Advances in Earth Science ›› 2010, Vol. 25 ›› Issue (11): 1166-1174. doi: 10.11867/j.issn.1001-8166.2010.11.1166

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Flux Footprint Analysis and Application for the Large Aperture Scintillometer

Cai Xuhui 1, Zhu Mingjia 2, Liu Shaomin 2, Xu Ziwei 2   

  1. 1.Department of Environmental Sciences, Peking University, Beijing 100871, China;
    2.State Key Laboratory of  Remote Sensing Science, School of Geography, Beijing Normal University, Beijing 100875, China
  • Received:2010-08-03 Revised:2010-09-07 Online:2010-11-10 Published:2010-11-10

Cai Xuhui, Zhu Mingjia, Liu Shaomin, Xu Ziwei. Flux Footprint Analysis and Application for the Large Aperture Scintillometer[J]. Advances in Earth Science, 2010, 25(11): 1166-1174.

Mean flux footprints were analyzed for long-term measurements of a large aperture scintillometer (LAS) in Miyun county, Beijing. A set of half-hourly mean, full-year turbulence data in 2008 was used for the analysis. As a quality control, one of the integral turbulent characteristics, σw/u*, was used to exclude that part of data which may violate the Monin-Obukhov similarity, in combining with other reasonability assessments. We yielded a sub-set data of 6 806 available from the total of 8 152 in the year. A footprint model based on an analytical solution was applied to calculate the 2-dimenasional footprints for the LAS measurements. Accordingly, seasonal mean footprints, as well as the mean footprints for 12 types of meteorological conditions at this site, were calculated. Wind direction, wind speed and atmospheric stability were used to determine the meteorological type. Finally, as an example, footprint climatology for sensible heat flux was derived, by averaging the footprints with the real flux measurements as the weight function. Results showed that: the mean footprint at this site varied little seasonally, stability and wind direction influenced the footprint size and location significantly  while the wind speed played a relatively weak role in it. Long-term mean turbulent fluxes and their spatial representativeness can be expressed better by the flux-weighted mean footprint, which differed from the simple mean footprint slightly at this site, for the case of sensible heat flux.

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