اثر تغییر اقلیم بر امواج گرمایی سواحل شمالی خلیج‌فارس

Climate change is one of the most significant threats facing the world today. One of the most important consequences of climate change is increasing frequency of climate hazards, mainly heat waves. This phenomena has a robust impacts on human and other ecosystems. The aim of this study is investigating changes of heat waves in historical (1980-2014) and projected (2040-2074) data in northern cost of Persian Gulf. The focus here is on Mean daily maximum temperature and Fujibe index to extract heat waves. For this purpose 6 weather stations locating in north coast of Persian Gulf, Iran, are used (table 1). Table1: weather stations Station Latitude Longitude Elevation(m) Abadan 30° 22' N 48° 20' E 6.6 Boushehr 28° 55' N 50° 55' E 9 Bandarabbas 27° 15' N 56° 15' E 9.8 Bandarlengeh 26° 35' N 54° 58' E 22.7 Kish 26° 54' N 53° 54' E 30   In addition, 4 model ensemble outputs from the Coupled Model Intercomparison Project Phase 5 (CMIP5) are used to project future occurrence and severity of heat waves (2040 to 2070), under Representative Concentration Pathways 8.5 (RCP8.5), adopted by the Intergovernmental Panel on Climate Change for its Fifth Assessment Report (AR5) (table 2). Table2: List of the AR5 CMIP5 Used Models Model Modeling Cener Country CanESM2 Canadian Earth System Model Canada MPI-ESM-MR Max-Planck-Institut für Meteorologie Germany CSIRO-Mk3-6-0 Commonwealth Scientific and Industrial Research Organization Australia CMCC-CESM         CMCC Carbon Earth System Model Italy The output of models is downscaled using artificial neural network method (ANN). A feed-forward network of multi-layer perceptron with an input layer, a hidden layer and an output layer is used for this purpose. 73 percent (1980 – 2000) of the data is used for training and 27 percent (2000-2005) for testing ANN models. Root Mean Square Error (RMSE) is used as an indicator of the accuracy of Models. RMSE= Here   is the outputs of ANN models (downscaled data) and is the observation data. Fujibe et all (2007) used an index based on Normalized Thermal Deviation (NTD) for extracting long-term changes of temperature extremes and day to day variability using following equations: Where N is the number of days in the summation except missing values. Then nine-day running average was applied three times in order to filter out day-to-day irregularities. =(i,j,n)=T(i,j,n)-T(I,j) The departure from the climatic mean is given by = If NTD >2 and at least lasts for 2 days it determine as a heat wave. Results Table 3 shows the results of downscaling selected GCM models. nodes RMSE Average RMSE Sigmoid function Linear function Abadan Bushehr Bandarabbas Bandar-e-Lengeh Kish CanESM2 5 1 9.6 6.1 4.85 4.7 4.5 5.97 MPI-ESM-MR 5 1 9.3 7.1 3.9 5 4.3 5.9 CSIRO-MK3-6-0 15 1 8.8 5.6 3.6 3.4 3.6 5 CMCC-CESM 10 1 9.2 5.8 3.9 4.7 3.9 5.5 Table 4 compares the frequency of heat waves for GCMs and historical data. CanESM2 MPI-ESM-MR CSIRO-Mk3-6-0 CMCC-CESM Historical data Abadan 434 401 448 387 430 Bushehr 376 423 420 406 407 Bandarabbas 441 405 457 382 410 Bandar-e-Lengeh 380 414 388 401 400 Kish 421 442 415 442 399 For historical data, heat waves are more frequent in Abadan station than other stations. There is an increasing trend in the occurrence of heat waves in historical data and monthly frequency of heat waves show the highest amounts for summer. For both historical and future data 2 days listening heat waves are more frequent. Table 5 shows seasonal changes of heat waves for historical data and GCMs. season The ratio of heat waves from total historical data (percent) The ratio of heat waves from total projected data (percent) Abadan Spring 30.43 24.02 Summer 29.19 27.87 Autumn 17.39 22.61 Winter 22.98 25.48 Bushehr Spring 21.42 24.23 Summer 25 26.21 Autumn 28.57 24.82 Winter 24 25.32 Bandarabbas Spring 21.73 24.7 Summer 26.81 27.01 Autumn 25.81 25.17 Winter 24.1 24.63 Bandar-e-Lengeh Spring 23.55 23.74 Summer 23.33 29.82 Autumn 23.74 25.81 Winter 25.17 20.8 Kish Spring 24.27 24.8 Summer 25.53       28.32 Autumn 23.35 25.21 Winter 23.1 23.8 In recent years the frequency of heat waves is increasing in all studied stations. Coincide with Russia and Europe, the highest amounts of heat waves is occurred in 2010 in northern coast of Persian Gulf and this is adopted Esmaeilnezhad et all (2013), Gavidel (2015) and Azizi (2011).