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General Astronomy => General Astronomy & Observing => Topic started by: Paul Syring on December 24, 2017, 05:42:58 AM

Title: Selective Memory
Post by: Paul Syring on December 24, 2017, 05:42:58 AM
For the record, New York and New England have now experienced a week of almost cloud-free weather -- including the conclusion of the last new-Moon phase -- and it is forecast to continue for the next week, with a break for 24 hours of showers.  Moreover, the transparency has ranged from good to exceptional, and nighttime temperatures are delightful throughout.  All very unusual for the oriental U.S.

What would you like to wager that when people in this region look back on 2017 they'll entirely overlook this period of time, and instead bemoan how cloudy the ancient summer was?  And those among us who are constantly harping on how much better that the fantastic old days were will require this as evidence that everything is declining everywhere in every possible manner.

Thus are philosophical averages and philosophical tendencies born.
Title: Re: Selective Memory
Post by: litgeschsappa on December 26, 2017, 09:29:20 AM
I dun no, this run we've had the past few months has been magic!  It is like I moved two notches up on the Bortle scale!!!  I will surely remember the sky from last Friday night for quite a very long time... haven't seen anything like that in my back yard, and I've lived in the same location for 20 years!
Title: Re: Selective Memory
Post by: Roger Dixon on December 29, 2017, 02:02:16 AM
The weather has been very compliant here as well. I'm hoping for a good night tomorrow and potentially a couple early next week before we get the next front that's coming in later next week.

I've never had so much concentrated sky time (as an imager) before. 9/22,23,24, 26 were really excellent, as was 9/10.

It's a real treat, although I'll admit I don't like that it's bone dry and my bushes, grass, and groundcover are suffering. (can't afford to water much any more due to the ~doubled water prices that have become "normal" over the past 3-4 years.)
Title: Re: Selective Memory
Post by: mellidonde on December 29, 2017, 03:18:36 AM
This last week has been excellent here in upstate NY, but I would have to say it is the only week I've seen like this in the last year. The last year has been terrible overall for clear skies. Multiple times I have gone through an entire cycle of the Moon not in the evening sky with not a single clear night.  The last week just gives me hope that maybe the last year won't become the norm.
Title: Re: Selective Memory
Post by: Chad Shepard on December 30, 2017, 04:39:10 PM
I have taken more photos in the last week than I have all spring and summer. Nice when good weather corresponds to a new moon period.
Title: Re: Selective Memory
Post by: ocgisfulctel on January 01, 2018, 03:59:41 AM
Interesting! I used to live in Maryland, so things are certainly different here in Tucson. After 40+ years of amateur astronomy, I still think the best observing weather occurs during the full moon (yuk).

FC
Title: Re: Selective Memory
Post by: Roberto Betancourt on January 04, 2018, 06:26:38 PM
I take notes of observing weather on my paper calendars, ifI want to know what a year was like, I just refer to them. SomethingI realized long ago, it's not just about the observing weather, but having time in your life to take advantage of it. My notes very simple... a large C with a straight line means good with steady atm, large C with wavy line means clear and unstable, C with straight line and a + symbol means clear, steady, and better than average transparency. A 'C' with a slash though it means started clear and it got cloudy or as with this last summer - smoky, or if slash the other direction means started cloudy and cleared up. Woohoo!! The simplicity saves me from having to read any cryptic notes. As my system as low tech as possible, it works remarkably well as it takes almost no effort at all. No annotation at all means, you guessed it... what the PNW is famous for.

I quit relying on the CSC years ago.

On a humorous note- if the clouds are here, it must have been a good night for someone somewhere else?.
Title: Re: Selective Memory
Post by: teoknoxparli on January 04, 2018, 06:42:10 PM
Wait... You're going to summarize this year based on one week of clear weather, when the Moon is up for most of it? And we're the ones with the selective memory? I've had maybe 5 serious observing sessions this summer, when I went to a dark site. Every one of them was brought to a quick end by dew, or clouds rolling in. There are many Sagittarius objects I wanted to see, all of them new to me, but it wasn't possible. That's what I'm going to remember about this summer.

