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Candidate examples of impact melt flows and debris flows have been identified at Tooting crater, an extremely young (<2 Myr), 29 km diameter impact crater in Amazonis Planitia, Mars. Using HiRISE and CTX images, and stereo-derived digital elevation models derived from these images, we have studied the rim and interior wall of Tooting crater to document the morphology and topography of several flow features in order to constrain the potential flow formation mechanisms. Four flow types have been identified; including possible impact melt sheets and three types of debris flows. The flow features are all located within 2 km of the rim crest on the southern rim or lie on the southern interior wall of the crater ∼1500 m below the rim crest. Extensive structural failure has modified the northern half of the crater inner wall and we interpret this to have resulted in the destruction of any impact melt emplaced, as well as volatile-rich wall rock. The impact melt flows are fractured on the meter to decameter scale, have ridged, leveed lobes and flow fronts, and cover an area >6 km × 5 km on the southern rim. The debris flows are found on both the inner wall and rim of the crater, are ∼1-2 km in length, and vary from a few tens of meters to >300 m in width. These flows exhibit varying morphologies, from a channelized, leveed flow with arcuate ridges in the channel, to a rubbly flow with a central channel but no obvious levees. The flows indicate that water existed within the target rocks at the time of crater formation, and that both melt and fluidized sediment was generated during this event. 相似文献
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The coupling of Shukla-Varma (SV) and convective cell modes is discussed in the presence of non-Boltzmannian electron response and parallel equilibrium shear flow. In the linear case, a new dispersion relation is derived and analyzed. It is found that the coupled SV and convective cell modes destabilize in the presence of electron shear flow. On the other hand, in the nonlinear regime, it is shown that Shukla-Varma mode driven counter rotating vortices can be formed for the system under consideration. It is found that these vortices move slowly by comparison with the ion acoustic or electron drift-wave driven counter rotating vortices. The relevance of the present investigation with regard to space plasmas is also pointed out. 相似文献
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Evidence of volcano-ground ice interactions on Mars can provide important constraints on the timing and distribution of martian volcanic processes and climate characteristics. Northwest of the Elysium Rise is Hrad Vallis, a ∼370 m deep, 800 km long sinuous valley that begins in a source region at 34° N, 218° W. Flanking both sides of the source region is a lobate deposit that extends ∼50 km perpendicular from the source and is an average of ∼40 m thick. Previous studies have suggested the formation of the Hrad Vallis source region was the result of explosive magma-ice interaction and that the lobate deposit is a mudflow; here we use newly available MOLA, MOC, and THEMIS data to investigate the evidence supporting this hypothesis. Within the lobate deposit we have identified 12 craters with thermal infrared signatures and morphologies that are distinct from any other craters or depressions in the region. The thermally distinct craters are distinguished by their cool interiors surrounded by warm ejecta in the nighttime THEMIS IR data and warm interiors surrounded by cool ejecta in the daytime THEMIS IR data. The craters are typically 1100-1800 m in diameter (one crater is ∼2300 m across) and 30-40 m deep, but may be up to 70 m. The craters are typically circular and have central depressions (several with interior dune fill) surrounded by ∼1 to >6 concentric fracture sets. The distribution of the craters and their morphology suggests that they are likely the result of the interaction between a hot mudflow and ground ice. 相似文献
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S. H. Sajjad Babar Hussain M. Ahmed Khan Asif Raza B. Zaman Ijaz Ahmed 《Climatic change》2009,96(4):539-547
Karachi is the largest city of Pakistan. The temperature change in Karachi is studied in this research by analyzing the time
series data of mean maximum temperature (MMxT), mean minimum temperature (MMiT) and mean annual temperature (MAT) from 1947
to 2005 (59 years). Data is analyzed in three parts by running linear regression and by taking anomalies of all time periods:
(a) whole period from 1947–2005; (b) phase one 1947–1975 and (c) phase two 1976–2005. During 1947 to 2005 MMxT has increased
about 4.6°C, MMiT has no change and MAT has increased 2.25°C. During 1947–1975, MMxT increased 1.9°C, in this period there
is − 1.3°C decrease in MMiT and MAT has raised upto 0.3°C. During 1976–2005, the MMxT, MMiT and MAT increased 2.7°C, 1.2°C
and 1.95°C, respectively. The analysis shows significantly the role of extreme vulnerability of MMxT in rising the temperature
of Karachi than the MMiT. 相似文献
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Jewgenij Torizin Michael Fuchs Adnan Alam Awan Ijaz Ahmad Sardar Saeed Akhtar Simon Sadiq Asif Razzak Daniel Weggenmann Faseeh Fawad Nimra Khalid Faisan Sabir Ahsan Jamal Khan 《Natural Hazards》2017,87(2):757-771
