Projections of temperature changes over South America during the twenty-first century using CMIP6 models

A 22-member ensemble from CMIP6 is used to analyze the projected changes and seasonal behavior in surface air temperature over South America during the twenty-first century. In the future projections, CMIP6 models shown a high dependency to the socioeconomic pathway over each country of South America. The multimodel ensemble projects a continuous increase in the annual mean temperature over South America during the twenty-first century under the three future scenarios (SSP1-2.6, SSP2-4.5 and SSP5-8.5). Besides, it was possible to identify consistent positive trends across all the models, with values between 0.45 ± 0.05 and 2.05 ± 0.31 °C cy⁻¹ under the historical experiment, however largest trends occurs for the projection periods (near, mid and far future), with values between − 0.87 ± 0.84 to 2.88 ± 0.60 °C cy⁻¹ (SSP1-2.6), 1.41 ± 0.88 to 5.32 ± 0.81 °C cy⁻¹ (SSP2-4.5) and 4.75 ± 0.58 to 8.76 ± 0.74 °C cy⁻¹ (SSP5-8.5) with maximum values at Bolivia, Brasil, Paraguay and Venezuela whilst minimum values for Argentina and Uruguay, regardless of the SSP scenario used. From the seasonal behavior analysis was possible to identify maximum values between January and March whilst minimum between June and July, except in Brasil, Venezuela and Guyana–Surinam–French Guayana, with annual range decreasing as the latidude decreases. By the end of the twenty-first century the annual mean temperature over South america is projected to increase between 0.92–2.11 °C, 0.97–3.37 °C and 1.27–6.14 °C under SSP1-2.6, SSP2-4.5 and SSP5-8.5 projection scenarios respectively. This projected increase of temperature across the continent will produce negative repercussions in the social, economic and political spheres. The results obtained in this study provide insights about the CMIP6 performance over this region, which can be used to develop adaptation strategies and might be useful for the adaptation to the climate change.

     

Characterization of activated carbon obtained from Saudi Arabian fly ash

This study investigated the potential application of heavy oil burning fly ash as a precursor to prepare activated carbon. The raw fly ash obtained from a power plant is cleaned by nitric acid/hydrochloric acid and activated at 550–800 °C with hold times of 30 and 60 min to obtain fly ash activated carbon. The phosphoric acid is used as a chemical agent to improve the surface characteristics of the cleaned fly ash. The effects of process variables such as amount of chemical reagents, activation time and temperature were investigated according to two-levels full factorial design. The resultant activated carbons were characterized in terms of Brunauer, Emmett and Teller surface area and total and pore volume. The maximum specific surface area was found of 148.30 m²/g at 800 °C temperatures with 60 min holding time. The test showed that the surface area and pore volumes of the material are also significantly enhanced by the activation process.     

Effect of land surface processes on the Tibetan Plateau’s past and its predicted response to global warming: an analytical investigation based on simulation results from the CMIP5 model

Complex interactions between the land surface and atmosphere and the exchange of water and energy have a significant impact on climate. The Tibetan Plateau is the highest plateau in the world and is known as “Earth’s third pole”. Because of its unique natural geographical and climatic characteristics, it directly affects China’s climate, as well as the world’s climate, through its thermal and dynamic roles. In this study, the BCCCSM1.1 model for the simulation results of CMIP5 is used to analyze the variation of the land surface processes of the Tibetan Plateau and the possible linkages with temperature change. The analysis showed that, from 1850 to 2005, as temperature increases, the model shows surface downward short-wave radiation, upward short-wave radiation, and net radiation to decrease, and long-wave radiation to increase. Meanwhile, latent heat flux increases, whereas sensible heat flux decreases. Except for sensible heat flux, the correlation coefficients of land surface fluxes with surface air temperature are all significant at the 99 % significance level. The model results indicate rising temperature to cause the ablation of ice (or snow) cover and increasing leaf area index, with reduced snowfall, together with a series of other changes, resulting in increasing upward and downward long-wave radiation and changes in soil moisture, evaporation, latent heat flux, and water vapor in the air. However, rising temperature also reduces the difference between the surface and air temperature and the surface albedo, which lead to further reductions of downward and upward short-wave radiation. The surface air temperature in winter increases by 0.93 °C/100 years, whereas the change is at a minimum (0.66 °C/100 years) during the summer. Downward short-wave and net radiation demonstrate the largest decline in the summer, whereas upward short-wave radiation demonstrates its largest decline during the spring. Downward short-wave radiation is predominantly affected by air humidity, followed by the impact of total cloud fraction. The average downward short-wave and net radiation attain their maxima in May, whereas for upward short-wave radiation the maximum is in March. The model predicts surface temperature to increase under all the different representative concentration pathway (RCP) scenarios, with the rise under RCP8.5 reaching 5.1 °C/100 years. Long-wave radiation increases under the different emission scenarios, while downward short-wave radiation increases under the low- and medium-emission concentration pathways, but decreases under RCP8.5. Upward short-wave radiation reduces under the various emission scenarios, and the marginal growth decreases as the emission concentration increases.     

