Difference between revisions of "Aerosol working group minutes"
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This page will hold minutes of meetings of the UKCA-GLOMAP-mode aerosol working group. |
This page will hold minutes of meetings of the UKCA-GLOMAP-mode aerosol working group. |
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+ | * [[Minutes_of_the_aerosol_working_group_meeting_12/12/2013|Minutes of meeting held 12/12/2013 over teleconf]] |
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* [[Minutes_of_the_aerosol_working_group_meeting_22/11/2013|Minutes of meeting held 22/11/2013 over teleconf]] |
* [[Minutes_of_the_aerosol_working_group_meeting_22/11/2013|Minutes of meeting held 22/11/2013 over teleconf]] |
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* [[Minutes_of_the_aerosol_working_group_meeting_12/09/2013|Minutes of meeting held 12/09/2013 over teleconf]] |
* [[Minutes_of_the_aerosol_working_group_meeting_12/09/2013|Minutes of meeting held 12/09/2013 over teleconf]] |
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− | Summary of actions: |
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− | 1) JM/AJ to try no-DMS run also to see how much the DMS is contributing to the AOD there. |
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− | 2) GM to try sensitivity study where multiply sedimentation velocity by 2 (modal underpredict sedi?) |
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− | 3) CJ to investigate precipitation rates in Southern Ocean region and whether wet dep may be inefficient there. |
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− | 4) JM to report how bias looks at GA6 CheT+GLOMAP job when all bug-fixes have been applied. |
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− | 5) CJ/BJ to try sensitivity run with convective scavenging coeffs reduced from 1.0 to 0.5 |
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− | 6) Next UKCA aerosol teleconf 2pm Thurs 12th Dec |
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− | Notes from UKCA aerosol teleconference held Friday 22nd November between Leeds & MO |
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− | Present: Ken Carslaw, Graham Mann, Colin Johnson, Jane Mulcahy, Ben Johnson, Steve Rumbold, Alastair Sellar. |
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− | There were 2 main topics of discussion for the teleconference aimed as resolving the two remaining issues re: the current v8.4 GA4 CheT+GLOMAP job – which are: |
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− | 1) AOD and sea-spray too high in Southern Ocean (and also Arctic) |
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− | 2) AOD and BC, OC (also sulphate?) column-mass too low in biomass burning regions |
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− | 1) S. Ocean AOD high bias |
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− | At Sept 12th telecon, discussion was held about the very high AODs in the model in the S. Ocean. |
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− | At that time job amtjn had large region with AOD>0.5 during SH summer (DJF) and max value of ~0.45 in JJA (winter). |
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− | Had identified either sea-spray or DMS as potential causes. |
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− | Had discovered S. Ocean DMS was very high-biased (b=0.29, 3.04, 3.31 at 3 S. Ocean sites). |
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− | Had resolved to try changing Wanninkhof Liss Merlivat sea-air transfer (known to generate much lower DMS emission). |
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− | Equivalent job ajkzi (using LM sea-air) reduced DMS high bias substantially (b=-0.11,1.66,1.22 for same sites). |
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− | AOD from ajkzi job (using LM sea-air) reduced AOD slightly in S. Ocean – peak now just below 0.5 in S. Ocean during DJF. |
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− | Comment from marine biogeochemistry group was why use Liss Merlivat since it was so old. |
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− | After a discussion MO folks resolved to try runs with Nightingale instead. |
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− | But Leeds commented this falls within Wann & LM so this not expected to reduce DMS high-bias. |
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− | Action: JM/AJ to try no-DMS run also to see how much the DMS is contributing to the AOD there. |
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− | 2nd progress since last time was that SW had found factor-0.5 was being applied in fall velocity due to code-merge error. |
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− | JM had circulated plots (5th Nov) showing impact of sedi bug-fix – DJF AOD in SO then peaks at 0.4 rather than 0.5. |
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− | Bigger impact on AOD during SH winter when sea-salt is dominant contribution (SO peak at ~0.35 rather than ~0.45). |
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− | But although AOD reduced, still much too high against collection-6 MODIS and AERONET which show AOD ~0.1 there). |
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− | BJ explained he had checked AODs in each mode in the region and found coarse mode AOD contributed ~0.3 AOD on the annual mean so main source of high-AOD likely to be sea-salt not DMS. |
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− | CJ explained budget analysis shows removal of sea-salt showed 45% by dry-dep-sedi and 55% by nucscav/imscav. |
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− | This was surprising as coarse mode expected to show sedimentation as dominant removal process. |
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− | Action: GM to try sensitivity study where multiply sedimentation velocity by 2 (modal underpredict sedi?). |
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− | Action: CJ to investigate precipitation rates in Southern Ocean region and whether wet dep may be inefficient there. |
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− | Note: CLASSIC sea-spray AOD was found to much higher at GA4 than GA3 or GA5 so expect reduction anyway GA4GA5/6. |
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− | Action: JM to report how bias looks at GA6 CheT+GLOMAP job when all bug-fixes have been applied. |
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− | 2) AOD too low in biomass burning regions |
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− | GM had suggested at UKESM-UKCA meeting on Wed that BC/OC seemed reasonable in biomass regions so why AOD low? |
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− | BJ had checked and although BC and OC mass burdens do show expected plumes in biomass regions, they are lower than at v7.3 which suggests AOD low-bias is consistent with BC/OC burdens so not an issue re: RADAER. |
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− | BJ explained that spatial patterns in column-integrated SO4, BC and POM suggested too much scavenging in tropical regions --- likely that convective (plume) scavenging implementation was too aggressively scavenging. |
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− | Omission of re-evaporation also likely to mean scavenging needs turning down. |
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− | Action: CJ/BJ to try sensitivity run with convective scavenging coeffs reduced from 1.0 to 0.5. |
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− | Next UKCA aerosol teleconf meeting will be held at 2pm on Thursday 12th December. |
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− | This is scheduled for 1 week ahead of UKESM-UKCA meeting on 19th Dec (target date for GA6 CheT+GLOMAP evaluation). |
Latest revision as of 23:22, 15 December 2013
This page will hold minutes of meetings of the UKCA-GLOMAP-mode aerosol working group.