The Impact Of Urbanization On Extreme Temperature Events

In recent decades,the rapid economic development of Shandong province promote the expansion of urban scale,making the original nature of the underlying surface change,will eventually appear the phenomenon of urban heat island.Temperature observation data is an important basic data in the study of extreme temperature events,but it is inevitably affected by urbanization,so accurately monitor the change of extreme temperature events must consider the influence of the rapid development of urbanization.Taking Shandong province as an example,this study explore the analysis of the effect of urbanization on extreme temperature events,find out the rapid development of urbanization on the change of extreme temperature events which aspects have an impact,and how impact.According to the observation data of temperature and the urbanization index statistics in Shandong province,comprehensive utilization of population data grid,land use,and night lights divide the urban and rural stations.The methods of comparative analysis of basing on the observation data were used to study the influence of urbanization on extreme temperature events in Shandong province.The research mainly includes the spatial and temporal variation characteristics of extreme temperature events and the impact of urbanization on extreme temperature events.The research of the temporal-spatial variation of extreme temperature in the first part show that:(1)the average,highest and lowest temperature in Shandong province show obvious increasing trend in the past 45 years.Among them,the rising trend of the lowest temperature is the most significant.The climate change in Shandong province is mainly reflected in the contribution of the lowest temperature rise.(2)In regard to temporal characters of extreme temperature events,the size and direction of the trend of cold and warm indexes show obvious asymmetry.Warm indexes show obvious increasing trend,while cold indexes show obvious decreasing trend.The abrupt changes of extreme temperature indexes and temperature has good synchronicity,both in the late 1980 s and early 90 s.This suggests that the change of extreme temperature index is closely linked to regional warming.Cold and warm indexes showed inter-annual scale fluctuation of quasi 2 years and 5-7 years,as well as inter-decadal scale fluctuation of quasi 10-15 years and 21-28 years.(3)In regard to spatial characters of extreme temperature events,except the high temperature days(high value centers in the west),the high value centers of warm days and warm nights are in the eastern coastal areas of Shandong province,while the high value center of the cold index is located in the western part of Shandong province.The warm(cold)indexes show consistent increasing(decreasing)trend over the study area.The variation trend of the eastern and central region is larger and the variation trend of the western region is smaller on the whole,except the high temperature days.The research of the impact of urbanization on extreme temperature events in the second part show that:(1)under the push of urbanization,warm events(except the warm night days)increase,while cold events decrease;At the same time,contribution of urbanization impact of warm events(except the warm night stays)is greater than the cold events;In addition,contribution of urbanization impact of extreme temperature indices calculated by the highest temperature is greater.(2)Urbanization will prompt an average field intensity of warm extreme events more strength.The scope of the equal strength warm events is more widely than before,but the intensity and scope of cold events contrary to the performance of warm events under the influence of urbanization;Urbanization prompt the space difference of average field distribution of extreme temperature warm and cold events more significant than before.(3)Urbanization will lead to the mutation time of extreme temperature indexes 1 to 3 years earlier.(4)Urbanization will affect the duration of extreme temperature events,especially the influence of the index duration associated with the highest temperature is great.(5)The asymmetrical influence of urbanization between extreme temperature indexes is complex and diversity.In this study,the effects of urbanization on extreme temperature events in Shandong Province are systematically analyzed.Under the influence of urbanization,the occurrence frequency of extreme temperature events in different regions has both generality and regional difference.For fully realizing the extreme temperature events on the impact of urbanization and regional differences,should be widely carried out in different areas of research,for comparison to draw on the impact of urbanization on extreme temperature events in each region of the commonness and characteristics.In theory,this study deepens the understanding of the change of extreme temperature events in the region and the impact of urbanization.In practice,in the process of urbanization,scientific planning layout and avoiding the disasters caused by extreme temperature weather have important reference value.