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 = 0

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

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. For ERA5 data, it is recommended to use set 6.

MET_PRESS_LEVEL_DEF	Name	bottom	top	number of levels
0	L137	1044.45 hPa	0.02 hPa	138
1	L91	1044.45 hPa	0.02 hPa	92
2	L60	1044.45 hPa	0.01 hPa	60
3	L137	1044.45 hPa	0.02 hPa	147
4	L91	1044.45 hPa	0.02 hPa	101
5	L60	1044.45 hPa	0.01 hPa	62
6	L137	1044.45 hPa	0.01 hPa	137
7	L60	1046.13 hPa	0.1 hPa	59