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Climate change is known as one of the key challenges of the 21st century for sustainable agricultural development over Southwest Asia. However, not much is known about the way that climate changes might affect precipitation, temperature, and climate zones as their consequence over Southwest Asia. Here we have analysed probable changes in modified Thornthwaite climate zones by using monthly temperature and precipitation data from 320 meteorological stations during the historical period of 1971–2015, as well as the future projections of 17 GCMs (General Circulation Models) outputs under the RCP4.5 and RCP8.5 scenarios in two future periods, 2041–2070 and 2071–2100. The CMIP5 climate projections were bias corrected using the correction factors derived in the historical period and applied to simulate future climatic conditions over Southwest Asia. Results derived from multi model ensemble projections of precipitation and temperature indicated that the regional mean annual temperature by the future period of 2071–2100 is expected to increase by 2.4 and 3.8°C, under RCP4.5 and RCP8.5, respectively. Also, except for the southern and eastern parts of the Arabian Peninsula, by 2071–2100, the mean annual precipitation would significantly decrease by on average 6.2 and 7.5%, under RCP4.5 and RCP8.5, respectively. Computing climate types based on averages from three climatic periods (1971–2015, 2041–2070, and 2071–2100) showed that Southwest Asia tends to become warmer and dryer. For example, by the end of the 21st century, the percentage of the area occupied by the torrid‐arid climate type (which already covers 13.8% of the total area) would be 29.3 and 36.4% under RCP4.5 and RCP8.5, respectively. These changes are important because they would definitely have profound ecological, hydrologic, and social consequences and may affect the basic components of sustainable agricultural systems like crop and livestock productions. [ABSTRACT FROM AUTHOR]

One of the most important goals of synoptic climatology is to analyse the relationships between atmospheric circulation and surface environmental conditions. Since manual (subjective) classification might reflect differently environmental phenomena as compared to computer assisted (semi-objective) classification, a comparison between both classifications was performed for the Eastern Mediterranean (EM) for 10 years. The overall frequencies of the 19 recurring synoptic types characterising the circulation regime over the EM are similar for both methods (correlation coefficient = 0.96, p-value < 0.0001). Nevertheless, comparing the classifications on a day-to-day basis for the three most common types showed a large degree of disagreement between the two. For synoptic types with a deep horizontal pressure gradient both classifications yielded the highest agreement (over 50%), improving the consistency between both classifications. Yarnal's (1993) 'environment-to-circulation' approach was tested on three surface environment processes: air pollutants, desert dust intrusions, and flash floods. Our results indicate that the weak pressure gradients associated with high ozone levels make the classification more difficult for both methods. Regarding dust outbreaks, classifications point on the importance of the cold cyclone location rather than its pressure gradient. As for flash floods, the flow pattern at the surface level is insufficient to predict atmospheric conditions prone for their occurrence, suggesting that upper air data is an essential factor for determining such highly convective events. Finally, two new approaches to evaluate the quality of classifications are presented, demonstrated on two frequent circulation systems persisting over the EM. A qualitative approach compares the composite mean sea level pressure maps from each classification, while a quantitative approach compares the resultant winds at a central site. This study demonstrates that comparing different synoptic classification methodologies and different environmental applications can lead to additional and valuable insights on the interaction between the environment and synoptic-scale circulation. Copyright © 2011 Royal Meteorological Society [ABSTRACT FROM AUTHOR]