土地利用类型变化通过改变地表-大气相互作用对区域气候产生影响,了解土地利用类型变化对区域气候的影响有助于未来土地利用规划和制定区域政策,特别是生态环境极端脆弱敏感的干旱半干旱地区。车尔臣河流域位于塔克拉玛干沙漠(TD)东缘,...土地利用类型变化通过改变地表-大气相互作用对区域气候产生影响,了解土地利用类型变化对区域气候的影响有助于未来土地利用规划和制定区域政策,特别是生态环境极端脆弱敏感的干旱半干旱地区。车尔臣河流域位于塔克拉玛干沙漠(TD)东缘,是保护且末县不被塔克拉玛干沙漠吞噬的唯一防线。近20年来,人为活动使当地植被增加、水体面积扩大,但这种变化对区域气候的影响尚不清楚。利用WRF(Weather Research and Forecasting)模式,分别使用2001年和2021年的MODIS MCD12Q16.1(MCD12Q1)版本全球土地利用类型数据集,设置对照实验研究车尔臣河流域土地利用类型变化对2021年7月区域气候的影响。结果表明:车尔臣河流域水体和绿地增加使地表蒸散总值增加了2.95 mm,地面2 m比湿均值增加了2×10^(-4)kg·kg^(-1);水汽的增加使流域南部山坡区域降水增加,流域北部受反气旋性气流控制,降水没有明显变化;地表绿化和水体增加导致的降水量增加不能补充地表蒸散增加损失的水分。台特玛湖面积恢复区域气温显著降低,平均最高温和最低温分别降低1.8℃和1.3℃;台特玛湖以外的区域,地表植被的增加通过调节蒸散、地表反照率和大气长波辐射等多种途径影响气温,使流域北部最高温升高、最低温降低,流域南部最高温降低、最低温升高;总体而言,地表反照率减小造成的地面净辐射增加起主导作用,净辐射平均增加7.35 W·m^(-2),地面平均气温升高0.21℃。车尔臣河流域水体和绿地增加区域向塔克拉玛干沙漠(TD)地区输送了部分水汽,使TD地区5 km以下水汽含量增加,通过调节辐射使TD地区温度升高,其中,大气逆辐射的增加占主导作用,使区域平均气温升高0.3℃;在反气旋性气流控制下,TD地区降水基本没有变化。展开更多
Pronounced climatic differences occur over subtropical South China(SC)and tropical South China Sea(SCS)and understanding the key cloud-radiation characteristics is essential to simulating East Asian climate.This study...Pronounced climatic differences occur over subtropical South China(SC)and tropical South China Sea(SCS)and understanding the key cloud-radiation characteristics is essential to simulating East Asian climate.This study investigated cloud fractions and cloud radiative effects(CREs)over SC and SCS simulated by CMIP6 atmospheric models.Remarkable differences in cloud-radiation characteristics appeared over these two regions.In observations,considerable amounts of low-middle level clouds and cloud radiative cooling effect appeared over SC.In contrast,high clouds prevailed over SCS,where longwave and shortwave CREs offset each other,resulting in a weaker net cloud radiative effect(NCRE).The models underestimated NCRE over SC mainly due to weaker shortwave CRE and less cloud fractions.Conversely,most models overestimated NCRE over SCS because of stronger shortwave CRE and weaker longwave CRE.Regional CREs were closely linked to their dominant cloud fractions.Both observations and simulations showed a negative spatial correlation between total(low)cloud fraction and shortwave CRE over SC,especially in winter,and exhibited a positive correlation between high cloud fraction and longwave CRE over these two regions.Compared with SCS,most models overestimated the spatial correlation between low(high)cloud fraction and SWCRE(LWCRE)over SC,with larger bias ranges among models,indicating the exaggerated cloud radiative cooling(warming)effect caused by low(high)clouds.Moreover,most models struggled to describe regional ascent and its connection with CREs over SC while they can better reproduce these connections over SCS.This study further suggests that reasonable circulation conditions are crucial to simulating well cloud-radiation characteristics over the East Asian regions.展开更多
As a type of clean and pollution-free energy source,solar energy plays an important role in achieving the goals of carbon neutrality and global sustainable development.Northwest China occupies an important position in...As a type of clean and pollution-free energy source,solar energy plays an important role in achieving the goals of carbon neutrality and global sustainable development.Northwest China occupies an important position in the national energy strategy due to its rich solar energy.Clarifying the long-term variations of Northwest China’s solar energy and understanding the associated mechanisms are crucial to improving the layout of new energy sources and the usage efficiency of solar energy within China.In this study,the authors first divide Northwest China into northwestern and southeastern sections by conducting a rotated empirical orthogonal function analysis on the surface solar radiation(SSR)from 1993 to 2022,and then explore the SSR’s variation trends and associated mechanisms within these subregions.It is found that the two subregions,both of which show a significant feature of decadal change,differ notably in their long-term trends:the northwestern section shows a significant increasing trend of∼8.1 kJ m^(-2)yr^(-1)in the annual mean SSR,and in each season the SSR increases significantly,with a maximum/minimum increasing rate of∼11.2/∼4.6 kJm^(-2)yr^(-1)appearing in summer/autumn.A possible mechanism for the SSR’s increasing trend is that global warming results in a lower relative humidity within the northwestern section,which decreases the total cloud cover,as it is harder for the atmosphere to reach saturation state.A decreasing total cloud cover results in an increasing SSR within the northwestern section.In contrast,the southeastern section shows no significant trend in annual mean SSR,as the SSRs in summer and autumn show significant decreasing trends,whereas the trends in spring and winter are not significant.展开更多
