated significant increase, with the rate being highest for higher extremes. In terms of extreme warm day temperatures, the study identified southern plateau, east and west coast plains, and north-eastern India as highly vulnerable. Using copula probability model, study showed that increase in ExWD from 20 to 60% may increase the probability of 5% or more yield loss from 17 to 53% for Kharif cereals, 11 to 43% for Rabi cereals and 19 to 63% for wheat crop. The results may be used for devising zone specific adaptation strategies.     

The effects of wildfires on the magnetic properties of soils in the Everglades

We present results of a rock‐magnetic study of soils that were affected by wildfires that burned portions of the Everglades in the Spring of 2008. Soils at sites that were extensively burned exhibit a pronounced surface magnetic enhancement effect with magnetizations of surface samples up to 16 times greater than that observed at depth (>7 cm) at these sites. The increase in magnetization results from an increased abundance of a low‐coercivity phase (maghemite) that occurs at the expense of the abundance of a high‐coercivity phase (goethite). These results indicate that fire‐induced heating caused goethite in the surface soils to convert into a more magnetic, low‐coercivity phase, such as maghemite. Goethite is an excellent adsorber of phosphorus, and therefore we hypothesize that the destruction of goethite as a result of burning may have important implications for phosphorus cycling in the Everglades ecosystem. Copyright © 2010 John Wiley & Sons, Ltd.     

Fluid Institutions: Commons in Transition in the Periurban Interface

Amidst growing concern about the decline of the commons, this case underscores the importance of understanding how the commons are refashioned and remade to address emerging challenges in periurban spaces. This article describes how institutions surrounding the use of common property resources get transformed and evolve in periurban contexts. What were once johads – common property village ponds – undergo a change in their usage from storing rainwater to storing waste water of the city for irrigation. This emerges as a collective response to the uncertainty attached to the availability of waste water. New institutions evolve with regard to contributions to waste water infrastructure, as well as the appropriation of waste water. Further research should document the changing use of village commons and the emergence of new institutions governing them.     

Propagation of surface waves on a nonhomogenous spherically aeolotropic shell

Summary This paper studies the propagation of Surface Waves on a spherically aeolotropic shell surrounded by vacuum. The elastic constantsc _ij and density of the material of the shell are assumed to be of the form _ij r ^l and _o r ^m respectively, where _{ij o} are constants andl, m are any integers.     

The Multiscale TROPIcal CatchmentS critical zone observatory M-TROPICS dataset III: Hydro-geochemical monitoring of the Mule Hole catchment,south India

Despite the importance of tropical ecosystems for climate regulation, biodiversity, water and nutrient cycles, only a few Critical Zone Observatories (CZOs) are located in the tropics. Among these, most are in humid climates, while very few data exist for semi-arid and sub-humid climates, due to the difficulty of estimating hydro-geochemical balances in catchments with ephemeral streams. We contribute to fill this gap by presenting a meteorological and hydro-geochemical dataset acquired at the Mule Hole catchment (4.1 km²), a pristine dry deciduous forest located in a biosphere reserve in south India. The dataset consists of time series of variables related to (i) meteorology, including rainfall, air temperature, relative humidity, wind speed and direction, and global radiation, (ii) hydrology, including water level and discharge at the catchment outlet, (iii) hydrogeology, including manual (monthly) and/or automated (from 15 min to hourly) groundwater levels in nine piezometers and (iv) geochemistry, including suspended sediment content in the stream and chemical composition of rainfall (event based), groundwater (monthly sampling) and stream water (storm events, 15 min to hourly frequency with an automatic sampler). The time series extend from 2003 to 2019. Measurement errors are minimized by frequent calibration of sensors and quality checks, both in the field and in the laboratory. Despite these precautions, several data gaps exist, due to occasional access restriction to the site and instrument destruction by wildlife. Results show that large seasonal and interannual variations of climatic conditions were reflected in the large variations of stream flow and groundwater recharge, as well as in water chemical composition. Notably, they reveal a long-term evolution of groundwater storage, suggesting hydrogeological cycles on a decadal scale. This dataset, alone or in combination with other data, has already allowed to better understand water and element cycling in tropical dry forests, and the role of forest diversity on biogeochemical cycles. As tropical ecosystems are underrepresented by Critical Zone Observatories, we expect this data note to be valuable for the global scientific community.     

