{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"5ed66aef3c551575d0b440a41bd3329762b4c879b3d1454147e23cbecf17e307","created":"2026-10-03T07:18:03Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"1efc551b3f43957fd896b51ad25ab278829f690a4d8a37835b320ef14689b8b0","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"fluid.particle-turbulence.rain-size-gap","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"Cloud droplets grow quickly by condensation while tiny and by sweeping up others once large, but in between, at a few tens of micrometers, both processes are slow. Yet rain appears within about 20 minutes, and which process bridges the gap is disputed.","posed_since":"","precise":"In warm (ice-free) cumulus, droplets grow by condensation to about 10-15 micron radius and by gravitational collection above about 40 micron, with slow growth in between, yet rain appears 15-30 min after cloud formation. Identify which process (turbulent collision enhancement, giant aerosol nuclei, entrainment mixing, lucky-droplet statistics, electrostatic forces) dominates growth across the gap for typical cloud dissipation rates $\\epsilon \\sim 10\\text{ to }1000\\,\\mathrm{cm}^2/\\mathrm{s}^3$.","problem_ref":null,"references":"","settled_by":"In-cloud measurements of droplet size distributions and turbulence compared with collision-coalescence simulations that include each candidate process with measured inputs.","status_note":"A 2024 kinetic analysis places the low-efficiency gap at about 3-30 micron and argues the turbulence pathway is unlikely (Poydenot and Andreotti, arXiv:2410.11072), against DNS reports of strong turbulent enhancement.","title":"How do cloud droplets cross the size gap to form warm rain?","topic_ref":"28a67e06c2d95a104488e4da0be70a03916f05f9e68b223b2403a21e1c4f018e"},"content_withheld":"false","files":[],"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"6e0f350309f814f4e1d69e9bf842015cff29b64a78fbbef2ce720a699d2c40b9","schema":"pubphys.attested/1"},"id_token":null,"id_token_withheld":"false","envelope":{"attested_hash":"ff2683f9b6af0532e89adac49055b689965be56adc484726dfa869b79447cb70","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"8q8j_WuvHeRoyglT3XDvTA5s