TY - JOUR
T1 - Impact of Roughness Length on WRF Simulated Land-Atmosphere Interactions Over a Hyper-Arid Region
AU - Nelli, Narendra Reddy
AU - Temimi, Marouane
AU - Fonseca, Ricardo Morais
AU - Weston, Michael John
AU - Thota, Mohana Satyanarayana
AU - Valappil, Vineeth Krishnan
AU - Branch, Oliver
AU - Wulfmeyer, Volker
AU - Wehbe, Youssef
AU - Al Hosary, Taha
AU - Shalaby, Abdeltawab
AU - Al Shamsi, Noor
AU - Al Naqbi, Hajer
N1 - Funding Information:
We acknowledge the National Center of Meteorology (NCM) for kindly providing weather station data used for model evaluation. This study is supported by the UAE Research Program for Rain Enhancement Science (UAEREP). We are also grateful to Hans-Dieter Wizemann from the University of Hohenheim for operating the eddy-covariance station and processing the raw measurements. We would like to thank Dr. Niranjan Kumar Kondapalli from the National Center for Medium Range Weather Forecasting, Noida, India for useful discussions during the preparation of the manuscript.
Publisher Copyright:
© 2020. The Authors.
PY - 2020/6/1
Y1 - 2020/6/1
N2 - The aerodynamic roughness length is a crucial parameter that controls surface variables including the horizontal wind, surface temperature, and heat fluxes. Despite its importance, in the Weather Research and Forecasting (WRF) model, this parameter is typically assigned a predefined value, mostly based on the dominant land-use type. In this work, the roughness length is first estimated from eddy-covariance measurements at Al Ain in the United Arab Emirates (UAE), a hyper-arid region, and then ingested into WRF. The estimated roughness length is in the range 1.3–2.2 mm, one order smaller than the default value used in WRF. In line with previous studies, and from WRF model simulations during the warm and cold seasons, it is concluded that, when the roughness length is decreased by an order of magnitude, the horizontal wind speed increases by up to 1 m s−1, the surface temperature rises by up to 2.5°C, and the sensible heat flux decreases by as much as 10 W m−2. In comparison with in situ station and eddy covariance data, and when forced with the updated roughness length, WRF gives more accurate 2-m air temperature and sensible heat flux predictions. For prevailing wind speeds >6 m s−1, the model underestimates the strength of the near-surface wind, a tendency that can be partially corrected, typically by 1–3 m s−1, when the updated roughness length is considered. For low wind speeds (<4 m s−1), however, WRF generally overestimates the strength of the wind.
AB - The aerodynamic roughness length is a crucial parameter that controls surface variables including the horizontal wind, surface temperature, and heat fluxes. Despite its importance, in the Weather Research and Forecasting (WRF) model, this parameter is typically assigned a predefined value, mostly based on the dominant land-use type. In this work, the roughness length is first estimated from eddy-covariance measurements at Al Ain in the United Arab Emirates (UAE), a hyper-arid region, and then ingested into WRF. The estimated roughness length is in the range 1.3–2.2 mm, one order smaller than the default value used in WRF. In line with previous studies, and from WRF model simulations during the warm and cold seasons, it is concluded that, when the roughness length is decreased by an order of magnitude, the horizontal wind speed increases by up to 1 m s−1, the surface temperature rises by up to 2.5°C, and the sensible heat flux decreases by as much as 10 W m−2. In comparison with in situ station and eddy covariance data, and when forced with the updated roughness length, WRF gives more accurate 2-m air temperature and sensible heat flux predictions. For prevailing wind speeds >6 m s−1, the model underestimates the strength of the near-surface wind, a tendency that can be partially corrected, typically by 1–3 m s−1, when the updated roughness length is considered. For low wind speeds (<4 m s−1), however, WRF generally overestimates the strength of the wind.
KW - Aerodynamic roughness length
KW - hyper-arid region
KW - near-surface wind speed
KW - sensible heat flux
KW - surface temperature
KW - WRF model
UR - http://www.scopus.com/inward/record.url?scp=85086846211&partnerID=8YFLogxK
U2 - 10.1029/2020EA001165
DO - 10.1029/2020EA001165
M3 - Article
AN - SCOPUS:85086846211
SN - 2333-5084
VL - 7
JO - Earth and Space Science
JF - Earth and Space Science
IS - 6
M1 - e2020EA001165
ER -