Surface Turbulent Flux Measurements over the Loess Plateau for a Semi-Arid Climate Change Study

• Published in: Advances in atmospheric sciences 2009-07, Vol.26 (4), p.679-691
• Main Author: 左金清 黄建平 王介民 张武 闭建荣 王国印 李维京 付培健
• Format: Article
• Language: English
• Subjects: Arid climates; Atmospheric Sciences; Carbon dioxide; Climate change; Climate science; Climate studies; Climatic data; Earth and Environmental Science; Earth Sciences; Fluctuations; Geophysics/Geodesy; Grasslands; Latent heat; Meteorology; Semiarid climates; Semiarid environments; Sensible heat; Turbulence models; 半干旱; 地表湍流通量; 气候变化; 黄土高原
• ISSN: 0256-1530; 1861-9533
• DOI: 10.1007/s00376-009-8188-2

In order to provide high quality data for climate change studies, the data quality of turbulent flux measurements at the station of SACOL （Semi-Arid Climate ＆ Environment Observatory of Lanzhou University）, which is located on a semi-arid grassland over the Loess Plateau in China, has been analyzed in detail. The effects of different procedures of the flux corrections on CO2, momentum, and latent and sensible heat fluxes were assessed. The result showed that coordinate rotation has a great influence on the momentum flux but little on scalar fluxes. For coordinate rotation using the planar fit method, different regression planes should be determined for different wind direction sectors due to the heterogeneous nature of the ground surface. Sonic temperature correction decreased the sensible heat flux by about 9%, while WPL correction （correction for density fluctuations） increased the latent heat flux by about 10%. WPL correction is also particularly important for CO2 fluxes. Other procedures of flux corrections, such as the time delay correction and frequency response correction, do not significantly influence the turbulent fluxes. Furthermore, quality tests on stationarity and turbulence development conditions were discussed. Parameterizations of integral turbulent characteristics （ITC） were tested and a specific parameterization scheme was provided for SACOL. The ITC test on turbulence development conditions was suggested to be applied only for the vertical velocity. The combined results of the quality tests showed that about 62%-65% of the total data were of high quality for the latent heat flux and CO2 flux, and as much as about 76% for the sensible heat flux. For the momentum flux, however, only about 35% of the data were of high quality.