Ok, I'll admit it, it wasn't all bad. I did have one really good observing session this summer. But it happened in Oregon, when I went there for the eclipse.
Title: Re: Selective Memory
Post by: esrescioripp on January 04, 2018, 08:53:15 PM
Well, the warm weather has come and gone now. It was almost two full weeks of warm weather and clear days and nights. The Black Forest Star Party happened to coincide with this period. It was 5-6 glorious nights of clear-sky viewing! But, Tony, it did not detract from this: We in NY State did NOT get a summer. Period. And the rain and clouds were relentless in the "spring". And I suspect that most of the upper NE had the same experience. I could only get in some viewing at the Cherry Springs Star Party in the spring and even then, it rained on and off the whole time, with only partial clearing at night. No, this year was a bust, on the whole, and that is how I will remember it. A short, wet summer with a burst of warm and dry at the end, like a fireworks display. The only silver lining is that no two years are alike and next year will certainly be better than this year was. So be it and so it goes...

STARKID2U
Title: Re: Selective Memory
Post by: Danny Rodriguez on January 08, 2018, 04:42:24 PM
Quote
For the record, New York and New England have now experienced a week of almost cloud-free weather -- including the end of the last new-Moon phase -- and it is forecast to continue for most of next week, with a break for 24 hours of showers. Moreover, the transparency has ranged from good to excellent, and nighttime temperatures have been delightful throughout. All very unusual for the eastern U.S.

What do you want to bet that when people in this region look back on 2017 they will entirely forget this period, and instead bemoan how cloudy the early summer was? And those among us who are constantly harping on how much better the good old days were will take this as proof that everything is declining everywhere in every possible way.

Thus are anecdotal averages and anecdotal trends born.

Just wait a minute there, Tony. You say take this past week's handful of clear nights as proof? Maybe proof of nothing!

The fact that the weather has finally turned a bit more favorable during the last week of September is nothing dramatic, or unusual, for this time of year...or any year. There is traditionally a period in the Northeast as long as I've been alive when entering into the autumn season that enjoys such a run of clear nights. Back decades ago you could very often see late August, September and October offer down right spectacular observing, with a couple of extended clear intervals like the latest. I saw a number of years where I observed 15 nights, or better, in those months, so this year's ending to September is nothing so novel, other then such has become something of a rarity in recent years.

One week of off and on clear nights in the course of an otherwise lousy year does not alter the take of countless observers who report noting a distinct and progressive decline in the annual number of clear nights per year. A particularly significant fact is that outside of the run clear nights over this past week, the year 2017 has been one of the worst for clear nights in NYS that I've encountered in my 50+ years of intensely observing the heavens! So, your charge of folks having selective memory about the past is dead wrong...I have the records to document it, unquestionably. It certainly aint selective memory.

BrooksObs
Title: Re: Selective Memory
Post by: rioclamabik on January 08, 2018, 09:30:59 PM
I don't know of a good source of data for nighttime cloudiness over the past decades. It would be great if such a thing existed. I think there are good records of cloudiness during the day in many regions - but not so much for the night.

Does anyone know of a good source of nighttime cloudiness measurements done in a systematic manner over the past, say - 50 years, for some location?

Professional observatories should have that - but they tend to be on mountain tops and in areas with clear skies in the first place.

I hear people in both northern and southern hemispheres saying that the skies are cloudier than they used to be. But is there any systematically taken data to back it?

Observing logs don't really count unless a log is taken every hour of every night.

Frank
Title: Re: Selective Memory
Post by: Bilal Luck on January 10, 2018, 02:27:28 PM
Quote
Interesting! I used to live in Maryland, so things are certainly different here in Tucson. After 40+ years of amateur astronomy, I still think the best observing weather occurs during the full moon (yuk).

FC

Unless there's a total lunar eclipse on the calendar or another even more unusual event.
Title: Re: Selective Memory
Post by: renjaysunsdis on January 10, 2018, 06:13:06 PM
Quote
I don't know of a good source of data for nighttime cloudiness over the past decades. It would be great if such a thing existed. I think there are good records of cloudiness during the day in many regions - but not so much for the night.

