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- Title
Simple Parameterization of Aerodynamic Roughness Lengths and the Turbulent Heat Fluxes at the Top of Midlatitude August‐One Glacier, Qilian Mountains, China.
- Authors
Guo, Shuhai; Chen, Rensheng; Liu, Guohua; Han, Chuntan; Song, Yaoxuan; Liu, Junfeng; Yang, Yong; Liu, Zhangwen; Wang, Xiqiang; Liu, Xiaojiao; Wang, Lei; Zheng, Qin
- Abstract
The fluxes of sensible heat (H) and latent heat (LE), which are generally the important parts of the energy and mass balances over glacier surfaces, are widely quantified by the bulk method. However, due to the difficulty of determining the aerodynamic roughness length z0m in this method, H and LE values may still have large uncertainties with significant inaccuracy. To acquire reliable varying and intrinsic z0m values, new simpler parameterizations for z0m values at different ranges of the friction velocity u*b were fitted in this study. The method was implemented using the related meteorological data and glacial sublimation/condensation measured at the top of the August‐one glacier (4817 m asl) in the Qilian Mountains from 1 July 2016 to 15 August 2017. The parameterization shows that z0m increased sharply when u*b exceeded 0.43 m/s (the approximate threshold value) and that the effect of snowdrift was slight for the hourly z0m values in the range 0.15 ≤ u*b ≤ 0.43 m/s, which could thus be used to calculate the daily z0m. During the wet period (1 July to 24 September 2016 and 5 May to 15 August 2017), the turbulent fluxes calculated by the bulk method showed that net radiation Rnet was the primary source of surface energy (60.7 w/m2), whereas during the dry period (25 September 2016 to 4 May 2017), the main heat sink was the positive H (28.5 w/m2) rather than the negative Rnet (−10.0 w/m2). Plain Language Summary: The profile method and the bulk method have been applied to quantify turbulent fluxes and sublimation/condensation, and the bulk method is more widely used because it is insensitive to observation errors. However, determination of the aerodynamic roughness lengths in the bulk method remains a large challenge. So we tried to acquire reliable varying and intrinsic roughness length for momentum through its parametric analysis. The related meteorological data and glacial sublimation/condensation were measured over a mountain glacier. Hourly roughness lengths in the transitional range affected slightly by snowdrift were found with the approximate threshold value. The comparison provided here verifies that these values are reliable, although this method is relatively rough. The z0m parameterization can be regarded as an important basis of turbulent heat flux research. Therefore, in addition to z0m parameterization, it can also be very meaningful to further discuss the temporal variation of meteorology and turbulent heat fluxes. Further research is needed and very important to improve our understanding of energy and mass exchange between the glacier surface and atmosphere, especially in arid and semiarid regions. Key Points: A parameterization method is proposed to easily estimate aerodynamic roughness lengths (z0m) at glacier surfaces, using the bulk and profile methodsHourly z0m values in the transitional range affected slightly by snowdrift are determined with the analysis of the parameterizations for z0m on the August‐one glacierThe discrepancy in turbulent heat fluxes for different periods is closely related to the variations in main meteorological variables
- Subjects
HEAT transfer; SUBLIMATION (Chemistry); RENEWABLE energy sources; SURFACE energy; EMISSIONS (Air pollution)
- Publication
Journal of Geophysical Research. Atmospheres, 2018, Vol 123, Issue 21, p12,066
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2018JD028875