A Model for the Common Origin of Jupiter Family and Halley Type Comets     

V. V. Emel’yanenko  D. J. Asher  M. E. Bailey 《Earth, Moon, and Planets》2013,110(1-2):105-130

A numerical simulation of the Oort cloud is used to explain the observed orbital distributions and numbers of Jupiter-family (JF) and Halley-type (HT) short-period (SP) comets. Comets are given initial orbits with perihelion distances between 5 and 36 au, and evolve under planetary, stellar and Galactic perturbations for 4.5 Gyr. This process leads to the formation of an Oort cloud (which we define as the region of semimajor axes a > 1,000 au), and to a flux of cometary bodies from the Oort cloud returning to the planetary region at the present epoch. The results are consistent with the dynamical characteristics of SP comets and other observed cometary populations: the near-parabolic flux, Centaurs, and high-eccentricity trans-Neptunian objects. To achieve this consistency with observations, the model requires that the number of comets versus initial perihelion distance is concentrated towards the outer planetary region. Moreover, the mean physical lifetime of observable comets in the inner planetary region (q < 2.5 au) at the present epoch should be an increasing function of the comets’ initial perihelion distances. Virtually all observed HT comets and nearly half of observed JF comets come from the Oort cloud, and initially (4.5 Gyr ago) from orbits concentrated near the outer planetary region. Comets that have been in the Oort cloud also return to the Centaur (5 < q < 28 au, a < 1,000 au) and near-Neptune high-eccentricity regions. Such objects with perihelia near Neptune are hard to discover, but Centaurs with characteristics predicted by the model (e.g. large semimajor axes, above 60 au, or high inclinations, above 40°) are increasingly being found by observers. The model provides a unified picture for the origin of JF and HT comets. It predicts that the mean physical lifetime of all comets in the region q < 1.5 au is less than ～200 revolutions.  相似文献   

FAO 56 Model and Remote Sensing for the Estimation of Crop-Water Requirement in Main Branch Canal of the Bhadra Command area, Karnataka State   总被引：1，自引：0，他引：1  

S. N. A. Abdul Karim  S. A. Ahmed  V. Nischitha  Surabhi Bhatt  S. Kiran Raj  K. N. Chandrashekarappa 《Journal of the Indian Society of Remote Sensing》2013,41(4):883-894

Remote sensing and FAO 56 crop water model are used for estimating crop water requirement for paddy crop located in the main branch canal of Bhadra Command Area in Karnataka, India. The estimation of crop-water requirement depends on the meteorological factors, soil type and crop coefficients. The result obtained showed that water requirements of rabi crops higher than those of the kariff crops. The total irrigated area estimated from the IRS image is 29,353 ha. It is found that the total paddy crop acreage is 18,257 ha covering 62 % in the total irrigated area of the command area, Arecanut 20 %, coconut 15 % and sugarcane with other crops 3 %. The water requirement for paddy is 1180.4 mm for its entire growth period. The total water requirement for irrigation supply for crops in the entire command area is 5,790 at a demand of 0.10501 cusecs per ha.  相似文献   

Emissions from grassland burning in Kaziranga National Park,India – analysis from IRS-P6 AWiFS satellite remote sensing datasets     

K. V.S. Badarinath  T. R. Kiran Chand  V. Krishna Prasad 《国际地球制图》2013,28(2):89-97

Biomass burning from vegetation fires is an important source of greenhouse gas emissions. In this study, we quantify biomass burning emissions from grasslands from the highly sensitive Kaziranga National Park, Assam, Northeast India. Most of the fires in the park are ‘controlled burning fires’ set by the park officials for management purposes. We evaluated the short-term impacts of fires and the resulting air pollution through integrating biomass burnt information from satellite remote sensing datasets. IRS-P6 Advanced Wide Field Sensor (AWiFS) data during March and April corresponding to dry season were evaluated to delineate the burnt areas. These burnt area estimates were then integrated with biomass data and emission factors for quantifying the greenhouse gas emissions. Results suggested that of the total study area of 37,822 ha, nearly 3163.282 ha has been burnt during March, 2005. Within one month, the burnt area increased to 7443.92 ha by April, i.e., from 8.36% to 19.68%. In total, biomass burning from the grasslands contributed to 29.65 Tg CO₂, 1.19 Tg CO, 0.071 Tg NOx, 0.042 Tg CH₄, 0.0625 Tg total non-methane hydrocarbons, 0.152 Tg of particulate matter, and 0.062 Tg of organic carbon and 0.008 Tg of black carbon during April. The importance of ‘fire’ as a management tool for maintaining the wildlife habitat has been highlighted in addition to some of the adverse affects of air pollution resulting from such management practices. The results from this study will be useful to forest officials as well as policy makers to undertake some sustainable forest management practices to maintain an ideal habitat for Kaziranga's wildlife.  相似文献   

