Statistical equilibrium distributions of baroclinic vortices in a rotating two-layer model at low Froude numbers     

Syed M. Assad 《地球物理与天体物理流体动力学》2013,107(6):503-524

The point-vortex equilibrium statistical model of two-layer baroclinic quasigeostrophic vortices in an unbounded f-plane is examined. A key conserved quantity, angular momentum, serves to confine the vortices to a compact domain, thereby justifying the statistical mechanics model, and also eliminating the need for boundary conditions in a practical method for its resolution. The Metropolis method provides a fast and efficient algorithm for solving the mean field non-linear elliptic PDEs of the equilibrium statistical theory. A verification of the method is done by comparison with the exact Gaussian solution at the no interaction limit of zero inverse temperature. The numerical results include a geophysically and computationally relevant power law for the radii at which the most probable vortex distribution is non-vanishing: For fixed total circulation, and fixed average angular momentum, the radii of both layers are proportional to the square root of the inverse temperature β. By changing the chemical potentials μ of the runs, one is able to model the most probable vorticity distributions for a wide range of total circulation and energy. The most probable vorticity distribution obtained at low positive temperatures are consistently close to a radially symmetric flat-top profiles. At high temperatures, the radially symmetric vorticity profiles are close to the Gaussian distribution.  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987111001265   总被引：3，自引：0，他引：3  

Syed Amer Mahmood  Richard Gloaguen 《地学前缘(英文版)》2012,3(4):407-428

Landscapes in tectonically active Hindu Kush（NW Pakistan and NE Afghanistan） result from a complex integration of the effects of vertical and horizontal crustal block motions as well as erosion and deposition processes.Active tectonics in this region have greatly influenced the drainage system and geomorphic expressions.The study area is a junction of three important mountain ranges （Hindu Kush-Karakorum-Himalayas） and is thus an ideal natural laboratory to investigate the relative tectonic activity resulting from the India-Eurasia collision.We evaluate active tectonics using DEM derived drainage network and geomorphic indices hypsometric integral（HI）,stream-length gradient （SL）.fractal dimension（FD）.basin asymmetry factor（AF）.basin shape index（B_s）,valley floor width to valley height ratio（Vf） and mountain front sinuosity(S_mf). The results obtained from these indices were combined to yield an index of relative active tectonics （IRAT） using CIS.The average of the seven measured geomorphic indices was used to evaluate the distribution of relative tectonic activity in the study area.We defined four classes to define the degree of relative tectonic activity:class 1 very high（1.0≤IRAT 1.3）;class 2-high（1.3≥IRAT<1.3）:class 3—moderate（1.5≥IRAT<1.8）;and class 4—low（l.8≥1RAT）.In view of the results.we conclude that this combinetl approach allows the identification of the highly deformed areas related to active tectonics.Landsat imagery and held observations also evidence the presence of active tectonics based on the dellected streams,deformed landforms.active mountain fronts and triangular facets.The indicative values of IRAT are consistent with the areas of known relative uplift rates,landforms and geology.  相似文献   

Integration between morphometric parameters,hydrologic model,and geo-informatics techniques for estimating WADI runoff (case study WADI HALYAH—Saudi Arabia)     

Jalal Basahi  Milad Masoud  Syed Zaidi 《Arabian Journal of Geosciences》2016,9(13):610

In arid and semiarid areas, the only surface and groundwater recharge source is the runoff generated through flash floods. Lack of hydrological data in such areas makes runoff estimation extremely complicated. Flash floods are considered catastrophic phenomena posing a major hazardous threat to cities, villages, and their infrastructures. The objective of this study is to assess the flash flood hazard and runoff in Wadi Halyah and its sub-basins. Integration of morphometric parameters, geo-informatics, and hydrological models has been done to overcome the challenge of scarcity of data.Advanced Spaceborne Thermal Emission and Reflection (ASTER) data was used to prepare a digital elevation model (DEM) with 30-m resolution, and geographical information system (GIS) was used in the evaluation of network, geometry, texture, and relief features of the morphometric parameters. Thirty-eight morphometric parameters were estimated and have been linked together for producing nine effective parameters for evaluation of the flash flood hazard in the study basin.Flash flood hazard in Wadi Halyah and its sub-basins was identified and grouped into three classes depending on nine effective parameters directly influencing the flood prone areas. Calculated runoff volume of Wadi Halyah ranges from 26.7 × 10⁶ to 111.4 × 10⁶ m³ with an inundation area of 15 and 27 km² at return periods of 5 and 100 years, respectively. Mathematical relationships among rainfall depth, runoff volume, infiltration losses, and rainfall excess demonstrate a strong directly proportional relationships with correlation coefficient of about 0.99.  相似文献   

Geology and Mineral Chemistry of the Deosai Volcanics, Baltistan, N. Pakistan     

Syed Hamidullah 《地学前缘》2000,(Z1)

GEOLOGY AND MINERAL CHEMISTRY OF THE DEOSAI VOLCANICS, BALTISTAN, N. PAKISTAN  相似文献   

Spatial modeling of Dengue prevalence and kriging prediction of Dengue outbreak in Khyber Pakhtunkhwa (Pakistan) using presence only data     

Ahmad  Hammad  Ali  Asad  Fatima  Syeda Hira  Zaidi  Farrah  Khisroon  Muhammad  Rasheed  Syed Basit  Ullah  Ihsan  Ullah  Saleem  Shakir  Muhammad 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(7):1023-1036

Stochastic Environmental Research and Risk Assessment - During the span of August–October, 2017 a major outbreak of Dengue fever happened in Khyber Pakhtunkhwa province of Pakistan. Cases...  相似文献   

洋中脊扩张速率对洋壳速度结构的约束          下载免费PDF全文

李龑  牛雄伟  阮爱国  刘绍文  Syed Waseem Haider  卫小冬 《地球物理学报》2020,63(5):1913-1926

洋中脊速度结构是揭示大洋岩石圈演化过程的重要约束.为探讨不同扩张速率下洋中脊的洋壳速度结构特征,挑选了全球152处快速(全扩张速率 90mm·a-1)、慢速(全扩张速率20～50mm·a-1)和超慢速(全扩张速率20mm·a-1)扩张洋中脊和非洋中脊的洋壳1-D地震波速度结构剖面,通过筛选统计、求取平均值等方法对分类的洋壳1-D速度结构进行对比研究,获得了不同扩张速率下洋中脊洋壳速度结构差异以及洋中脊与非洋中脊洋壳速度结构差异的新认识:(1)快速、慢速和超慢速扩张洋中脊的平均正常洋壳厚度分别为6.4km、7.2km和5.3km,其中洋壳层2的厚度基本相似,洋壳厚度差异主要源自洋壳层3;其洋壳厚度变化范围分别为4.9～8.1km、4.6～8.7km和4.2～10.2km,随着洋中脊扩张速率减小,洋壳厚度的变化范围逐渐增大;(2)快速扩张洋中脊的洋壳速度大于慢速和超慢速,可能与快速扩张脊洋壳生成过程中深部高密度岩浆上涌比较充足有关;(3)非洋中脊(10Ma)的洋壳比洋中脊(10Ma)的洋壳厚～0.3km,表明洋壳厚度与洋壳年龄有一定的正相关性.  相似文献   

西南印度洋中脊49.5°E离轴地壳结构          下载免费PDF全文

王伟  牛雄伟  阮爱国  Syed Waseem Haider  胡昊  王奥星  卫小冬  张洁 《地球物理学报》2018,61(11):4406-4417

超慢速扩张西南印度洋中脊岩浆的集中供给在空间维度上表现为岩浆扩张段（NVR）与相邻的非转换断层不连续带（NTD）地壳结构的差异,而在时间维度上表现为离轴与沿轴地壳结构的差异.为了进一步揭示岩浆集中供给的时空分布特征,本文选取西南印度洋中脊热液区2010年海底地震仪深部探测中平行于洋中脊距轴部偏北约10 km的离轴测线d0d10,使用射线追踪正演和反演的方法,得到了NVR和NTD北侧离轴区域的地壳及上地幔P波速度结构,并与轴部速度结构进行了对比分析.研究结果表明：（1）NTD北侧离轴区域的地壳厚度约5.2 km,其厚度明显大于轴部NTD下方地壳厚度（~3.2 km）,由此推测洋脊轴部NTD区域形成的地壳在不断减薄;（2）NVR北侧离轴区域的地壳厚度约7.0 km,其厚度亦大于轴部NVR地壳厚度（~5.8 km）,表明在洋中脊演化过程中洋脊轴区域的岩浆供给在不断减少,其活动性在不断减弱.  相似文献   

Full-scale experimental investigations on the response of a flooded passenger vehicle under subcritical conditions     

Al-Qadami  Ebrahim Hamid Hussein  Mustaffa  Zahiraniza  Shah  Syed Muzzamil Hussain  Matínez-Gomariz  Eduardo  Yusof  Khamaruzaman Wan 《Natural Hazards》2022,110(1):325-348

Natural Hazards - Vehicles can be easily swept away by floodwaters once the flow velocity and depth reach certain critical limits, with probabilities toward fatality reported to be nearly 50%....  相似文献