Document Type : Research Article

Authors

1 Natural Geography, Climatology, Faculty of Social Sciences, University of Mohaghegh Ardabili, Ardabil, Iran.

2 Department of Climatology, Faculty of Humanities, Mohaghegh Ardabili University Department of Climatology, Faculty of Humanities, Mohaghegh

3 Postdoctoral researcher at the Department of Climatology,, Faculty of Natural Resources, University of Kurdistan

Abstract

Introduction: Heat waves (HWs) are one of the most important climatic disasters that have devastating environmental consequences in nature every year). The purpose of this study is investigation of the effect of heat waves on the intensification of thermal islands in Sanandaj city from 1989 to 2018. The constant rise in temperature of the city as an urban heat island and the sudden occurrence of HW's as one of the major climatic hazards, is an important concern of urban management policy makers; because intensify heat of this city and cause a lot of environmental damage.
Materials and Methods: In order to identify HWs in Sanandaj city, from 1989 to 2018, by using Fumiaki Index and MATLAB software, days whit temperature above +2 standard deviation or above the mean Normalized Thermal Deviation (NTD) that lasted at least two days, were identified as the day with HWs and calculated by equation 1.

(1)

Where, T (i, j, n) is temperature of day ith from month jth in year nth  indicates the average temperature of day i from month j. To eliminate the noise in the mean, a 9-day moving average filter was performed on these data three times and calculated by the following equation.

(2)

Where, ∆T= (i, j, n) indicates absolute deviation of temperature from the average on day jth of the month i th, in year n th compared to the average temperature of the same day. In order to the values of temperature deviation of different times and places to be comparable at a certain time and place, it is necessary to standardize these absolute values of temperature deviation by means of temperature diffraction. Like day-to-day changes, diffuse T∆ at 31 days for each day is calculated by the following equation.

(3)

The value  is the average temperature deviation in 31 days that is calculated by the following equation.

(4)

Finally, (NTD) is calculated by the following equation.

(5)

Where .Then in MATLAB software, days with temperatures +2 above average (NTD) and lasting at least two days, were selected as the day with the HW.

(6)

Then the thermal island was calculated in Sanandaj city using Equation 7.

SUHI= MLSTurban –FLSTrural

(7)

Where, SUHI is the island surface heat index, MLSTurban and FLSTrural are the average surface temperature of urban and rural areas, respectively.
Results and Discussion: The results showed that, during the study period (1989-2008), the highest frequency of HW hazards in this city was in September, February, March, and October 1991. The maximum duration of HWs was 6 days, which occurred in December 2017 and 2005, therefore long-term HWs have been experienced in this city. Results also showed, in both HW and NHW conditions, in the hot and cold months of the year, often a cold island is formed in the city center during the day and a heat island is formed at night. Results also showed that short-time heat waves have been effective in intensifying heat islands. Examination of the intensity of thermal islands in this city showed that during the day in both HW and NHW conditions, which in the HW conditions dominance of the cold island compared to normal day, it has been reduced and in the last months of winter (February), even during the day, a heat island has been created in the center of the city. At night time, in both HW and NHW conditions, a heat island was created in Sanandaj center, but the intensity of night- time heat islands in HW conditions is often significantly higher than normal conditions especially in the winter. Investigation of the condition of thermal islands in the warm months of the year showed that in both HWs, a cold island has been created in the city center that the intensity of cold islands during the HW conditions, especially in the summer months, was often higher than NHW conditions. At night time, there was often a heat island in the city center that was more intense than normal day. Also, in HW conditions, wind speed and especially relative humidity has decreased significantly more than the cold months of the year.
Conclusion: According to the results the highest incidence of HW hazards occurred in the winter and early spring. Also, long-term (6-days) HW occurred in this period. The increasing trend, frequency and continuation of HW, especially in the cold months of the year, can be the effects of climate change and global warming. Severe and continuous HWs occurred in Sanandaj city, especially in late winter, can cause early germination and flowering of crops and gardens and it will negatively affect agriculture and horticulture and will lead to great economic losses. The effects of HWs on heat islands occurred in the suburbs due to having a clear sky without pollution, with minimal vegetation and lack of surface water resources and ground with low heat capacity is affected by HWs faster than the city center and as the land surface around the city becomes warmer than its center, a cold island is formed in the city center. At night, the suburbs due to low heat capacity, lose absorbed heat faster and as a result, the heat island is formed in the city center. In general, the occurrence of heat waves in the intensification of thermal islands in the Sanandaj city, especially in the warm months of the year, has a significant effect, and it is likely to intensify in the coming decades, especially at night during the hot months of the year.

