Investigating the impact of Land-use and land-cover change on Aerosol-Cloud-precipitation interactions using Polarimetric Radar retrievals (ILACPR)

Project based at the
University of Bonn: Prabhakar Shrestha (PI)

Project ILACPR provides new insights on the impact of anthropogenic land-use and land-cover changes on precipitating cloud structure and its dynamics. Multiple ensemble simulations with the Terrestrial Systems Modeling Platform terrsysmp along with observations from Bonn X Band Polarimetric Radar (BoxPol) over the northwestern part of Germany, bordering Netherlands, Belgium, Luxemburg and France will provide synthetic and observed polarimetric fingerprints for common analysis of microphysical and macrophysical processes, including sensitivity to prescribed large scale forcing.

Figure 1: Spatial patterns of topography and vegetation cover for the Bonn Radar domain. The major cities and the stream networks derived from the topography using pre-processing tools for the model are also shown.

Current Status : 2021

Figure 1: Cross-sections of observed and synthetic radar data of summertime convective storm. Also shown is the modeled hydrometeors in the lower panel, including 0 𝐶 line showing location of melting layer, hail mixing ratio in solid lines with QG. The blue arrow indicates the location of maximum vertical velocity.

Evaluation of synthetic radar data (processed using B-PRO) with observations provides valuable insights to the microphysical processes of the summertime convective storms. The simulated ZDR column is primarily contributed by rain drops (with size > 1 mm). Graupel dominates the frozen hydrometeor categories above the melting layer. Low concentration of hail is present on the adjacent size of the peak updraft, but dominates much of the radar reflectivities.

Figure 2: Ensemble frequency distribution for different land-cover types with low (10 mm) and high (> 10 mm) accumulated precipitation.

Sensitivity experiments with large scale aerosol perturbations and land-cover change was found to have less impact on the statistics of domain average precipitation, but effects the partitioning of low and high precipitation. It’s effect on polarimetric variables is currently being processed using the recently released EMVORADO-Pol with lookup tables. The TerrSysMP was also updated to include the chemical transport model ART (Aerosols and Reactive Trace gases). The ensemble simulations with TerrSysMP-ART for the summertime convective storm cases are currently ongoing at JSC supercomputers.

A new input data for a model domain (Figure 1) covering the extent of the BoxPol was prepared. The data consists of land-use and subsurface representation in terms of vegation types, multiple year phenology, soil texture, aquifers and slopes derived from topography. The hydrological component of the model was used to generate initial soil-vegetation-groundwater states for multiple years using a recursive and transient spinup.

Figure 2: CFADs of horizontal and differential reflectivity for one ensemble member of Terrestrial Systems Modeling Platform (TSMP).

Using the spinup soil-vegetation states, diurnal scale ensemble simulation with data from COSMO-DE Ensemble Prediction System (EPS) was conducted for a hail storm event. Statistical properties of polarimetric quantities were evaluated using Contoured Frequency Altitude Diagrams (Figure 2). Additional ensemble sensitivity simulations were conducted for the same storm case using large scale aerosol perturbations and landuse change. Further, additional simulations for multiple storms are under progress to generalize the findings.

This work is funded by Deutsche Forschungsgemeinschaft (DFG) as a subproject of the priority programme SPP 2115. The synthetic polarimetric output from the model was obtained using the Bonn Polarimetric Forward Operator. The computing time for this project was additionally funded by the Gauss Centre for Supercomputing e.V. through the John von Neumann Institute for Computing (NIC) on the GCS Supercomputer JUWELS at Jülich Supercomputing Centre (JSC).