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Turbulent Flux Transfer over Bare-Soil Surfaces: Characteristics and Parameterization.
- Source :
- Journal of Applied Meteorology & Climatology; Jan2008, Vol. 47 Issue 1, p276-290, 15p, 8 Charts, 10 Graphs
- Publication Year :
- 2008
-
Abstract
- Parameterization of turbulent flux from bare-soil and undercanopy surfaces is imperative for modeling land–atmosphere interactions in arid and semiarid regions, where flux from the ground is dominant or comparable to canopy-sourced flux. This paper presents the major characteristics of turbulent flux transfers over seven bare-soil surfaces. These sites are located in arid, semiarid, and semihumid regions in Asia and represent a variety of conditions for aerodynamic roughness length (z<subscript>0</subscript><subscript>m</subscript>; from <1 to 10 mm) and sensible heat flux (from -50 to 400 W m<superscript>-2</superscript>). For each site, parameter kB<superscript>-1</superscript> [=ln(z<subscript>0</subscript><subscript>m</subscript>/z<subscript>0</subscript><subscript>h</subscript>), where z<subscript>0</subscript><subscript>h</subscript> is the thermal roughness length] exhibits clear diurnal variations with higher values during the day and lower values at night. Mean values of z<subscript>0</subscript><subscript>h</subscript> for the individual sites do not change significantly with z<subscript>0</subscript><subscript>m</subscript>, resulting in kB<superscript>-1</superscript> increasing with z<subscript>0</subscript><subscript>m</subscript>, and thus the momentum transfer coefficient increases faster than the heat transfer coefficient with z<subscript>0</subscript><subscript>m</subscript>. The term kB<superscript>-1</superscript> often becomes negative at night for relatively smooth surfaces (z<subscript>0</subscript><subscript>m</subscript> ∼ 1 mm), indicating that the widely accepted excess resistance for heat transfer can be negative, which cannot be explained by current theories for aerodynamically rough surfaces. Last, several kB<superscript>-1</superscript> schemes are evaluated using the same datasets. The results indicate that a scheme that can reproduce the diurnal variation of kB<superscript>-1</superscript> generally performs better than schemes that cannot. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 15588424
- Volume :
- 47
- Issue :
- 1
- Database :
- Complementary Index
- Journal :
- Journal of Applied Meteorology & Climatology
- Publication Type :
- Academic Journal
- Accession number :
- 30033616
- Full Text :
- https://doi.org/10.1175/2007JAMC1547.1