Project start: 01.10.2021

Duration: 1 Jahr

Funding: Bavarian State Ministry for the Environment and Consumer Protection

Project lead: Prof. Dr. Harald Kunstmann

Involved scientists: M.Sc. Jan N. Weber

Project partners:

Prof. Dr.-Ing. Markus Disse, M.Sc. Lucas Alcamo, Dipl.-Geoökol. Michael Tarantik, TU Munich, LS Hydrology and River Basin Management

Head

The summers of 2018 and 2019, as particularly dry and at the same time particularly hot months, have put the vegetation in Franconia and in the Steigerwald in particular under high stress. As a consequence of climate change, such extreme summers will occur more frequently and more intensively in the future, so that a better strategy for the adaptation and mitigation of long dry periods and droughts urgently needs to be developed. This project is intended to be a puzzle piece of that approach.

STUDIO is a joint project of the University of Augsburg and the Technical University of Munich. In pillar 1 of the project, the University of Augsburg, under the direction of Prof. Harald Kunstmann, analyzes seasonal forecasts for their performance in Franconia. The predictions are improved using mathematical methods such as statistical downscaling and bias corrections, and a prototype for display is developed on this basis. With the help of these forecasts, significantly improved statements about the weather of the next 40 days up to seven months are possible.

In pillar 2 of the project, the Technical University of Munich, led by Prof. Markus Disse, is researching the efficiency of decentralized small-scale reservoirs in forested areas. These small-scale reservoirs could play a decisive role in the storage of rainwater and the accumulation of soil moisture and thus contribute significantly to strengthening the resilience of forests to drought. For this purpose, measurement stations were set up on site in the Steigerwald, which are further supported by LIDAR measurements and model-based evaluations.

Pillar 1:

The objectives of this part of the project are:

• Downscaling and bias correction of the predictions.
• Evaluation of the corrected forecasts
• Calculation of drought indicators
• Creation of a prototype for the operationalization of a prediction product

The project part of the University of Augsburg focuses on the evaluation of seasonal forecasts for Franconia and their presentation. The aim is to create a prototype for operationalizing a forecast product that extends up to seven months into the future and provides more reliable values than a purely climatological forecast. The resulting forecasts, along with hindcast data, can be used to drive Pillar 2 hydrologic models. The SEAS5 model of the European Centre for Medium-Range Weather Forecasts (ECMWF) is used as the forecast model. The reference is the E-OBS data of the European Climate Assessment & Dataset (ECA&D) project. To achieve the largest possible data set, the years 1981–2020 are considered.

The raw SEAS5 data are relatively coarse with 25 km resolution and have both a systematic bias and a tendency to drift in a certain direction with increasing prediction time (model drift). Without a correction the data are not reliable, thereforew they have to be processed in several steps. This increases the resolution sixfold and removes the bias.

Due to climate change, pronounced periods of drought are increasing, especially in Franconia. These droughts are most devastating when, in addition to a water shortage, exceptionally hot temperatures occur at the same time, so-called compound events. Therefore, drought indicators such as the Standardized Precipitation Evaporation Index (SPEI) or the Palmer Drought Severity Index (PDSI) are calculated in addition to the variables provided by ECMWF.

In order to display the forecasts we have corrected and evaluated, the prototype of a visualization tool is to be created. This could look, for example, like the figure above, in which the tercile prediction of one month is shown. The darker the color, the more likely the prediction is to occur. In this example, you can see a wet forecast for central and northern Germany, coupled with maximum temperatures that are likely to be lower than usual.

Pillar 2:

For more detailed information on the second pillar of the STUDIO project, we would like to refer to the website of our colleagues at the TU Munich:

https://www.cee.ed.tum.de/hydrologie/forschung/laufende-projekte/studio/

The development of this project takes place in close cooperation with local stakeholders, such as the forest administration and the Steigerwald Center. The findings will subsequently be made available to potential decision-makers.