Impact of the 2004 Sumatran tsunami on the diversity of intertidal brachyuran assemblages of Maavah, Laamu Atoll, Maldives

A 2-year spatio-temporal survey of intertidal brachyuran crabs involving five sites was conducted in the Maavah reef system, Laamu Atoll, Maldives, from April 2001 to March 2003. In December 2004, the sites were hit by the catastrophic Sumatran tsunami. An 8-month-long study was carried in the same five sites after the tsunami, and the data obtained were compared with the pre-impact baseline data. A sand dune formed at the north-eastern side of the island as a result of the tsunami was also included in the post-tsunami study (site 6). Nine brachyuran crab species not recorded during pre-tsunami sampling in the five study sites were collected after the event. Of these, six species were recorded in site 6 during January 2005, and they started to appear in the other sites in the following months. Nine species of crabs collected during the pre-tsunami periods from four sites were not represented in the post-tsunami collections. Abundance, evenness and diversity of the post-tsunami brachyuran communities of sites 1 and 2 exhibited downward trends, and the evenness and diversity of the post-tsunami communities of site 4 exhibited upward trends when compared with pre-tsunami patterns. Multivariate analyses revealed that the tsunami had changed the post-tsunami brachyuran communities of sites 1?C4. However, tests revealed that in site 4, the pre-tsunami brachyuran assemblage 1 (2001?C2002) differed from pre-tsunami assemblage 2 (2002?C2003) and post-tsunami assemblages. The roles of tsunami-transported species and site-specific dominant species in contributing to faunal dissimilarities between the pre- and post-tsunami brachyuran assemblages were found to be patchy. Further studies would reveal whether the population of any newly added species increases or decreases in the long term.     

An evaluation of the CIC model of210Pb dating of sediments

Both linear and polynomial regression analysis techniques are used to assess the CIC (constant initial concentration) model of²¹⁰Pb dating. Results obtained using published²¹⁰Pb and porosity profiles in 12 freshwater sediment cores show that linear regression affords more reliable results. The polynomial regression, while capable of predicting the values of the constant or derived from porosity data, gives reasonable results only when all the coefficients of the polynomial are of appropriate sign. Lower values for all the parameters are obtained in all cases if the effect of compaction is not considered.     

Spectroscopic study of rocks of Hutti-Maski schist belt,Karnataka

Recent developments in sensor technology have given an onset for studying the earth surface features based on the detailed spectroscopic observation of different rocks and minerals. The spectroscopic profiles of the rocks are always quite different than their constituent minerals however, the spectral profile of a rock can be broadly reconstituted from the spectral profile of each constituent minerals. Interpretation of rock spectra using the spectra of constituent minerals based on relative spectral matching can bring out interesting information on the rock. Present study is an effort toward this and it highlights how visible-near infrared-shortwave-infrared (VNIR-SWIR) rock spectroscopy acts as an useful tool for understanding the rock-mineralogy in indirect and rapid way. It has also been observed that spectral signatures of rocks; studied in present case, are related to spectral signatures of constituent minerals although absorption features of constituent mineral in the rock are also modified by the other minerals juxtaposed in the rock fabric. However, each rock of the study area has their significant absorption features, but many of the absorption signatures are closely spaced, as altered rock has significant absorption at 2305 nm whereas amphibolite has its important absorption signature in 2385 nm and metabasalt has its significant absorption at 2342 nm. Therefore spectral measurement of high spectral resolution with appreciable signal to noise ratio (SNR) only can detect rocks from each other based on the absorption signatures mentioned above (each of which is 10 to 20 nm apart from the other) and therefore spectroscopy of rock is an innovative technique to map rocks and minerals based on the spectral signatures.     

Geology, petrochemistry, and genesis of the bimodal lavas of Osham Hill, Saurashtra, northwestern Deccan Traps

The Saurashtra region in the northwestern Deccan continental flood basalt province (India) is notable for compositionally diverse volcano-plutonic complexes and abundant rhyolites and granophyres. A lava flow sequence of rhyolite-pitchstone-basaltic andesite is exposed in Osham Hill in western Saurashtra. The Osham silicic lavas are Ba-poor and with intermediate Zr contents compared to other Deccan rhyolites. The Osham silicic lavas are enriched in the light rare earth elements, and have ε_Nd (t = 65 Ma) values between −3.1 and −6.5 and initial ⁸⁷Sr/⁸⁶Sr ratios of 0.70709-0.70927. The Osham basaltic andesites have initial ε_Nd values between +2.2 and −1.3, and initial ⁸⁷Sr/⁸⁶Sr ratios of 0.70729-0.70887. Large-ion-lithophile element concentrations and Sr isotopic ratios may have been affected somewhat by weathering; notably, the Sr isotopic ratios of the silicic and mafic rocks overlap. However, the Nd isotopic data indicate that the silicic lavas are significantly more contaminated by continental lithosphere than the mafic lavas. We suggest that the Osham basaltic andesites were derived by olivine gabbro fractionation from low-Ti picritic rocks of the type found throughout Saurashtra. The isotopic compositions, and the similar Al₂O₃ contents of the Osham silicic and mafic lavas, rule out an origin of the silicic lavas by fractional crystallization of mafic liquids, with or without crustal assimilation. As previously proposed for some Icelandic rhyolites, and supported here by MELTS modelling, the Osham silicic lavas may have been derived by partial melting of hot mafic intrusions emplaced at various crustal depths, due to heating by repetitively injected basalts. The absence of mixing or mingling between the rhyolitic and basaltic andesite lavas of Osham Hill suggests that they reached the surface via separate pathways.