Keywords

Main Subjects

###### ##### References
• Almasi F., Tawoosi T., and Hosseinabadi N. 2016. Analysis of Behavior and Frequency Changes in the Occurrence of Heat Waves in Ahvaz, Journal of Spatial Planning 19: 150-137. (In Persian with English abstract)
• Almusaed A. The Urban Heat Island Phenomenon upon Urban Components. Biophilic and Bioclimatic Architecture 21: 139-150.
• Azizi Gh. 2004. Climate change, Tehran, Ghoms Publishing, first edition, 434.
• Bai L., Gangqiang D., Shaohua G., Peng B., Buda S., Dahe Q., Ramamurthy P., and Bou‐Zeid E. 2017. Heatwaves and urban heat islands: A comparative analysis of multiple cities. Journal of Geophysical Research Atomospheres an. 122: 168-178.
• Basara J., Basara H., Bradley I., and Kenneth C. 2018. The Impact of the Urban Heat Island during an Intense Heat Wave in Oklahoma City. Advances in Meteorology 7: 1-10.
• Ceccherini G., Russo S., Ameztoy I., Patricia R., Claudia C., and Moreno C. 2016. Magnitude and frequency of heat and cold waves in recent decades: the case of South America. Nat. Hazards Earth System 16: 821–831.
• De Ridder K., Maiheu B., Lauwaet D., Daglis I A., Keramitsoglou I., Kourtidis K., Manunta P., and Paganini M. 2016. Urban Heat Island Intensification during Hot Spells-The Case of Paris during the Summer of 2003. Urbanscience 1: 1-11.
• Dobrovolny P., and Krahula L. 2015. The spatial variability of air temperature and nocturnal urban heat island intensity in the city of Brno, Czech Republic, Moravian Geographical Reports 23: 8-16.
• Feng C., Xuchao Y., and Weiping Z. 2014. WRF simulations of urban heat island under hot-weather synoptic conditions: The case study of Hangzhou City, China. Atmospheric Research 138: 364–377.
• Feron R., Sarah R., Cordero P., Alessdro J., Damiani L., Jorquera E., sepulveda V., Asencio Laroze D., Labbe F., Carrasco J., and torres G. 2019, observations and projections of Heat Waves in south Americas. Scientific Reports 9: 1-15.
• Founda D., and Santamouris M. 2017. Synergies between Urban Heat Island and Heat Waves in Athens (Greece), during an extremely hot summer (2012), Scientific Reports 7: 1-16.
• Fujibe F., Yamazaki N., Kobayashi K., and Nakamigawa H. 2007. Long-term changes of temperature extremes and day-to-day variability in Japan, papers in Meterology and Geophysics, IPCC 85: 63-70.
• Fumiaki F., Yamazaki N., Kobayashi K., and Nakamigawa H. 2007. Long-term changes of temperature extremes and day-today variability in Japan, papers in Meterology and Geophysics, 58.
• Ghasemifar E., and Naserpour S. 2019. Synoptic analysis of heat and cold waves on the southern shores of the Caspian Sea, Journal of Geographical Information (Sepehr) 103: 146-137. (In Persian with English abstract)
• Ghavidel F. 2014. Identification, classification and synoptic analysis of heat waves in northwest of Iran, M.Sc. Thesis, University of Tabriz, Supervisor: Saeed Jahanbakhsh. (In Persian with English abstract)
• Ghobadi A., Khosravi M., and Tavousi T. 2017. Surveying of Heat waves Impact on the Urban Heat Islands: Case study, the Karaj City in Iran. Urban Climate 10: 1-16.(In Persian with English abstract)
• Hoshyar M., Sobhani B., and Hoseyni S.A. 2018. Perspective Changes Maximum Temperatior Urmia Using Disposition Statistics Contact CanESM2 Model, Journal of Geography and Planning 63: 325-305. (In Persian with English abstract)
• Hosseini A. 2016. Assessment of Urban Heat Island based on the relationship between land surface temperature and Land Use/Land Cover in Tehran, Sustainable Cities and Society 23: 94-104.(In Persian with English abstract)
• https://search.earthdata.nasa.gov/.
• Ismail Nejad M., Khosravi M., Alijani B., and Masoudian A. 2013. Identification heat waves of Iran, Geography and Development 3: 39-54. (In Persian with English abstract)
