An improved non-iterative surface layer flux scheme for atmospheric stable stratification conditions

Abstract

Abstract. Parameterization of turbulent fluxes under stably stratified conditions has always been a challenge. Current surface fluxes calculation schemes either need iterations or suffer low accuracy. In this paper, a non-iterative scheme is proposed to approach the classic iterative computation results using multiple regressions. It can be applied to the full range of roughness status 10 ≤ z/z 0 ≤ 10 5 and −0.5 ≤ log(z 0 /z 0h ) ≤ 30 under stable conditions 0 < Ri B ≤ 2.5. The maximum (average) relative errors for the turbulent transfer coefficients for momentum and sensible heat are 12 % (1 %) and 9 % (1 %), respectively.

Evaluating the impacts of cumulus, land surface and ocean surface schemes on summertime rainfall simulations over East-to-southeast Asia and the western north Pacific by RegCM4

“…It is noticed that, between these ocean surface schemes, the crucial difference is the determination of ocean surface roughness length which plays important roles in estimating various air-sea fluxes (e.g., Garratt 1992;Fairall et al 1996;Powell et al 2003;Li et al , 2014. BATS1e uses a constant roughness length of 2 × 10 −4 m, while those for Zeng1 and Zeng2 are calculated based on the friction velocity (u * , see Eqs.…”

The efficient urban canopy dependency parametrization (SURY) v1.0 for atmospheric modelling: description and application with the COSMO-CLM model for a Belgian summer

“…They are taken as input for the SURY. The default urban canopy parameters correspond to the recommended values for the medium urban category in Loridan and Grimmond (2012); see their one-dimensional heat equation of a vertical column commonly used in existing land-surface schemes. In the methodology, the buildings and pavements are considered as massive impermeable structures stacked on the natural soil.…”

“…On the one hand, they are suitable for extensive offline evaluations of the urban land-surface schemes (e.g. Loridan and Grimmond, 2012;Grimmond et al, 2011). On the other hand, such detailed canopy inventories form a basis for spatially varying data sets with a world-wide coverage, such as Faroux et al (2013), Loveland et al (2010), Jackson et al (2010) and Bartholomé and Belward (2005).…”

An Update of Non-iterative Solutions for Surface Fluxes Under Unstable Conditions

“…To avoid iterations, non-iterative schemes that directly calculate the stability parameter ζ from the bulk Richardson number (Ri B ) and roughness lengths (z 0 and z 0h ), have been proposed and widely used (e.g., Launiainen 1995;Kot and Song 1998;Yang et al 2001;Li et al 2010Li et al , 2014Wouters et al 2012;Sharan and Srivastava 2014). For example, the recently proposed non-iterative scheme of Li et al (2010), which is valid for −2 ≤ Ri B ≤ 1, 10 ≤ z/z 0 ≤ 10 5 and 0.5 ≤ z 0 /z 0h ≤ 100, has been implemented in the Weather Research and Forecasting (WRF) model version 3.4 and later versions (e.g., http://www.nco.…”

“…The WRL12 scheme is valid for −5 ≤ Ri B ≤ 2.5, 10 ≤ z/z 0 ≤ 10 5 and −0.5 ≤ ln(z 0 /z 0h ) ≤ 30, and the SS14 scheme is valid for −5 ≤ Ri B ≤ 0, 10 ≤ z/z 0 ≤ 10 5 and 0 ≤ ln(z 0 /z 0h ) ≤ 29. However, Li et al (2014, LGL14 hereafter) divided the roughness lengths (z 0 and z 0h ) into eight regions in which the bulk Richardson number (Ri B ) range was further separated into several (4-7) sections, and then performed regression for each section. The LGL14 scheme is valid for 0 ≤ Ri B ≤ 2.5, 10 ≤ z/z 0 ≤ 10 5 and −0.5 ≤ ln(z 0 /z 0h ) ≤ 30.…”