Modeling the exceptional south Foehn event (Garmij) over the Alborz Mountains during the extreme forest fire of December 2005     

Abbas Mofidi  Iman Soltanzadeh  Yadollah Yousefi  Azar Zarrin  Mohsen Soltani  Jafar Masoompour Samakosh  Ghasem Azizi  Samuel T. K. Miller 《Natural Hazards》2015,75(3):2489-2518

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The effect of the Zagros Mountains on the formation and maintenance of the Iran Anticyclone using RegCM4   总被引：3，自引：0，他引：3  

Azar Zarrin  Hooshang Ghaemi  Majid Azadi  Abbas Mofidi  Ebrahim Mirzaei 《Meteorology and Atmospheric Physics》2011,112(3-4):91-100

Iran anticyclone is one of the main features of the summer circulation over the Middle East in the middle and upper troposphere. To examine the effect of the Zagros Mountains on the formation and maintenance of the Iran anticyclone, an experiment was conducted by Regional Climate Model (RegCM4) in an area between 22°?C44°N and 35°?C70°E with a 40?km horizontal grid spacing. The NCEP/NCAR re-analysis data set were used to provide the initial and lateral boundary conditions in a control run and in a simulation run by removing the Zagros Mountains. The result reveals that the Zagros Mountains have an important effect on the formation and maintenance of the low-level cyclonic circulation and mid-level anticyclonic circulation in summer. Examining the diabatic heating shows that the elimination of the Zagros Mountains causes a significant change in the heating values and its spatial distributions over the study area. Comparing the diabatic heating terms, the vertical advection term has the main contribution to the total heating. In the absence of the Zagros Mountains, the vertical advection and the mid-troposphere anticyclonic circulation are apparently weak and, therefore, the Iran subtropical anticyclone vanishes over the west of Iran. The study indicates that the Zagros Mountains as an elevated heat source have the main impact in the formation of a thermally driven circulation over the Middle East.  相似文献   

Sample geometric mean versus sample median in closed form framework of seismic reliability evaluation: a case study comparison     

Abyani  M.  Asgarian  B.  Zarrin  Mohamad 《地震工程与工程振动(英文版)》2019,18(1):187-201

Earthquake engineers have made a lot of efforts to derive a comprehensive set of closed form expressions for performance evaluation of frames, which are already presented in guidelines such as SAC/FEMA. These analytical expressions have been developed to estimate the annual probability of exceeding a limit state. In the process of such seismic assessments, some essential assumptions are adopted to simplify the process. One of these fundamental assumptions declares that drift demand at any seismic intensity level follows a lognormal distribution around its median. To investigate the validity of this assumption, this paper describes a case study of the types of errors that could be produced by using the sample median as the central tendency. Based on the Maximum Likelihood Estimation method as well as other statistical evidence, this paper proposes the use of the sample geometric mean instead of the sample median for the central tendency. Further, the results of seismic reliability evaluations of 4 sample frames are compared based on utilizing both the geometric mean and the sample median. In this process, both first and second order power law fits of the hazard curve are implemented to compare the effects of hazard estimation and the selection of the central tendency on the final results. It is observed in the application example that the sample geometric mean could lead to more accurate results.  相似文献