Sima Rahimi Bondarabadi; Saeed Jahanbakhsh; Behrooz Sari Saraf
Abstract
Any change in the concentration of greenhouse gases will upset the balance between the components of the climate system. But, the change in the concentration of these gases and how they will affect in the future is unknown. To study the effects of climate change on different systems in the future, climate ...
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Any change in the concentration of greenhouse gases will upset the balance between the components of the climate system. But, the change in the concentration of these gases and how they will affect in the future is unknown. To study the effects of climate change on different systems in the future, climate variables must first be simulated under changes in greenhouse gases (climate scenarios). There are several ways to do this, the most reliable of which is the use of climatic models. AOGCMs can simulate climate parameters globally in large scale, while these may not be suitable for small scales. One of the most important downscaling methods is dynamic methods that are based on increasing the resolution and analysis of planetary climate models. Here, in this research, climate change status in Karkheh River Basin where a major basin for water and agricultural yields is studied. For this purpose, the PRECIS model was used. PRECIS is an exponential dynamics downscaling model used to estimate the temperature and precipitation rates for the period of 2070 to 2100 under A2 and B2 scenarios. According to the results of climate change assessment under scenario A2, precipitation would increase up to 11% and up to five degree centigrade would rise in average maximum and minimum temperature while concerning B2 scenario, an increase in precipitation up to 7% and a rise in temperature rise up to three degree centigrade are estimated. However, under both the scenarios, despite, the fall’s precipitation is higher than the winter’s precipitation.
sima rahimi bondarabadi
Abstract
The increase of greenhouse gases caused imbalance in the amount of air and water in the Earth, which called climate changed. Increasing the greenhouse gases not only impact on the weather parameters, but also impact on water resources, agriculture, environment, health and the economy as well. For the ...
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The increase of greenhouse gases caused imbalance in the amount of air and water in the Earth, which called climate changed. Increasing the greenhouse gases not only impact on the weather parameters, but also impact on water resources, agriculture, environment, health and the economy as well. For the effects of climate change on different systems in the future, first the climatic variables which are affected under the greenhouse gases should be simulated (different climate scenarios). There are several simulation methods where the climate model methods are most suitable. The AOGCM model is able to simulate global climate in large scale, while not suitable for small and regional scale. So, it is necessary to identify the variations (climate) in small scale. For this reasons it is necessary to use the downscaling methods such as dynamic methods which are based on high resolution and analysis of climate models. This method is suitable and appropriate for Iran since it suffers from lacks of observed data as well as lack of long term and enough stations in the country. In this study, PRECIS model (a dynamical downscaling climate model) was evaluated for simulation of precipitation and temperature. In general, the results of PRECIS model indicate this model can be a good estimate of temperature and precipitation in the region. Although for the rainfall in autumn and spring, due to the local nature of the precipitation, the model is not very strong. Also, comparison of spatial and point evaluation of the model showed that areal evaluation is appropriate as opposed to a point.
Saeed Jahanbakhsh; Behrouz Sari Sarraf; Abdolmohammad Ghafouri Roozbahani; Sima Rahimi Bandarabadi
Abstract
Hydrologic drought can be studied in different ways. One of the common methods is the use of low flow indexes. In this study for the purpose of determine of the identity of aspects of low flow, the homogenous zones, the extraction of regional regression models, and finally, the study of low flow trends ...
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Hydrologic drought can be studied in different ways. One of the common methods is the use of low flow indexes. In this study for the purpose of determine of the identity of aspects of low flow, the homogenous zones, the extraction of regional regression models, and finally, the study of low flow trends of Karkheh river basin, applied the data of 13 hydrometric stations during the statistical period of 1960-2000. After qualitative and quantitative controlling and the retrieval of missing data used flow duration curves for indexes such as Q75, Q90 and Q95. Also frequency analysis of 10-day, and 20-day low flows was carried out for indexes such as Q10,5, Q10,50, Q10,100, Q30,5, Q30,50, Q30,100 and some more indexes. Afterwards, some other factors like physiographic, climatic, geologic and vegetation cover were applied as influential parameters in the regional analysis. These factors were used in cluster analysis and stepwise regression estimations. Final step was the trend analysis of times series of the indexes. Results indicate that among the indexes being calculated, Q10,100 and Q95 had the minimum quantities, whose amounts reduced as the return periods increased. On the hand, the time spans of 1998-1999, 1999-2000, 2000-2001 have undergone severe and long droughts in most of the stations. The review of the spatial distribution of indexes show better conditions of the south-eastern parts of the study area compared to the northern and southern sections in terms of dryness. Results of cluster analysis divided the area into two distinct homogenous units (in 0.01 significant level). In the area No. 1, the elevation factor, in the area No. 2, the drainage density, and in general, the factors such as the mean of area and drainage density have the highest effects. The Spearman statistic, and Mann-Kendall findings also indicate that the low flow in upper basin have negative trend during the statistical period.