Diabatic transport
Set-up for diabatic transport calculations
For diabatic transport, MPTRAC loads the fields \(\dot{\zeta}\), \(\zeta\), and \(p\) in the original \(\eta\) hybrid coordinate system from the CLaMS dataset. This approach avoids additional interpolation from \(\zeta\) to \(p\). However, other fields remain in pressure coordinates since several MPTRAC modules require a pressure-based formulation.
To ensure compatibility, \(\zeta\) and \(p\) are converted back and forth before and after advection. Consequently, vertical model pressure levels must be explicitly defined. The following configuration is required for proper reading and transformation of CLaMS data:
MET_CLAMS = 1
MET_VERT_COORD = 1
MET_PRESS_LEVEL_DEF = 3
To enable vertical advection in \(\zeta\) coordinates with diabatic transport, set the following parameters and include \(\zeta\) as an atmospheric quantity:
ADVECT_VERT_COORD = 1
NQ = 1
QNT_NAME[0] = zeta
Eta-coordinate transport
MPTRAC can also advect parcels with the model-level eta tendency \(\dot{\eta}=d\eta/dt\). The eta coordinate is calculated from the full-level hybrid coefficients as
Set MET_VERT_COORD = 3, provide the full-level A and B coefficients via
MET_NLEV, MET_LEV_HYAM, and MET_LEV_HYBM, and include an etadot or
ETADOT field in each meteorological netCDF file. Eta-coordinate advection
also requires the prognostic parcel quantity eta:
MET_VERT_COORD = 3
ADVECT_VERT_COORD = 3
NQ = 3
QNT_NAME[0] = eta
QNT_NAME[1] = eta_dot
QNT_NAME[2] = eta_d
Here, eta is the prognostic coordinate used by the advection scheme,
eta_dot is the meteorological eta tendency interpolated to the parcel
position, and eta_d is eta diagnosed independently from parcel pressure on
the native model levels. The diagnostic eta_d is available with
MET_VERT_COORD = 2 or 3. Missing etadot or ZETA_DOT input is treated
as an error when the corresponding vertical-advection mode is enabled.
Predefined pressure level sets
The MET_PRESS_LEVEL_DEF parameter allows selection from several
predefined vertical pressure level sets, based on ECMWF model level
definitions. Additional
near-surface levels have been added (down to ~1045 hPa) to reduce
extrapolation errors.
By default, MET_PRESS_LEVEL_DEF = -1, meaning predefined sets are
ignored. Sets 0, 1, and 2 are disabled because their near-surface spacing can
require extrapolation where the local surface pressure exceeds 1013.25 hPa.
Set 6 is the recommended default for ERA5-like model-level data. Set 7 keeps
the coarser ERA-Interim/L60 spacing near the surface and is intended for
ERA-Interim- and JRA-55-like data.
| MET_PRESS_LEVEL_DEF | Name | bottom | top | number of levels | notes |
|---|---|---|---|---|---|
| 0 | L137 | disabled | disabled | disabled | replaced by set 3 |
| 1 | L91 | disabled | disabled | disabled | replaced by set 4 |
| 2 | L60 | disabled | disabled | disabled | replaced by set 5 |
| 3 | L137 | 1044.45 hPa | 0.02 hPa | 147 | extended L137 with fine near-surface spacing |
| 4 | L91 | 1044.45 hPa | 0.02 hPa | 101 | extended L91 with fine near-surface spacing |
| 5 | L60 | 1044.45 hPa | 0.01 hPa | 62 | extended L60 |
| 6 | L137 | 1044.45 hPa | 0.01 hPa | 137 | recommended default for ERA5-like data |
| 7 | L60 | 1046.13 hPa | 0.1 hPa | 59 | ERA-Interim/JRA-55-like L60 grid with extrapolated lower levels |
Recommended settings for common meteorological data sources:
| Data source | MET_PRESS_LEVEL_DEF | notes |
|---|---|---|
| ERA5 | 6 | recommended default |
| ERA-Interim | 7 | keeps the ERA-Interim/L60-like spacing and 0.1 hPa top |
| MERRA-2 | 6 | uses a 0.01 hPa top, matching the native upper model domain |
| JRA-3Q | 6 | uses a 0.01 hPa top for the extended upper model domain |
| JRA-55 | 7 | closer to the 60-level, 0.1 hPa-top setup |