twolayermodel

[chrisroadmap]

• update docstrings to be fully PEP-compliant
• SECPERYEAR needs updating to mean tropical year length (365.24219 days): two repositories use 365 days so this will need to be in a later release (better still, make days_per_year an input with a default)
• Refactoring: pylint has graffitied all over it
• increase coverage