{"action":"created","issue":{"url":"https://api.github.com/repos/StrikeNP/trac_test/issues/389","repository_url":"https://api.github.com/repos/StrikeNP/trac_test","labels_url":"https://api.github.com/repos/StrikeNP/trac_test/issues/389/labels{/name}","comments_url":"https://api.github.com/repos/StrikeNP/trac_test/issues/389/comments","events_url":"https://api.github.com/repos/StrikeNP/trac_test/issues/389/events","html_url":"https://github.com/StrikeNP/trac_test/issues/389","id":332175720,"node_id":"MDU6SXNzdWUzMzIxNzU3MjA=","number":389,"title":"Relax clipping on wpxp when xp2 is small (Trac #389)","user":{"login":"StrikeNP","id":2577059,"node_id":"MDQ6VXNlcjI1NzcwNTk=","avatar_url":"https://avatars0.githubusercontent.com/u/2577059?v=4","gravatar_id":"","url":"https://api.github.com/users/StrikeNP","html_url":"https://github.com/StrikeNP","followers_url":"https://api.github.com/users/StrikeNP/followers","following_url":"https://api.github.com/users/StrikeNP/following{/other_user}","gists_url":"https://api.github.com/users/StrikeNP/gists{/gist_id}","starred_url":"https://api.github.com/users/StrikeNP/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/StrikeNP/subscriptions","organizations_url":"https://api.github.com/users/StrikeNP/orgs","repos_url":"https://api.github.com/users/StrikeNP/repos","events_url":"https://api.github.com/users/StrikeNP/events{/privacy}","received_events_url":"https://api.github.com/users/StrikeNP/received_events","type":"User","site_admin":false},"labels":[{"id":963997231,"node_id":"MDU6TGFiZWw5NjM5OTcyMzE=","url":"https://api.github.com/repos/StrikeNP/trac_test/labels/Migrated%20from%20Trac","name":"Migrated from Trac","color":"FFFFFF","default":false},{"id":963997516,"node_id":"MDU6TGFiZWw5NjM5OTc1MTY=","url":"https://api.github.com/repos/StrikeNP/trac_test/labels/clubb_src","name":"clubb_src","color":"FFFFFF","default":false},{"id":963997249,"node_id":"MDU6TGFiZWw5NjM5OTcyNDk=","url":"https://api.github.com/repos/StrikeNP/trac_test/labels/defect","name":"defect","color":"FFFFFF","default":false},{"id":963997501,"node_id":"MDU6TGFiZWw5NjM5OTc1MDE=","url":"https://api.github.com/repos/StrikeNP/trac_test/labels/dschanen@uwm.edu","name":"dschanen@uwm.edu","color":"FFFFFF","default":false}],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":{"url":"https://api.github.com/repos/StrikeNP/trac_test/milestones/7","html_url":"https://github.com/StrikeNP/trac_test/milestone/7","labels_url":"https://api.github.com/repos/StrikeNP/trac_test/milestones/7/labels","id":3423174,"node_id":"MDk6TWlsZXN0b25lMzQyMzE3NA==","number":7,"title":"Improve CLUBB's accuracy at coarse vertical grid spacing","description":null,"creator":{"login":"StrikeNP","id":2577059,"node_id":"MDQ6VXNlcjI1NzcwNTk=","avatar_url":"https://avatars0.githubusercontent.com/u/2577059?v=4","gravatar_id":"","url":"https://api.github.com/users/StrikeNP","html_url":"https://github.com/StrikeNP","followers_url":"https://api.github.com/users/StrikeNP/followers","following_url":"https://api.github.com/users/StrikeNP/following{/other_user}","gists_url":"https://api.github.com/users/StrikeNP/gists{/gist_id}","starred_url":"https://api.github.com/users/StrikeNP/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/StrikeNP/subscriptions","organizations_url":"https://api.github.com/users/StrikeNP/orgs","repos_url":"https://api.github.com/users/StrikeNP/repos","events_url":"https://api.github.com/users/StrikeNP/events{/privacy}","received_events_url":"https://api.github.com/users/StrikeNP/received_events","type":"User","site_admin":false},"open_issues":28,"closed_issues":8,"state":"open","created_at":"2018-06-13T20:02:02Z","updated_at":"2018-06-14T15:37:59Z","due_on":null,"closed_at":null},"comments":2,"created_at":"2018-06-13T21:44:20Z","updated_at":"2018-06-14T22:59:54Z","closed_at":null,"author_association":"OWNER","body":"**Introduction**\n\nHuan Guo recently presented some output from GFDL SCM-CLUBB at coarse vertical grid spacing (L48) for 5 cases: BOMEX, RICO, ATEX, RF01, and RF02 (https://github.com/larson-group/gfdl_scm/issues/11, also see attachments below).  