Premium
Regional sensible heat flux and thermal roughness length of an inhomogeneous landscape
Author(s) -
Mölder Meelis,
Sugita Michiaki,
Hiyama Tetsuya,
Bergström Hans
Publication year - 1998
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/(sici)1099-1085(19981030)12:13/14<2115::aid-hyp724>3.0.co;2-5
Subject(s) - radiosonde , environmental science , roughness length , sensible heat , atmospheric sciences , flux (metallurgy) , boundary layer , planetary boundary layer , heat flux , surface roughness , meteorology , heat transfer , geology , geography , turbulence , wind speed , materials science , physics , wind profile power law , metallurgy , composite material , thermodynamics
Knowledge of regional roughness parameters is needed for remote sensing and large‐scale modelling purposes. The presently available estimates of the most problematic parameter, namely the regional thermal roughness length ( z 0t ), have mostly been determined for dry areas and are often contradictory with each other. In this study, radiosonde measurements of temperature profiles within the atmospheric boundary layer were carried out at Marsta (10 km north of Uppsala in Sweden), and local sensible heat flux and radiometric surface temperature data were collected at the same site over barley and at the Norunda forest site. Regional fluxes and surface temperatures were calculated as weighted means by assuming the measured fluxes and surface temperatures at the barley and forest stations, respectively, represent all fields and forests within the studied region. Atmospheric surface layer equations were fitted with the radiosonde temperature profiles in a mean height range of 40 to 120 m. The average logarithmic ratio ln( z 0u / z 0t ) was found to be about 1·5 for the representative 10 km upwind area. This value is much lower than has been reported earlier for various region‐scale studies. As the region comprised a large amount of forests (up to 50%), the regional z 0t was closer to the larger local value of z 0t for forest than to the smaller value of z 0t found for barley. Copyright © 1998 John Wiley & Sons, Ltd.