Characteristics Of Urban Heat Island And The Influence Of Its Urbanization In Yinchuan City From 1960 To 2015

The city is a symbol of human civilization and the most active places for the earth's surface material,energy and information exchange.Because of the incomplete and fragile of the city environment system,the most intense place for human intervention in the natural environment is also the city.The urban heat island effect is a significant consequence of urbanization and has intensified with the increase of the urbanization,as well as it has been one of the most important problems in urban ecology because of its adverse effects on urban climate and urban ecological environment,however,the extensive research on the urban heat island has been confined to the big cities in the central and eastern China,while the study of arid oasis city is relatively lacking attention.Yinchuan city,as the most developed oasis city of Hetao plain oasis,the urbanization showed the regional characteristics of northwest arid region oasis city owe to the unique natural geographical environment.However,studies on the urban heat island in Yinchuan city only based on few remote sensing data to inversion of the land surface temperature or brightness temperature,but relatively few of the research on the urban heat island of Yinchuan city that based on the meteorological observation of conventional data,whether the existence of the"urban heat island"or oasis"cold island effect",characterized by how,and how does urbanization affect the heat island effect?Are not clear,it is a scientific question worthy to explore.Therefore,this study based on the daily mean temperature in the Yinchuan station,Helan station and Yongning station from 1960 to 2015 to analyze the temporal characteristics of urban heat island in Yinchuan city(In this paper,?T_yh represents the average heat island intensity in Yinchuan city compared with Helan county,and?T_yy represents the average heat island intensity in Yinchuan city compared with Yongning county).Combined the remote sensing data of Landsat TM/ETM⁺and Landsat 8 TIRS that obtained from 1989,1995,2000,2005,2010 and2015,through further applied the computer visual interpretation of remote sensing image to get the expansion of urban built-up area,land-use types in Yinchuan city and combined with the social and economic statistics to explore the impact of urbanization on heat island effect from the aspects of urban construction area expansion,LUCC,urban population growth,urban road traffic development and energy consumption increase in Yinchuan city.The main conclusions are as follows:?1?From the time point of view,the annual average heat island intensity of the?T_yh showed an increasing trend at the rate of 0.06?/decade and the?T_yy showed a decreasing trend at the rate of 0.05?/decade from 1960 to 2015.The annual average urban heat island intensity are 0.24?and-0.01?,respectively.Additionally,the seasonal heat island intensity of?T_yh in winter showed the maximum while the minimum in summer,however,?T_yy showed the opposite exactly.Moreover,the maximum temperature heat island intensity of the?T_yh and the?T_yy showed"coldification phenomenon"obviously,while the minimum temperature heat island intensity of the?T_yh and?T_yy are greater than the heat island intensity of maximum temperature and average temperature,the heat island phenomenon is significant.?2?With the rapid development of urbanization in Yinchuan city,the contribution of urbanization on the heat island effect is more and more significant,the urban expansion area reached 165.02km²,expansion speed was 6.35km²/a,expansion intensity was 9.82%and the urban center of gravity shifted to the northeast in Yinchuan city,it has promoted?T_yh significantly from 1989 to 2015.While the rapid urban expansion in Yinchuan significant enhancement effect on the heat island intensity?T_yy only in 1989-2006,however,the rapid expansion of the built area in Yongning county play a certain weakened effect on?T_yy even lead to"cold island"phenomenon after 2006.Additionally,the migration of Yinchuan station,Helan station and Yongning station have a significant influence on the change of urban heat island in Yinchuan city in the 21st century.?3?LUCC research showed that the contribution of land use/land cover to the urban heat island effect in Yinchuan city is significant.The construction land showed the maximum relative change rate of 233%,it contributed the most to the heat island effect in Yinchuan city.The construction land area increased by 188.27km² and the cultivated land area decreased by 202.49km² significantly in Yinchuan city from 1989to 2015,which was exacerbated the?T_yh in 1989-2015 and the?T_yy in 1989-2006significantly.However,the construction land area increased by 56.85km² in Yongning county and the relative change rate of construction land is higher than that of Yinchuan city in the same period of 11%after 2006,so that the rapid development of urbanization in Yongning county contributed to the decreasing of?T_yy from 2006 to2015.Additionally,the increase of forest area and water area in Yinchuan city had alleviated the heat island effect to a certain extent.?4?From the relationship between the average heat island intensity and population in Yinchuan city,the urban resident population increased significantly and the inclination rate is 23.74×10⁴ people/10a,and the tendency rate of urban population density is 65.08?people/km²?/10a.The rapid increases of urban population has led to a significant increase in the release anthropogenic heat and then have an impact on the heat island effect in Yinchuan city in recent 56 years.In addition,there is a closely relationship between the urban heat island intensity and the rapid increase of the urban road area,the urban road length,the electricity consumption of the urban residents,the energy consumption of whole society and the finished area of various types of houses in Yinchuan city from 1984 to 2015,which has promoted the urban heat island effect of Yinchuan city to a certain extent and more significant especially after the 21st century.