Multi-model weighting approach for future projections of solar radiation, temperature and precipitation under global warming effect in Tehran, Iran
Article Type:
Research/Original Article (دارای رتبه معتبر)
In order to investigate the scope of uncertainty in projections of GCMs for Tehran province, a multi-model projection composed of 15 models is employed. The projected changes in minimum temperature, maximum temperature, precipitation, and solar radiation under the A1B scenario equivalent to RCP4.5 for Tehran province are investigated for 2011-2030, 2046-2065, and 2080-2099. GCM projections for the study region are downscaled by the LARS-WG5 model. In climate change impact assessment studies, due to the influence of different sources of uncertainty on the output of the predicting system, projections do not have sufficient confidence. Therefore, it is recommended that for quantifying the range of uncertainty in the projections, the maximum number of available GCM models be used in simulations. In this regard, 15 GCMs used in this study are a subset of the CMIP4 models  used in the IPCC 4th assessment report published in 2007. All these models are the coupled Atmospheric-Oceanic models and have been run for the 1960-2100 period. Uncertainty among the projections is evaluated from three perspectives: large-scale climate scenarios, downscaled values, and mean decadal changes. 15 GCMs unanimously project an increasing trend in the temperature for the study region. Also, uncertainty in the projections for the summer months is greater than projection uncertainty for other months. The mean absolute surface temperature increase for the three periods is projected to be about 0.8°C, 2.4°C, and 3.8°C in the summers, respectively. The uncertainty of the multi-model projections for precipitation in summer seasons and the radiation in the springs and falls is higher than in other seasons for the study region. Model projections indicate that for the three future periods and relative to their baseline period, springtime precipitation will decrease about 5%, 10%, and 20%, and springtime radiation will increase about 0.5%, 1.5%, and 3%, respectively. The projected mean decadal changes indicate an increase in temperature and radiation and a decrease in precipitation. Furthermore, the performance of the GCMs in simulating the baseline climate by the MOTP method does not indicate any distinct pattern among the GCMs for the study region. The future projection of temperature confirms that Tehran will experience hotter summers in the future compared to the base period. This, together with the increased sunshine in the springs and summers, can increase the frequency of temperature- and radiation-related phenomena such as photochemical pollution and may degrade the future summertime air quality in the study region. Moreover, the projected reduction in winter and spring precipitation, together with increased temperature, may increase the demands in the region.
Iranian Journal of Geophysics, Volume:16 Issue: 4, Winter 2023
19 to 35  
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