Are there any linked Issues or Pull Requests?
No response
Brief description
This replicates ticket 895 on trac
LFRic, and previously the UM, uses sea ice melt pond area fraction, and melt pond thickness, for surface albedo calculations (in JULES). Until now, these variables have been passed as mean over sea ice (melt pond area fraction) and as mean over melt pond area (melt pond thickness). Where there is covariance between these variables and sea ice area fraction within ocean cells underlying an LFRic grid cell, this can lead to surface albedo biases. Passing these variables as grid box means (GBM) is preferable, as it lets the atmosphere see a more representative sample of surface types.
A NEMO branch to allow melt pond variables to be sent as GBM has already been written; correspondingly, LFRic must be configured to receive them as such. After receipt, melt pond area fraction must be divided through by sea ice area fraction; melt pond thickness by sea ice area fraction and melt pond area fraction (or alternatively, by GBM melt pond area fraction in a single step).
Given that this change will be included in the first released coupled configuration using LFRic (GC6) it's suggested that the behaviour is included without a switch. There are no configurations that will need to use the old behaviour.
Further details of the issue.
No response
Are there any linked Issues or Pull Requests?
No response
Brief description
This replicates ticket 895 on trac
LFRic, and previously the UM, uses sea ice melt pond area fraction, and melt pond thickness, for surface albedo calculations (in JULES). Until now, these variables have been passed as mean over sea ice (melt pond area fraction) and as mean over melt pond area (melt pond thickness). Where there is covariance between these variables and sea ice area fraction within ocean cells underlying an LFRic grid cell, this can lead to surface albedo biases. Passing these variables as grid box means (GBM) is preferable, as it lets the atmosphere see a more representative sample of surface types.
A NEMO branch to allow melt pond variables to be sent as GBM has already been written; correspondingly, LFRic must be configured to receive them as such. After receipt, melt pond area fraction must be divided through by sea ice area fraction; melt pond thickness by sea ice area fraction and melt pond area fraction (or alternatively, by GBM melt pond area fraction in a single step).
Given that this change will be included in the first released coupled configuration using LFRic (GC6) it's suggested that the behaviour is included without a switch. There are no configurations that will need to use the old behaviour.
Further details of the issue.
No response