Optimizing the parameterization of deep mixing and internal seiches in one-dimensional hydrodynamic models: a case study with Simstrat v1.3

Abstract

Abstract. This paper presents an improvement of a onedimensional lake hydrodynamic model (Simstrat) to characterize the vertical thermal structure of deep lakes. Using physically based arguments, we refine the transfer of wind energy to basin-scale internal waves (BSIWs). We consider the properties of the basin, the characteristics of the wind time series and the stability of the water column to filter and thereby optimize the magnitude of wind energy transferred to BSIWs. We show that this filtering procedure can significantly improve the accuracy of modelled temperatures, especially in the deep water of lakes such as Lake Geneva, for which the root mean square error between observed and simulated temperatures was reduced by up to 40 %. The modification, tested on four different lakes, increases model accuracy and contributes to a significantly better reproduction of seasonal deep convective mixing, a fundamental parameter for biogeochemical processes such as oxygen depletion. It also improves modelling over long time series for the purpose of climate change studies.

Toward an open access to high-frequency lake modeling and statistics data for scientists and practitioners – the case of Swiss lakes using Simstrat v2.1

“…For the pe- riod of 1981-2015, the ascending trend in solar radiation is 5 W m −2 decade −1 , which corresponds to an equilibrium temperature increase of about 0.2 • C decade −1 . The warming rate at the surface of Lake Brienz is larger than observed trends in neighboring lakes with reported increases of +0.46 • C decade −1 for upper Lake Constance (1984-2011Fink et al, 2014), +0.41 • C decade −1 for lower Lake Zürich (1981-2013, Schmid and Köster, 20161955-2013, Livingstone, 2003, and +0.55 • C decade −1 for lower Lake Lugano (1972-2013Lepori and Roberts, 2015). This can be explained by the lower light penetration in Lake Brienz (ranging from ∼ 1 to ∼ 10 m) compared to other lakes, the increase in solar radiation being distributed into a shallower layer and thereby warming the lake surface slightly more.…”

“…The uncertainty quantification finally allows an appropriate informed use of the output data. Yet more advanced methods for both parameter estimation and uncertainty quantification such as Bayesian inference (Gelman et al, 2013) should be applied to Simstrat.…”

“…We use the 1-D lake model Simstrat v2.1 to model 54 Swiss lakes or reservoirs (see Appendix A for details of modeled lakes) in an automated way. Simstrat was first introduced by Goudsmit et al (2002) and has been successfully applied to a number of lakes (Gaudard et al, 2017;Perroud et al, 2009;Råman Vinnå et al, 2018;Schwefel et al, 2016;Thiery et al, 2014). Recently, large parts of the code were refactored using the object-oriented Fortran 2003 standard.…”

Answers to reviewer 1

“…Data availability. CTD profiles are available from the Office of Water Protection and Waste Management of the Canton of Bern (GBL/AWA) at: http://www.bve.be.ch/bve/ de/index/wasser/wasser/messdaten.html (GBL/AWA, 2017). Meteorological data are available from the Swiss Federal Office of Meteorology and Climatology (MeteoSwiss) at: http://www.meteoswiss.admin.ch/home/services-and-publications/ beratung-und-service/data-portal-for-teaching-and-research.html (MeteoSwiss, 2017).…”

MFIT 1.0.0: Multiflow inversion of tracer breakthrough curves in fractured and karst aquifers

“…Both the optimization and uncertainty analysis of model parameters are carried out using PEST routines (Doherty, 2019a(Doherty, , 205 2019b. PEST is a public domain model-independent program suite that has been widely used over the past two decades, notably in the field of surface and subsurface hydrology (e.g., Long, 2015;Woodward et al, 2016;Gaudard et al, 2017;Wang et al, 2019). The theoretical framework and full range of capabilities of the PEST software are well documented (Doherty et al, 2010;Doherty, 2015Doherty, , 2019aDoherty, , 2019b and are not repeated here.…”