Suggested Changes to "MM5" Met Input

[wperkins]

I propose some changes to the [MM5] met input:

1. Terrain: Currently, the MM5 Terrain File must contain an elevation map for every simulation time step. This seems unnecessary. I propose one of

   1. Just assume the MM5 Terrain File be assumed constant, and so it's only read once; or

   2. Add a new [MM5] phrase, MM5 Terrain File Frequency, with the following choices:

      • single: A single map of lapse rate held constant through the simulation;
      • continuous: One map for each time step, as it is now.

      I prefer the former.

2. Temperature Lapse: The MM5 Temp Lapse File must also contain a lapse rate map for every simulation time step. This seems unnecessary. I propose the following modifications:
   1. MM5 Temp Lapse File = none be the default, in which case the specified Temperature Lapse Rate in [CONSTANTS] is used basin-wide.
   2. When MM5 Temp Lapse File is specified, I propose a frequency option be added to handle this map in a manner similar to the MM5 Precipitation Distribution File. A new [MM5] phrase MM5 Temperature Lapse Frequency would be added with the following choices:
      • single: A single map of lapse rate held constant through the simulation;
      • month: A set of 12 maps of lapse rate, one for each month of the year; and
      • continuous: One map for each time step, as it is now.

Thoughts?

[Lizzy0Sun]

As the elevation map doesn't change at each simulation time step, i agree we just make it a constant and let the program read it once and for all as you suggested in 1.1. I haven't use the MM5 option so I added Zhuoran to review your proposed change.

[zrduan]

@wperkins I agree with you.

For the terrain file I think one input layer is sufficient to cover most of the applications and represent the meteorology data terrain.

For temperature lapse file, I think the 4 options you have listed meets different types of user needs. And having the constant lapse rate value set as default option provides a efficient workflow for calibration and for cases where spatial varied lapse rates are not needed.

[Lizzy0Sun]

@wperkins I say go ahead with the code modification as you suggested above.

[zrduan]

@wperkins On second thought about the lapse rate - could the spatial varied lapse rate an option in both [CONSTANTS] section and the [MM5] section?

[wperkins]

@wperkins On second thought about the lapse rate - could the spatial varied lapse rate an option in both [CONSTANTS] section and the [MM5] section?

@zrduan So, you want temperature lapse to be a "mapped" constant like the snow parameters. I made a separate issue (#28) for this. If MM5 Temp Lapse File = none then the temperature lapse would be handled as defined in [CONSTANTS].

[zrduan]

@wperkins Yes. I think it's helpful to have spatial varied temperature lapse but independent from the MM5 format.

[wperkins]

Can we keep this open until the changes are actually made?