KLACP, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China.
KLACP, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; Center for Excellence in Urban Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China; Shanghai Key Laboratory of Meteorology and Health, Shanghai 200030, China; National Center for Atmospheric Research, Boulder, CO 80303, USA.
Sci Total Environ. 2017 Nov 15;598:307-318. doi: 10.1016/j.scitotenv.2017.04.101. Epub 2017 Apr 25.
The Tibetan Plateau (TP) plays important roles in global climate and environment. This study combines in-situ BC measurements in the Himalayas and the Indo-Gangetic Plain (IGP) with a regional dynamical and chemical model (WRF-Chem model) to investigate the effect of the trans-Himalayas on black carbon (BC) from the IGP to the TP during Indian summer monsoon. To determine topographic effects of the trans-Himalayas on BC concentrations over the TP, sensitive experiments were conducted by applying the WRF-Chem model. The results showed that the reduction of the altitude of the Himalayas had an important effect on the trans-Himalayas transport of BC. There was an obvious increase in BC concentration over the trans-Himalayas region, but no significant increase over the TP because the TP (a.m.s.l ~4km) always acted as a wall to prevent BC transport from the IGP to the TP. The trans-Himalayas transport of BC was strongly dependent upon meteorological conditions over the IGP. During summer monsoon, there were three types of cyclones at different locations and one kind of convergent circulation in the IGP. Under the condition of convergent airflows, a strong northeastward wind produced the trans-Himalayas transport of BC. As a result, BC concentrations in the southeastern TP significantly increased to 0.6-0.8μgm. When the cyclone located in the eastern IGP, high BC concentrations over the IGP were transported along the foothill of the Himalayas, resulting in a significant reduction of the trans-Himalayas transport. When the cyclone moved to the west, the dynamical perturbations for the trans-Himalayas transport were weaker than the eastern cyclone, and the trans-Himalayas transport were enhanced in the middle and eastern Himalayas. This study will be helpful to assess the impacts of BC particles emitted from South Asia on regional climate change and ecological environment over the TP in the future.
青藏高原（TP）在全球气候和环境中发挥着重要作用。本研究将喜马拉雅山脉和印度-恒河平原（IGP）的现场黑碳（BC）测量与区域动力和化学模型（WRF-Chem 模型）相结合，研究印度夏季季风期间从 IGP 到 TP 的跨喜马拉雅山脉对 BC 的影响。为了确定喜马拉雅山脉对 TP 上空 BC 浓度的地形影响，通过应用 WRF-Chem 模型进行了敏感实验。结果表明，喜马拉雅山脉的海拔降低对跨喜马拉雅山脉的 BC 传输有重要影响。在喜马拉雅山脉地区，BC 浓度明显增加，但 TP 上空没有明显增加，因为 TP（海拔~4km）始终充当阻止 BC 从 IGP 向 TP 传输的墙壁。BC 跨喜马拉雅山脉的传输强烈依赖于 IGP 上空的气象条件。在夏季季风期间，IGP 上有三种不同位置的气旋和一种辐合环流。在辐合气流条件下，东北风产生了跨喜马拉雅山脉的 BC 传输。结果，TP 东南部的 BC 浓度显著增加到 0.6-0.8μg/m3。当气旋位于 IGP 的东部时，IGP 上空的高 BC 浓度沿着喜马拉雅山脉的山麓被输送，导致跨喜马拉雅山脉的传输明显减少。当气旋向西移动时，跨喜马拉雅山脉的动力扰动比东部气旋弱，而在喜马拉雅山脉中部和东部的跨喜马拉雅山脉传输得到增强。本研究将有助于评估未来南亚排放的 BC 颗粒对 TP 区域气候变化和生态环境的影响。
