Present Day Climate

Whith this set of simulations we aim at answering the first question:

How well can models reproduce the broad range of observed mesoscale shallow cloud patterns over the sub-tropical oceans?

Partecipants are invited to follow the guidelines to parecipate with:

Storm Resolving Models (SRMs)

Domain, Period and Resolution

We want to be as flexible as possible to the participants. Therefore the only requirement we impose is that the domain size should contain at least a common analysis domain spanning 10 N to 20 N and 48 W to 61 W. The actual used domain should be larger and preferable be extended to the upstream Eastern direction. A typical used domain grid would be 6 N to 24 N and 35 W to 63 W. Due to input availability, the maximum accepted domain is 0 N to 30 N and 20 W to 76 W.

The horizontal resolutions should be in the range of 1 to 2.5 km. Multiple submissions with a high (1km) and a lower resolution are encouraged. No specific vertical resolution is prescribed as many SRM’s use their own preferred variable vertical resolution. However we encourage to use vertical resolutions of around 20 meter near the surface, and around 100 meter in the cloud layer between 1000 and 2000 m height.

The simulation period is from 0 UTC on January 1st 2020 to 0 UTC on March 1st 2020.

Initial and Boundary Conditions

The simulations of the Limited-area Models (LAMs) require a initialisation and lateral boundary conditions using (re)-analysis data of operational numerical weather prediction as well as prescribed Sea Surface Temperature (SST) observations as a lower boundary condition

Lateral Boundary Conditions are provided from the ERA5 reanalysis. The necessary ERA5 fields are provided here on a hourly frequency in a netcdf format for a domain covering 0 N to 30 N and 20 W to 76 W . The initialisation field at January 1st  0 UTC can also be obtained from the ERA5 data set. Daily SST fields are available here.

Required Output

The list of required output for simulations with SRMs is described in detail here.

Analysis domain for SRMs 

Large Eddy Models (LEMs)

Domain Period and resolution

Because of the higher computational costs a smaller domain and a shorter period has been selected for LEMs. The domain is is centered at 13.3º N and 57.7º W and comrises the HALO circle.  It is elongated on the zonal (East-West ) direction for a total domain size of 250x400 km2: from the centre, the domain spans 125km North and South, and 200 km East and West. For the vertical domain size and resoliution, the requrements are specified differetnly for open boundary LEMs and periodic boundary LEMs (please see below).

Partecipants are encouraged to use an horizontal resolutions as close as possible to 100 m, coarser resolutions up to 400 m are also accepted as alternative, or in addition.

The simulation period is from  00 UTC on February 1st 2020 to 00 UTC on February 12th 2020. The first day is to be discarded because of the spin-up so that analysis will cover the 10 day period from February 2nd to Februay 11th  2020.

Analysis domain for LEMs 

Open Boundary LEMs

Participants using LEMs with open boundary conditions should extend the vertical domain to about 21 km using a stretched grid with a resolution of 20 meter near the surface and around 100 meter at 2000 meter. An example of a vertical stretched grid can be found here.

Initial and Boundary Conditions

Lateral Boundary Conditions are provided from a simulation of the SRM COSMO and can be found here. The characteristics of the COSMO lateral boundary fields are

  • Provided fields ( T, u, v, qv, qi, , qi )  ( Temperature, horizontal wind components, water vapour specific humidity, liquid cloud water and cloud ice),
  • Spatial resolution of 2.2 km provided on a hourly basis.

Daily varying SST fields can be found here.

Periodic Boundary LEMs

Participants using LEMs with periodic boundary conditions should limit the vertical domain to 7 km using a stretched grid with a resolution <20 m near the surface and <100 m at 2000 m:  there should be about 150 model levels. An example of a vertical stretched grid can be found here.

Initial and Boundary Conditions

ERA5 is used to prescribe forcings to the model. This is done throuh the provided:

  • Houlry large scale tendencies of temperature (T), total specific humidity (qt), zonal and meridional  winds (u, v).
  • Initial profiles of temperature (T), total specific humidity (qt), zonal and meridional  winds (u, v).

Relaxation 

With peridoic boundary conditions and focings that only involve tendencies runaway effects are easy to occur. For this reason participants are required to use relaxation towards prescribed ERA5 mean profiles of temperature (T), total specific humidity (qt), zonal and meridional  winds (u, v).

The relaxation period should be height dependent following the profile available here (and image here).

Required Output

The list of required output for simulations with LEMs is described in detail here.


Back to top