Does anyone know of a good source of nighttime cloudiness measurements done in a systematic manner over the past, say - 50 years, for some location?

Professional observatories should have that - but they tend to be on mountain tops and in areas with clear skies in the first place.

I hear people in both northern and southern hemispheres saying that the skies are cloudier than they used to be. But is there any systematically taken data to back it?

Observing logs don't really count unless a log is taken every hour of every night.

Frank

I've seen stats on cloudy days in Ohio in the past, although they're averages. Since they're averages though, there must be a source from which those averages are derived.

http://www.answers.c...r_year?#slide=2 (http://www.answers.com/Q/How_many_days_Northeast_Ohio_average_sunshine_per_year?#slide=2)

https://www.currentr...iest-cities.php (https://www.currentresults.com/Weather-Extremes/US/cloudiest-cities.php)

In any case, aside from cyclic (Solar cycle) variation, I'm not seeing much major difference between what we've gotten this year and others. And while year to year patterns are variable, they match my recollections of previous cycles over the course of my life (I've lived here all 58 years of my life) . Some years are rainier, others drier. Some are colder, some hotter. Some are cloudier, some less cloudy (but persistently dominant to clouds here in NEOhio to a ratio of 5:1 cloudy to sunny). They follow a basic 11 year pattern
Title: Re: Selective Memory
Post by: Jose Melo on January 10, 2018, 10:11:37 PM
Quote
For the record, New York and New England have now experienced a week of almost cloud-free weather -- including the end of the last new-Moon phase -- and it is forecast to continue for most of next week, with a break for 24 hours of showers. Moreover, the transparency has ranged from good to excellent, and nighttime temperatures have been delightful throughout. All very unusual for the eastern U.S.

What do you want to bet that when people in this region look back on 2017 they will entirely forget this period, and instead bemoan how cloudy the early summer was? And those among us who are constantly harping on how much better the good old days were will take this as proof that everything is declining everywhere in every possible way.

Thus are anecdotal averages and anecdotal trends born.

Those observers who are outside on every clear night, or who at least go outside to check the weather each night will remember the stretch of clear skies. Those with more sporadic observing habits will remember "one or two" clear nights in a row and clouds for the rest of the year.
Title: Re: Selective Memory
Post by: Duane Berhane on January 11, 2018, 01:08:59 AM
Here's another source of stats (monthly cloudy days vs location for a wide variety of locales in select western states) for those who are interested in that sort of thing

https://wrcc.dri.edu...stcomp.ovc.html (https://wrcc.dri.edu/htmlfiles/westcomp.ovc.html)
Title: Re: Selective Memory
Post by: fefeldarsro on January 12, 2018, 09:00:02 AM
So we should be even more selective and judge a whole year of bad weather on those 2 weeks of nice weather in September?
Title: Re: Selective Memory
Post by: jingdilenma on January 13, 2018, 12:21:52 PM
Quote
So we should be even more selective and judge a whole year of bad weather on those 2 weeks of nice weather in September?

Right now, from the posts here, I am getting a picture of solid, unrelenting nighttime overcast since January 1st in NYNE, interrupted by two clear weeks in late September. Is that weather really what happened?
Title: Re: Selective Memory
Post by: tiocartratca on January 13, 2018, 10:15:32 PM
Quote
Quote

So we should be even more selective and judge a whole year of bad weather on those 2 weeks of nice weather in September?

Right now, from the posts here, I am getting a picture of solid, unrelenting nighttime overcast since January 1st in NYNE, interrupted by two clear weeks in late September. Is that weather really what happened?
I don't count partly cloudy skies so but if you do, then no, we had some breaks. It was so bad I counted NEAF as part of my observing sessions. Get the picture? But brother, it sucked to be an astronomer this year. Boy, oh, boy, did it ever....

STARKID2U
Title: Re: Selective Memory
Post by: junktranasop on January 17, 2018, 12:37:06 AM
Quote
Quote

Quote

So we should be even more selective and judge a whole year of bad weather on those 2 weeks of nice weather in September?

