{"action":"opened","issue":{"url":"https://api.github.com/repos/StrikeNP/trac_test/issues/580","repository_url":"https://api.github.com/repos/StrikeNP/trac_test","labels_url":"https://api.github.com/repos/StrikeNP/trac_test/issues/580/labels{/name}","comments_url":"https://api.github.com/repos/StrikeNP/trac_test/issues/580/comments","events_url":"https://api.github.com/repos/StrikeNP/trac_test/issues/580/events","html_url":"https://github.com/StrikeNP/trac_test/issues/580","id":328296846,"node_id":"MDU6SXNzdWUzMjgyOTY4NDY=","number":580,"title":"Calculate Nc in terms of Ncn (Trac #580)","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":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":0,"created_at":"2018-05-31T21:04:50Z","updated_at":"2018-05-31T21:04:50Z","closed_at":null,"author_association":"OWNER","body":"Migrated from http://carson.math.uwm.edu/trac/clubb/ticket/580\n```json\n{\n    \"status\": \"closed\", \n    \"changetime\": \"2014-05-08T03:09:58\", \n    \"description\": \"\\nOne problem with CLUBB's formulation is that CLUBB uses instantaneous saturation adjustment, but the joint normal-lognormal PDF of s and Nc allows cloud droplets to exist in subsaturated air, that is, the PDF has mass in the second (positive Nc, negative s) quadrant.  \\n\\nTo avoid this, Brian is writing Nc in terms of a new variable Ncn, where Nc can be related to Ncn in a number of ways, such as \\n{{{\\n    Nc = Ncn H(s)\\n}}}\\nWith this formulation, the joint PDF of s and Nc is like the joint PDF of s and Ncn, but with all mass in the second quadrant moved to the s axis.  Thus, the marginal PDF of Nc becomes a delta function plus a lognormal-like component.  A within-cloud process that depends on Nc, such as autoconversion, remains unchanged, because the mass within the 1st quadrant (positive Ncn, positive s), is the same for Nc and Ncn.  \\n\\nThe new formulation no longer makes it easy to prescribe within-cloud Nc.  However, the option to use a prescribed double-delta (prescribed value in-cloud and zero out of cloud) Nc still exists (l_const_Nc_in_cloud), and this solution is recovered when Ncnp2_on_Ncnm2 = 0.      \\n\\nWe could interpret Ncn in several ways.\\n\\n * We could interpret Ncn as truly the CCN, and we could argue that the formula above that we're using is a diagnostic relationship between CCN and Nc, as do Boucher and Lohmann (1995).  This is simple, but most authors seem either to prescribe Nc or prognose it, rather than diagnose it.\\n\\n * We could interpret Ncn as a \\\"conserved\\\" CCN that includes unactivated CCN and CCN that have already nucleated and are residing within droplets.\\n\\n * We could interpret Ncn as a simplifying but abstract mathematical device, akin to Mellor's s.  It allows us to use simple PDF shapes without having droplets in subsaturated air.\\n\\n * We could move, in the far future, toward prognostic Nc.  Then we could compute (dNc/dt)_activation in terms of Ncn.\\n\\nBrian has committed the code changes in r6252, r6254, r6256, r6257, and r6258.\", \n    \"reporter\": \"vlarson@uwm.edu\", \n    \"cc\": \"vlarson@uwm.edu\", \n    \"resolution\": \"fixed\", \n    \"_ts\": \"1399518598126052\", \n    \"component\": \"clubb_src\", \n    \"summary\": \"Calculate Nc in terms of Ncn\", \n    \"priority\": \"minor\", \n    \"keywords\": \"\", \n    \"time\": \"2013-05-21T21:34:01\", \n    \"milestone\": \"\", \n    \"owner\": \"bmg2@uwm.edu\", \n    \"type\": \"enhancement\"\n}\n```\n"}}
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