Hydrogeochemical investigations of thermal waters in the northeastern part of Morocco

Northeastern Morocco is characterised by a large number of surface geothermal manifestations. Thermal waters are hosted within sedimentary rocks, and in particular the Liassic dolomitic limestones act as a reservoir. The presence of geothermal waters is closely related to important fault systems. Meteoric water infiltrates along those fractures and faults, gets heated, and then returns to the surface through hydrothermal conduits. Most of the thermal waters are of Na–Cl and Ca–Mg–HCO₃ types. In this paper different geochemical approaches were applied to infer the reservoir temperature. Na–K–Mg^1/2 ternary diagram points to temperatures ranging from 100 to 180 °C. Cation geothermometers suggest an average reservoir temperature of about 100 °C. Mineral solution equilibria analysis yields temperatures ranging from 50 to 185 °C. The silica enthalpy mixture model gives an average value (about 110 °C) higher than that inferred from cation geothermometers.     

Dynamics of land surface temperature (LST) in response to land use and land cover (LULC) changes in the Weigan and Kuqa river oasis,Xinjiang, China

Land use and land cover (LULC) changes caused by human activities have strong influences on regional environment. Land surface temperate plays an important role in studying the impact of LULC changes on regional environment. In this paper, remotely sensed thermal infrared data were used to assess land surface temperature (LST) in the Weigan and Kuqa river oasis, Xingjiang, one of the important agricultural areas in the northwestern China. The present study deals with the extraction of LST and the relationship between LULC changes using Landsat 5 TM acquired on September 25, 1989, and September 6, 2011. The results indicate that the surface temperature of water body, bare land, and desert changed significantly between 1989 and 2011. In general, the LST was lower in 1989 than in 2011. There were no lower, higher, and highest temperature zones in 1989. However, the minimum temperature was 10.7 °C in 1989 and 15.8 °C in 2011. The maximum temperature was 29.3 °C in 1989 and 41.8 °C in 2011. Regarding the LULC types, the desert features in the Gobi Desert warmed more quickly than the oasis. So, the temperature of the oasis was lower than the surrounded areas, resulting in a so-called “cold island” phenomenon. Oasis cold island effect index (OCIEI) shows that stability of oasis had rising trend from 1989 to 2011. In addition, the impact of LULC changes on LST was analyzed and the driving forces were also analyzed from 1977 to 2011. This study is significant for further understanding of the energy exchange status of soil-plant-atmospheric system and the regional heat distribution in arid and semi-arid areas of the northwest China.     

Effect of the activation temperature over activated carbon production from castor cake and its evaluation as dye adsorbent

In this work, castor cake produced as a by-product in castor oil extraction was used for activated carbon production. Castor cake was chemically treated with a K₂CO₃ solution, and the effect of the pyrolysis temperature in the 500–900 °C range was studied. Materials were characterized by X-ray powder diffraction, thermogravimetric analysis, scanning electron microscopy and nitrogen adsorption–desorption at ?196 °C. Methylene blue adsorption was selected as a test probe to stress the removal capacity of the prepared materials. By the X-ray powder diffraction analysis, carbon obtaining in its graphite allotropic form together with other inorganic compounds was verified. Scanning electron microscopy images evidenced the generation of porosity in the thermally treated samples compared with the pristine compound. In addition, the specific surface area values augmented progressively with the thermal treatment increment achieving a value of 1015 m² g^?1 in the 900 °C calcined sample. Calcination at 800 °C and m/V = 0.003 ratio were the best parameter combination to achieve a 99.6% methylene blue uptake.     

