| With the continuous improvement of China’s economic strength,accelerating the process of urbanization,rapid urbanization process makes people’s living standards continue to improve,but also with a series of urban ecological problems,urban heat island is one of the most serious urban ecological problems.How to alleviate the serious urban ecological problems brought by urban heat island has become a difficult problem to be solved urgently by academia and governments.The study of urban heat island effect has also become a hot topic.It is an important influencing factor of urban microclimate,Cognition of its formation process,spatial characteristics and temporal and spatial changes will not only help people to understand the local urban microclimate,but also help to explore the measures to alleviate the urban heat island effect,for the future urban planning to provide an indispensable reference value.Lanzhou City,as a typical valley-type city,its special valley-type fall basin characteristics make Lanzhou city boundary layer structure and surface heat radiation energy balance than other plain city is very different,it is a heavy industry polluted city,special Industrial development process,resulting in unreasonable industrial structure layout,industrial space and urban planning has not been able to achieve a healthy interaction,so that the urban ecological problems in Lanzhou City is more serious,so for the city of Lanzhou city heat island effect research,help to put forward Effective urban ecological management measures to improve the daily living environment of the people has immeasurable value,Lanzhou City,scientific and rational industrial layout and urban planning has important reference value.In this paper,the main urban area of Lanzhou City is studied,and the characteristics of urban heat island evolution in Lanzhou City from 1994 to 2015 are studied by means of remote sensing,geographic information spatial analysis and landscape ecology.Quantitative analysis of surface temperature and urban And the seasonal distribution of urban heat island in Lanzhou City was studied on the basis of Landsat8 remote sensing data,and the following conclusions were obtained:(1)Lanzhou City heat island area mainly to secondary heat island,and the fastest expansion rate for the strong heat island,heat island expansion direction and urban land extension direction;heat island evolution process for the heat island → heat island → normal area → green island → cold island,the reverse process is to the opposite direction of gradual evolution,the possibility of leapfrog change is relatively small,strong heat island for the city’s underlying surface changes are most sensitive.The urban heat island effect was positively correlated with soil moisture index(NDMI),enhanced water index(EWI)and soil brightness index(NDSI),and negatively correlated with the modified soil regulation index(MSAVI).(2)The order of the urban heat island effect in Lanzhou is the spring season> summer> winter> autumn,in which the distribution of the thermal field in the urban surface is the most complex.In addition to the winter,the distribution of the urban heat island in the other three seasons Which shows that the low temperature zone of the Yellow River is an important factor affecting the distribution of thermal environment in the valley in these three seasons.Based on the transition probability matrix method in the landscape ecology of the landscape ecology,the most stable heat patches in the seasons are found in the normal area,but once the change is made,the possibility of changing to the heat island is greater than that of the heat The transition to the cold island and the green island,the second heat island and the strong heat island to the four seasons change in the spring to summer weakened,weakened from summer to autumn,autumn to winter to enhance.(3)The spatial distribution of surface temperature is closely related to the structure of the underlying bedding layer.The more the coverage of the underlying surface layer is,the more the degree of the surface temperature profile is fluctuating,the more uneven the surface temperature,the urban heat island intensity The bigger ones.Small greenhouses,botanical gardens and other vegetation coverage are high places where varying degrees of low temperature areas,improve the greening rate of urban vegetation can effectively reduce the urban heat island effect,in addition,in the Golden Harbor such a residential area also appeared in the low temperature area,The planning layout can also alleviate the urban heat island effect to a certain extent.(4)Lanzhou city expansion is more significant,its main expansion direction is gradually from Chengguan District to Xigu District,Anning District extension,showing the expansion from west to east trend,from 1994 to 2004,urban land Chengguan District to Yantan Expansion,the main extension of the main area is mainly to Chengguan District,scattered sporadic distributed expansion,and from 2004 to 2015,its main to the Qilihe District,Anning District,high-paying development zones and Xigu District direction expansion,expansion of the way Was a large area contiguous expansion.The spatial distribution of different heat islands in different years is basically the same as that of urban land distribution.The expansion of urban heat island distribution is the same as that of urban land,which is mainly due to the change of urban land,so that the original natural surface is A large number of artificial surface replacement,resulting in enhanced urban heat island effect,indicating that the characteristics of urban structure of the underlying surface of the city heat island play a decisive role.Lanzhou City,mainly to enhance the heat island mainly heat island,Lanzhou City,the growing heat island effect. |
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