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Thursday, 20 Jul 2017

Radiation column-model

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Like several other EMAC submodels, the aerosol optical-properties and radiation models operate on a vertical column of the atmosphere. For such submodels, the analogue to box models for developing and testing submodels operating on a single grid cell of the atmosphere (e.g., chemistry submodels) are column models. As one major goal of the climate activities at the Cyprus Institute is to advance the aerosol and radiation code in EMAC, we have implemented a column model which calls the original EMAC subroutines to compute aerosol optical properties, radiative fluxes and heating rates for a vertical column of the atmosphere. Once implemented and tested in the column model, new features are immediately available for global model runs. Our initial implementation is already actively used, but at the same time is constantly extended and improved.


In the EMAC output required to run the initial version of the column model, data redundancy has been reduced. The amount of data written to disk at each EMAC time step has been reduced by a factor of 1000. This allows obtaining the data needed for later analysis in the column model even for long term simulations.


ClimateAtmospheric column in an EMAC simulation. A single vertical column of grid cells is highlighted with white edges.
The data is taken from a simulation performed on Cy-Tera.


The data format used been switched from CSV to NetCDF. This increased IO performance significantly both during global model runs with enabled column-model data output and in column-model runs. In addition, the code now takes advantage of the clarity and flexibility of the NetCDF data model.


A set of shell scripts to support benchmarking and comparing the effects of any changes made to the MESSy AEROPT module has been developed. The scripts employ the column version of AEROPT and use the R programming language for post-processing and visualisation (R replaces the initially employed Ferret visualisation and data analysis tool, as it has proven to be better suited for this task). By this testing procedure many global simulation test-runs on Cy-Tera are avoided and thereby the computational load reduced. In addition, without the need of (wall-clock) time consuming global runs for testing, the workflow for modifying the AEROPT module is vastly accelerated.


The column model and results obtained therewith have been presented at the conference "Energy Water and Climate Change (EWACC) - Building bridges between Europe and Middle East/North Africa 2012" [1, 2] as well as on a workshop at the Weizmann Institute of Science in Israel [3]. A journal publication is in preparation.


[1] K. Klingmueller, B. Steil, C. Bruehl, J. Lelieveld; Mixing-state sensitivity of aerosol absorption in EMAC; Poster, EWACC 2012

[2] S. Metzger, K. Klingmueller, P. Hadjinicolaou, N. Mihalopoulos, B. Steil, C. Bruehl, J. Lelieveld; The importance of aerosol water for air pollution effects on weather and climate; Poster, EWACC 2012

[3] K. Klingmueller; On the parametrisation of absorption by black carbon; Talk, GIF (German-Israeli Foundation for Scientific Research and Development) meeting, Weizmann Institute of Science, Rehovot, Israel, March 2013