High Resolution regional reanalysis from a Mars GCM and MM A. M. Valeanu, P. L. Read, S. R. Lewis, L. Montabone 29/08/2018 Hello everyone, I’m AV, and I’ll be talking about <title>. Initially I wanted to make a presentation of our studies of the planetary boundary layer which obviously required a higher resolution approach, thus the use of the mesoscale model… but then I realized that I can bring more to the workshop by shifting the focus towards proving set-up itself.

Nonetheless, I will have to swiftly introduce our main project, just to put everything in context. OK! So the plan was to study the PBL from direct comparison between the REMS instrument onboard the Curiosity rover (which is obviously in the PBL) and the environment at Gale Crater where Curiosity is located. So what this sketch tries to prove is the following: - first, a direct comparison from spacecraft observations (like the MRO MCS here) is unfeasible due to the lack of spatio-temporal coverage of Gale Crater - so then, why not assimilate in a global model, and then locate the region and we solved the coverage problem. - but the resolution was limiting such a study. - so in the end, we instead constructed 1. DA and the PBL

1. DA and the PBL Better resolution can be obtained from the downscaler The MGCM+MMM set-up is relevant for studies involving resolved Physics at lower scale than a global model and future spacecraft missions (forecasting MGCM) OK so to summarize, we get better resolution from using the downscaler system. And this is another depiction of the codes in action which also shows the specific region where we embedded the MMM. The interface between the two codes is done automatically, so we can chose any other region for study.

2. The models The UK/LMD Mars GCM (MGCM) The LMD Mars MM (MMM) Dynamical core: pseudo-spectral model based on Hoskins & Simmons (1975) in the horizontal, with sigma levels in the vertical. The Analysis Correction DA scheme was used to assimilate MCS temperatures The LMD Mars MM (MMM) Dynamical core: non-hydrostatic real-grid model adapted from the ARW-WRF, with eta coordinates in the vertical Both models have similar physical core schemes Now the models that we chose, have actually a traditional bond, which is the similarity in the physical cores. The two models are: <read from slide>

2. Models – viable set-up? Information flow – connectivity between scales One may argue that the purpose of data assimilation is to force the atmospheric states of the MGCM to couple with the MCS temperatures, independent of information flow (energy) However, the strict one-way influence from the MGCM to the MMM does require validation. OK so we already know that this is a common tool for Earth’s atmosphere, but is it viable for Mars as well? Or in other words, is the atmosphere manifesting this direction of information from higher scales to lower scales naturally? To answer this, we must look at the information flow of the atmosphere itself. The mesoscale model stage downscales the resolution of the atmospheric states at Gale Crater, hence the MGCM+MMM set-up is just effectively trying to match MCS' observations, thus rendering the information flow-argument irrelevant. It is only when taking into account the strict one-way influence between the two models that information flow becomes important. So again, is this actually happening in reality?

2. Models – Spectral Lorenz Energy Budget To answer this question, we turned to the diagnostic tool initially developed by LA, 2013. We adapted this for Mars’ atmosphere and it turned out that the MGCM+MMM setup is viable! I will explain this in the next slide. But currently, I wanted to discuss what I highlighted here as well. They authors developed this diagnostic tool for a direct comparison of the energy spectra of two well known Earth models. And amusingly, the higher resolution model performed poorly at reproducing all the spectrum analyses, so the AFES performed better at this. So what I’m saying is that this method can be essential if we want to do an inter-comparison between reanalyses

3. Spectral energy studies But returning to the spectral energy fluxes, this complicated plot is just a glimpse of what are the capabilities of this method. We can also compute the energy spectrum of the KE and APE reservoirs but also look at spectral vertical fluxes. I won’t go into more detail, as the most important feature for our set-up is the direction of energy flux. And we can see that the total energy flux is positive along the spectrum, which means that energy is indeed flowing to lower scales and hence the MGCM+MMM set-up is proven.

3. Spectral energy studies The spectrally resolved energetics of the Martian atmosphere proves that information flows from the MGCM to the MMM Good diagnosis tool for MGCMs and reanalyses in general!

4. Results And finally, we can look at the models in action

4. Results So why do we want to study the atmosphere in spectral space? We know with a reduced number of exceptions, that a smooth function on a sphere at each moment in time can be expanded as a superposition of spherical harmonics. Think of this function as one of the parameters which describe the atmosphere (like velocity or temperature).

4. Results So why do we want to study the atmosphere in spectral space? We know with a reduced number of exceptions, that a smooth function on a sphere at each moment in time can be expanded as a superposition of spherical harmonics. Think of this function as one of the parameters which describe the atmosphere (like velocity or temperature).

5. Conclusions The MGCM+MMM set-up is valid and a powerful tool The spectral energetics study is a good tool for proving the set-up above and also for reanalyses intercomparison So why do we want to study the atmosphere in spectral space? We know with a reduced number of exceptions, that a smooth function on a sphere at each moment in time can be expanded as a superposition of spherical harmonics. Think of this function as one of the parameters which describe the atmosphere (like velocity or temperature).

Thank you! So why do we want to study the atmosphere in spectral space? We know with a reduced number of exceptions, that a smooth function on a sphere at each moment in time can be expanded as a superposition of spherical harmonics. Think of this function as one of the parameters which describe the atmosphere (like velocity or temperature).