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2.
The interannual variation of precipitation in the southern part of Iran and its link with the large-scale climate modes are examined using monthly data from 183 meteorological stations during 1974–2005. The majority of precipitation occurs during the rainy season from October to May. The interannual variation in fall and early winter during the first part of the rainy season shows apparently a significant positive correlation with the Indian Ocean Dipole (IOD) and El Ni?o-Southern Oscillation (ENSO). However, a partial correlation analysis used to extract the respective influence of IOD and ENSO shows a significant positive correlation only with the IOD and not with ENSO. The southeasterly moisture flux anomaly over the Arabian Sea turns anti-cyclonically and transport more moisture to the southern part of Iran from the Arabian Sea, the Red Sea, and the Persian Gulf during the positive IOD. On the other hand, the moisture flux has northerly anomaly over Iran during the negative IOD, which results in reduced moisture supply from the south. During the latter part of the rainy season in late winter and spring, the interannual variation of precipitation is more strongly influenced by modes of variability over the Mediterranean Sea. The induced large-scale atmospheric circulation anomaly controls moisture supply from the Red Sea and the Persian Gulf.  相似文献   
3.
Iran is one of the most seismically active areas of the world and frequently suffers from destructive earthquakes. Rare studies on anthropogenic-induced seismicity in Iran may be related to less attention to triggered events and more concern to natural origin of earthquakes. Hence, the present study as a frontier research aims to investigate the mining-induced earthquakes in Iran. For this purpose, distribution of ~?76,000 seismic events was investigated between the years 2006 and 2013. This study considered a correlation test to investigate the possible mining triggering of the seismic events based on a network of 194 geographical pixels (1°?×?1°) in ArcGIS. Results conveniently confirmed a positive meaningful relation between all earthquake events with magnitudes M?>?0.5 and mining activities in Iran (R?=?0.42). Detailed results confirmed that the most of earthquake swarms (at least ~?60%) had mining-induced origin, which were spatially located in same pixels of metallic mineral mining sites. The correlation test between earthquake swarms and mining activities indicated positive and meaningful relationships in four regions of Alborz, Kopet Dag, Kerman, and Zagros, respectively (R?=?0.61, 0.54, 0.51, and 0.50). Hence, aforementioned seismic regions exposed sensitive seismic responses toward mining triggering effects in Iran.  相似文献   
4.
Several studies have reported the increased values of surface-latent heat flux (SLHF) and rainfall events prior to the earthquakes as the seismic precursors. In order to investigate the variation of two mentioned atmospheric variables, we analyzed 39 major earthquakes in the Middle East based on the time series of NASA remote sensing data. On this basis, we observed that accumulated rainfall and SLHF of about 29 earthquakes were higher than 10 mm and 50 W/m2, respectively (~75 %), over 3–23 days prior to the main shock of major earthquakes. We believed that the records of atmospheric variables are the consequence of a seismic-triggered chain including of air ionization, surface-latent heat exhalation, water vapor condensation and subordinate rainfall as the atmospheric responses to lithospheric motions. This seismic triggering in the Middle East has averagely caused to accumulated rainfall of ~35 mm and maximum SLHF of ~115 W/m2 over the 3–23 days prior to 39 major earthquakes. To investigate of spatial correlation between earthquakes and atmospheric variations, we clustered 39 major earthquakes in eight seismological regions. Then, we estimated the moderate and strong correlation (R 2) between preceding times of earthquakes with magnitude of major earthquakes and their hypocenter depth equal to 0.48 and 0.68, respectively.  相似文献   
5.
Rainfalls with short persistency are the tangible characteristics of arid and semiarid regions such as Iran. Iran is an arid and semiarid region with dramatic tempo-spatial changes of rainfall. In this regard, the short persistency of rainfall is approximately observed from 1 to 7 days in whole parts, while the greater ones are only separated in eastern parts of Iran. According to the results, the rainfall persistency is ranged from 1 to 45 days, but the maximum amount and rainy days are generated by rainfalls with short persistency. So, the rainfall events with long persistency are considered as an extreme event with extreme variability. One-day precipitations generate the maximum rainy days and rainfall amounts, especially in eastern parts of Iran. Decrease in the one-day precipitations contribution to eastern parts may indicate to decrease in regional precipitation. However, decrease in contribution in western parts may indicate to increased amounts of rainfall at other persistency rates. Our results revealed that the contribution of the one-day precipitation to general rainfall has reductive trends in almost 17.5 % of the whole Iran. The most integrated and significant reductive trend of one-day precipitation contribution to rainfall spreads northeastern and eastern parts of Iran. However, in the western parts of Iran, decreasing one-day precipitation contribution to rainy days affects to increase in the diurnal rainfall. The mentioned variability can be considered as the climate change signals in respect of one-day precipitation.  相似文献   
6.