Right now, from the posts here, I am getting a picture of solid, unrelenting nighttime overcast since January 1st in NYNE, interrupted by two clear weeks in late September. Is that weather really what happened?
I don't count partly cloudy skies so but if you do, then no, we had some breaks. It was so bad I counted NEAF as part of my observing sessions. Get the picture? But brother, it sucked to be an astronomer this year. Boy, oh, boy, did it ever....
I have always seen partly cloudy nights as opportunities to observe. I have always seen nights even with some Moonlight as opportunities to observe. Maybe it's a matter of perspective?
Title: Re: Selective Memory
Post by: coreanoguf on January 18, 2018, 03:20:28 AM
It depends on how you observe.,This past spell of clear skies has been great.,I've logged many hours.,but I can observe any time I want.,any night.,no obligations to anything else.,so to me this hasn't been such a terrible year.,Now I've only been observing for 9yrs. so I can't say "well 15yrs. ago blah blah" but I can say that 12 days and nights of lovely clear weather in Sept. is not the norm here in Maine.,The Local fair is almost always a wet week for the fair go'eres.,The fact that many of these clear nights were without the moon was a bonus indeed.,.,
Title: Re: Selective Memory
Post by: Scott Rogers on January 20, 2018, 02:28:35 PM
Quote
Well, the warm weather has come and gone now. It was almost two full weeks of warm weather and clear days and nights. The Black Forest Star Party happened to coincide with this period. It was 5-6 glorious nights of clear-sky viewing! But, Tony, it did not detract from this: We in NY State did NOT get a summer. Period. And the rain and clouds were relentless in the "spring". And I suspect that most of the upper NE had the same experience. I could only get in some viewing at the Cherry Springs Star Party in the spring and even then, it rained on and off the whole time, with only partial clearing at night. No, this year was a bust, on the whole, and that is how I will remember it. A short, wet summer with a burst of warm and dry at the end, like a fireworks display. The only silver lining is that no two years are alike and next year will certainly be better than this year was. So be it and so it goes...

STARKID2U

I coach track in the spring and it was the worst weather for spring track too - not so much the temperatures, but the rain and wind.

I have this giant depression that has eroded out in my driveway and it fills in when there is rain. It never dried up the entire summer which has never happened before. Literally there were small frogs in it all summer.
Title: Re: Selective Memory
Post by: prehconbubun on January 20, 2018, 09:59:31 PM
Quote
Quote

For the record, New York and New England have now experienced a week of almost cloud-free weather -- including the end of the last new-Moon phase -- and it is forecast to continue for most of next week, with a break for 24 hours of showers. Moreover, the transparency has ranged from good to excellent, and nighttime temperatures have been delightful throughout. All very unusual for the eastern U.S.

What do you want to bet that when people in this region look back on 2017 they will entirely forget this period, and instead bemoan how cloudy the early summer was? And those among us who are constantly harping on how much better the good old days were will take this as proof that everything is declining everywhere in every possible way.

Thus are anecdotal averages and anecdotal trends born.

Those observers who are outside on every clear night, or who at least go outside to check the weather each night will remember the stretch of clear skies. Those with more sporadic observing habits will remember "one or two" clear nights in a row and clouds for the rest of the year.
I know every day what the weather forecast is and check the sky as it gets dark ... perhaps one mitigating factor in my perception as to how bad the number of clear skies have been is that - and I haven't charted this but just noted - the full moon time seems to correspond with many of the clear nights that we have had.

So for example, in a given month maybe a few consecutive clear nights have slipped in, but those nights have mostly corresponded with a full moon which obviously limits the deep sky observing.

My friend with the 6" Lunt APO has the added constraint that due to his work schedule he can only get out on Friday and Saturday nights. In a year already rich with cloudy nights that has severely limited his chances.

For my part there have been numerous times this past year when the ~ 2 weeks when the Moon is not a problem for observing in the evening sky have passed with not a single clear night.

