Improving lake mixing process simulations in the Community Land Model by using &amp;lt;i&amp;gt;K&amp;lt;/i&amp;gt; profile parameterization

Qunhui Zhang,Sarah E. Null,Nick Barrett,Phaedra Budy,Xiaochun Wang,Jiming Jin

doi:10.5194/hess-23-4969-2019

Abstract

Abstract. We improved lake mixing process simulations by applying a vertical mixing scheme, K profile parameterization (KPP), in the Community Land Model (CLM) version 4.5, developed by the National Center for Atmospheric Research. Vertical mixing of the lake water column can significantly affect heat transfer and vertical temperature profiles. However, the current vertical mixing scheme in CLM requires an arbitrarily enlarged eddy diffusivity to enhance water mixing. The coupled CLM-KPP considers a boundary layer for eddy development, and in the lake interior water mixing is associated with internal wave activity and shear instability. We chose a lake in Arctic Alaska and a lake on the Tibetan Plateau to evaluate this improved lake model. Results demonstrated that CLM-KPP reproduced the observed lake mixing and significantly improved lake temperature simulations when compared to the original CLM. Our newly improved model better represents the transition between stratification and turnover. This improved lake model has great potential for reliable physical lake process predictions and better ecosystem services.

Highlights

Lake thermal processes are vital to improving our understanding of regional climate systems
The root mean square error (RMSE) of water surface temperature (WST) decreased from 0.8 ◦C with Community Land Model (CLM)-ORG to 0.4 ◦C with CLM-K profile parameterization (KPP) (Fig. 2)
Insignificant differences were seen between CLM-ORG and CLM-KPP when compared to observations for the period before 16 August (Table 1), while remarkable improvements were achieved with CLM-KPP during 16–31 August after a strong wind event occurred (Fig. 3d and e)

Summary

Introduction

Lake thermal processes are vital to improving our understanding of regional climate systems. Lakes significantly affect regional temperature, precipitation, and surface heat fluxes (Jeffries et al, 1999; Lofgren, 2004; Long et al, 2007; Rouse et al, 2008; Thiery et al, 2015). Lakes can reduce diurnal temperature variation by cooling near-surface air temperature during the day and warming it at night (Bonan, 1995; Krinner, 2003; Samuelsson et al, 2010). Regional climate modeling has shown that lakes can have a strong effect on seasonal precipitation (Diallo et al, 2018; Zhu et al, 2017). Rouse et al (2005) indicated that lakes affect surface energy balance, with higher net radiation, subsurface heat storage, and evaporation than the nearby land

Objectives

Results

Conclusion