Vertical structure of sea-breeze circulation over Thumba (8.5°N,?76.9°E,?India) in the winter months and a case study during W-ICARB field experiment     

T. J. Anurose  D. Bala Subrahamanyam  C. B. S. Dutt  N. V. P. Kiran Kumar  Sherine Rachel John  Sandhya K. Nair  M. Santosh  Mannil Mohan  P. K. Kunhikrishnan  S. Sijikumar  S. S. Prijith 《Meteorology and Atmospheric Physics》2012,115(3-4):113-121

This research article aims at characterization of the sea-breeze circulation over Thumba (8.5°N,?76.9°E,?India) in the winter season from December 2008 to February 2009, when this mesoscale circulation over the study domain was prominent. The characteristics of sea-breeze circulation cell comprising sea-breeze and compensatory return flow are investigated for clear-sky and cloudy days. The study indicated delayed onset of sea-breeze on the cloudy days as compared to the clear-sky days and the vertical thickness of sea-breeze circulation cell was found to be larger for the clear-sky days. Vertical thickness of the return flow for both clear-sky and cloudy days was larger than that of the sea-breeze flow. Simultaneous observations of upper-air meteorological parameters obtained through balloon-borne GPS sonde ascents carried out from Thumba and its adjoining coastal ocean on 29 January 2009 as part of the Winter phase of Integrated Campaign for Aerosols, gases and Radiation Budget (W-ICARB) are utilized for a case study towards investigation of diurnal evolution of the sea-breeze circulation cell. Results obtained from this study indicated systematic evolution of sea-breeze circulation over Thumba, however, it was not very clear over ocean which is attributed to cloudy conditions that prevailed on the day of measurement.  相似文献   

Hydrodynamic control of microphytoplankton bloom in a coastal sea     

K Narasimha Murty  Nittala S Sarma  Sudarsana Rao Pandi  Gundala Chiranjeevulu  Rayaprolu Kiran  R Muralikrishna 《Journal of Earth System Science》2017,126(6):82

The influence of hydrodynamics on phytoplankton bloom occurrence/formation has not been adequately reported. Here, we document diurnal observations in the tropical Bay of Bengal’s mid-western shelf region which reveal microphytoplankton cell density maxima in association with neap tide many times more than what could be accounted for by solar insolation and nutrient levels. When in summer, phytoplankton cells were abundant and the cell density of Guinardia delicatula reached critical value by tide caused zonation, aggregation happened to an intense bloom. Mucilaginous exudates from the alga due to heat and silicate stress likely promoted and stable water column and weak winds left undisturbed, the transient bloom. The phytoplankton aggregates have implication as food resource in the benthic region implying higher fishery potential, in carbon dioxide sequestration (carbon burial) and in efforts towards improving remote sensing algorithms for chlorophyll in the coastal region.  相似文献   

Explosive felsic volcanism at Palaeo-Mesoproterozoic boundary from Vindhyan Supergroup,Son Valley,Central India—Evidences of crustal contamination     

Meenal Mishra  Shinjana Sen  Kiran Kumari 《Geochemistry International》2017,55(5):474-488

Vindhyan basin witnessed a widespread explosive type of felsic volcanism at Palaeo-Mesoproterozoic boundary which is manifested as Chopan porcellanite shale. This is exposed as a linear belt along the Son valley in Central India. Porcellanite shale is pyroclastics deposit comprising strongly welded to unwelded ignimbrites. CIA values coupled with A–CN–K systematics provide strong evidence regarding their igneous origin and proximity of the source. The pyroclastics are rhyodacitic to rhyolitic in nature. The enriched LREE, LILE, depleted HFSE and incompatible element ratios such as Nb/Th, La/Sm and Zr/Nb indicate contamination and mixing between mantle-derived rocks and the average continental crust. Five distinct phases of volcanic activity have been identified based on field observations and petrological evidences. Pyroclastics at various stratigraphic levels indicate repeated occurrences of intrabasinal felsic volcanism, pointing to episodic extension, rifting and eruption over a period of time. The present studies have suggested that volcanic activity in Son valley and pyroclastic detritus resulted from a common chamber due to the rejuvenation and activation of deep seated faults like Son-Narmada lineament.  相似文献   

Equilibria of the marine multiphase ammonia system   总被引：3，自引：0，他引：3  

P. K. Quinn  W. E. Asher  R. J. Charlson 《Journal of Atmospheric Chemistry》1992,14(1-4):11-30

A lack of empirical data has made it difficult to ascertain whether ammonia is in equilibrium between the oceanic, atmospheric gas and atmospheric particle phases in the remote marine environment. Reported here are simultaneous measurements of the saturation concentration of ammonia relative to ammonia concentrations in ocean surface waters; total seawater ammonia; atmospheric gas phase ammonia; and atmospheric particulate-phase ammonium, non-seasalt sulfate, methanesulfonate, and nitrate. Sampling was performed in May of 1987 in the northeast Pacific Ocean environment and in April and May of 1988 in the central Pacific Ocean environment.These measurements were used to determine the degree to which ammonia approached equilibrium between the oceanic and atmospheric gas and aerosol particle phases. The experimental atmospheric gas phase ammonia concentrations were compared with calculated equilibrium concentrations assuming a Henry's law type of partitioning between the gas and condensed phases. Characteristic times of the processes controlling the fate of ammonia in the marine environment also were compared.The measured atmospheric gas phase and oceanic concentrations of ammonia indicate that ammonia is not in a Henry's law equilibrium across the air/sea interface. This disequilibrium is a result of the long air/sea exchange equilibration time relative to the lifetime of ammonia in the atmosphere. Comparison of the calculated equilibrium gas phase ammonia concentrations with the measured gas phase ammonia concentrations shows that attainment of equilibrium between the atmospheric gas and particle phases is a strong function of the chemical composition of the aerosol particles. The data suggest that fully neutralized aerosol particles are not in Henry's law equilibrium with the gas phase while equilibrium is observed for particles with an average ammonium to non-seasalt sulfate molar ratio less than 1.8.  相似文献   

Using the Relative Operating Characteristic to Quantify Certainty in Prediction of Location of Land Cover Change in India   总被引：4，自引：0，他引：4  

R Gil Pontius Jr  Kiran Batchu 《Transactions in GIS》2003,7(4):467-484

This paper describes a methodology by which modelers, ecologists and planners can quantify the certainty in predicting the location of change for a given quantity of change. The specification of the quantity of a land cover category and the specification of the location of a land cover category are two distinct fundamental concepts in geographical analysis. It is crucial that scientists have appropriate quantitative tools to analyze each of these two concepts independently of one another. This paper gives methods whereby a scientist can convert a map of relative propensity for disturbance to a map of probability of future disturbance, based on a quantifiable validation of a map's predictive ability. The required inputs are: (1) maps that show a Boolean categorical variable at times 0, 1 and 2, (2) a technique to create a map that shows the relative propensity for membership in the Boolean category, and (3) a predicted proportion of the category at time 3.  相似文献   

Geotechnical properties of stabilised Indian red earth     

P. V. Sivapullaiah  H. Lakshmi Kantha  K. Madhu Kiran 《Geotechnical and Geological Engineering》2003,21(4):399-413

Locally available soils amended with sufficient bentonite are generally used for construction of liners for water and waste retention facilities. The amount of bentonite required to keep the hydraulic conductivity low varies with the nature of the local soil. Many studies have shown that bentonite content higher than 20% by weight is not usually required. This is also the case with Indian red earth containing predominantly quartz and kaolinite minerals. Incorporating bentonite, though keeps the hydraulic conductivity of soil low, increases the swelling and shrinkage potential; increases the loss of strength due to reduction in cohesion. This paper aims to improve the geotechnical properties of red earth and bentonite mixture with lime or cement. The studies reveal that the geotechnical properties of red earth with 20% by weight bentonite stabilised with 1% by weight of lime or cement are greatly enhanced, particularly after curing for 28 days. it has been shown that the early gain in strength is better with cement whereas its long-term strength gain is better with lime.  相似文献   

Terrain mapping camera for Chandrayaan-1     

A. S. Kiran Kumar  A. Roy Chowdhury 《Journal of Earth System Science》2005,114(6):717-720

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