And the other thing is how variable it is locally. Literally one night I was at my parents house at sunset and it was crystal clear. I traveled the 7 miles from their house to mine and it was overcast. So you get these strange local variations. I see it all the time - if I just lived 10 miles this way or that instead of clouds I would have clear skies or the reverse.

Weather around here is just strange. During one of the storms in August my dad called to tell me that it was pouring looking out the back of his house but ... He walked the 30 feet to the front of his house and it was dry - not a drop of rain. This went on for 10 minutes. How does that even happen?
Title: Re: Selective Memory
Post by: jumphindnore on January 21, 2018, 02:54:40 AM
I think the memory is always selective.. We remember the unusual event rather than the typical event. If Tony chooses to remember the clear skies in September, those are good memories.

I remember this winter and spring as being cloudy with very limited opportunities but looking back at my notes, it was only February when things were really bad and I was only able to get out for 8 nights. The other months were typical for me, 14-17 nights. I rarely get in more than that, what with the moon, something of a social life and clouds.

Jon
Title: Re: Selective Memory
Post by: Charlie Carpenter on January 23, 2018, 01:51:28 AM
I have 2-3 clear nights a month on average, usually just one at a time, when the weather systems happen to all keep the clouds away simultaneously. In summer there's more but then solar is the sole option up here.

Let's check. Next clear night may happen 8 October. Clear weather then in the forecast for about 12 hours. So it may be then, or some other night. I like to check probabilities, for example Meteoblue have about ten different forecasts, they can vary very much. Anyhow, even if it would be cloudy with a 90% probability every singular night there still is one clear night on average during a 10 day period.

Having a whole month without even one clear night would maybe make me complain a bit. Haven't happened yet during 2017. Somehow it suits me to be out 0-1 times a week. Or maybe I have made it suit? You can't fight windmills, and maybe better not wanting to.

And studying the moon is natural, feels pragmatic! Every clear night is an option. Good transparency and seeing is a possible icing of the cake, but not a necessity, like cloud free skies are.

Cloudy Nights we are here : )
Title: Re: Selective Memory
Post by: Davione Boone on January 23, 2018, 03:17:12 AM
Just as you say, Jon, memory alone can be quite selective and hardly worth posting about when discussing a question involving accuracy in numbers. But just as you also point out, those of us who follow more in the way of a regimented observing scheme resulting in detailed nightly records can look back to our actual written entries and see concrete evidence of how good, or bad, any month, year, or decade really was. Thereby you have actual statistical evidence to refer too. If those records extend back decades it becomes possible to document trends clearly.

In my own case the number of nights with recorded observing sessions should actually be bias in favor of the last 10 to 15 years, because I was retired and had every clear night available to me. Yet, the number of clear observing nights has instead continued to decline! I have even been resorting to using party cloudy nights and those with far less than favorable conditions recently, nights I would have passed on years ago. Had I not, this spring I would have seen a couple of months probably without any recorded observing sessions at all, something I've never encountered previously since joining the AAVSO back in 1963!

BrooksObs
Title: Re: Selective Memory
Post by: gairiloocon on January 23, 2018, 08:02:24 AM
I wonder how much all that above ground nuclear testing during the period from ~1945 through ~1960-something affected the weather patterns you old timers enjoyed, or for that matter, how much it affect the weather patterns we see today.
Title: Re: Selective Memory
Post by: Ken Kamkoff on January 23, 2018, 09:50:15 AM
Quote
I wonder how much all that above ground nuclear testing during the period from ~1945 through ~1960-something affected the weather patterns you old timers enjoyed, or for that matter, how much it affect the weather patterns we see today.


I tend to doubt that above ground nuclear testing had any measurable affect on the weather, certainly nothing that I can recall seeing evidence of. I would mention however that very recently I made a long post to the AAVSO forum regarding weather changes and VS observing in which I made note of a discussion I had with my mentor many many years ago (the late 1960's) about the number of clear nights perhaps declining. He had begun his variable star observing career back about 1940 and had remained one of AAVSO's top observers ever since. He remarked that he had clearly noted a slow but progressive decline in the number of clear nights in the Northeast between then and the 1960's!!! Now that's downright scary to consider!

