Simple Parameterization of Aerodynamic Roughness Lengths and the Turbulent Heat Fluxes at the Top of Midlatitude August‐One Glacier, Qilian Mountains, China

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 z(0m) in this method, H and LE values may still have large uncertainties with significant inaccuracy. To acquire reliable varying and intrinsic z(0m) values, new simpler parameterizations for z(0m) 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 z(0m) 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 z(0m) values in the range 0.15 <= u(*b) <= 0.43 m/s, which could thus be used to calculate the daily z(0m). 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 R-net was the primary source of surface energy (60.7 w/m(2)), whereas during the dry period (25 September 2016 to 4 May 2017), the main heat sink was the positive H (28.5 w/m(2)) rather than the negative R-net (-10.0 w/m(2)). 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 z(0m) parameterization can be regarded as an important basis of turbulent heat flux research. Therefore, in addition to z(0m) 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.