| The city is the most concentrated geographical space for production of humanlife and achievements of civilization, as well as the most active places for the earth’ssurface material, energy and information exchange. Today’s world, especially indeveloping countries, is experiencing an unprecedented wave of urbanization. Sincethe reform and opening up, China entered a rapid development stage of urbanization,China’s future is still in the process of rapid urbanization over a long period of time,which led to the urban heat island effect and other environmental problems willbecome more apparent. Urban heat island effect(UHI) is a consequence of asignificant and increasing urbanization along with strengthened. Due to produce avariety of disadverse effects on the urban climate and urban ecological environment,urban heat island has been one focus of urban ecological research.Land surfacetemperature(LST) is one of the important parameters of the ground-gas energy andmaterial exchange processes, it has important applications in hydrology, climate andso on. Because of remote sensing technology with multi-band, multi-temporal, fast,continuous, large surface area to obtain the advantages of information, has beenwidely used in quantitative surface temperature inversion. The city in oasis is thelargest concentration of human activities, the most complex and sensitive area forrelationship between people and land. Urbanization promote oasis prosperity. The cityin oasis not only have the features in general, but also located in the oasis, whether theexistence of urban heat island or oasis "cold island effect", characterized by how, andhow the mechanism work, is a scientific question worth exploring. Therefore, thispaper use of remote sensing, geographic information systems, urban geography, landuse/land cover change and other multi-disciplinary theories and methods, using asingle window algorithm, split window algorithm to inversion of the8typical citiesland surface temperature at late1980s,2000,2006and2013in Northwest Oais, thereare Kanawha city, Shizuishan city, Yinchuan city, Jinchang city, Jiayuguan city,Golmud city, Urumqi city and Karamay city. Application of natural break get sevencategories of city land surface temperature level and analysis of the spatial andtemporal variation, by divided inflow river basin oasis city, outflow river basin oasiscity and different types of cities to discusses regional differences in land surface temperature. Through further use of computer visual interpretation of remote sensingimage method to obtain the eight cities districts extended range, land-use types,normalized difference vegetation index (NDVI), combined with social and economicstatistics and8meteorological stations near the city with53years average annualtemperature, the reasons which arouse land surface temperature changes in NorthwestOais cities were analyzed. Finally, five coping strategies have been proposed for thenegative impact of land surface temperature in Northwest Oais city. The mainconclusions are as follows：(1) From the spatial perspective, at the end of1980s-2013, land surfacetemperature distribution range of each are not indentical, but also has generality in8cities in the Northwest Oais.The range of high temperature zone of surfacetemperature and extreme high temperature zone is mainly distributed in the cityperipheral bare land and sandy land. Low and very low temperature region is mainlydistributed in the oasis farmland, woodland, grassland and waters. The lowertemperature region, middle temperature and high temperature distribution range is thebiggest changes. With the remarkable expansion city built-up area, the spatialdistributions of surface temperature changes.(2) From the time point of view, at the end of1980s-2013, variation of landsurface temperature of eight cities in the Northwest Oais is not uniform. Among them,Kanawha City, Yinchuan City and Shizuishan City heat island effectsignificantchanges in the first two heat island effect are consistent trends have alsoexperienced weak-strong-strong-weak process of change, and Yinchuan City wasstrong-stronger-more strong-weak. The remaining five cities "cold island effect"obvious trends are: Jinchang City experienced a strong-weak-enhanced-more changeprocess; Jiayuguan City and Urumqi City, experienced weak-strong-weak-strongprocess of change; Golmud City and Karamay City same experienced weak-strong-stronger-stronger process of change.(3) From the inflow river basin and outflow river basin, the5oasis cities ininflow river basin "cold island effect" highlights, the3cities in outflow river basinprominent the urban heat island effect, and the trends are not the same. From thedifferent types of the city, the capital city of Yinchuan City and Urumqi City population is large in scale, city expansion speed, urban heat island effect in YinchuanCity area with the expansion of city built-up area expanded rapidly. Urumqi Citybrought by the city of population increase, expansion of prominent heat island effectbuilt area of the city, but did not weaken the oasis "cold island effect".The resourcetype city, Shizuishan City, Jinchang City, Golmud City, Jiayuguan City, and KaramayCity, small population size, city expansion speed is slow, in addition to the ShizuishanCity is the urban heat island effect, the rest of the city as the "cold island effect". Thesmall city of Kanawha City is heat island effect from8cities in the Northwest Oais,even the same type of city, trend of temperature changes of the surface is notcompletely consistent.(4) City annual growth rate calculations show that: Urumqi City is the fastestpace of expansion in eight oasis cities, has entered the high-speed growth period.Yinchuan City expands very fast, in the second row, Jinchang City and Jiayuguan Cityranked third, other four cities are in slow growth period. LUCC research shows, at theend of1980s-2013, the eight oasis cities’s construction land growth significantly, inaddition to Jiayuguan City and Golmud City cultivated area increased, Karamay Cityin2013than in2006reduced the area of cultivated land, the remaining five oasiscities were reduced in different degree. Unused land and construction land have thehighest land surface average temperature, but the standard deviation is generally small.The land surface average temperature of cultivated land, forest land and watercompared to other types of land use is low, besides, they are the cold source of surfacetemperature. Therefore, the protection of arable land, woodland, grassland and watercan effectively reduce the land surface temperature of the oasis city. Correlationanalysis of NDVI and LST showed that, NDVI and LST has a significant negativecorrelation for eight cities in Northwest Oais. the correlation coefficient between0.825~0.540, they all belong to the significant correlation. Global warming andregional response analysis show that, in the past53years, the average temperature ofeight cities in Northwest Oasia showed an upward trend, the response is consistentwith global warming. Influence on the annual mean temperature of land use changefrom city (0.09℃/10a), except for Urumqi City (0.104℃/10a), the rest are still higherthan the global warming trend of0.18℃/10a (1980-2009). (5) According to the land surface temperature negative effects of eight cities inNorthwest Oasis, five countermeasures are put forward from the effective planning,reasonable layout of city; rational planning of city land use, to ensure that landresource sustainable development; the protection of arable land, improve landutilization; play the oasis "cold island effect"; to control the population, reduce thepressure of population. |
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