Within UKCA, N2O5 hydrolysis
N2O5 + H2O --> HONO2 + HONO2
is actually covered by 2 separate reactions, H04 and B85. There is actually considerable overlap of these reactions in the troposphere, leading to overcounting.
A fix is to ensure, using the tropospheric mask, that only H04 works in the stratosphere and B85 only works in the troposphere.
This will be controlled with a temporary logical and changes are required to the UM (MetOffice/um#61), lfric_apps (MetOffice/lfric_apps#432), and UKCA to account for this, along with new STASH output to be able to check that the logic is working as intended.
This issue was originally identified by Dr Yao Ge (@yg460-cam) in Cambridge, and she provided the original UM and UKCA code changes at UM13.9.
het_rxn_diffs.pdf shows comparisons between two simulations performed by Yao at UM13.9, highlightning the improvement given by this change (top) compared to the default behaviour (bottom).
Within UKCA, N2O5 hydrolysis
N2O5 + H2O --> HONO2 + HONO2
is actually covered by 2 separate reactions, H04 and B85. There is actually considerable overlap of these reactions in the troposphere, leading to overcounting.
A fix is to ensure, using the tropospheric mask, that only H04 works in the stratosphere and B85 only works in the troposphere.
This will be controlled with a temporary logical and changes are required to the UM (MetOffice/um#61), lfric_apps (MetOffice/lfric_apps#432), and UKCA to account for this, along with new STASH output to be able to check that the logic is working as intended.
This issue was originally identified by Dr Yao Ge (@yg460-cam) in Cambridge, and she provided the original UM and UKCA code changes at UM13.9.
het_rxn_diffs.pdf shows comparisons between two simulations performed by Yao at UM13.9, highlightning the improvement given by this change (top) compared to the default behaviour (bottom).