| Ningxia plays a pivotal role in China’s economic and social development and ecological security,and is an important ecological function area in China.The good or bad ecological environment of Ningxia affects the construction and development of the region,and the timely and accurate access to the evolution trend and spatio-temporal pattern of the ecological environment quality of Ningxia and the analysis of the factors affecting the ecological environment quality are of great significance to the ecological environmental protection and construction of Ningxia.In this paper,the Landsat TM/OLI remote sensing images in summer(June-September)of the target years(2001,2006,2011,2016,2021)were selected,and based on the geographical location characteristics and surface coverage features of Ningxia region,the remote sensing radiation transmission of surface temperature applicable to the study area was constructed based on Landsat TM/OLI satellite remote sensing data The SEBAL model for the remote sensing inversion of surface evapotranspiration in Ningxia region was established based on the principle of surface energy balance based on the uneven moisture and energy distribution in Ningxia region,Based on Landsat TM/OLI data,the daily surface evapotranspiration of Ningxia from 2001 to 2021 was inferred using the SEBAL model.The improved remotely sensed ecological index(MRSEI)applicable to Ningxia was constructed based on greenness,surface evapotranspiration,dryness and heat indexes,and the calculated values of MRSEI for each period in Ningxia were obtained,and the ecological classes of Ningxia were analyzed.The spatial and its change pattern were analyzed.The following conclusions were obtained:(1)The surface temperature inversion results were verified by using MOD11A2 surface temperature product data,and the correlation coefficients reached above 0.81,and the mean values of root mean square error and deviation were 2.99 and 4.64,respectively,so the inversion obtained surface temperature has high accuracy.Finally,the influencing factors of surface temperature were analyzed.Therefore,the inversion of the surface temperature model using Landsat has a higher resolution and wider applicability,thus identifying the potential use of the method.(2)The inversion results were verified by using the Penman-Monteith model to calculate the potential surface evapotranspiration and the MOD 16 surface evapotranspiration product.The mean values of correlation coefficients were maintained above 0.90,and the mean values of root mean square error and deviation were 1.03 and 1.76,respectively,which indicated that the surface evapotranspiration obtained by the SEBAL model inversion had high accuracy.Then,the spatial and temporal variation characteristics of surface evapotranspiration in Ningxia were analyzed,and it was found that the spatial distribution pattern of daily surface evapotranspiration was consistent in general,basically showing the increasing trend characteristics from the northern plain to the southern mountainous area,mainly due to the better vegetation cover and higher precipitation in the southern mountainous area.Finally,using land use type data,we analyzed the distribution patterns of surface evapotranspiration of different land use types and found that the magnitude of evapotranspiration in the study area was not only influenced by natural geographic conditions and climate,but also related to the land use and vegetation cover of the substrate.The inversion of surface evapotranspiration using the SEBAL model based on Landsat data has a higher resolution and wider applicability,thus identifying the potential use of the model.(3)The calculated values of MRSEI index for each period of 2001-2021 in Ningxia are 0.65,0.61,0.60,0.57 and 0.60,respectively.Combining the ecological condition of the study area and the statistical MRSEI index of each period,the study on the spatial and temporal changes of ecological environment quality in the study area from 2001 to 2021 is carried out by using the method of dynamic change analysis of ecological quality,which is graded by MRSEI index The results show that the area of poor and poorer ecological quality grades increased from 3737.16km2 to 5958.73km2 during 2001-2021,with a total increase of 2221.57km2,up 59.44%,and the area of good and excellent grades decreased from 33440.46km2 to 27000,65km2,down 19.25%,and the improved remote sensing ecological The overall trend of the improved remote sensing ecological index values is decreasing.However,during 2001-2021,the sum of the areas with poor and poor ecological quality are both much smaller than the sum of the areas with good and excellent ecological quality,indicating that the places suitable for human habitation are generally larger than those unsuitable for human habitation.The analysis of the change of the improved remote sensing ecological index difference can be concluded that the improved remote sensing ecological index increased by an average of 7.16%and decreased by an average of 13.53%during 2001-2021,in which the improved remote sensing ecological index difference in Ningxia from 2001 to 2016 showed a decreasing trend,and the improved remote sensing ecological index difference in Ningxia from 2016 to 2021 showed an increasing trend. |
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