An experimental study of the Fe oxidation states in garnet and clinopyroxene as a function of temperature in the system CaO–FeO–Fe2O3–MgO–Al2O3–SiO2: implications for garnet–clinopyroxene geothermometry

Samples with eclogitic composition in the system CaO–FeO–Fe₂O₃–MgO–Al₂O₃–SiO₂ were produced from various kinds of starting materials held in graphite-lined Pt capsules at a pressure of 2.5–3.0 GPa and temperatures of 800–1,300 °C using a piston-cylinder or Belt apparatus. Garnets and clinopyroxenes were characterized by analytical transmission electron microscopy and electron probe micro-analysis (EPMA). Fe³⁺/ΣFe ratios determined by electron energy-loss spectroscopy (EELS) decrease in clinopyroxene from 22.2 ± 3.4 % at 800 °C to 13.3 ± 5.4 % at 1,300 °C, while in garnet, they vary between 10.8 ± 1.5 and 15.4 ± 4.7 %, respectively. Temperature estimates according to Krogh (Contrib Mineral Petrol 99:44–48, 1988) reproduce the experimental temperature to ±60 °C without systematic deviations if total iron is used in the calculation. If only the Fe²⁺ content is used, which was obtained by combining EPMA and EELS results, the experimental temperature is underestimated by 33 °C on average at 800–1,200 °C and overestimated by 77 °C on average at 1,300 °C. These systematic deviations can be explained by the temperature-dependent ratio of Fe²⁺/ΣFe in garnet divided by that in clinopyroxene. Since the difference between the calculated and experimental temperature is relatively small, a Fe²⁺-based recalibration of the thermometer appears not to be necessary for the investigated system in the range of pressure, temperature and composition covered by the experiments of this study.     

Calcite and aragonite saturation States of Kamaran strait surface seawater, Yemen: summer time

Surface seawater samples from Kamaran Strait of Yemen were collected for physical and chemical parameter determinations. This work reports the results of air and surface seawater temperature, salinity, pH, and total alkalinity measurements. The air temperature ranged from 29.9°C to 36.5°C with an average value of 31.5?±?1.5°C, whereas the seawater surface temperature ranged from 34.0°C to 36.0°C with a mean value of 34.5?±?0.5°C. The salinity was observed to be high, ranging from 38.03 to 38.81 with an average value of 38.45?±?0.22. The pH ranged from 7.74 to 8.27 with a mean value of 8.11?±?0.10. The total alkalinity was found to range from 2.3860 to 2.5000 meq L^?1 with an average value of 2.4288?±?0.0351 meq L^?1. The result of the study showed that there was a negative correlation between the pH and surface seawater temperature and salinity. The surface seawater of the Kamaran Strait was found to be several fold supersaturated with respect to calcium carbonate. The measured percent degree of saturation ranged from 454% to 668% with respect to calcite and from 246% to 361% with respect to aragonite. The lowest value of supersaturation with respect to both calcite and aragonite were found in front of as-Salif port, where human and developmental activities are intensively increased. The visual inspection of coral reefs distribution and their intensity were obviously observed in areas of high value of supersaturation with respect to both minerals, high transparency of seawater column, and low human activities. Further studies are needed to investigate the occurrence, distribution, and mineralogy of corals and the effects of physical and chemical parameters upon their growth in the region.     

