Spectropolarimetery of umbral fine structures from Hinode: evidence for magnetoconvection     

Lokesh Bharti †  Chandan Joshi  S. N. A. Jaaffrey  Rajmal Jain 《Monthly notices of the Royal Astronomical Society》2009,393(1):65-70

We present spectropolarimetric analysis of umbral dots and a light bridge fragment that show dark lanes in G -band images. Umbral dots show upflow as well as associated positive Stokes V area asymmetry in their central parts. Larger umbral dots show downflow patches in their surrounding parts that are associated with negative Stokes V area asymmetry. Umbral dots show weaker magnetic field in central part and higher magnetic field in peripheral area. Umbral fine structures are much better visible in total circularly polarized light than in continuum intensity. Umbral dots show a temperature deficit above dark lanes. The magnetic field inclination shows a cusp structure above umbral dots and a light bridge fragment. We compare our observational findings with 3D magnetohydrodynamic simulations.  相似文献   

Producing nature and making the state: Ordenamiento territorial in the Pacific lowlands of Colombia     

Kiran Asher 《Geoforum》2009,40(3):292-302

In this paper, we explore how ordenamiento territorial, a territorial zoning policy in the 1991 Colombian Constitution remakes nature and helps constitute the state in the “economically backward” but “biodiversity rich” Pacific lowlands region. We draw on Gramscian insights on hegemony and the importance of conjunctures to trace how changes in the new Constitution and global biogeopolitics reconfigure nature and state power through the mandates of sustainable development, economic growth, and the conservation of biological and cultural diversity. Finally, we contribute to the literature on political ecology by showing how the political power of the state, nature, and capital are interwoven materially and symbolically in complex and contradictory ways.  相似文献   

Impact of cyclonic wind field on interaction of surge–wave computations using finite-element and finite-difference models     

A. D. Rao  Indu Jain  M. V. Ramana Murthy  T. S. Murty  S. K. Dube 《Natural Hazards》2009,49(2):225-239

Both finite-element and finite-difference numerical models are applied to simulate storm surges and associated currents generated by tropical cyclones that struck the coast of Andhra Pradesh, located on the east coast of India. During a cyclone, the total water level at any location on the coast is made up of the storm surge, surge–wind wave interaction and the tide. The advanced circulation two-dimensional depth-integrated (ADCIRC-2DDI) model based on finite-element formulation and the two-dimensional finite-difference model of storm surges developed at IIT Delhi, hereafter referred as IITD storm surge model, are used. These models are driven by astronomical tides at the open ocean boundary and cyclonic asymmetric winds over the surface of the computational domain. Comparison of model simulated sea-surface elevations with coarse and finer spatial resolutions suggests that the grid resolution near the coast is very crucial for accurate determination of the surges in addition to the local bathymetry. The model underpredicts surges, and the peak surge location shifts more to the right of the landfall as the spatial resolution of the model becomes coarser. The numerical experiments also demonstrate that the ADCIRC model is robust over the IITD storm surge model for surge computations as the coastline is better represented in the former.  相似文献   

Storm surge modelling for the Bay of Bengal and Arabian Sea     

S. K. Dube  Indu Jain  A. D. Rao  T. S. Murty 《Natural Hazards》2009,51(1):3-27

Most of the countries around the North Indian Ocean are threatened by storm surges associated with severe tropical cyclones. The destruction due to the storm surge flooding is a serious concern along the coastal regions of India, Bangladesh, Myanmar, Pakistan, Sri Lanka, and Oman. Storm surges cause heavy loss of lives and property damage to the coastal structures and losses of agriculture which lead to annual economic losses in these countries. About 300,000 lives were lost in one of the most severe cyclones that hit Bangladesh (then East Pakistan) in November 1970. The Andhra Cyclone devastated part of the eastern coast of India, killing about 10,000 persons in November 1977. More recently, the Chittagong cyclone of April 1991 killed 140,000 people in Bangladesh, and the Orissa coast of India was struck by a severe cyclonic storm in October 1999, killing more than 15,000 people besides enormous loss to the property in the region. These and most of the world’s greatest natural disasters associated with the tropical cyclones have been directly attributed to storm surges. The main objective of this article is to highlight the recent developments in storm surge prediction in the Bay of Bengal and the Arabian Sea.  相似文献   

Drinking water quality in villages of southwestern Haryana,India: assessing human health risks associated with hydrochemistry   总被引：1，自引：0，他引：1  

Vinod K. Garg  Surindra Suthar  Sushma Singh  Aleenjeet Sheoran  Garima  Meenakshi  Sandeep Jain 《Environmental Geology》2009,58(6):1329-1340

The chemical quality of groundwater of western Haryana, India was assessed for its suitability for drinking purposes. A total of 275 water samples were collected from deep aquifer based hand-pumps situated in 37 different villages/towns of Bhiwani region. The water samples were analyzed for different physico-chemical properties, e.g., pH, total dissolved solids (TDS), total harness (TH), total alkalinity (TA), calcium, magnesium, carbonate, bicarbonate, sulphate, chloride and fluoride concentrations. In this study, the average TDS content was greater ranging 1,692 (Bhiwani block) to 2,560 mg l⁻¹ (Siwani block), and other important parameters of water, e.g., TA (442–1,232 mg l⁻¹), TH (437–864 mg l⁻¹) and bicarbonate (554–672 mg l⁻¹), were also higher than maximum permissible limit by WHO or BIS. The fluoride appeared as a major problem of safe drinking water in this region. We recorded greater fluoride concentration, i.e., 86.0 mg l⁻¹ from Motipura village that is highest fluoride level ever recorded for Haryana state. The average fluoride concentration ranged between 7.1 and 0.8 mg l⁻¹ in different blocks of western Haryana. On the basis of fluoride concentration, Siwani block showed the maximum number of water samples (84% of total collected samples) unsuitable for drinking purposes (containing fluoride >1.5 mg l⁻¹) followed by Charki Dadri block (58%), Bhiwani block (52%), Bawani Khera block (33%) and Loharu block (14%). This study clearly suggest that some health deteriorating chemicals in drinking water were at dangerous level and; therefore, water quality could be a major health threat for local residents of western Haryana. The high fluoride level in drinking water has posed some serious dental health risks in local residents.  相似文献   

Chemical composition of rain water and influence of airmass trajectories at a rural site in an ecological sensitive area of Western Ghats (India)     

Jetta Satyanarayana  Loka Arun Kumar Reddy  Monika Jain Kulshrestha  R Nageswara Rao  Umesh Chandra Kulshrestha 《Journal of Atmospheric Chemistry》2010,66(3):101-116

Samples of rain water were collected during monsoon season (June to September) of 2006 and 2007 at Hudegadde, a rural site located in an ecological sensitive area of Western Ghats. The collected samples were analyzed for pH, conductivity and major ions. At this site, rainwater pH varied from 4.20 to 7.39 with 5.65 as volume weighed mean. The observed mean was slightly lower than the average pH reported at most of the Indian continental sites. Monthly variation showed that average pH of rain water was the lowest during September (end of monsoon) and the highest during July (peak of monsoon). Overall, marine sources had dominating influence at this site. However, significant influence of anthropogenic and crustal sources from local as well as inter-continental regions was also noticed. As compared to NO₃⁻, higher concentration of SO₄²⁻ was noticed which might be due to contribution from industrial activities responsible for SO₂ emission. At this site, influence of five types of airmass trajectories was noticed i.e. i) C.I.O. (Central part of Indian Ocean)-when air masses blown from Maldives and nearby region of central Indian ocean. These airmasses had higher concentrations of nss Ca²⁺ which did not show any adverse impact on the pH; ii) N.W.I.O.(North-West Indian Ocean)-when airmasses travelled from oceanic region close to north-east Africa. These airmassses had higher concentrations of nss sulphate and nitrate and gave rise to acid rain; iii) S.W.I.O. (South -West Indian Ocean)- when airmasses came from southern part of Indian ocean (close to Mauritius). During these airmasses, rain water samples had almost equal ratio of nss SO₄²⁻ and nss Ca²⁺ similar to N.W.I.O but very low NO₃⁻ ; iv) Gulf-when airmasses were observed coming from Gulf region. Although these airmasses contributed only 2% of the total number of samples but carried high amount of nss SO₄²⁻ which gave rise to acid rain. The second lowest pH was observed during these airmasses which might be due to very high nssSO₄²⁻/nssCa²⁺ ratios; v) N.W.I.O. + S.W.I.C. (North-West Indian Ocean+South-West Indian Continental)- when airmasses originated from north-west Indian Ocean travelling towards south continental part of India and then arriving to the site. During these airmasses, samples showed typical influence of urban activities having high concentrations of nss SO₄²⁻ and NO₃⁻ leading to the lowest pH of rain water.  相似文献   

Learning about the ocean carbon cycle from observational constraints and model simulations of multiple tracers     

Long Cao  Atul K. Jain 《Climatic change》2008,89(1-2):45-66

A key question in studies of the potential for reducing uncertainty in climate change projections is how additional observations may be used to constrain models. We examine the case of ocean carbon cycle models. The reliability of ocean models in projecting oceanic CO₂ uptake is fundamentally dependent on their skills in simulating ocean circulation and air–sea gas exchange. In this study we demonstrate how a model simulation of multiple tracers and utilization of a variety of observational data help us to obtain additional information about the parameterization of ocean circulation and air–sea gas exchange, relative to approaches that use only a single tracer. The benefit of using multiple tracers is based on the fact that individual tracer holds unique information with regard to ocean mixing, circulation, and air–sea gas exchange. In a previous modeling study, we have shown that the simulation of radiocarbon enables us to identify the importance of parameterizing sub-grid scale ocean mixing processes in terms of diffusive mixing along constant density surface (isopycnal mixing) and the inclusion of the effect of mesoscale eddies. In this study we show that the simulation of phosphate, a major macronutrient in the ocean, helps us to detect a weak isopycnal mixing in the upper ocean that does not show up in the radiocarbon simulation. We also show that the simulation of chlorofluorocarbons (CFCs) reveals excessive upwelling in the Southern Ocean, which is also not apparent in radiocarbon simulations. Furthermore, the updated ocean inventory data of man-made radiocarbon produced by nuclear tests (bomb ¹⁴C) enable us to recalibrate the rate of air–sea gas exchange. The progressive modifications made in the model based on the simulation of additional tracers and utilization of updated observational data overall improve the model’s ability to simulate ocean circulation and air–sea gas exchange, particularly in the Southern Ocean, and has great consequence for projected CO₂ uptake. Simulated global ocean uptake of anthropogenic CO₂ from pre-industrial time to the present day by both previous and updated models are within the range of observational-based estimates, but with substantial regional difference, especially in the Southern Ocean. By year 2100, the updated model estimated CO₂ uptake are 531 and 133 PgC (1PgC?=?10¹⁵ gram carbon) for the global and Southern Ocean respectively, whereas the previous version model estimated values are 540 and 190 PgC.  相似文献   

