tag:blogger.com,1999:blog-4572286363399496963.post5408057729951835936..comments2024-03-27T04:17:21.221-08:00Comments on Deep Cold: Alaska Weather & Climate: Warming from CloudsRickhttp://www.blogger.com/profile/03946704894714514716noreply@blogger.comBlogger10125tag:blogger.com,1999:blog-4572286363399496963.post-49469898348253561102017-12-07T20:09:04.814-09:002017-12-07T20:09:04.814-09:00Hello again, Richard,
Just checking on an email I...Hello again, Richard,<br /><br />Just checking on an email I sent you a few days ago. It was from maltoss37@aol.com. Not sure if it was delivered properly, or ended up in the Junk folder. Please, let me know if you got it.<br /><br />Regards,<br />Fred.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4572286363399496963.post-65584806039268903502017-11-30T05:16:28.746-09:002017-11-30T05:16:28.746-09:00Fred, I simply took the hourly METAR reports and d...Fred, I simply took the hourly METAR reports and did a crude conversion to oktas, i.e. FEW=1.5, SCT=3.5, BKN=6. The ASOS measures cloud cover in percent, but I doubt those raw values are available anywhere. I don't know how the CF6 values are computed, but note the CF6 data are supposedly only for sunrise-sunset (although Barrow is still reporting daily values).<br /><br />As for the excel chart it was just a matter of overlaying a couple of series with appropriate formatting of the markers.<br /><br />Feel free to send your findings to me at richard.james (at) prescientweather (dot) com. I'd be happy to take a look at your methodology and findings.<br />Richard Jameshttps://www.blogger.com/profile/08313902028896263276noreply@blogger.comtag:blogger.com,1999:blog-4572286363399496963.post-87851541876302189452017-11-29T18:54:44.831-09:002017-11-29T18:54:44.831-09:00What is needed to make such graphs? I'm partic...What is needed to make such graphs? I'm particularly interested in graphical depiction of cloud cover properties.. Unfortunately, NOWData doesn't provide sky cover values, even though suggestions have been made. Iowa State University has a neat set of graphs, though most cover only MidWest. I have an access to the sky cover data of interest, however, there are ambiguities present in converting FEW, SCT and BKN to a numerical values format. Do you know if it's possible to aggregate the codes into tenths, as is usually done on CF6's? Finally, earlier this year I did an independent research on historical sky cover data in Nashville, TN and came to similar conclusions you did years before (unaware, at the time, of your study). Due to great distances and very different climatic conditions between Alaska and Tennessee, these [conclusions] shouln't be overlooked. The purpose of my research was to validate the perceived change in cloud cover, as well as to support a hypothesis that it may, at least partially, account for increased frequency of very warm years in recent decades. Though the cause and effect aren't clear in this case, the data can hardly be considered a statistical phantom. If interested, I could provide a summary of my findings.<br />Best regards,<br />Fred Estes.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4572286363399496963.post-87718131860443585372017-11-29T06:39:10.692-09:002017-11-29T06:39:10.692-09:00Thanks. I may have used ACIS charts on occasion i...Thanks. I may have used ACIS charts on occasion in the past, but this one was made in excel.<br />Richard Jameshttps://www.blogger.com/profile/08313902028896263276noreply@blogger.comtag:blogger.com,1999:blog-4572286363399496963.post-54426871095025616352017-11-28T19:44:41.697-09:002017-11-28T19:44:41.697-09:00Nice graphs on this site! Are they ACIS-generated?...Nice graphs on this site! Are they ACIS-generated?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-4572286363399496963.post-75507169396217242922017-11-26T17:10:48.746-09:002017-11-26T17:10:48.746-09:00Sorry, yes - one okta equals one eighth of the sky...Sorry, yes - one okta equals one eighth of the sky covered with cloud. Note that the ASOS ceilometer points vertically up and only reports clouds below 12,000 feet AGL, but nevertheless the data are very useful. Pros and cons of the instrument are discussed here<br /><br />http://www.nws.noaa.gov/asos/pdfs/aum-toc.pdf<br /><br />The effect of downslope breezes will vary with location, but in general with a shallow inversion even a light breeze will tend to produce surface warming as the vertical gradient is mixed out. In general I think the coldest valley temps develop in-situ rather than draining in from elsewhere; but as you note it is rarely calm on sloping terrain owing to the cold air drainage.<br />Richard Jameshttps://www.blogger.com/profile/08313902028896263276noreply@blogger.comtag:blogger.com,1999:blog-4572286363399496963.post-71273764155837165062017-11-26T10:51:13.180-09:002017-11-26T10:51:13.180-09:00Please explain an “okta”. Eighths of the sky? Sect...Please explain an “okta”. Eighths of the sky? Sectors? Or weighted toward the zenith? Also during radiation cooling with little wind, (it seems) a downslope breeze develops. How much does this horizontal circulation add to cold temps in valleys?Coyoteshttps://www.blogger.com/profile/03348519788709268425noreply@blogger.comtag:blogger.com,1999:blog-4572286363399496963.post-23932181113020246852017-11-26T10:00:34.088-09:002017-11-26T10:00:34.088-09:00Yesterday afternoon Fairbanks was at the northerly...Yesterday afternoon Fairbanks was at the northerly edge of a southerly low deck of cloud cover. It was clear in the hills north of town with them well lit by sunlight passing over the clouds, while at the airport snow crystals fell and we were in an overcast. I suspect the clouds blanketed the lower Tanana valley with reduced visibilities in spots.<br /><br />When it finally cleared it cooled quickly. <br /><br />GaryNL7Yhttps://www.blogger.com/profile/15874712728971005352noreply@blogger.comtag:blogger.com,1999:blog-4572286363399496963.post-45838055510184463772017-11-26T04:13:53.773-09:002017-11-26T04:13:53.773-09:00Good question; it depends on what sort of duration...Good question; it depends on what sort of duration we're talking about for the inversion conditions. Short-lived surface-based temperature inversions can form overnight almost anywhere on earth under the right circumstances, but at low latitudes they are removed shortly after sunrise. Speaking from experience, inversions can last a few days at latitude 50° in winter without snow on the ground (when strong high pressure is overhead), so I imagine a few days of continuous inversion are possible even at 40-45° if there is snow cover under a cold Arctic air mass (in central Asia, for instance).<br /><br />Semi-permanent winter inversions must be confined to latitudes closer to 60°, but I can't guess what the limit might be. Perhaps I'll take a look at some data to find out!<br />Richard Jameshttps://www.blogger.com/profile/08313902028896263276noreply@blogger.comtag:blogger.com,1999:blog-4572286363399496963.post-6819479213230795042017-11-25T22:39:58.616-09:002017-11-25T22:39:58.616-09:00Thank you James for explaining in details to us or...Thank you James for explaining in details to us ordinary folks how cloud cover can impact temperatures in high latitudes locations. Having lived in the tropics/subtropics for most of my life, we experience cooling temps during thick cloud cover, and warmer temps with clear skies in the winter and summer alike. I never understood why it would be the opposite for places up north. What is the minimal latitude for inversion to take place?Troyhttps://www.blogger.com/profile/13807874169764252521noreply@blogger.com