Extreme weather impacts on freight railways in Europe

Four cases are studied in this assessment of how the harsh 2010 winter weather affected rail freight operations in Norway, Sweden, Switzerland and Poland and also of the reactive behaviour rail managers mobilised to reduce the adverse outcomes. The results are utilised in a fifth case assessing the proportion of freight train delays in Finland during 2008–2010 by modelling the odds for freight train delays as a function of changes in met-states on the Finnish network and weather-induced infrastructure damage. The results show that rail operators were totally unprepared to deal with the powerful and cascading effects of three harsh weather elements—long spells of low temperatures, heavy snowfalls and strong winds—which affected them concurrently and shut down large swathes of European rail infrastructure and train operations. Rail traffic disruptions spread to downstream and upstream segments of logistics channels, causing shippers and logistics operators to move freight away from rail to road transfer. As a result, railways lost market share for high-value container cargo, revenues and long-term business prospects for international freight movement. Analyses of measures employed to mitigate the immediate damage show that managers improvised their ways of handling crises rather than drew on a priori contingency, i.e. fight-back programmes and crisis management skills. Modelling the co-variation between extreme weather and freight train delays in Finland during 2008–2010 revealed that 60 % of late arrivals were related to winter weather. Furthermore, the combined effect of temperatures below ?7 °C and 10–20 cm changes in snow depth coverage from 1 month to the next explained 62 % of the variation in log odds for freight train delays. Also, it has been shown that changes in the number of days with 10–20 cm snow depth coverage explained 66 % of the variation in late train arrivals, contributing to 626 min or 10.5 additional hours’ delay. Changes in the number of days with snowfalls over 5 mm accounted for 77 % variation in late train arrivals, implying that each additional day with this snowfall could contribute to 19.5 h’ delay. Finally, the combination of increased mean number of days with 5 mm snowfall and temperature below ?20 °C explained 79 % of the variation in late arrivals, contributing to 193 min or 3.25 h’ delay. All results were significant (p = 0.00).     

Alteration of fluid properties during the initial operation of a geothermal plant: results from in situ measurements in Groß Schönebeck

Recently, the thermal fluid loop has been established and continuosly operated for 7 days at the geothermal in situ laboratory in Groß Schönebeck (North German Basin). During this initial phase of fluid production, the fluid temperature, measured at the surface, continuously increased until a stable value of about 98 °C was established. Fluid physicochemical properties (pH, redox, density, temperature, and pressure) were measured online and in situ with a newly developed fluid monitoring system (FluMo). Additionally, fluid samples have been collected at various temperatures (in 5–10 °C steps) directly at the production well at about 10 bar pressure. From the pressurized sampling tool, the fluid was directly transferred into a heated autoclave, which allowed filtration (0.2 μm) in the absence of oxygen. Physicochemical parameters [pH, redox, electric conductivity, total dissolved solids (TDS)] as well as acid capacity (K _S 4.3) of these samples have been measured onsite at atmospheric conditions. Concentrations of anions, total organic carbon, and metals were analyzed later in the laboratory. Both, measurements in collected samples or in situ (FluMo) analysis of most the parameters density, electric conductivity, or TDS indicated relatively constant values over the whole production time (1.17–1.18 g · cm^?3, 215–221 mS · cm^?1, 241–260 g · L^?1, respectively). Good correlation was also found for pH values (pH = 6.6–6.9), whereas the redox values varied between ?1 and 46 mV when determined at 25 °C and decreased strongly when measured in situ with increasing temperature (?110 mV at 90 °C). The elemental composition of collected samples remained also relatively constant for most compounds and was clearly higher as compared with samples collected in 2011. Results of this study demonstrate that realistic, comprehensive, and time-resolved physicochemical data can be obtained by FluMo. These detailed data sets can be crucial to understand the complex geochemical processes in a thermal water loop and eventually to take required measures on time.     