• Karampoor M., Rafiyi J., and Jafari A. 2017. Synoptic identification and analysis of heat waves in western Iran (Ilam, Khuzestan, Lorestan, Kermanshah), Environmental Hazard Management (former hazard knowledge) 3: 263-279. (In Persian with English abstract)
• Kashki A., Karami M., Baaghideh M., and Ali Moradi M.R. 2019. Statistical analysis of Zabul heat waves, Changes and Weather Hazards 1: 40-55. (In Persian with English abstract)
• Khandelwal S., Goyal R., Kaul N., and Mathew A. 2017. Assessment of land surface temperature variation due to change in elevation of area surrounding Jaipur, India. The Egyptian Journal of Remote Sensing and Space Science 21: 1-8.
• Lazzarini M., Marpu P.R., and Ghedira H. 2013. Temperature-land cover interactions: the inversion of urban heat island phenomenon in desert city areas. Remote Sensing of Environment 130: 136-152.
• Lemonsu A., Viguié V., Daniel M., and Masson V. 2015. Vulnerability to heat waves: Impact of urban expansion scenarios on urban heat island and heat stress in Paris (France). Urban Climate 14: 586–605.
• Meteorological Organization of Iran .http: //www.irimo.ir.
• Mojarad F., Nasiriyah M., and Hashemi S. 2018. Investigation of periodic and seasonal changes of day and night heat island in Kermanshah City using satellite images, Earth and Space Physics 44: 479-494. (In Persian with English abstract)
• Muhire I., and Ahmed F. 2016. Spatiotemporal trends in mean temperatures and aridity index over Rwanda. Theoretical and Applied Climatology 123: 399-414.
• Omidvar K., Mahmoud Abadi M., Olfati S., and Moradi Kh. 2016. Investigation of the possibility of heat waves in selected stations of Kermanshah province, Journal of Environmental Hazards 10: 1-20. (In Persian with English abstract)
• Paravantis J., Santamouris M., Constantinos C., Efthymiou, and Kontoulis N. 2017. Mortality Associated with High Ambient Temperatures Heat waves, and the Urban Heat Island in Athens, Greece, June 2013, Sustainability .1-22.
• Rahimi D., Mir Hashemi H., and Alizadeh T. 2016. Analysis of heat waves structure in the west and northwest of Iran, Geography and Environmental Planning 3: 69-80. (In Persian with English abstract)
• Ramamurthy P., and Bou‐Zeid E. 2017. Heatwaves and urban heat islands: A comparative analysis of multiple cities. Journal of Geophysical Research: Atmospheres 1: 168-178.
• Rohini P., Pajeevan M., and Mukhopahay P. 2019. Future projections of heat waves over India from CMIP5 models, Climate Dynamics53: 975–988.
• Solomon S., Qin D., Manning M., Chen M., and Marquis K.B, IPCC. 2007.
• Sadeghi H., Aghighi M.A., and Suri D. 2017. Investigation of the occurrence of the phenomenon of urban thermal islands using Aster satellite images (Study area: Shiraz city), Third International Conference on Research in Engineering Sciences, 9th of September. (In Persian with English abstract)
• Tan J., Zheng Y., Tang X., Guo C., Li Li., Song Y.,Kalkstein A.J., and Furong Li. 2010. The Urban heat island and its impact on heat waves and human health in shanghai. International Journal of Biometeorology 54: 75-84.
• Weihe Z., Shuang Ji., Tsun-Hsuan Ch., Hou Y., and Zhang K. 2014. The 2011 heat wave in Greater Houston: Effects of land use on temperature. Environmental Research 135: 81–87.
• Wilks D. 2006. Statistical Methods in the Atmospheric Sciences, Second Edition, Academic Press is an imprint of Elsevier, Cornell University USA,Volume 100 3rd Edition: 706.
• Zhou B., Lauwaet D., Hooyberghs H., De Ridder K., Kropp J.B., and Rybski D. 2016. Assessing Seasonality in the Surface Urban Heat Island of London, Journal of Applied Meteorology and Climatology 55: 493-505.