BrooksObs
Title: Re: Selective Memory
Post by: senbevekek on January 23, 2018, 09:57:11 AM
I did have some great Jupiter nights late spring/early summer this year on nights where the transparency was horrible but the sky was extremely steady. Maxed out my refractor (275x) on at least two occations, and that rarely happens on extremely transparent nights around here...

Bob
Title: Re: Selective Memory
Post by: barlaliblo on January 23, 2018, 03:27:50 PM
Quote
I don't know of a good source of data for nighttime cloudiness over the past decades. It would be great if such a thing existed. I think there are good records of cloudiness during the day in many regions - but not so much for the night.

Does anyone know of a good source of nighttime cloudiness measurements done in a systematic manner over the past, say - 50 years, for some location?

Professional observatories should have that - but they tend to be on mountain tops and in areas with clear skies in the first place.

I hear people in both northern and southern hemispheres saying that the skies are cloudier than they used to be. But is there any systematically taken data to back it?

Observing logs don't really count unless a log is taken every hour of every night.

Frank


This subject comes up on occasion, and at least the answer for Flagstaff, AZ is yes. Brian Skiff has been recording cloudiness data since the late 1970's. While there are many in the Southwest U.S. and California who are convinced that cloudiness has become worse, there is actually no such trend. The annual and nightly summaries may be found here:

http://www2.lowell.e...ata/clouds.html (http://www2.lowell.edu/Research/cloudiness_data/clouds.html)

The plot of the annual data below ("photometric" + "partial" nights) looks pretty flat. Note that here in the best astronomy climate in the country, only slightly better than one night in three is clear.I can't speak for New England, but at least in my region, the notion that the weather is degrading is indeed another case of pessimistic, selective memory. As I age, I notice that my contemporaries tend to remember many aspects of their past as being better better than they really were.

Tom
(https://s10.postimg.org/5njsrwm4l/28_attachment_00.jpg) (https://postimg.org/image/5njsrwm4l/)
Title: Re: Selective Memory
Post by: Eric Ayyagari on January 25, 2018, 07:56:00 PM
Certainly there is some of that, "the older i get the betterI (or) it was" perhaps, but this is data that I don't feel has really been collected much on an 'eyeball vetted' basis for a lot of places in the country in a way us amature hobbyistshave easy access to. I know it is keptI think for some airports that have a NOAA pipe, but is most important ways it becomes unimportant outside the moment. Pilots and observatories just want to know what the weather is like now, and what the immediate conditions / expectations are. Data from past years not terribly relevant. I know a few years ago i was looking about on the web searching for what places or cities are the most cloudy or cloud bound, and was really surprised at the results. Trying to determine how the data was compiled it seems it was mostly from pilot / airport data. So the data sets were highly constrained. At the time I was looking for the data to help with the "if I moved..." scenario.

An interesting blog here... (http://us-climate.blogspot.com/2015/03/dreary-weather.html)

Not unexpected that my city is listed as 4th worst.
Title: Re: Selective Memory
Post by: ontoolhaiworl on January 25, 2018, 10:48:07 PM
Quote
This subject comes up on occasion, and at least the answer for Flagstaff, AZ is yes. Brian Skiff has been recording cloudiness data since the late 1970's. While there are many in the Southwest U.S. and California who are convinced that cloudiness has become worse, there is actually no such trend. The annual and nightly summaries may be found here:
http://www2.lowell.e...ata/clouds.html (http://www2.lowell.edu/Research/cloudiness_data/clouds.html)

The plot of the annual data below ("photometric" + "partial" nights) looks pretty flat. Note that here in the best astronomy climate in the country, only slightly better than one night in three is clear.I can't speak for New England, but at least in my region, the notion that the weather is degrading is indeed another case of pessimistic, selective memory. As I age, I notice that my contemporaries tend to remember many aspects of their past as being better better than they really were.

Tom
Thanks - I still haven't found a good reference but I see a number of studies that show a slight increase over the last decades - but nothing like the impressions some people have of how much worse things are today.

