New TopoFlow glacier energy balance component

[bolotinl]

PR Description:

• Copied the snow base class/snow energy balance component over to a glacier base class/glacier energy balance component, and added necessary functionality for glacier routines
  • Changes to original snow functions: add new cold content for newly fallen snow first, then account for land surface energy fluxes, and if there is no snow, don't allow cold content to accumulate
  • Unique features of the glacier class: user adjustable static glacier active layer for use in cold content calculations
• Adjusted TopoFlow architecture to recognize and use the new component/output the new variables
  • New variables:
    • ice meltrate
    • ice thickness
    • ice water equivalent
    • ice cold content
    • combined ice and snow meltrate (for later feeding to GIUH)
• Created a config file for the new glacier energy balance component, based on the snow energy balance config file
• Incorporated and tested the rain vs. snow threshold temperature in the meteorology config file

Data to run the Sagehen Creek synthetic test case is located in the glacier Google Drive folder we share (I think it may have been too large to push to GitHub).

[bolotinl]

Thanks for taking a look Naoki. In response to your question, the answer is yes. This component does both snow and ice energy balance and melt, so it is intended for use in areas that are glaciated, but in theory could still run the snow routines if initialized without any ice. But it is maybe more likely that the user would just use the existing snow component in this case, though this PR includes some adjustments to the snow routines (e.g. cold content calculations).

[peckhams]

This look great, Lauren. Sorry for the delay in merging. Looking forward to your next PR. :)