Ozone in ambient air at a tropical megacity, Delhi: characteristics, trends and cumulative ozone exposure indices     

Sachin D. Ghude  S. L. Jain  B. C. Arya  G. Beig  Y. N. Ahammed  Arun Kumar  B. Tyagi 《Journal of Atmospheric Chemistry》2008,60(3):237-252

Seven year data of hourly surface ozone concentration is analyzed to study diurnal cycle, trends, excess of ozone levels above threshold value and cumulative ozone exposure indices at a tropical megacity, Delhi. The ozone levels clearly exhibit a diurnal cycle, similar to what has been found in other urban places. A sharp increase in the ozone levels during forenoon and a sharp decrease in the early afternoon can be observed. The average rate of increase in ozone concentration between 09 and 12 h has been observed to be 7.1 ppb h⁻¹. We find that the daily maximum and daytime 8-h (10–17 h) ozone levels are increasing at a rate of about 1.7 (± 0.7) and 1.3 (± 0.56) ppb y⁻¹, respectively. The directives on ozone pollution in ambient air provided by United Nations Economic Commission for Europe and World Health Organization for vegetation (AOT40) and human health protection were used to assess the air quality. The present surface ozone levels in the city are high enough to exceed “Critical Levels” which are considered to be safe for human health, vegetation and forest. The human health threshold was exceeded for up to ~45 days per year. The AOT40 (Accumulated exposure Over a Threshold of 40 ppb) threshold was exceeded significantly during winter (D-J-F) and pre-monsoon (M-A-M) (Rabi crop growing season) season in India. Translating AOT40 exceedances during pre-monsoon into relative yield loss we estimate yield loss of 22.7%, 22.5%, 16.3% and 5.5% for wheat, cotton, soybean and rice, respectively.  相似文献   

Analysis of current trends in climatic parameters and its effect on discharge of Satluj River basin,western Himalaya     

Riyaz Ahmad Mir  Sanjay K. Jain  Arun K. Saraf 《Natural Hazards》2015,79(1):587-619

  相似文献   

An assessment of regional vulnerability of rice to climate change in India   总被引：1，自引：0，他引：1  

Naresh Kumar Soora  P. K. Aggarwal  Rani Saxena  Swaroopa Rani  Surabhi Jain  Nitin Chauhan 《Climatic change》2013,118(3-4):683-699

A simulation analysis was carried out using the InfoCrop-rice model to quantify impacts and adaptation gains, as well as to identify vulnerable regions for irrigated and rain fed rice cultivation in future climates in India. Climates in A1b, A2, B1 and B2 emission scenarios as per a global climate model (MIROC3.2.HI) and a regional climate model (PRECIS) were considered for the study. On an aggregated scale, the mean of all emission scenarios indicate that climate change is likely to reduce irrigated rice yields by ~4 % in 2020 (2010–2039), ~7 % in 2050 (2040–2069), and by ~10 % in 2080 (2070–2099) climate scenarios. On the other hand, rainfed rice yields in India are likely to be reduced by ~6 % in the 2020 scenario, but in the 2050 and 2080 scenarios they are projected to decrease only marginally (<2.5 %). However, spatial variations exist for the magnitude of the impact, with some regions likely to be affected more than others. Adaptation strategies comprising agronomical management can offset negative impacts in the near future—particularly in rainfed conditions—but in the longer run, developing suitable varieties coupled with improved and efficient crop husbandry will become essential. For irrigated rice crop, genotypic and agronomic improvements will become crucial; while for rainfed conditions, improved management and additional fertilizers will be needed. Basically climate change is likely to exhibit three types of impacts on rice crop: i) regions that are adversely affected by climate change can gain in net productivity with adaptation; ii) regions that are adversely affected will still remain vulnerable despite adaptation gains; and iii) rainfed regions (with currently low rainfall) that are likely to gain due to increase in rainfall can further benefit by adaptation. Regions falling in the vulnerable category even after suggested adaptation to climate change will require more intensive, specific and innovative adaptation options. The present analysis indicates the possibility of substantial improvement in yields with efficient utilization of inputs and adoption of improved varieties.  相似文献