Linkage of urban expansion and land surface temperature using geospatial techniques for Jaipur City,India

The aim of this study is to understand the land use change and urban expansion of Jaipur City of Rajasthan (India). Landsat 5 TM and Landsat 8 OLI satellite data of 4 years, i.e., 1993, 2000, 2010, and 2015 are used for land use and land surface temperature (LST) analysis. ERDAS Imagine and ArcGIS software are used to conduct the analysis. Urban settlement increased from 13.5 to 57.3% in the study period. Open land is mainly changed to urban areas. Urban settlement is also expanded to peri-urban area of Jaipur City. Jaipur City expanded along three directions i.e., north, west, and south and less development is found in the east direction. Based on radial analysis, it is observed there is not much development within the periphery of 2 km (close to city center) but maximum growth is observed within the distance from 4 to 6 km radius of city center. Expansion intensity was observed highest in the period 2015–2010 from 6 km onwards and reached to a maximum value close to 17 km²/year. In LST analysis, there is less change in extreme temperature, but more areal increase in average temperature range (30–35 °C). Urbanization is the main driving process of land cover changes and consequently changes in LST.     

Variations in annual winter mean temperature in South China since 1736

Modern meteorological observations in South China from 1960 to 2009 show a strong correlation between winter temperatures and two snowfall parameters, the southern boundary of the snow and the number of snowy days. Based on this relationship, the variation in annual winter mean temperature in South China from 1736 to 2009 was reconstructed using data acquired from Chinese historical documents dating from the Qing dynasty, such as memos and local gazettes. The reconstructed time series were used to analyse variations in winter temperature in South China. Significant interannual and interdecadal changes were found. The maximum temperature difference between neighbouring years was 3.1 °C for 1958–2009 and 3.0 °C for 1736–1957, whereas the maximum temperature difference between adjacent decades was 0.8 °C for the 1960s–2000s and 0.6 °C for the 1740s–1950s. The 2000s was the warmest decade; the mean temperature was 1.6 °C higher than that of the 1870s, which was the coldest decade between the 1740s and the 2000s. The mean winter temperature was warmer in the 18th and 20th centuries and coldest in the 19th century.     

Aquifer heat storage: sulphate reduction with acetate at increased temperatures

Aquifer thermal energy storage in urban and industrial areas can lead to an increase in subsurface temperature to 70 °C and more. Besides its impacts on mineral and sorption equilibria and chemical reaction kinetics in an aquifer, temperature sensitively influences microbial activity and thus redox processes, such as sulphate reduction. Microorganism species can only operate within limited temperature ranges and their adaptability to temperature is a crucial point for the assessment of the environmental consequences of subsurface heat storage. Column experiments with aquifer sediment and tap water at 10, 25, 40, and 70 °C showed that under the constant addition of acetate sulphate reduction could be initiated after 26–63 pore volumes exchanged at all temperatures. Fastest initiation of sulphate reduction with the highest reduction rates was found at 40 °C. Maximum rate constants during experimental run-time were 0.56 h^?1 at 40 °C and 0.33, 0.36, and 0.25 h^?1 at 10 and, 25, and 70 °C, respectively. Hence, microbial activity was enhanced by a temperature increase to 40 °C but was significantly lowered at 70 °C. At 25 °C methane was found in solution, indicating the presence of fermenting organisms; at 10, 40, and 70 °C no methane production was observed. It could be shown that redox processes in an aquifer generally can adapt to temperatures significantly higher than in situ temperature and that the efficiency of the reduction process can be enhanced by temperature increase to a certain limit. Enhancement of sulphate reduction in an aquifer due to temperature increase could also allow enhanced degradation of organic ground water contaminants such as BTEX, where sulphate is an important electron acceptor.     

Soil temperatures in four metropolitan cities of Korea from 1960 to 2010: implications for climate change and urban heat