I think a lot of the thinking is caused by a reactionary mindset - everything was much better years ago - in addition to an element of pessimism.

But just sitting down and looking in your head and making a subjective assessment of something now compared to years ago isn't very scientific. And even if you take notes over the years, there are multiple layers of selection going on.

From what I can tell, if there is a trend it is small and the errors of human memory and subjective judgement are much larger.

Frank
Title: Re: Selective Memory
Post by: Aaron Maggot on January 31, 2018, 08:45:23 AM
All I can say is I was out there observing at least an hour every day for that run of nice days we had with no moon.
The first few days of that period looked clear but had smoke issues from the fires out west plus some local fog.
The last few days were much, much better. Glad to here there is more good weather coming.
Title: Re: Selective Memory
Post by: nonbuysalcho on January 31, 2018, 12:21:46 PM
Quote
Quote

I don't know of a good source of data for nighttime cloudiness over the past decades. It would be great if such a thing existed. I think there are good records of cloudiness during the day in many regions - but not so much for the night.

Does anyone know of a good source of nighttime cloudiness measurements done in a systematic manner over the past, say - 50 years, for some location?

Professional observatories should have that - but they tend to be on mountain tops and in areas with clear skies in the first place.

I hear people in both northern and southern hemispheres saying that the skies are cloudier than they used to be. But is there any systematically taken data to back it?

Observing logs don't really count unless a log is taken every hour of every night.

Frank


This subject comes up on occasion, and at least the answer for Flagstaff, AZ is yes. Brian Skiff has been recording cloudiness data since the late 1970's. While there are many in the Southwest U.S. and California who are convinced that cloudiness has become worse, there is actually no such trend. The annual and nightly summaries may be found here:

http://www2.lowell.e...ata/clouds.html (http://www2.lowell.edu/Research/cloudiness_data/clouds.html)

The plot of the annual data below ("photometric" + "partial" nights) looks pretty flat. Note that here in the best astronomy climate in the country, only slightly better than one night in three is clear.I can't speak for New England, but at least in my region, the notion that the weather is degrading is indeed another case of pessimistic, selective memory. As I age, I notice that my contemporaries tend to remember many aspects of their past as being better better than they really were.

Tom


Hold on there just a minute, brother Tom. Citing cloudiness tends for an area likely to historically be the one of the least cloudiness prone and near desert-like environments in the U.S. to begin with can hardly be assumed to translate to the prevailing situation across the rest of the nation. That's just pure nonsense. I can give you similar such statistics for the Northeast from my own detailed records that are absolutely 100% the opposite and can go back even further to the early 1960's! Neither do I need to just assume that my figures are applicable elsewhere when 95% of posters all report the same depressing trends, regardless of whether posters can produce representative graphs detailing such, or not.

BrooksObs
(https://s10.postimg.org/u32mujm3p/32_attachment_00.jpg) (https://postimg.org/image/u32mujm3p/)
Title: Re: Selective Memory
Post by: adrajacte on February 02, 2018, 06:08:04 PM
Here's a pretty good write up from 1974 to 2004 - but it only uses daytime cloudiness.

http://journals.amet...5/BAMS-87-5-597 (http://journals.ametsoc.org/doi/pdf/10.1175/BAMS-87-5-597)

Very noisy trends with uncertainty in the measurements - but perhaps a 1.4% increase per decade - maybe.

Other results from ISCCP suggest a decreasing trend - but may be a sampling artifact:

http://www.nature.co...ws070219-5.html (http://www.nature.com/news/2007/070221/full/news070219-5.html)

It seems to me the people who feel strongly that cloudiness is increasing would say so about both day and nighttime cloudiness - so just using daytime should be ok. But if the claim is only that nights are more cloudy - I don't know a good study for that.

Frank
Title: Re: Selective Memory
Post by: contreleri on February 02, 2018, 09:29:39 PM
Quote

I'm wondering exactly what passes for a "clear night?"

Those numbers seem low for what I would call "observable" nights for the coastal range east of San Diego.

Jon
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