1oVte833R46NEDEHmbcq3Lpbz8WZWUOT7sBw5VQvUgE9dsheXJbpc2jumpD-CQ"},"schema":"pubphys.envelope/1"},"ots":{"attested":["AE9wZW5UaW1lc3RhbXBzAABQcm9vZgC_ieLohOiSlAEI_yaD-bavBTLomtrEkFW2iZZb5WrcSEcm36hpt5RHy3DwIP9Zbc_S3CogIbsX6LZMJW-kX8qzA_VTgkley9y8pNMICPEg_lDUtCerJW3zu__9heJbNRgRjfheEX13qa3NeBLOumMI8SAmj1-WNhhk308SL6BMYyHbMsxbntPaIltwIe2t-T9jxQjwIN5SHmaMGXpsGJ3KTrIGThq9PQOnYxGB7bo8GVtT9LC8CPAgNa_cE8BMyQCErYgWZxItydGyiQDuszb47LoE3kcvJkoI8SACJr05RVmn3OQf1U4wSUK6iLp4YooVnJ9h8__schleEAjxINaUvsjN879zBjF9p1oOag9WnS2m0-bDZeZhpTgkx7_CCP_wCHbghVgOFMuNCPAQPZK2lHbTMqcCYUotzOQcmQjwIJ7ruRIs6HnufKxCpmLUgeUl0aUu0ov4_3PqcppS-bddCPEgI530vHzdwz_3o9jYQ3WablSaV64Wfn7Pmby5WLyI-A0I8QRqwKw78AhITF7Tr3a1xP8Ag9_jDS75DI4sK2h0dHBzOi8vYm9iLmJ0Yy5jYWxlbmRhci5vcGVudGltZXN0YW1wcy5vcmcI8CBXWeNiWFWltfHE0nkDXsVKIykUUwuObhsnN-2fvBt98gjwIM5Vf7j68sOFgVysYMc5S09Hho-fqxYW3oQ4oKUX7JpPCPAgaKHHQB3sdd9w1hu4NMh7vmb-p0X2r4uyVKKCj1G7S28I8SAW2Mg6Bzi9ygjrrjIYB7w90fwMcxH24SsqLmzPyAMGfwjwIMQ863zlveYIpNKWVrZaDOa4vowwoOg2CcTW8gXtxK3dCPEgrZxGGAf-t8jhz_eLMUyBN1IhNrdYDRcNHWvQcwNG9woI8CCVOUHG1YXudbaFIgUYvrCIevRWvb2ubhQAo-z0duD0rQjxIDBeKerVGkO3J2eXDwdraSioXbIWsdIPEN1s8pIwJIS2CPAgV2kB3n3JZ5HwBQjpRL1CWKnqvdCjZk3RcALk6N2wHigI8CB-wbljNlfqElD25uZkNg6taS81YDRU2vfMqGVQ420O9AjxWQEAAAABJM43UU6MLMRrPlCUqossvu1q_knons5yylyWTgxZzWUAAAAAAP7___8CLgABAAAAAAAWABQrYt3E7OllKRCEmL3FL589l78_5wAAAAAAAAAAImog8ATiyw4ACAjxILmbcIO7ixv3pCtwUMZ1VQGKus54F9lZ8-w5ECD5ZuiICAjwIG6ynCyFTLPE7Rgk-0ZGCtBDyqNQx8YvaSZNHy8D8p8jCAjwIMX8zoD2Be1YWvcx_bexVPRmBX0hK-do8b8t9SarimQVCAjxIG6XtpqIEclLlhzcK1LVjqoPGrjjmLnyno8tcETMzECECAjwIF6mlfXOFY51JhrK4eze8zQlKV75OYZYqbtyi8BWxmAsCAjwIKKUcJmVoz-u-geiRV_-ZHdF0VEPXaEPFWf_JX_0e7G2CAjxIGMeD0Z5QWNKBcAEpHht007FFIILW6aSJ8f3CMkKNsneCAjwIBFr6Je8rkB7kwhPGbq0yRgFwZsvW9JhY5sXDRtrq0QwCAjwIAHAwXaus-yUgKICJB5mVvx8VZuJgjwnpb0qWPg1pi6DCAjxIAJhb8cefkVHTAMymdsxa-_i-tUua62LcpALQnPG7R9_CAjwIDvsFqBhPfAL6TCtXZd7gBWmMpx6iiZ-Ug0Jf_LlcstgCAjwIDJRBX6Q0Vge-ra-k1_g76yJWTEp6WWF13I3JpTnsZPJCAjwILykZCbkC9VQgl5gytPKKir6T9nTvKR6y05iWSHBTQgzCAgABYiWDXPXGQED45c78Ah-sGbmQAwfZwjwEAYqxtHnZiPZnJEGPx_JvKsI8SDXkqDg17YsZIrEz5acRx7mBXCKW5mKNgRYnw_-U2cpDgjxBGrArDrwCEfK6Mono428_wCD3-MNLvkMji4taHR0cHM6Ly9hbGljZS5idGMuY2FsZW5kYXIub3BlbnRpbWVzdGFtcHMub3JnCPAg10nyJ6Jn4kshQQQCKE0Lvj3hBC6nLRBVIzaPV4eh8VwI8CCQaAqWlxEbac_XOq1MOlf9iOKHEsxXspzbjK0vLpy8BwjwII3iRbRXUcDxrhAdkZmFlI15nySCSEZ7g922tF1Xln5DCPEgYYvZ1L4v4rPu_UqLfcHPtwSb2OH2GhPgVcVhhH6DpkQI8CDZCIoR20sC-uchP40oAmcLm9EJFV7xzwplj54AeVadXQjxILvLBjPFpCoz29m9Yf2qRnV7PI9GqxE8ozVQfk9QwCqrCPEgZXcMudvEoB_MJ8tqOW2PLTKAIeQBnE-1bfzptRc2gR8I8VkBAAAAAfXq-bmxWqOz7B5wKkwjzHGv2R4s7Y0Z76LqXWYNhmz0AAAAAAD-____Av0cAAAAAAAAFgAUl-skmdZDtn7Hnub6mF4HP2uVn7oAAAAAAAAAACJqIPAE4MsOAAgI8CBDmQsbEXc46Hu8DivhCBM1LGExa4TTM-wo7HpoCVjBTQgI8CCty5vkQtPHzzs8xqArOYhVSjgaDoG1ou3cojv5_P7wQQgI8SDQWB0kdXCTwbk-TqTt0QfRMyzDNLOtU1XXFgvGSRlW8wgI8CC2PKa_QCIBZtrXodq1GdEzppISMsMRDOnzr2gFjLKOAAgI8CCwQ_QF67bcFk_uJ2s0VCZmf5PGIjTmTCpt_qnVY5p_8AgI8SAbzyx7z-oxPMju6PvtQhzrJIQyH2ZAc9oyLuYemzbmZQgI8CC5bh7J74uUk91r8LwybHQFCNBC3PWeuwtMCCNFKWj19AgI8SAf4R2TUNPjaX_PWDUImpoITK0JoW89zaMKnD1wlEEi8AgI8SC2vNmdm7eyP5Ytl1yTzT0njliMdALl1ViKG-s3bG2zswgI8CCpbIVNz1GFVXdJk2zd82hBUoNFFemUPBt7IJdWEOciPwgI8CBtYdRQcrtX1FtCm1SxF7sx-5cO04U8KzbJh8fqBkyReAgI8CBHs2LGmX6gI-lV7yp1RrV7_tGfdiBAwnEFF6B6yXHzAQgI8CATotVmbXBMAixhZ-QKy5Q4lR0FusdA_wcIC1TbB7GmxAgIAAWIlg1z1xkBA-KXOw"],"envelope":["AE9wZW5UaW1lc3RhbXBzAABQcm9vZgC_ieLohOiSlAEISpbLwq_aEZuma1aV3AHdyLKl4J7PIKMcmGEnudPYWT_wIEqduDVflp3LLsQ0-53TkIypOjxehpACw-YaKR1BIfjjCPEgQ6XBdvhmg_-8sg-DYlH9oI-aPGW6VbBzEsewk5PdFRcI8SAZpo4IQunpb8jW8sRRDkuyGypoy6mHG3kl-9e61Kid3AjwIN85TfDwYrS468eSjZUguDL2zC0XIfCQqMIt-DGKTEkJCPAgysNF-BgqD3hp3czr0ythmpUqXMUwHVgZeQeULIWZJvkI8CDHtrxowIx6FimPIvh69X07RB6BXKqX3RN5DhqUvhKq9AjxIA8Mvjd87ZtpxfGaeH-X_AyCvFZCuMJEG65d8GBPbZfZCPEgsPKCRq0mf_8ht2OmXvMNFmmqll5AzUTeepEqQILv1TUI8CDcBxRb7fDApTWNNvjZ_r2lDpQT60DYte3pStKjciGgOAjwIK9SXvHBwgJE5CknXtp2lOqKcbHlJ-ncP9sNjnTHUJsmCPEgytIBB3x7TFDT-XqOV-9vpqw1NKoAu0dhtsCbAMql2L0I8CCtNZgmApuKULvPC9nsMCaM05arV-F3o5FTlnJCnRvdMgjwIBGYo5Vxy-d7U5zKv5vp3Ii7hJPH_BDLCzA13c47p9q7CP_wCHbghVgOFMuNCPAQPZK2lHbTMqcCYUotzOQcmQjwIJ7ruRIs6HnufKxCpmLUgeUl0aUu0ov4_3PqcppS-bddCPEgI530vHzdwz_3o9jYQ3WablSaV64Wfn7Pmby5WLyI-A0I8QRqwKw78AhITF7Tr3a1xP8Ag9_jDS75DI4sK2h0dHBzOi8vYm9iLmJ0Yy5jYWxlbmRhci5vcGVudGltZXN0YW1wcy5vcmcI8CBXWeNiWFWltfHE0nkDXsVKIykUUwuObhsnN-2fvBt98gjwIM5Vf7j68sOFgVysYMc5S09Hho-fqxYW3oQ4oKUX7JpPCPAgaKHHQB3sdd9w1hu4NMh7vmb-p0X2r4uyVKKCj1G7S28I8SAW2Mg6Bzi9ygjrrjIYB7w90fwMcx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