Changes in aerosol effective radiation forcing from CESM2 to CESM3_development. Short wave or long wave? #47
Replies: 4 comments 3 replies
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I haven't look in detail at the ERF breakdown, but our latest estimate is about -0.7 W/m2. I just calculated the breakdown of cloudy and clear-sky components from 2x10 year runs as: ![]() I'm not seeing a very large LWCF effect. How large is it for you? @brianpm @cmcclus @islasimpson have you looked at all at the precipitation differences and/or changes to the circulation? Run details are here: NCAR/amwg_dev#641 |
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Thank you for the information. I get much higher numbers except for net: dRESTOM -0.42; dSWCF -1.41; dLWCF 0.93; dFSNTC -0.17; dFLNTC=-0.22 Now granted I use a different aerosol formulation although the difference has not been that large before. Also I use 2014 -1850 aerosols but that should not matter too much. I plan to run ERF for individual compounds next (Sulfur; BC; OM). I hope that this can give me some ideas as the dLWCF should not be anywhere near what I am getting. |
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I should probably need to check the implementation of hetfreez as well, in case BC has received more weight than it should. Thank you for providing your ERF numbers. |
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The SST field is a PI estimate, but I do not think that is critical (sst_HadOIBl_bc_1x1_clim_pi_c101029.nc) |
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Hi
Although NorESM has a different aerosol parameterisation than CESM, the numbers for ERF have been fairly close for released versions. The same seems to hold true for NorESM3-development / CESM3 development as both are decreasing compared to NorESM2 / CESM2. My latest estimate for NorESM3-development version is -0.7 W m-2 and if I have not misunderstood the same reduction is also found in CESM3. However when I look more into the details it seem that the reason for change is not some much a reduction in cloud short wave effect but a quite large positive LW cloud effect. Is this the case also for the CESM3 development version?
What I also find interesting is that the increase in LWCF is less local to the aerosol regions than the more negative SWCF so it looks more like a circulation response than impact from the aerosols themselves. In particular there seems to be a southward shift in Atlantic and Eastern Pacific ITCZ even without the change in SST pattern as one typically finds in a coupled simulation with increased NH aerosols. As in CAM we do not in general underestimate / overestimate the precipitation in Amazon / West Africa in uncoupled simulations but the impact of the added aerosol is to increase the precipitation in the Amazon region. Do you find the same for CESM3.
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