At the present study, factor and cluster analysis were applied to evaluate the agrometeorological suitability zonation of 39 plains in Khorasan Razavi Province, NE Iran. For this purpose, the extracted 98 variables were processed, resulted in eight factors which explain about 90 % of the total variance. The explained variances of these factors are varied from 42.99 to 2.74 % for factors 1 and 8 after the Varimax rotation, respectively. The spatial classification maps of factor scores are extracted after the studied plains and the calculated scores were then classified by cluster analysis. It was revealed that five clusters were enough to classify the studied plains. The “negligible,” “low,” “moderate,” “high,” and “very high” classes included 4, 14, 9, 7, and 5 plains with 8.0, 35.6, 23.0, 15.1, and 18.3 % of the total surface area, respectively. The geographical distribution of the five major zones revealed that the plains with very high suitability are laid on the center and north parts of the study area, while the rest which are negligible and low suitability zones are mainly concentrated in the west, south, and southeast of the study area. Comparing the agrometeorological suitability between the corresponding zones revealed a general reducing trend from north to south along 3° geographical latitudes.  相似文献   
7.
Landslide hazard zonation is essential for planning future developmental activities. At the present study, after the preparation of a landslide inventory of the study area, nine factors as well as sub-data layers of factor class weights were tested for an integrated analysis of landslide hazard in the region. The produced factor maps were weighted with the analytic hierarchy process method and then classified into four classes—negligible, low, moderate, and high. The final produced map for landslide hazard zonation in Golestan watershed revealed that: (1) about 53.85 % of the basin is prone to moderate and high threats of landslides. (2) Landslide events at the Golestan watershed were strongly correlated to the slope angle of the basin. It was observed that the active landslide zones, including moderate to high landslide hazard classes, have a high correlation to slope classes over 30° (R 2?=?0.769). (3) The regions most susceptible to landslide hazard are those located south and southwest of the watershed, which included rock topples, falls, and debris landslides.  相似文献   
8.
Theoretical and Applied Climatology - The present study is aimed at evaluation of a rain gauge network in order to optimize a network design. In this regard, point rainfall estimations were...  相似文献   
9.
Two main goals are considered in this paper: (1) modification and computation of the local coefficients of the space-time windows in the well-known declustering algorithm introduced by Gardner and Knopoff (1974) and (2) checking the independence of the Iranian mainshocks obtained from applying the new modified model. First, 21 of the well-documented earthquake sequences of Iran in the time period of 1972 to 2008 with the mainshock magnitude ranged from M w = 5.4–7.1 were used to define the new local space-time windows of declustering. Generally, using these Iranian earthquake sequences led to introduce bigger space-time windows for the new model in comparison to the Gardner and Knopoff’s (1974) windows. In the next step, to control the independence of Iranian mainshocks, the events of the Iranian earthquake catalog in the time span of 1964–2010 with moment magnitude of M w = 3.5–7.4 were used. In this respect, dependent events corresponding to the seven seismotectonic zones of Iran were removed using the new modified space-time windows. After declustering, the mainshock catalog was examined by the Kolmogorov–Smirnov goodness-of-fit test, and it was found to follow a Poisson distribution in all the studied seismotectonic zones of Iran. The same test on times between successive declustered events shows that the inter-event times of all catalogs follow an exponential distribution.  相似文献   
10.
Watershed degradation due to soil erosion and sedimentation is considered to be one of the major environmental problems in Iran. In order to address the critical conditions of watershed degradation in arid and semiarid regions, a study based on the Modified Pacific Southwest Inter-Agency Committee (MPSIAC) model was carried out at Golestan watershed, northeast of Iran. The model information layers comprising nine effective factors in erosion and sedimentation at the watershed site were obtained by digitalization and spatial interpolation of the basic information data in a GIS program. These factors are geology, soil, climate, runoff, topography, land cover, land use, channel, and upland erosion. The source data for the model were obtained from available records on rainfall and river discharge and sediment, topography, land use, geology, and soil maps as well as field surveys and laboratory analysis. The results of the MPSIAC model indicated that 60.75 % (194.4 km2) and 54.97 % (175.9 km2) of the total watershed area were classified in the heavy sedimentation and erosion classes, and the total basin sediment yield and erosion were calculated as 4,171.1 and 17,813.4 m3 km?2 year?1, respectively. In the sensitivity analysis, it was found that the most sensitive parameters of the model in order of importance were topography (slope), land cover and use, runoff, and channel erosion (R 2?=?0.92–0.94), while geology, climate (rainfall), soil, and upland erosion factors were found to have moderate effect to the model output (R 2?=?0.74–0.59).  相似文献   
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