The accurate determination of surface-layer turbulent fluxes over urban areas is critical to understanding urban boundary layer （UBL） evolution. In this study, a remote-sensing technique using a large aperture scint...The accurate determination of surface-layer turbulent fluxes over urban areas is critical to understanding urban boundary layer （UBL） evolution. In this study, a remote-sensing technique using a large aperture scintillometer （LAS） was investigated to estimate surface-layer turbulent fluxes over a highly heterogeneous urban area. The LAS system, with an optical path length of 2.1 km, was deployed in an urban area characterized by a complicated land-use mix （residential houses, water body, bare ground, etc.）. The turbulent sensible heat （QH） and momentum fluxes （z） were estimated from the scintillation measurements obtained from the LAS system during the cold season. Three-dimensional LAS footprint modeling was introduced to identify the source areas （＂footprint＂） of the estimated turbulent fluxes. The analysis results showed that the LAS-derived turbulent fluxes for the highly heterogeneous urban area revealed reasonable temporal variation during daytime on clear days, in comparison to the land-surface process-resolving numerical modeling. A series of sensitivity tests indicated that the overall uncertainty in the LAS-derived daytime QH was within 20%-30% in terms of the influence of input parameters and the non- dimensional similarity function for the temperature structure function parameter, while the estimation errors in z were less sensitive to the factors of influence, except aerodynamic roughness length. The 3D LAS footprint modeling characterized the source areas of the LAS-derived turbulent fluxes in the heterogeneous urban area, revealing that the representative spatial scales of the LAS system deployed with the 2.1 km optical path distance ranged from 0.2 to 2 km2 （a ＂micro-a scale＂）, depending on local meteorological conditions.展开更多
对荒漠草原下垫面显热通量的时空特征分析对于提高区域水热交换规律认识和了解其在气候变化中的作用有重要意义。本研究基于内蒙古荒漠草原2021年5—12月的大孔径闪烁仪观测与相应的气象、环境观测资料,分析了荒漠草原区不同时间尺度显...对荒漠草原下垫面显热通量的时空特征分析对于提高区域水热交换规律认识和了解其在气候变化中的作用有重要意义。本研究基于内蒙古荒漠草原2021年5—12月的大孔径闪烁仪观测与相应的气象、环境观测资料,分析了荒漠草原区不同时间尺度显热通量变化特征及其源区分布。结果表明:大气不稳定条件下显热通量日变化曲线呈单峰型,相比于晴天,多云和阴天的日变化存在无规律波动;显热通量季节变化明显,5月以后不断减少;通量源区按照闪烁仪光径走向朝上风向延伸分布,越靠近光径对通量贡献能力越大;受稳定度、风速风向和下垫面植被特征共同影响,各时间尺度的通量源区特征不同,源区范围日变化与大气稳定度变化基本一致,研究期间11月源区面积最大,7月最小,相差约70000 m 2,整个生长季的通量贡献区小于非生长季;大气稳定度和风向是影响通量源区分布的重要因素。展开更多
基金supported by the Korea Meteorological Administration Research and Development Program (Grant No. CATER 2012-3081)
文摘The accurate determination of surface-layer turbulent fluxes over urban areas is critical to understanding urban boundary layer （UBL） evolution. In this study, a remote-sensing technique using a large aperture scintillometer （LAS） was investigated to estimate surface-layer turbulent fluxes over a highly heterogeneous urban area. The LAS system, with an optical path length of 2.1 km, was deployed in an urban area characterized by a complicated land-use mix （residential houses, water body, bare ground, etc.）. The turbulent sensible heat （QH） and momentum fluxes （z） were estimated from the scintillation measurements obtained from the LAS system during the cold season. Three-dimensional LAS footprint modeling was introduced to identify the source areas （＂footprint＂） of the estimated turbulent fluxes. The analysis results showed that the LAS-derived turbulent fluxes for the highly heterogeneous urban area revealed reasonable temporal variation during daytime on clear days, in comparison to the land-surface process-resolving numerical modeling. A series of sensitivity tests indicated that the overall uncertainty in the LAS-derived daytime QH was within 20%-30% in terms of the influence of input parameters and the non- dimensional similarity function for the temperature structure function parameter, while the estimation errors in z were less sensitive to the factors of influence, except aerodynamic roughness length. The 3D LAS footprint modeling characterized the source areas of the LAS-derived turbulent fluxes in the heterogeneous urban area, revealing that the representative spatial scales of the LAS system deployed with the 2.1 km optical path distance ranged from 0.2 to 2 km2 （a ＂micro-a scale＂）, depending on local meteorological conditions.
文摘对荒漠草原下垫面显热通量的时空特征分析对于提高区域水热交换规律认识和了解其在气候变化中的作用有重要意义。本研究基于内蒙古荒漠草原2021年5—12月的大孔径闪烁仪观测与相应的气象、环境观测资料,分析了荒漠草原区不同时间尺度显热通量变化特征及其源区分布。结果表明:大气不稳定条件下显热通量日变化曲线呈单峰型,相比于晴天,多云和阴天的日变化存在无规律波动;显热通量季节变化明显,5月以后不断减少;通量源区按照闪烁仪光径走向朝上风向延伸分布,越靠近光径对通量贡献能力越大;受稳定度、风速风向和下垫面植被特征共同影响,各时间尺度的通量源区特征不同,源区范围日变化与大气稳定度变化基本一致,研究期间11月源区面积最大,7月最小,相差约70000 m 2,整个生长季的通量贡献区小于非生长季;大气稳定度和风向是影响通量源区分布的重要因素。
