Assessing the potential of semi-empirical estimates of evapotranspiration from peatlands in Bavaria by means of remote sensing
Authors: Kuch Verena , Marzahn Philip , Klatt Janina , Ramsauer Thomas , Huber García Verena , Ludwig Ralf , Drösler Matthias 
Published: March 2022

&lt;p&gt;Understanding the water balance of peatlands requires a more profound knowledge of spatiotemporal patterns of evapotranspiration (ET). Resulting fluctuations in water table can further have a substantial impact on carbon storages or emissions. In Bavaria, peatland management is recently gaining increasing attention due to its potential to contribute reaching ambitious climate change mitigation targets.&lt;/p&gt;&lt;p&gt;In the framework of the KliMoBay project (www.klimobay.de), spatially-distributed ET was modeled over the representative peatland &amp;#8220;Schechenfilz&amp;#8221; (latitude: 47.806/ longitude: 11.327) in the South of Bavaria from 2015 to 2020, as an initial testbed. The project requires spatially explicit ET information, as key input variable for modelling water table dynamics, for all peatland areas in Bavaria and uses remote sensing techniques to obtain full spatial coverage.&lt;/p&gt;&lt;p&gt;The following two models were tested and compared: i) Triangle Method by Jiang und Islam (1999) and ii) DATTUTDUT (Deriving Atmosphere Turbulent Transport Useful To Dummies Using Temperature) model by Timmermans et al. (2015). Both are based on the land surface energy balance as well as land surface temperatures (LST) to calculate ET. The DATTUTDUT model, which scales between LST values representing hydrologic limits of potential ET and non-evaporative fraction, only needs LST information for the calculation, but can be supported with auxiliary observed net radiation data. The Triangle Method typically depends on measured ground data (here: net radiation and air temperature) and uses an extension of Priestley-Taylor equation and a relationship between LST and NDVI.&lt;/p&gt;&lt;p&gt;Comparison with in situ measurements of Eddy-Covariance-Towers indicate that the retrieval from the DATTUTDUT model improves from a RMSD of 0.18 mm/h to 0.11 mm/h when additionally measured net radiation is utilized. The Triangle Method, initially designed for applications in arid and semi-arid regions, gives the best results (RMSD of ET = 0.26 mm/h), when the relationship of LST and NDVI fits a triangle between extreme wet and dry conditions of the existing data points. Tests show that an adjustment of the triangle shape taking very wet conditions into account, further improves the results. Both models show promising results and bare potential for modeling ET over Bavarian peatlands.&lt;/p&gt;&lt;p&gt;KliMoBay is funded by the Bavarian State Ministry of Environment and Consumer Protection through the European Regional Development Fund.&lt;/p&gt;&lt;p&gt;References&lt;/p&gt;&lt;p&gt;Jiang, Le; Islam, Shafiqul (1999): A methodology for estimation of surface evapotranspiration over large areas using remote sensing observations. In: &lt;em&gt;Geophysical Research Letters &lt;/em&gt;(17), S. 2773&amp;#8211;2776.&lt;/p&gt;&lt;p&gt;Timmermans, Wim J.; Kustas, William P.; Andreu, Ana (2015): Utility of an Automated Thermal-Based Approach for Monitoring Evapotranspiration. In: &lt;em&gt;Acta Geophys. &lt;/em&gt;63 (6), S. 1571&amp;#8211;1608.&lt;/p&gt;