Some major problems are that in BOMEX, RICO, and ATEX, cloud fraction is too large, especially at higher altitudes, and the time series are too intermittent.  \n\nI examined the BOMEX simulations, and the intermittency appears to be caused by the following problem.  1) At some points in time, for unknown reasons, rtp2 = rt_tol**2 over a range of several points in the vertical.  2) Because rtp2 is small, wprtp must be clipped to a very small value in order to prevent a correlation with magnitude greater than 1.  3) However, the source terms in rtp2 all depend on wprtp.  Since wprtp is small, rtp2 remains small.  4) Finally, after an hour or so, the deadlock is broken and a burst of cumulus clouds form.\n\n**Technical spec**\n\nThe best solution that I can think of is to relax the clipping on wpxp.  Clipping is important when xp2 is large, but I doubt that it matters much when xp2 is small.  Furthermore, a correlation has little meaning when both the denominator and numerator are nearly zero.  Therefore, I think we should try relaxing the clipping on wpxp when xp2 is below some threshold value.  \n\nWe can do this by replacing ```xp2``` by \n```max( clip_factor*xp2_threshold, xp2)``` in the appropriate  calls to clip_covariance in clip_explicit.F90 and advance_xm_wpxp_module.F90.  clip_factor might have to be quite large (e.g. 1e6).  \n\nOther code modifications that may improve the coarse-res simulations are smoothing Skw_velocity or using upwind differencing in xp2_ta.  Also, we could try setting l_upwind_wpxp_ta = .true.  Finally, we could try smoothing Skw_velocity in wp3_ta (https://github.com/larson-group/clubb/issues/386).\n\n**Tests**\n\nDo a plotgen of all cases at L48 using the code before and after the code changes.  Repeat for L128 and standard grid spacing.  \n\n\nAttachments:\n\n[Atex_CF_qc_Ndcld_CLUBB_Riga_L48_L67.jpg](https://github.com/larson-group/trac_attachment_archive/blob/master/clubb/Atex_CF_qc_Ndcld_CLUBB_Riga_L48_L67.jpg)\n[Bomex_CF_qc_Ndcld_CLUBB_Riga_L48_L67.jpg](https://github.com/larson-group/trac_attachment_archive/blob/master/clubb/Bomex_CF_qc_Ndcld_CLUBB_Riga_L48_L67.jpg)\n[LWP_5cases_L48.jpg](https://github.com/larson-group/trac_attachment_archive/blob/master/clubb/LWP_5cases_L48.jpg)\n[Rico_CF_qc_Ndcld_CLUBB_Riga_L48_L67.jpg](https://github.com/larson-group/trac_attachment_archive/blob/master/clubb/Rico_CF_qc_Ndcld_CLUBB_Riga_L48_L67.jpg)\n\nMigrated from http://carson.math.uwm.edu/trac/clubb/ticket/389\n```json\n{\n    \"status\": \"closed\", \n    \"changetime\": \"2011-02-01T22:32:08\", \n    \"description\": \"'''Introduction'''\\n\\nHuan Guo recently presented some output from GFDL SCM-CLUBB at coarse vertical grid spacing (L48) for 5 cases: BOMEX, RICO, ATEX, RF01, and RF02 (gfdl_scm:ticket:11, also see attachments below).  Some major problems are that in BOMEX, RICO, and ATEX, cloud fraction is too large, especially at higher altitudes, and the time series are too intermittent.  \\n\\nI examined the BOMEX simulations, and the intermittency appears to be caused by the following problem.  