air2water

General Information
Acronym of the model	air2water
Full name of the model	air2water
Model components	Hydrodynamics (water temperature only)
Supported platforms	Windows, Linux
Programming Language	Written in Fortran but executable provided
Still maintained	Yes, by: Sebastiano Piccolroaz
Most recent version	Version 2.0.0
Model structure
Executables are available
0D
Model description
Model objective	A model to predict lake surface temperature using air temperature
Background knowledge needed to run model	Basic understanding of lake surface temperature dynamics
Basic procedures	1. Set-up inut files, as shown in the exampke test case 2. Run the pre-processing scripts 3. Run the executable 4. Run post-processing scripts
The air2water model can be classified as a hybrid model, which combines a physically-based equation with a stochastic calibration of model parameters. In this way, the data directly inform model parameters, whose values can provide insight into the thermal behavior of the lake due to the physically based structure of the governing equation. Model parameters are calibrated using Monte Carlo techniques that exploit an optimization algorithm, with RMSE as the relevant metric. In addition, the following indexes are used for model performance evaluation: Nash-Sutcliffe Efficiency index (NSE) as a normalized metric, the mean error (ME) as a measure of the bias of simulated LSWT compared to observations, and the maximum absolute error (MaxAE) as a very stringent index particularly sensitive to outliers (see Appendix for details).
Link to website/manual	air2water Github
Model characteristics
Input variables	Obligatory: Air temperature at daily resolution
Input file format	ASCII
Output variables	Lake surface water temperature
Output file format	ASCII
Biogeochemical model components	None
Model structure/mathematical framework	The air2water model is a simple lumped model to predict lake surface temperature using air temperature as the only external forcing. The model is derived from the volume integrated equation of heat applied to the upper volume of the lake that is directly linked to heat exchanges with the atmosphere.
Temporal resolution	Input air temperature data has to be at daily resolution
Minimal spatial resolution	none
Variables needing calibration	When predicting lake surface temperature, the model used air temperature and lake temperature during a calibration period. So, essentially the predicted lake temperatures are calibrated with those observed.
Has successfully been used in
Climate Change Scenario	Piccolroaz S, N.C. Healey, J.D. Lenters, S.G. Schladow, S.J. Hook, G.B. Sahoo, and M. Toffolon (2017), On the predictability of lake surface temperature using air temperature in a changing climate: A case study for Lake Tahoe (U.S.A.), Limnology and Oceanography, doi:10.1002/lno.10626
Shallow Lake/Reservoir	Toffolon M., S. Piccolroaz, B. Majone, A.M. Soja, F. Peeters, M. Schmid and A. Wüest (2014), Prediction of surface water temperature from air temperature in lakes with different morphology, Limnology and Oceanography, 59(6), 2185-2202, doi:10.4319/lo.2014.59.6.2185
Deep lake/Reservoir	Piccolroaz, S., M. Toffolon M., and B. Majone (2015), The role of stratification on lakes’ thermal response: The case of Lake Superior, Water Resources Research, 51(10), 7878-7894, doi:10.1002/2014WR016555
Countries in which the model has been applied	USA, Canada, Italy, Switzerland, Austria, Hungary, Russia
Which institutes have applied the model	University of Trento, Italy Eawag, Switzerland Austrian Institute of Technology, Austria University of Konstanz, Germany EPFL, Switzerland
Accessibility
Open-Source
Available tools for pre- and post-processing	Matlab scripts for pre and post-processing provided
Support	Contact authors
Can be coupled to the following models	Standalone model
How can someone get access to this model	Download from air2water Github
Miscellaneous
Useful tricks and hints	TThere is a working example provided on the github site. This shows how the model should be set-up for an example lake (Lake Superior)
Form was updated: 2018-09-05

Reference list:

Piccolroaz S., M. Toffolon, and B. Majone (2013), A simple lumped model to convert air temperature into surface water temperature in lakes, Hydrol. Earth Syst. Sci., 17, 3323-3338, doi:10.5194/hess-17-3323-2013

Toffolon M., S. Piccolroaz, B. Majone, A.M. Soja, F. Peeters, M. Schmid and A. Wüest (2014), Prediction of surface water temperature from air temperature in lakes with different morphology, Limnology and Oceanography, 59(6), 2185-2202, doi:10.4319/lo.2014.59.6.2185

Piccolroaz, S., M. Toffolon, and B. Majone (2015), The role of stratification on lakes’ thermal response: The case of Lake Superior, Water Resources Research, 51(10), 7878-7894, doi:10.1002/2014WR016555

Piccolroaz S. (2016), Prediction of lake surface temperature using the air2water model: guidelines, challenges, and future perspectives, Advances in Oceanography and Limnology, 7:36-50, DOI: http://dx.doi.org/10.4081/aiol.2016.5791

Piccolroaz S, N.C. Healey, J.D. Lenters, S.G. Schladow, S.J. Hook, G.B. Sahoo, and M. Toffolon (2017), On the predictability of lake surface temperature using air temperature in a changing climate: A case study for Lake Tahoe (U.S.A.), Limnology and Oceanography, in press, doi:10.1002/lno.10626