Effects of Ecological Restoration on Local Climate in the Middle of Loess Plateau in Northern Shaanxi
Based on the MOD13Q1 data of MODIS products in the Loess Plateau of Northern Shaanxi from 2000 to 2019,the monthly(annual)average temperature,maximum(minimum)temperature,rainfall and rainfall days of Dingbian,Ansai,Zhidan,Zichang,and Yan'an meteorological stations from 1990 to 2019,the changes of meteorological elements in the ecological restoration significant areas(SIER;Zhidan,Ansai,Zichang,Yan'an)and non-significant area(NSIER;Dingbian)of the Loess Plateau in northern Shaanxi were compared and analyzed before ecological restoration(1990-1999;BER)and during ecological restoration(2000-2019;DER),by using the difference(ratio),correlation coefficient and linear regression.The results showed that:(1)The normalized differential vegetation index(NDVI)in SIER and NSIER at DER increased by 0.123 and 0.081/10 a,and the rate in SIER was 1.5 times that in NSIER.The annual average temperature in SIER and NSIER increased by 0.164 and 0.467 ℃/10 a,respectively,and the annual average rainfall increased by 39.95 and 25.56 mm/10 a,respectively.The temperature increased in SIER was significantly slower than that in NSIER,but the increase rate of average rainfall was significantly greater than that in NSIER.(2)Significant restoration of ecology had a prominent inhibitory effect on the annual average temperature rise after 2012.The abrupt change in the annual average temperature difference of SIER and NSIER occurred in 2013,which was a key time point for the impact of ecological restoration on the annual average temperature.In the vegetation growth season(April-September),the inhibition of the annual average temperature rise in SIER was more obvious,especially in July.The annual average temperature in SIER was 1.05 ℃ lower than that in NSIER.The inhibition of the highest temperature appeared in July-August,and the inhibition of the lowest temperature appeared in May-June.(3)The number of rainfall days in SIER at DER(2013-2019)was significantly less than that BER by nearly 6 days.The decrease was mainly due to the decrease of light rain days.The number of rainfall days above moderate rain showed an increasing trend with the development of ecological restoration.The increase of rainfall in the vegetation growth season in SIER was the most obvious,and the increase of rainfall was mainly manifested in the increase of the number of rainy days above moderate rain.From January to July,with the continuous increase of vegetation coverage,the difference between different grades of rainfall days in SIER and NSIER gradually increased,reaching the maximum values in July.From August to December,with the decrease of vegetation coverage,the difference of rainfall days gradually decreased.
central Loess Plateauecological restorationNDVIlocal climateeffect