This study was conducted to reveal the trends of the air temperature and soil temperature for 51 years (1960–2010) and their relationship in four of Korea’s largest metropolitan cities (Seoul, Incheon, Busan and Daejeon). Also, the trends of the air and soil temperatures between the studied metropolitan cities and a rural area (Chupungryong) were compared to examine the effect of urban heat. Among the metropolitan cities, the long-term mean soil temperatures (depth 0.0, 0.5, 1.0, 1.5, 3.0, 5.0 m) were lowest (13.34–14.80 °C) in Seoul and highest (16.24–16.54 °C) in Busan, which is mainly the effect of the latitude. The soil temperature exponentially increased with depth in the three cities except for Busan and was closely related to the air temperature. The soil temperatures responded well to the air temperature change (maximum correlation coefficients 0.88–0.98) but this response was slightly delayed with depth. The air and soil temperatures increased at the rates of 0.24–0.40 and 0.11–0.73 °C/decade, respectively, for the period. The increasing rate of the soil temperature was the largest in Daejeon as 0.39–0.73 °C/decade, which was almost 2–4 times greater than those of the other cities (0.11–0.40 °C/decade), and it rose with depth. The increase of the soil temperature was coincident with the increase of the air temperature, which indicates that the soil temperature was largely affected by the increasing of the air temperature. In contrast, the increase in air temperature in Chupungryong (0.06 °C/decade) was significantly lower than in the metropolitan cities. In addition, the increase of the soil temperature in the rural area (0.13 °C/decade) was also much lower than that in the inland cities (0.20–0.27 °C/decade) while it showed no substantial difference from that in the coastal cities (0.11–0.15 °C/decade). Therefore, it is inferred that the soil temperature of the metropolitan cities increased with the increase of the air temperature due to global warming as well as the anthropogenic urban heat.     

Impact analysis of climate change on Kolahoi Glacier in Liddar Valley,north-western Himalayas

Glaciers are among the most conspicuous and dynamic features on the earth’s surface and are also highly sensitive to changes in climatic parameters. Glaciers in the Kashmir Himalayas have been reported to be retreating due to climate forcing. Kolahoi Glacier is one of the largest and important glaciers of the Kashmir Himalayas and is the main source of Liddar River, which is the largest tributary of the Jhelum River system. In the present study, an analysis to assess the response of Kolahoi Glacier to the changing climate was carried out using the Survey of India (SoI) map and multi-temporal Landsat satellite data. The results show a significant change in the spatial extent of Kolahoi Glacier. The total area of this glacier has reduced from 12.21 km² in 1962 to 11.61 km² in 2010. An analysis of meteorological data (temperature and precipitation) shows that the average annual temperature increased from 9.1 °C in 1980–1989 to 10.3 °C in 2000–2009, while the precipitation decreased from 1329.44 to 1126.89 mm during the same period. The results suggest that this glacier will be annihilated completely if the same retreating trend continues.     

9,400 yr B.P.: the mortality of mollusk shell (<Emphasis Type="Italic">Mya truncata</Emphasis>) at high Arctic is associated with a sudden cooling event

An 118-cm-long, well-preserved sediment profile was collected from a paleo-notch formed by ocean wave action before rising to the terrace on Ny-Ålesund, Svalbard, Norway. A large number of mollusk shell fragments, predominantly Mya truncata, were found in the sediment profile. AMS ¹⁴C dating and stable oxygen and carbon isotope analyses were performed on the shell fragments samples. The reservoir-corrected radiocarbon ages averaged ~9,400 yr B.P., which accurately dates the raised terrace and the upper marine limit after Kongsfjorden was completely deglaciated. The calibrated aragonite isotopic temperature equation was established for Ny-Ålesund by comparing the δ¹⁸O profiles of modern mollusks as follows: T (°C) = 16.26 ? 3.68(δ¹⁸O_{aragonite–PDB} ? δ¹⁸O_{water–VSMOW}). The reconstructed paleotemperature range was ?0.52 to +4.78°C, warmer than today by about 1°C, which was further confirmed by reconstructed sea surface temperature (SST) in west Svalbard. Moreover, the mortality of mollusks was very likely caused by an abrupt cooling event at about 9,400 yr B.P., which was triggered by reduced insolation, weakened thermohaline circulation, and abruptly decreased SST. More evidences for this distinct but short cooling event centered at about 9,400 yr B.P. were found in Northern Siberia, North Atlantic, Alps, and Eastern Europe.     

