Publications

Sun, GH; Hu, ZY; Wang, JM; Xie, ZP; Lin, Y; Huang, FF (2016). Upscaling analysis of aerodynamic roughness length based on in situ data at different spatial scales and remote sensing in north Tibetan Plateau. ATMOSPHERIC RESEARCH, 176, 231-239.

Abstract
The aerodynamic roughness length (Z(0m)) is a crucial parameter in quantifying momentum, sensible and latent heat fluxes between land surface and atmosphere, and it depends greatly on spatial scales. This paper presents a tentative study on the upscaling analysis of z(0m) in the north Tibetan Plateau based on in situ data from eddy covariance (EC) and large aperture scintillometer (LAS) and leaf area index (LAI) of MODerate-resolution Imaging Spectroradiometer (MODIS) with 250 m and 2 km spatial resolutions. The comparison of z(0m) calculated from EC (z(0m_EC)) and LAS (z(0m_LAS)) data indicates that z(0m) at both scales has apparent seasonal variations and is in good agreement with the LAI result However, z(0m_LAS) is higher than z(0m_EC) which is attributed to the differences in roughness elements in their footprints. An upscaling relationship for z(0m) is developed with Z(0m_EC), Z(0m_IAS) and LAI with 250 m spatial resolution of MODIS. In addition, an altitude correction factor is introduced into the vegetation height estimation equation because the cold environment in the north Tibetan Plateau, which is due to its high altitude, has a strong influence on vegetation height. The z(0m) retrieval with 250 m spatial resolution in the rain season is validated with z(0m_EC) at sites Nagqu/Amdo, Nagqu/MS3478 and Nagqu/NewD66, and the agreement is acceptable. The spatial distribution of z(0m) retrievals at small spatial scale in the north Tibetan Plateau from June to September 2012 shows that the z(0m) values are less than 0.015 m in most areas, with the exception of the area in the southeast part, where z(0m) reaches 0.025 m owing to low altitudes. The z(0m), retrievals at large spatial scale in the north Tibetan Plateau from June to September 2012 range from 0.015 to 0.065 m, and high values appear in the area with low altitudes. The spatial distribution and frequency statistics of Z(0m) retrievals at both spatial scales reveal the influence of altitude and LAI on the z(0m) in the north Tibetan Plateau, suggesting the uniqueness of the Tibetan Plateau. (C) 2016 Elsevier B.V. All rights reserved.

DOI:
10.1016/j.atmosres.2016.02.025

ISSN:
0169-8095