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库布齐沙漠植被恢复对局地对流活动的影响研究

Study on the Impact of Vegetation Restoration on Local Convective Activity in Kubuqi Desert

  • 摘要: 植被增加会改变地表土壤湿度,增强局地水循环,影响局地陆面过程及大气环流。库布齐沙漠是中国生态修复和荒漠化逆转最为成功的地区之一,为研究库布齐沙漠植被增加对局地对流活动的影响,本文利用1962~2022年库布齐沙漠及周边站点小时降水、气温、相对湿度数据及1982~2022年PKU GIMMS全球归一化植被指数数据研究库布齐沙漠植被恢复对局地对流活动的影响。研究发现1982~2022年库布齐沙漠年平均NDVI与生长季NDVI均呈增加趋势,且黄河北岸绿洲区年平均NDVI增加显著。沙漠腹地伊克乌素站治理前期(1982~1984年)00:00~12:00对流性降水占比80%,治理后期(2020~2022年)占比仅有51.6%,13:00~17:00、21:00~23:00占比分别增加到21.0%与15.4%。磴口站、临河站、五原站植被治理后期对流降水出现时间均出现推迟现象。数值模拟敏感性试验显示植被增加10%,敏感性试验的地表温度比控制试验降低0.1℃~0.4℃,感热通量降低1~24W m-2,对流触发时间及降水开始时间晚20~40min。实况观测与数值模拟证实,植被增加会改变地表与大气湿热量交换,进而影响对流系统的生消演变。

     

    Abstract: Increased vegetation alters surface soil moisture, enhances local water cycle processes, and influences land surface dynamics and atmospheric circulation. The Kubuqi Desert is one of the most successful regions in China for ecological restoration and desertification reversal. To investigate the impact of vegetation increase on local convective activity in the Kubuqi Desert, this study utilizes hourly precipitation, temperature, relative humidity data from the Kubuqi Desert and surrounding stations during 1962–2022, as well as PKU GIMMS global normalized difference vegetation index (NDVI) data during 1982–2022. The results show that both annual mean NDVI and growing-season NDVI in the Kubuqi Desert exhibited an increasing trend from 1982 to 2022, with a significant increase in the oasis area north of the Yellow River. At the Yikesu station, located in the desert hinterland, convective precipitation accounted for 80% of the total during 00:00–12:00 in the early treatment period (1982–1984), but this proportion decreased to 51.6% in the later treatment period (2020–2022), while the proportions during 13:00–17:00 and 21:00–23:00 increased to 21.0% and 15.4%, respectively. At Dengkou, Linhe, and Wuyuan stations, the occurrence time of convective precipitation was delayed in the later treatment period. Numerical sensitivity experiments show that when vegetation increases by 10%, the surface temperature in the sensitivity experiment is 0.1°C–0.4°C lower than that in the control experiment, sensible heat flux decreases by 1–24 W m?2, and the convective initiation time and precipitation onset time are delayed by 20–40 minutes. Both observational data and numerical simulations confirm that increased vegetation alters surface heat and moisture exchanges, thereby influencing the generation and evolution of convective systems.

     

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