Photoluminescence properties of green and red luminescence from natural and heat-treated sodalite

The sodalite sample used in this investigation did not exhibit the characteristic orange-yellow luminescence due to the $ {\text{S}}_{ 2}^{ - } $ center, because there was no trace of sulfur impurity. The heat-treated samples exhibited green and red luminescence with maximum intensity at 496 and 687 nm, respectively, under 264 nm excitation at room temperature. Their luminescence intensities were extensively dependent on the treatment temperature. The green luminescence efficiency of the sample heat-treated at 900 °C was 6.5 times higher than that of unheated natural sodalite. At 8.5 K, the green luminescence showed a vibronic structure. After heating at 1,300 °C, the crystal structure of sodalite was transformed to NaAlSiO₄ (carnegieite), and the intense red luminescence was exhibited in the NaAlSiO₄ sample. The peak wavelength of the red luminescence shifted from 687 nm at 300 K to 726 nm at 8.5 K. The luminescence lifetimes of the green and red luminescence at room temperature were 2.1 and 5.1 ms, respectively. It was proposed that the origin of the green luminescence is Mn²⁺ replacing Na⁺, and that of the red luminescence is Fe³⁺ replacing Al³⁺ in sodalite or NaAlSiO₄ (carnegieite).     

Salient features of Andhra Pradesh cyclonic storm in the Bay of Bengal during September 1997

During 23–30 September 1997, a rare cyclonic storm has developed close to the Andhra coast, and it has later travelled parallel to coastline northward and finally crossed the land at Chittagong (22°N, 91°E) on 27 September. While translating along the east coast of India, it has produced heavy to very heavy rainfall on the coastal stations causing devastating floods. In this study, we made an attempt to understand the salient causes of this unique cyclone movement. We have analyzed daily fields of wind and relative humidity for 850, 700, 500 hPa and mean daily OLR data to understand the plausible reasons for its movement. The buoy data deployed by National Institute of Ocean Technology, Chennai, Viz. DS5 (15°N, 81°E), DS4 (19°N, 88°E) and SW7 (20°N, 86°E) were analyzed to understand the ocean–atmosphere interaction processes in the west Bay of Bengal during formation of the system. Analysis of OLR over the cyclonic storm region has revealed that the heavy rainfall areas coincide with low OLR (120–180 W m^?2). The persistent southward movement of 500 hPa ridge on the eastern wedge of the system along with the steering current at 200 hPa has helped in maintaining the movement of the system parallel to the east coast of India during its life cycle.     

Low-temperature evolution of OH bands in synthetic forsterite, implication for the nature of H defects at high pressure

We performed in situ infrared spectroscopic measurements of OH bands in a forsterite single crystal between ?194 and 200 °C. The crystal was synthesized at 2 GPa from a cooling experiment performed between 1,400 and 1,275 °C at a rate of 1 °C per hour under high silica-activity conditions. Twenty-four individual bands were identified at low temperature. Three different groups can be distinguished: (1) Most of the OH bands between 3,300 and 3,650 cm^?1 display a small frequency lowering (<4 cm^?1) and a moderate broadening (<10 cm^?1) as temperature is increased from ?194 to 200 °C. The behaviour of these bands is compatible with weakly H-bonded OH groups associated with hydrogen substitution into silicon tetrahedra; (2) In the same frequency range, two bands at 3,617 and 3,566 cm^?1 display a significantly anharmonic behaviour with stronger frequency lowering (42 and 27 cm^?1 respectively) and broadening (~30 cm^?1) with increasing temperature. It is tentatively proposed that the defects responsible for these OH bands correspond to H atoms in interstitial position; (3) In the frequency region between 3,300 and 3,000 cm^?1, three broad bands are identified at 3,151, 3,178 and 3,217 cm^?1, at ?194 °C. They exhibit significant frequency increase (~20 cm^?1) and broadening (~70 cm^?1) with increasing temperature, indicating moderate H bonding. These bands are compatible with (2H)_Mg defects. A survey of published spectra of forsterite samples synthesized above 5 GPa shows that about 75 % of the incorporated hydrogen belongs to type (1) OH bands associated with Si substitution and 25 % to the broad band at 3,566 cm^?1 (type (2); 3,550 cm^?1 at room temperature). The contribution of OH bands of type (3), associated to (2H)_Mg defects, is negligible. Therefore, solubility of hydrogen in forsterite (and natural olivine compositions) cannot be described by a single solubility law, but by the combination of at least two laws, with different activation volumes and water fugacity exponents.