id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
257	Introduction of Lev2a Tdry variable	Ian Culverwell	Ian Culverwell	"Kent Bækgaard Lauritsen at DMI has suggested the following development:

{{{

Hi Dave, Ian

As we've discussed at previous PT meetings DMI uses the dry temperature. 
It can be derived by the ROPP code and is then stored in the temp variable 
in the level 2b block. Currently its value is stored in our 'atm' file that 
contains the BA and REF values.

We foresee two potential problems with this approach:

- in our 'wet' files (output from the 1dvar) there will be the T and q 
variables. A user having both atm and wet files may then get confused 
about these two different temperature values stored in a variable with 
the same name. Even though it may be described clearly in the PUM, 
we know that in reality not all users will read this document carefully.

- we would also like to 'forward model' the model T,q,P values to not 
only BA and REF but also to Tdry. Since the background files (the 'bgr' files) 
already has a temperature stored in the T variable in the level 2b block, 
Tdry cannot be stored there.


We think that the optimal solution for us would be to have an extra field 
in the level 2a block and store Tdry there. We think this would be a 
logical choice since Tdry is on the same levels as the refractivity.


DMI would therefore like to suggest the following:

1. DMI will do the necessary coding needed to introduce a Tdry variable in 
the level 2a block.

2. DMI will write a new routine for the forward modelling of T,q into Tdry 
using the forward modelling present in ROPP_PP.
This should also be part of the routine for forward modelling a BG file 
into BA and REF.

3. Met Office will make the final polishing of this code and update the 
documentation.


The DMI contributions will be done by Kjartan and Stig.
They will be in close contact with the ROPP DT in order that they 
follow as closely as possible the ROPP logic.

Please let us know your comments to this suggestion.


Kent

}}}

Sounds good to me.  Timescales?  Any further comments?
 "	enhancement	closed	normal	6.1	ROPP (all)	5.0	fixed	Tdry, Twet, Lev2a