Investigating incomplete solves on a LES benchmark case
I ran an experiment that was prepared by Richard.Maier, namely run offline radiative transfer computations of a high resolution cumulus cloud field with high temporal resolution. The experiment is run with a 25m horizontal resolution at timesteps of 10sec output. The solar zenith is changing from 41 deg to …

Incomplete solves runtime comparison on KCS cluster
To assess the runtime performance gain from incomplete solves, I ran a 256 x 256 pixel LES cloud field with dx=25m for 100 timesteps at dt=10 sec. The simulations use 512 cores, i.e. 16 nodes with 32 processes each. Compared are shortwave and longwave solve times for …

Ideal hill example in WRF
Presented are some results with 3D radiation (TenStream) in an idealized gaussian hill simulation in WRF-LES. The results show the capability to run with terrain following sigma coordinate meshes and highlight the importance of 3D radiative transfer effects beyond just using a slope correction of surface irradiances Setup terrain …

Performance Testing of various pprts solvers
As it turns out, the PETSc preconditioner performance is quite dependent on the direction of the sun. We find that the normal SOR sweeps are okayisch for the south west quadrant but deteriorates quite strongly if the sun is in the north east. The suspicion is that the loop structure …

Implementation of Buildings into PPRTS
The main task for us in the Mosaik-2 project is to implement immersive buildings into the TenStream and think about how to handle resolved canopies. This article is status report on the first task and is a follow up on Solar Reflection of a Diagonal vs a Zigzagged Street. The …

RayLi wrapper in pprts
Today finished the work on a new external solver for PPRTS, namely a wrapper for the MonteCarlo Raytracer RayLi from Tobi. This allows to compute irradiances and absorption in the cartesian mesh solvers (PPRTS) aswell as take virtual photographs of the simulations. The main reason to implement the raytracer was …

Solar Reflection of a Diagonal vs a Zigzagged Street
A question that came up with the way that Palm-LES handles buildings in urban environments is related to diffuse reflection of radiation. Palm uses a structured rectangular mesh and therefore can only represent grid aligned edges. So instead of having a diagonal wall fassade as in a), the buildings …

Benchmarking Tenstream in DALES
Recent runs of Menno on their cluster give tremendously bad runtime performance of the Tenstream solver in his DALES simulations. So to check what is going on, I tried to run his benchmark setup here in Munich on our linux machines. The setup is as follows: Running 64x64 pixel simulations …

Comparison Plexrt Longwave Radiation in ICON
Felix found a weird discrepancy in fluxes between the RRTMG solver and the Tenstream solvers which he used in his WRF experiments. For his purposes, it was not really necessary to have the solver to be perfectly tuned so, after we couldnt immediately find the reason behind it, we just …

Studying the partitioning between direct and diffuse components (Menno`s work)
Menno gave me some DALES cloud fields that he is working with with a request to compute the the partitioning of diffuse and direct radiation in comparison to 3D MonteCarlo results (MYSTIC). The simulations assume a constant surface albedo of 0.15 and solar zenith angle of \(60^\circ\). Next …

Effective emission of thermal radiation of a single layer
I recently changed the emission of thermal radiation. It used to be the planck emission of the mean temperature of a layer and use that in all directions, i.e. upward and downward emission have been the same. To be more consistent with DISORT and RRTMG calculations I opted to …

Tag der offenen Tuer der Physik, LMU
For the Tag der offenen Tuer der Physik we collected a couple of animations from scientists at the meteorological institute and stitched em up to present our groups research efforts. So, here you go, enjoy: Download .mp4 (297M)

Comparing 1D solvers in the TenStream lib vs the new DISORT implementation
Experiment setup: We run a small simulations for the solar and thermal spectral range and compare the results to various 1D solvers in the TenStream lib. There is a cloud with LWC=\(0.01\ [g / kg]\) between 800 and 700 hPa. The dynamics grid extends up to 250 hPa and …

Howto Generate LibRadtran Cloud files in NetCDF format
Generating a test cloud field The following snippet generates a netcdf cloud field with xarray so that it can be handled by libRadtran 3D def create_librad_netcdf_cldfile(fname, lwc, reff, hhl, dx, dy, reff_min=2.51, reff_max=55): """ Creates a netcdf cloud file for libRadtran calculations Provide: lwc and reff arrays …

Influence of the initial guess on the number iterations
Testing the influence of the initial guess on the number of iterations needed The setup is as follows: Start a ex_plex_rrtmg_fish simulation with a fish (torus) mesh with 553 columns and 65 levels and solve for direct radiation. The spectral integration goes over the 112 solar and 140 thermal spectral …

Profiling with Perf and HotSpot
Profiling with Perf and HotSpot For years I used the valgrind tool suite to find memory bugs but also for profiling with toolboxes like callgrind and cachegrind. And while those are indeed super powerful and I wouldnt want to miss em they are really slow and not particularly well suited …

Phase Diagram of param_phi and param_theta
The current implementation / handling of critical azimuth and zenith angles for ICON wedges: For a given Wedge Element out of an ICON Mesh, we define the side face which is most illuminated by the sun as the Base-face. In clockwise rotation we then have a left and right face. E …

Conference in Berlin, Poster Presentation on PlexRT, UCP2019
On this years international conference, the UCP2019 in Berlin I presented a poster with latest news and developments on the radiative transfer solver for the next generation numerical weather prediciton model, ICON. UCP stands for Understanding Clouds and Precitipation and it was the de-facto wrap up conference for the HDCP2 …

Introducing new solvers into pprts
This document briefly introduces ongoing work to enhance the 3D radiative transfer solver which is coupled to the DALES model. It turns out that strong aspect ratios lead to an enhanced downward direction of radiation propagation in the Tenstream radiative transfer solver. To overcome this, at least partially, I played …

Implementation, validation and use of the TenStream Solver coupled to the Dutch Atmospheric Large-Eddy Simulation (Menno`s Internship)
n the course of Menno Veeermans Internship at LMU Munich, he prepared a repot with the following abstract: Althought radiative transfer is an important atmospheric process, it is often solved in one dimension only. While the use of 1D radiative transferwq schemes results in considerable savings of computational time, it …

1D vs. 3D Solar Upwelling Radiation Comparison for an ICON HDCP2 Simulation
For the Added Value paper of Bjorn Stevens I did a 1D and a 3D simulation with MYSTIC for an ICON HDCP2 simulation output field. The scene is from 20140729T120230Z, i.e. file 3d_fine_day_DOM03_ML_20140729T120230Z at 156m horizontal resolution. This day starts with precipitation in the morning followed by small thunderstorms …

Penetration Depth of Thermal Radiation into Clouds
The following graph depicts the thermal cooling rates at the top of a homogeneous cloud with varying liquid water content. Notably, thermal cooling rates can be found up to 100m inside a cloud counting from the top. However, for thicker clouds the mean penetration depth is more like 25 to …

Radiative Cloud Streets Feedback and its Influence on Model Evolution
In The role of 1-D and 3-D radiative heating in the organization of shallow cumulus convection and the formation of cloud streets I simulated plenty of shallow cumulus convection with varying solar zenith angles, wind speeds and surface properties to investigate how radiation might interfere with the organization of convection …