Simulations for assessing model extensions using the obstacle-resolving model MITRAS

Project: Investigating climate change related impacts on the urban winter climate of Hamburg - Influences of climate change on urban climate are often investigated in the context of increased values for high temperatures or precipitation extremes. As a consequence, many studies concentrate on the climate change impacts that happen during summer. When looking at projected temperature and precipitation changes, mean changes are larger in winter than in summer, at least for northern Germany. At the same time, the distribution of temperature is broadened, which implies that winters with temperatures below freezing point or snowfall will still happen in the future.

The aim of this project is to quantify climate change related impacts on the winter climate of Hamburg in detail. For this purpose, an existing canopy resolving model (MITRAS) will be expanded to allow a detailed analysis of precipitation including snow and of frost distribution at the local scale. With this tool the impact on the local winter climate, as well as of adaption measures developed for a changed summer climate are investigated. To ensure model results occur in time a code optimisation and parallelisation is part of this project.

This project was financed within the framework of the Helmholtz Institute for Climate Service Science (HICSS), a cooperation between Climate Service Center Germany (GERICS) and University Hamburg, Germany (https://www.hicss-hamburg.de/projects/urban_winter_hamburg/).
Summary: This dataset contains the results of nine simulations performed for the validation of the snow cover and precipitation scheme used in the microscale, obstacle-resolving model MITRAS v3.0 (Salim et al., 2013; Schluenzen et al., 2018), v3.1 (Ferner et al. 2023), and v3.3 (Samsel et al. 2025, in review). The model domain extends 240 m x 210 m horizontally and includes orography, slanted roofs, obstacle corners and different surface cover classes. The simulations were performed using different model versions, initial temperatures, precipitation and processing modes. The simulations cover 62 minutes model time, starting at 7:30 am model time, with a temporal resolution of 5 seconds or 5 minutes. This dataset contains a selection of output variables, control variables are not included.

The file names of the data sets are composed as follows.

{temperature}_{intensity}_{model version}_{comment}_{case ID}.nc

There are 3 intensities for temperature: low, medium, high
Associated values are:
T_low = 272 K, T_medium = 280 K, T_high = 288 K
Three versions are considered: v3p0 = MITRAS v3.0 (initial version), v3p1 = MITRAS v3.1 (inclusion of warm rain scheme), v3p3 = MITRAS v3.3 (inclusion of winter parameterisation scheme)
Special cases are 'noparallel', where the simulation was performed with the parallelisation mode switched off, and 'noprecip', where no precipitation is initialised.

Example:
T_high_v3p1_Hwr.nc