Hello All,

there are standard names for a number of upwelling and downwelling fluxes, 
defined clearly as the component of radiation which is travelling upwards or 
downwards. The sign convention of these fluxes is not specified .. CMIP uses 
the convention that downwelling is positive down and upwelling is positive 
upwards, but in the atmospheric literature you can find people using the 
convention that both are positive upwards. Both approaches make sense, but it 
leaves us with some ambiguity in the standard names.

Since 2008 there are a few terms like 
minus_one_times_surface_upwelling_longwave_flux_in_air which are defined as 
having the opposite sign convention to terms without "minus_one_times_". But 
surface_upwelling_longwave_flux_in_air has no explicit sign convention. The 
inclusion of the minus_one_times terms implies that at least some people 
thought that the existing standard names should have a specific sign convention 
... and I hope, if that is the case, that it can be consistent with CMIP. If 
so, can we clear up the ambiguity by adding a line in the description of these 
standard names to say that the sign convention is positive upwards/downwards 
for upwelling/downwelling fluxes?

regards,
Martin
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