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991.
Drought is a complex phenomenon in meteorology and can affect agriculture. Its impacts vary greatly since they depend not only on the magnitude, timing, duration, and frequency of rainfall deficits but also on the differing responses of various plants to water stress. The essence of good drought management is to use this range of responses to the best advantage. Iran is one of the world’s largest and most productive suppliers of food and fiber. The objective of this study was, therefore, to gather and analyze standardized information on the Role of Early Warning Systems for Sustainable Agriculture for cereals and leguminous and industrial crops in Iran environmental zones. Annual average rainfall (mm year?1) and ETO (mm year?1) are 76.56 and 3001, respectively, in stations with very dry climate; 195.41 and 2249, respectively, in stations with dry climate; 343.9 and 1351, respectively, in stations with semi-dry climate; 583.8 and 1153, respectively, in stations with semi-humid climate; and 1272 and 949, respectively, in stations with humid climate. The maximum and minimum of annual average rainfall happened in Rasht (1337 mm year?1) and Zabol (57 mm year?1) stations, and the maximum and minimum for annual average ETO happened in Chabahar (3909.15 mm year?1) and Anzali harbor (890.6 mm year?1), respectively. Therefore, 13.63 % of stations have suitable conditions for crop productions and 86.37 % are in critical conditions.  相似文献   
992.
模糊证据权方法在镇沅(老王寨)地区金矿资源评价中的应用   总被引:11,自引:0,他引:11  
成秋明  陈志军 《地球科学》2007,32(2):175-184
采用模糊证据权方法和GeoDASGIS技术开展了镇沅(老王寨)及其邻区的金矿资源潜力评价.分别采用GeoDASGIS软件提供的局部奇异性分析技术、S-A异常分解技术、主成分分析技术、证据权、模糊证据权等技术对相关地球化学元素进行了系统的处理和分析.应用主成分分析方法确定了可能的2种不同成矿类型,并采用主成分得分确定了组合异常点,在此基础上分别采用普通证据权和模糊证据权方法编制了成矿后验概率图,圈定了有利成矿地段.对比普通证据权方法与模糊证据权方法所得结果表明,模糊证据权方法可减小图层离散化造成的有用信息损失,提高预测结果精度.  相似文献   
993.
This study records length-weight relationships(LWRs)for eleven commercially important marine catfi sh species of the family Ariidae(sea catfi shes)and Plotosidae(eel catfi shes)from the northern Arabian Sea coast of Pakistan.The specimens were sampled from December 2014 to November 2015,using bottom trawls with various mesh sizes by commercial vessels.The species were Nemapteryx caelatus,Sciades sona,Arius gagora,Batrachocephalus mino,Netuma thalassina,N.bilineata,Osteogeneiosus militaris,Plicofollis dussumieri,P.tenuispinis,Plotosus limbatus,and P.lineatus.Of the eleven species,two species A.gagora and N.bilineata were recorded for the fi rst time and LWRs for four species A.gagora,N.bilineata,S.sona,and B.mino still have no data in the Fish Base database.In addition,new maximum length for each of the three species N.bilineata,O.militaris and B.m ino was also found.  相似文献   
994.
The occurrence of the genus Aquilapollenites in Upper Cretaceous and Neogene sediments of northwestern Pakistan is reported here. Aquilapollenites amplus, Aquilapollenites reductus, and Aquilapollenites sp. occur in the Maastrichtian palynomorph assemblage from an outcrop sample of the Mir Ali section, northern Waziristan. Aquilapollenites medeis in the Neogene Murgha Faqir Zai Formation of the Pishin Basin, Balochistan, is considered a reworked Cretaceous specimen. The Upper Cretaceous sediments of the Asian plate on the Tethys margin are considered to be the source of Aquilapollenites spp. in these samples.  相似文献   
995.
The development of location-aware technologies, such as smartphones, raises serious questions regarding locational privacy and the ethical use of geographic data. The degree to which these concepts are taught in undergraduate geographic information science (GISci) courses is unknown. A survey of GISci educators shows that issues of privacy and ethics are important in a GISci education. However, a large proportion of GISci educators are not concerned about the loss of locational privacy and many do not devote classes to the subject. Those not teaching the subject cite lack of course time and the need for more information.  相似文献   
996.
Concentrations of Fe, Mn, Zn, Cu, Pb, Ni, and Cd were measured in several species and genera of Recent benthic foraminifera from three coastal lagoons, namely Abu-Shaar, Umm al-Huwaytat, and Marsa Shuni lagoons located along the Egyptian Red Sea coast. Spatially significant differences in the metal concentrations of benthic foraminifera were recorded among different sites. However, some foraminiferal species display deformation in their coiling, general shape of chambers and the apertures. Abu-Shaar and Umm al-Huwaytat lagoons are virtually influenced by anthropogenic activities while Marsa Shuni lagoon is affected by natural inputs. Benthic foraminifer shows high concentrations of Fe and Mn, especially in Umm al-Huwaytat lagoon. Foraminiferal black tests support this result and reflect selectivity for iron absorption. Among the metals analyzed, Cd, Pb, and Cu showed significant high concentrations in benthic foraminifera at the study areas. The anthropogenic activities and natural inputs are responsible for the abnormalities in benthic foraminifera. Therefore, benthic foraminifera can be used as a good indicator of the environmental changes.  相似文献   
997.
This paper examines the potential for the use of artificial neural networks (ANNs) to estimate the reference crop evapotranspiration (ET0) based on air temperature data under humid subtropical conditions on the southern coast of the Caspian Sea situated in the north of Iran. The input variables for the networks were the maximum and minimum air temperature and extraterrestrial radiation. The temperature data were obtained from eight meteorological stations with a range of latitude, longitude, and elevation throughout the study area. A comparison of the estimates provided by the ANNs and by Hargreaves equation was also conducted. The FAO-56 Penman–Monteith model was used as a reference model for assessing the performance of the two approaches. The results of this study showed that ANNs using air temperature data successfully estimated the daily ET0 and that the ANNs with an R 2 of 0.95 and a root mean square error (RMSE) of 0.41 mm day?1 simulated ET0 better than the Hargreaves equation, which had an R 2 of 0.91 and a RMSE of 0.51 mm day?1.  相似文献   
998.
Developed is a scheme of the long-range forest fire danger (FD) forecasting based on the computation of the Nesterov??s index and on hydrodynamic forecasts of air temperature and precipitation of the SLAV model. The satellite information on the climatic distribution of the snow cover was taken into account for the forecast issuance. It is proposed to express the FD index not using traditional classes of fire danger but in ??above the norm,?? ??norm,?? and ??below the norm?? gradations. Presented are the results of author??s trials of the method based on the retrospective model data for six years. Discussed are the approaches to the improvement of the method of long-range fire danger forecasting.  相似文献   
999.
Multimodel forecast fields of temperature at 850 hPa and seasonal precipitation are combined using a procedure of two-step averaging. It is shown that the resulting forecasts averaged over the multimodel ensemble outperform the forecasts of individual models. The verification of forecast production has been carried out on cross-validated hindcasts according to WMO requirements. The simulation of spatiotemporal variability of atmospheric variables is assessed. The results indicate that the combined models are rather skillful in the tropical oceans, while the accuracy in the extratropics is poor.  相似文献   
1000.
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