Here you find information about the ongoing model simulations that are done within the HD(CP)² project.
For each simulation day there is a short scientific reasoning, accompanied with a little video. The videos are from the imaging radiometer SEVIRI aboard the geostationary Meteosat satellite. They show a composition of visible reflected solar and thermal infrared information. The land surfaces appear in green, oceans / lakes are dark. Low- to medium-level clouds (primarily liquid) appear in white to gray colors and glaciating cloud tops lead to an increased cyan portion. The high and cold clouds have been lightlighted using their infrared brightness temperature: from blue at -33°C to dark red at -63°C. The convectively-active regions are therefore visually enhanced to catch the attention. Information about spatial texture is also included for cold clouds, which increases the visibility of cloud-top features like overshooting tops, propagating and breaking gravity waves as well as wave interference patterns.
Seviri data, 02.05.2013
The 2nd of May 2013 has been selected as a first day to be simulated with perturbed aerosol concentrations since on this day, multiple different cloud regimes are covered within the model domain so that different hypotheses about aerosol-cloud interactions can be investigated in parallel.
Seviri data, 05.05.2013
This day shows a typical development of a cloudy boundary layer, typical for a continental-European, early-summer day. Processes of interest that can be analyzed in this day are, for example, turbulence, entrainment, spatial and temporal aerosol and cloud variability.
Seviri data, 15.08.2014
The 15. August 2014 case is characterised by isolated convective systems, randomly distributed over Germany. It is a clean case in the sense that the systems develop and grow during the afternoon, but they remain mostly stationary without strong interactions between them.
Seviri data, 28.05.2013
On May 28th, 2013 the area over Central Europe is characterized by a meridional weather situation with a trough over France and a cut-off over Poland. A low over Great Britain is weather-determining for the western part of Germany.
A core mission of the HD(CP)² project is to advance climate prediction. One of the key uncertainties about climate prediction is the effective radiative forcing due to aerosol-cloud interactions in response to anthropogenic aerosol emissions. The ability of the ICON model to simulate cloud distributions and -processes depending on (perturbed) aerosol distributions and to thus deliver a consistent 3D field of all relevant parameters is the key to interpret the observational data. The 2nd of May 2013 has been selected as a first day to be simulated with perturbed aerosol concentrations since on this day, multiple different cloud regimes are covered within the model domain so that different hypotheses about aerosol-cloud interactions can be investigated in parallel.
A cloud condensation nuclei concentration representative for 1985 has been chosen, because in the mid-1980s the aerosol concentration was about twice the one in 2013. The decline is due to air quality legislation over entire Europe, and due to economic restructuring over Eastern Europe. The perturbation is thus very large, so a good signal-to-noise ratio may be obtained.
The simulations for this day are done and can be found at our Redmine page. If you don't have access to the HD(CP)² Redmine, please contact Matthias Brück.
May 5th of 2013 is a day that was part of project's first phase observation campaign HOPE. This day shows a typical development of a cloudy boundary layer, typical for a continental-European, early-summer day. With this day it is investigated if ICON_LEM at its high resolution (spatial resolution of 150 m) is capable of reproducing the observed boundary layer structures. By employing both detailed column observations from ground-based supersites and 3D-field satellite observations of the full domain, we will be able to assess the high-resolution ICON_LEM on different spatial and temporal scales.
Processes of high interest are turbulence and entrainment, spatial and temporal aerosol and cloud variability, cloud microphysics (some of the clouds are developing precipitation in the observations), the resulting variability in irradiance at the surface, as well as the resulting atmospheric heating rate profiles.
The simulations for this day are done and the data can be found at our Redmine page.
The main tasks of the project S5 are to characterise convective organization in observations and models and to assess the importance of convective organization for climate. To that aim, cases characterised by different degrees of convective organization are needed. The organization index SCAI was applied to brightness temperature retrievals over Germany. From this analysis, the 15. August 2014 with a maximum SCAI around 0.3 was obtained. A large SCAI index means a smaller degree of organization. The 15. August 2014 case is characterised by isolated convective systems, randomly distributed over Germany. It is a clean case in the sense that the systems develop and grow during the afternoon, but they remain mostly stationary without strong interactions (e.g. merging).
Similarly as May 5th, May 28th is first characterized by a classical boundary layer development (mixing layer height growing rapidly from 8 to 10 UTC) with first cumulus humilis occuring around 10:00. First cirrus clouds appear around 16:00 announcing an occlusion front which passed over Jülich at around 18-20 UTC (see gop.meteo.uni-koeln.de/ag_crewell/doku.php. In contrast to May 5, we are not able to observe a full BL evoulution throughout the day in Jülich nor in Lindenberg. However, ICON assessment of a transition from a locally forced to a synopically forced weather situation is possible on this day and would provide valueable insights not only on low-level boundary layer cloud processes, but also on ICON_LEM's capability for capturing frontal ice clouds and precipitation (scattered thunderstorm were possible during the occlusion passage).
The data from the simulations can be found at our Redmine page.
Seviri data, 24.11.2015
On 24th November 2015, a typical widespread Atlantic frontal system passed Germany from the North-West caused by a low pressure system over Island. The descending ice clouds associated with the warm front showed sublimating ice and snow on the cloud bottom which transformed over the day into light drizzle.
Seviri data, 02.05.2013
To assess the signature of rapid cloud adjustments, a simulation for 2nd May 2013 will be conducted with a quadrupled CO2 concentration. The day was chosen since it features a large variety of cloud regimes. The perturbed simulation will be compared to the existing control simulation with current CO2 concentrations.
Improving the representation of ice and mixed-phase clouds is a key requirement for improving climate predictions and numerical weather forecasts, which are core objective of the HD(CP)² project. It is currently unclear to which extent resolved dynamics and model resolution or potentially insufficiently represented microphysical processes like depositional growth/sublimation, aggregation, riming, and melting contribute to the often observed discrepancies between simulations and observations. The challenge of predicting the precipitation on the ground was connected to the dry air close to ground which caused most of the precipitation to evaporate on its way to the ground. Such situations are typical situations when the forecast predicts to early and too much light rain on the ground because the dry air layer is not well captured in the model. It is expected that the high-resolution ICON simulation are better able to capture this dry layer and hence sublimating precipitation within the boundary layer.
Intensive observations with multi-frequency Doppler cloud radar and surrounding scanning polarimetric radars in combination with four radiosonde launches at JOYCE also revealed the presence of riming and strongly aggregating snow regions within the cloud.
A central uncertainty in greenhouse warming is the response of clouds to the initial radiative forcing by greenhouse gases. It became clear recently that only a part of the cloud response occurs at slow time scales as sea surface temperatures warm. In turn, a considerable fraction (~ a third) is due to rapid adjustments of clouds occurring at the response time scales of the atmosphere and land surfaces. A substantial fraction of this response occurs at very short (hours to days) time scales in response to altered radiative heating profiles in the atmosphere, and changed surface fluxes and boundary layer structure. The high-resolved model can serve as a reference for these uncertain responses in climate models.
In order to assess the signature of rapid cloud adjustments, a simulation for 2nd May 2013 will be conducted with a quadrupled carbon dioxide concentration in the high-resolved model seen by the radiation scheme. The day was chosen since it features a large variety of cloud regimes. The perturbed simulation will be compared to the existing control simulation with current CO2 concentrations.