This paper presents laboratory experiments and numerical simulations of effects of submerged obstacles on tsunami-like solitary wave and its run-up. This study was carried out for the breaking and non-breaking solitary waves on 1:19.85 uniform slope which contains a submerged obstacle. New laboratory experiments are performed to describe the mitigation of tsunami amplitude and run-up under the effect of submerged obstacles. We are based on experimental results obtained to validate the numerical model. The numerical modeling using COULWAVE aims essentially to show the effect of the obstacle on the shape of solitary wave and the limit of this effect. Using a multiple nonlinear regression, we have determined a model to estimate height of run-up according to the amplitude of the wave and the obstacle peak depth. 相似文献
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Spatio-temporal estimation of precipitation over a region is essential to the modeling of hydrologic processes for water resources management. The changes of magnitude and space–time heterogeneity of rainfall observations make space–time estimation of precipitation a challenging task. In this paper we propose a Box–Cox transformed hierarchical Bayesian multivariate spatio-temporal interpolation method for the skewed response variable. The proposed method is applied to estimate space–time monthly precipitation in the monsoon periods during 1974–2000, and 27-year monthly average precipitation data are obtained from 51 stations in Pakistan. The results of transformed hierarchical Bayesian multivariate spatio-temporal interpolation are compared to those of non-transformed hierarchical Bayesian interpolation by using cross-validation. The software developed by [11] is used for Bayesian non-stationary multivariate space–time interpolation. It is observed that the transformed hierarchical Bayesian method provides more accuracy than the non-transformed hierarchical Bayesian method. 相似文献
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Ijaz Ahmad Zulfiqar Ahmad Siraj Munir Obaid-ur-Rehman Syed Roshaan Ali Shah Yasir Shabbir 《Arabian Journal of Geosciences》2018,11(15):419
Snowcover dynamics and associated accumulation and depletion of snowcover along with its spatial and temporal scale mainly constitute hydrological phenomena of the given basin and are mostly controlled by the local climate variables. Snow accumulation and melting time and duration determine the cyclic volume of water resources and downstream availability. In this study, snowcover area (SCA) was extracted from remotely sensed Moderate Resolution Imaging Spectroradiometer (MODIS) snow products (MOD10A2) for the period 2000–2016. Data for hydro-meteorological parameters was obtained from relevant departments acquired through their field stations. The analysis of 16-year satellite data shows that there is a slight increase in cryospheric area at high altitude. In Astore basin, the study concluded that 15–20% of the basin area is covered by glacier and snowcover may reach around 90–95% of the basin area due to accumulation of seasonal snow from the westerly wind circulation. Analysis of hydro-meteorological parameters showed significant correlation between temperatures (Tmax, Tmin) and river runoff while no significant correlation was observed between river runoff and rainfall. Similarly, significant inverse correlation was found between river runoff and Astore mean snowcover. At sub-altitudinal zone level (zones 1, 2, 3), river runoff has significant correlation with snowcover. Analysis of 20-year climate data along with river runoff depicts that river runoff is a general phenomenon of snowmelt when minimum temperature starts to rise above 4 °C during mid of April. The study highlights the importance and interdependence of meteorological parameters and snowcover dynamics in determining the hydrological characteristics of Astore Basin. 相似文献
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Pakistan is a developing country existing geographically at a pivoted location between two of the world’s largest pollution emitting countries (China and India) which adds to the severity of environmental issues faced by the country. These concerns include air pollution, climate change, and extreme weather situations prevailing in Pakistan. This increasing air pollution is deteriorating the health, threatening the food security and adding up its share to the already existing global warming. The initial step in devising a wide ranging, multifaceted, economically feasible, and sustainable solution to deal with the severity of this issue is the quantification of the air pollution and greenhouse gas emission in Pakistan. The GAINS model is one of the most comprehensive tools, dealing with the air pollutants and greenhouse gases covered by the Kyoto Protocol. This study has utilized this model to analyze the source-based anthropogenic emissions of air pollutants (NH3 and SO2), volatile organic compounds (VOCs), and greenhouse gases (CH4 and CO2), their impacts and abatement cost, for the duration of 1990–2030, in the Khyber Pakhtunkhwa and Balochistan regions of Pakistan. An overall increasing trend was observed during 1990–2030 for (a) air pollutants: NH3 (223.52–568.87kT/Y); SO2 (50.52–332.95kT/Y), (b) VOCs (121.76–246.81kT/Y), and (c) greenhouse gases: CO2 (7.83–62.45MT/Y) and CH4 (1120-2314kT/Y). The emission inventories created for all greenhouse gases together estimated the increase of 42.37 to 138.57 MTCO2eq. for greenhouse gases over the time duration of 1990–2030. 相似文献