文摘土地利用类型变化通过改变地表-大气相互作用对区域气候产生影响,了解土地利用类型变化对区域气候的影响有助于未来土地利用规划和制定区域政策,特别是生态环境极端脆弱敏感的干旱半干旱地区。车尔臣河流域位于塔克拉玛干沙漠(TD)东缘,是保护且末县不被塔克拉玛干沙漠吞噬的唯一防线。近20年来,人为活动使当地植被增加、水体面积扩大,但这种变化对区域气候的影响尚不清楚。利用WRF(Weather Research and Forecasting)模式,分别使用2001年和2021年的MODIS MCD12Q16.1(MCD12Q1)版本全球土地利用类型数据集,设置对照实验研究车尔臣河流域土地利用类型变化对2021年7月区域气候的影响。结果表明:车尔臣河流域水体和绿地增加使地表蒸散总值增加了2.95 mm,地面2 m比湿均值增加了2×10^(-4)kg·kg^(-1);水汽的增加使流域南部山坡区域降水增加,流域北部受反气旋性气流控制,降水没有明显变化;地表绿化和水体增加导致的降水量增加不能补充地表蒸散增加损失的水分。台特玛湖面积恢复区域气温显著降低,平均最高温和最低温分别降低1.8℃和1.3℃;台特玛湖以外的区域,地表植被的增加通过调节蒸散、地表反照率和大气长波辐射等多种途径影响气温,使流域北部最高温升高、最低温降低,流域南部最高温降低、最低温升高;总体而言,地表反照率减小造成的地面净辐射增加起主导作用,净辐射平均增加7.35 W·m^(-2),地面平均气温升高0.21℃。车尔臣河流域水体和绿地增加区域向塔克拉玛干沙漠(TD)地区输送了部分水汽,使TD地区5 km以下水汽含量增加,通过调节辐射使TD地区温度升高,其中,大气逆辐射的增加占主导作用,使区域平均气温升高0.3℃;在反气旋性气流控制下,TD地区降水基本没有变化。
基金Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)National Natural Science Foundation of China(72293604,42275026)Open Grants of the State Key Laboratory of Severe Weather(2023LASW-B09)。
文摘Pronounced climatic differences occur over subtropical South China(SC)and tropical South China Sea(SCS)and understanding the key cloud-radiation characteristics is essential to simulating East Asian climate.This study investigated cloud fractions and cloud radiative effects(CREs)over SC and SCS simulated by CMIP6 atmospheric models.Remarkable differences in cloud-radiation characteristics appeared over these two regions.In observations,considerable amounts of low-middle level clouds and cloud radiative cooling effect appeared over SC.In contrast,high clouds prevailed over SCS,where longwave and shortwave CREs offset each other,resulting in a weaker net cloud radiative effect(NCRE).The models underestimated NCRE over SC mainly due to weaker shortwave CRE and less cloud fractions.Conversely,most models overestimated NCRE over SCS because of stronger shortwave CRE and weaker longwave CRE.Regional CREs were closely linked to their dominant cloud fractions.Both observations and simulations showed a negative spatial correlation between total(low)cloud fraction and shortwave CRE over SC,especially in winter,and exhibited a positive correlation between high cloud fraction and longwave CRE over these two regions.Compared with SCS,most models overestimated the spatial correlation between low(high)cloud fraction and SWCRE(LWCRE)over SC,with larger bias ranges among models,indicating the exaggerated cloud radiative cooling(warming)effect caused by low(high)clouds.Moreover,most models struggled to describe regional ascent and its connection with CREs over SC while they can better reproduce these connections over SCS.This study further suggests that reasonable circulation conditions are crucial to simulating well cloud-radiation characteristics over the East Asian regions.
基金supported by the National Key R&D Program of China[grant number 2022YFB2403002]。
文摘As a type of clean and pollution-free energy source,solar energy plays an important role in achieving the goals of carbon neutrality and global sustainable development.Northwest China occupies an important position in the national energy strategy due to its rich solar energy.Clarifying the long-term variations of Northwest China’s solar energy and understanding the associated mechanisms are crucial to improving the layout of new energy sources and the usage efficiency of solar energy within China.In this study,the authors first divide Northwest China into northwestern and southeastern sections by conducting a rotated empirical orthogonal function analysis on the surface solar radiation(SSR)from 1993 to 2022,and then explore the SSR’s variation trends and associated mechanisms within these subregions.It is found that the two subregions,both of which show a significant feature of decadal change,differ notably in their long-term trends:the northwestern section shows a significant increasing trend of∼8.1 kJ m^(-2)yr^(-1)in the annual mean SSR,and in each season the SSR increases significantly,with a maximum/minimum increasing rate of∼11.2/∼4.6 kJm^(-2)yr^(-1)appearing in summer/autumn.A possible mechanism for the SSR’s increasing trend is that global warming results in a lower relative humidity within the northwestern section,which decreases the total cloud cover,as it is harder for the atmosphere to reach saturation state.A decreasing total cloud cover results in an increasing SSR within the northwestern section.In contrast,the southeastern section shows no significant trend in annual mean SSR,as the SSRs in summer and autumn show significant decreasing trends,whereas the trends in spring and winter are not significant.
