Improved Modeling of Surface Layer Parameters in a AGCM Using Refined Vertical Resolution in the Surface Layer
Abstract
Surface layer (SL) parameters in atmospheric models - such as 2-m air temperature (T2), 10-m wind speed (U10), and surface turbulent fluxes - are computed by applying the Monin-Obukhov Similarity Theory (MOST) to the lowest model level height (LMH) in the models. The underlying assumption is that LMH is within surface layer height (SLH), but most AGCMs hardly meet the condition in stable boundary layers (SBLs) over land. To assess the errors in modeled SL parameters caused by this, offline computations of the MOST are performed with different LMHs from 1 to 100 m, for an idealized SBL case with prescribed surface parameters (surface temperature, roughness length and Obukhov length), and vertical profiles of temperature and winds. The results show that when LMH is higher than SLH, T2 and U10 are underestimated by O(1 K) and O(1 m/s), respectively, and the biases increase as LMH increases. Based on this, the refined vertical resolution with an additional layer in the SL is applied to the GFDL AGCM, and it reduces the systematic cold biases in T2 and the systematic underestimation of U10.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.A51A2028S
- Keywords:
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- 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSES;
- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 3379 Turbulence;
- ATMOSPHERIC PROCESSES;
- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES