In mountainous lake areas, lake–land and mountain–valley breezes interact with each other, leading to an "extended lake breeze". These extended lake breezes can regulate and control energy and carbon cycle...In mountainous lake areas, lake–land and mountain–valley breezes interact with each other, leading to an "extended lake breeze". These extended lake breezes can regulate and control energy and carbon cycles at different scales. Based on meteorological and turbulent fluxes data from an eddy covariance observation site at Erhai Lake in the Dali Basin,southwest China, characteristics of daytime and nighttime extended lake breezes and their impacts on energy and carbon dioxide exchange in 2015 are investigated. Lake breezes dominate during the daytime while, due to different prevailing circulations at night, there are two types of nighttime breezes. The mountain breeze from the Cangshan Mountain range leads to N1 type nighttime breeze events. When a cyclonic circulation forms and maintains in the southern part of Erhai Lake at night, its northern branch contributes to the formation of N2 type nighttime breeze events. The prevailing wind directions for daytime, N1, and N2 breeze events are southeast, west, and southeast, respectively. Daytime breeze events are more intense than N1 events and weaker than N2 events. During daytime breeze events, the lake breeze decreases the sensible heat flux(Hs) and carbon dioxide flux(F_(CO_2)) and increases the latent heat flux(LE). During N1 breeze events, the mountain breeze decreases Hs and LE and increases F_(CO_2). For N2 breeze events, the southeast wind from the lake surface increases Hs and LE and decreases suppress carbon dioxide exchange.展开更多
本文基于北京325米气象塔在47,140,和280米三层高度的5年涡动相关观测资料,研究了城市下垫面与大气间的CO_(2)交换过程.由于北京市2011年开始实行工作日汽车尾号限行,140米高度CO_(2)通量的年增长率由2008-2010年的7.8%降低到2010-2012...本文基于北京325米气象塔在47,140,和280米三层高度的5年涡动相关观测资料,研究了城市下垫面与大气间的CO_(2)交换过程.由于北京市2011年开始实行工作日汽车尾号限行,140米高度CO_(2)通量的年增长率由2008-2010年的7.8%降低到2010-2012年的2.3%.140米高度通量源区内植被比例最小且人口密度最大,因此140米高度的5年平均CO_(2)通量年总量(6.41 kg C m^(−2) yr^(−1)(大于47米)5.78 kg C m^(−2) yr^(−1)(和280米)3.99 kg C m^(−2) yr^(−1)).在年尺度上,北京汽车总保有量和总人口是最重要的CO_(2)通量控制因子.CO_(2)通量随风向的变化主要与风向对应的通量源区内下垫面土地利用方式有关.三层高度的夏季CO_(2)通量均与道路的比例呈正相关关系.47,140,和280米的决定系数分别为0.69,0.57,和0.54(P<0.05).植被比例的下降,会导致CO_(2)年总量上升,两者存在近似于指数的关系.城市人口密度的上升会引起CO_(2)年总量上升.展开更多
基金supported by funds from the National Key Research and Development Program of China (Project no: 2017YFC1502101)the National Natural Science Foundation of China (Projects no: 41775018, and 41805010)。
文摘In mountainous lake areas, lake–land and mountain–valley breezes interact with each other, leading to an "extended lake breeze". These extended lake breezes can regulate and control energy and carbon cycles at different scales. Based on meteorological and turbulent fluxes data from an eddy covariance observation site at Erhai Lake in the Dali Basin,southwest China, characteristics of daytime and nighttime extended lake breezes and their impacts on energy and carbon dioxide exchange in 2015 are investigated. Lake breezes dominate during the daytime while, due to different prevailing circulations at night, there are two types of nighttime breezes. The mountain breeze from the Cangshan Mountain range leads to N1 type nighttime breeze events. When a cyclonic circulation forms and maintains in the southern part of Erhai Lake at night, its northern branch contributes to the formation of N2 type nighttime breeze events. The prevailing wind directions for daytime, N1, and N2 breeze events are southeast, west, and southeast, respectively. Daytime breeze events are more intense than N1 events and weaker than N2 events. During daytime breeze events, the lake breeze decreases the sensible heat flux(Hs) and carbon dioxide flux(F_(CO_2)) and increases the latent heat flux(LE). During N1 breeze events, the mountain breeze decreases Hs and LE and increases F_(CO_2). For N2 breeze events, the southeast wind from the lake surface increases Hs and LE and decreases suppress carbon dioxide exchange.
基金funded by the National Key Research and Develop-ment Program of China[grant number 2017YFC1502101]the National Natural Science Foundation of China[grant numbers 41905010 and 41675013].
文摘本文基于北京325米气象塔在47,140,和280米三层高度的5年涡动相关观测资料,研究了城市下垫面与大气间的CO_(2)交换过程.由于北京市2011年开始实行工作日汽车尾号限行,140米高度CO_(2)通量的年增长率由2008-2010年的7.8%降低到2010-2012年的2.3%.140米高度通量源区内植被比例最小且人口密度最大,因此140米高度的5年平均CO_(2)通量年总量(6.41 kg C m^(−2) yr^(−1)(大于47米)5.78 kg C m^(−2) yr^(−1)(和280米)3.99 kg C m^(−2) yr^(−1)).在年尺度上,北京汽车总保有量和总人口是最重要的CO_(2)通量控制因子.CO_(2)通量随风向的变化主要与风向对应的通量源区内下垫面土地利用方式有关.三层高度的夏季CO_(2)通量均与道路的比例呈正相关关系.47,140,和280米的决定系数分别为0.69,0.57,和0.54(P<0.05).植被比例的下降,会导致CO_(2)年总量上升,两者存在近似于指数的关系.城市人口密度的上升会引起CO_(2)年总量上升.