1) At some points in time, for unknown reasons, rtp2 = rt_tol**2 over a range of several points in the vertical.  2) Because rtp2 is small, wprtp must be clipped to a very small value in order to prevent a correlation with magnitude greater than 1.  3) However, the source terms in rtp2 all depend on wprtp.  Since wprtp is small, rtp2 remains small.  4) Finally, after an hour or so, the deadlock is broken and a burst of cumulus clouds form.\\n\\n'''Technical spec'''\\n\\nThe best solution that I can think of is to relax the clipping on wpxp.  Clipping is important when xp2 is large, but I doubt that it matters much when xp2 is small.  Furthermore, a correlation has little meaning when both the denominator and numerator are nearly zero.  Therefore, I think we should try relaxing the clipping on wpxp when xp2 is below some threshold value.  \\n\\nWe can do this by replacing {{{xp2}}} by \\n{{{max( clip_factor*xp2_threshold, xp2)}}} in the appropriate  calls to clip_covariance in clip_explicit.F90 and advance_xm_wpxp_module.F90.  clip_factor might have to be quite large (e.g. 1e6).  \\n\\nOther code modifications that may improve the coarse-res simulations are smoothing Skw_velocity or using upwind differencing in xp2_ta.  Also, we could try setting l_upwind_wpxp_ta = .true.  Finally, we could try smoothing Skw_velocity in wp3_ta (comment:17:ticket:386).\\n\\n'''Tests'''\\n\\nDo a plotgen of all cases at L48 using the code before and after the code changes.  Repeat for L128 and standard grid spacing.  \\n\", \n    \"reporter\": \"vlarson@uwm.edu\", \n    \"cc\": \"vlarson@uwm.edu\", \n    \"resolution\": \"Verified by V. Larson\", \n    \"_ts\": \"1296599528000000\", \n    \"component\": \"clubb_src\", \n    \"summary\": \"Relax clipping on wpxp when xp2 is small\", \n    \"priority\": \"critical\", \n    \"keywords\": \"\", \n    \"time\": \"2011-01-09T22:07:27\", \n    \"milestone\": \"Improve CLUBB's accuracy at coarse vertical grid spacing\", \n    \"owner\": \"dschanen@uwm.edu\", \n    \"type\": \"defect\"\n}\n```\n"},"comment":{"url":"https://api.github.com/repos/StrikeNP/trac_test/issues/comments/397463518","html_url":"https://github.com/StrikeNP/trac_test/issues/389#issuecomment-397463518","issue_url":"https://api.github.com/repos/StrikeNP/trac_test/issues/389","id":397463518,"node_id":"MDEyOklzc3VlQ29tbWVudDM5NzQ2MzUxOA==","user":{"login":"StrikeNP","id":2577059,"node_id":"MDQ6VXNlcjI1NzcwNTk=","avatar_url":"https://avatars0.githubusercontent.com/u/2577059?v=4","gravatar_id":"","url":"https://api.github.com/users/StrikeNP","html_url":"https://github.com/StrikeNP","followers_url":"https://api.github.com/users/StrikeNP/followers","following_url":"https://api.github.com/users/StrikeNP/following{/other_user}","gists_url":"https://api.github.com/users/StrikeNP/gists{/gist_id}","starred_url":"https://api.github.com/users/StrikeNP/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/StrikeNP/subscriptions","organizations_url":"https://api.github.com/users/StrikeNP/orgs","repos_url":"https://api.github.com/users/StrikeNP/repos","events_url":"https://api.github.com/users/StrikeNP/events{/privacy}","received_events_url":"https://api.github.com/users/StrikeNP/received_events","type":"User","site_admin":false},"created_at":"2018-06-14T22:59:54Z","updated_at":"2018-06-14T22:59:54Z","author_association":"OWNER","body":"**Trac update on 2011/01/09 at 22:11**\n\n* vlarson@uwm.edu changed attachment from \"\" to \"LWP_5cases_L48.jpg\"\n* **vlarson@uwm.edu commented:**\n\nLiquid water path for BOMEX, RICO, ATEX, etc. at L48\n\n"}}
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