| 气候影响下的荒漠下的荒漠化监测 |
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| 引用本文： | A.N.左洛托克瑞林.气候影响下的荒漠下的荒漠化监测[J].干旱区地理,2007,30(6):797-804. |
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| 作者姓名： | A.N.左洛托克瑞林 |
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| 作者单位： | 俄罗斯科学院地理研究所,莫斯科 109017,俄罗斯联邦共和国 |
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| 摘 要： | 根据揭示沙漠化扩张内在规律的相关气候驱动因子的假说,气候作用影响之下的沙漠化是在具反射率-降水正、负反馈特点的气候系统之中的区域干旱化过程与干旱土壤退化过程相互作用的结果。在辐射调节下的地表下垫面温度占主导的条件下,气候成因的沙漠化是由区域气候系统反馈所形成。正反馈的外部调节因子是降水量的变化和极端降水事件(特别是旱灾)的出现频率,降水量减少以及降水频率的降低直接影响沙漠化的程度。20世纪下半叶,人类因素导致的干旱土地退化作为另外的正反馈调节因子,其重要性正在增加。通常正反馈的扩大趋势会被通过蒸腾而进行的地表温度调节的负反馈所抑制。由正反馈到负反馈的转换是通过地球表面与大气层之间的热量交换的调节所确定的,其中非潜热因子处于增加状态。上述情况在反射率和地表温度同时增加的条件下发生。在超出绿色植物生物量及其NDVI指数阈值的条件下,负反馈向正反馈的转换就会发生。人为作用导致的植被退化加快了向绿色植物生物量阈值逼近的进程,从而引起气候因素驱动的沙漠化扩大。一个主要由气候因素影响的荒漠化区域,在大多数情况下,其绿色生物量均在季节变化和年际变化中达到了阈值。在中度的人为影响的植被退化条件下,这些地域一般都包括部分干旱与半干旱土地。然而有时,人类活动也会导致干旱的半湿润土地退化。本文运用Turan和Sahel地区1982-2001年NDVI指数的监测结果,分析了全球变暖和人为作用导致的土地退化。
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| 关 键 词： | 土地退化 反馈反射率 地表温度 降水 NDVI指数 干旱区 |
Monitoring of climate-related desertification |
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| A. N. Zolotokrylin.Monitoring of climate-related desertification[J].Arid Land Geography,2007,30(6):797-804. |
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| Authors: | A N Zolotokrylin |
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| Abstract: | Hypothesis of climate-related component of desertification that reveals nature and logic of climate-driven desertification expansion is proposed.According to this hypothesis,climate-related desertification is a result of interaction between regional processes of aridization and degradation of dry lands within the climate system with positive and negative albedo-precipitation feedbacks.Climate-related desertification is maintained by regional climate system feedbacks,if radiative regulation of underlying surface temperature prevails.External regulator of positive feedback is variation of precipitation amount and frequency of extreme precipitation(especially droughts).It is shown that desertification is predetermined by the decreased precipitation as well as by the decrease in frequency of precipitation.In the second half of 20th century importance of man-induced degradation of dry lands as additional regulator of positive feedback has been increased.Usually the expansion of positive feedback is blocked by negative one related to regulation of surface temperature through evapotranspiration.A switch from positive feedback to negative one is predetermined by the modification of heat-exchange between Earth's surface and the atmosphere,which non-latent component increases.The above takes place in case of simultaneous increase in the albedo and surface temperature.Threshold value for green phytomass and its NDVI-indicator beyond which the negative feedback switches to the positive one has been found.Man-induced degradation of vegetation accelerates the approaching of the threshold value of phytomass,and,subsequently,the expansion of climate-related desertification.An area dominated by climate-related desertification includes territories at which,in most cases,green phytomass attains threshold value in its seasonal and inter-annual variations.As a rule,the range partly includes arid and semiarid lands in case of moderate man-induced degradation of vegetation cover.However,sometimes dry sub-humid lands degraded in result of human activities are also included in the area.First results of monitoring the climate-related desertification and its analysis with the use of NDVI-indicator for the Turan area and the Sahel in 1982-2001 under global warming and man-induced degradation of lands are presented. |
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| Keywords: | Desertification aridization degradation of lands feedbacks albedo surface temperature precipitation-NDVI-indicator dry-lands regions |
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