Frequency of Winter Thaws

[blizzard1024]

Has anyone studied the frequency of winter thaws especially in the northeast U.S, Great Lakes and Upper Plains where we get Arctic air masses more regularly?  With global warming, I would imagine the frequency of maximum daily temperatures above a certain threshold, like 50F is rising. This past December in upstate NY was classic. The month as a whole was cold, averaging 3-4F below normal until we had a 3-4 day warm-up which essentially wiped out the cold anomaly and actually made the month slightly above normal. This January might turn out the same way too. Anyway, I have not seen anything in the literature on this. I have run calculations for my local airport and it varies. But there is a strong trend upward from the cooler 1960s and 70s for more thaws as defined by number of days with maximum daytime temperature above 50F in the Dec-Feb time frame. But the 1950s were close to the recent numbers at my location. Records only go back to 1951 where I looked at. This would be an interesting study if it has not been done already. But if you start  the study in the cold 1960s you will no doubt have an upward  trend. You really need at least 100 years of good data without UHI etc. 

[Jonger]

Has anyone studied the frequency of winter thaws especially in the northeast U.S, Great Lakes and Upper Plains where we get Arctic air masses more regularly?  With global warming, I would imagine the frequency of maximum daily temperatures above a certain threshold, like 50F is rising. This past December in upstate NY was classic. The month as a whole was cold, averaging 3-4F below normal until we had a 3-4 day warm-up which essentially wiped out the cold anomaly and actually made the month slightly above normal. This January might turn out the same way too. Anyway, I have not seen anything in the literature on this. I have run calculations for my local airport and it varies. But there is a strong trend upward from the cooler 1960s and 70s for more thaws as defined by number of days with maximum daytime temperature above 50F in the Dec-Feb time frame. But the 1950s were close to the recent numbers at my location. Records only go back to 1951 where I looked at. This would be an interesting study if it has not been done already. But if you start  the study in the cold 1960s you will no doubt have an upward  trend. You really need at least 100 years of good data without UHI etc. 

 

 

You pretty much know what answer you will get depending on the poster. 

 

Lansing, MI from 1970-1980, 7 out of 10 years had a thaw in the month of January that exceeded the average high by more than 15 degrees above normal. Those were the coldest winters in the 20th century here.

[donsutherland1]

Has anyone studied the frequency of winter thaws especially in the northeast U.S, Great Lakes and Upper Plains where we get Arctic air masses more regularly?  With global warming, I would imagine the frequency of maximum daily temperatures above a certain threshold, like 50F is rising. This past December in upstate NY was classic. The month as a whole was cold, averaging 3-4F below normal until we had a 3-4 day warm-up which essentially wiped out the cold anomaly and actually made the month slightly above normal. This January might turn out the same way too. Anyway, I have not seen anything in the literature on this. I have run calculations for my local airport and it varies. But there is a strong trend upward from the cooler 1960s and 70s for more thaws as defined by number of days with maximum daytime temperature above 50F in the Dec-Feb time frame. But the 1950s were close to the recent numbers at my location. Records only go back to 1951 where I looked at. This would be an interesting study if it has not been done already. But if you start  the study in the cold 1960s you will no doubt have an upward  trend. You really need at least 100 years of good data without UHI etc. 

 

When it comes to thaws across the northern tier of the U.S., natural variability is probably sufficiently great that one can't get a clear climate-related signal. If one takes the standardized anomalies from past events and then applies them to the current baseline, one can get a better sense e.g., yesterday's 2 standard deviation high temperature might have been 50°, but today's could have been 52°. Then one can better understand possible (key word) outcomes from the past synoptic patterns e.g., the abnormally warm 1949-50 prevalent pattern. 

[skierinvermont]

When it comes to thaws across the northern tier of the U.S., natural variability is probably sufficiently great that one can't get a clear climate-related signal. If one takes the standardized anomalies from past events and then applies them to the current baseline, one can get a better sense e.g., yesterday's 2 standard deviation high temperature might have been 50°, but today's could have been 52°. Then one can better understand possible (key word) outcomes from the past synoptic patterns e.g., the abnormally warm 1949-50 prevalent pattern. 

 

Don I would imagine that the warming trend across most of the northern tier is sufficiently large enough that the number of days exceeding 45 or 50F in January in most locations has significantly increased. 

[donsutherland1]

Don I would imagine that the warming trend across most of the northern tier is sufficiently large enough that the number of days exceeding 45 or 50F in January in most locations has significantly increased. 

If one is dealing with 30-year moving averages or some other statistically meaningful period, I believe the frequency has increased. If one is dealing with decade-by-decade figures, there's probably a lot of noise from natural variability. I had assumed that blizzard1024 was dealing with decadal time periods.

[Jonger]

If one is dealing with 30-year moving averages or some other statistically meaningful period, I believe the frequency has increased. If one is dealing with decade-by-decade figures, there's probably a lot of noise from natural variability. I had assumed that blizzard1024 was dealing with decadal time periods.

 

I found that 1959-1969 had the exact same amount of sub zero nights per year on average as 2000-2010 in Detroit, I could do a reverse and find the number of equal warm anomalies in a winter. Detroit has to go 15 degrees below normal to achieve a sub zero night in the heart of winter, so I guess a high 15 degrees over the mid winter average max of 31F would be a fitting place to start. Not exactly perfect science, but worth figuring out for fun.

 

I would assume that 1970-1980 would have less +15 daily max high temps than 2000-2010, its not really even worth looking.

[ORH_wxman]

Out of curiosity, I ran the numbers for ORH on number of occurances of 50F temperatures in the December-February period...a definite increase from the minimum of the 1960s, but the overall trend back to the early 20th century is very noisy. The 1950s and 1930s were very high frequency for 50F days.

 

 

 

 

 

 

 

 

 

 

I'll have to run the numbers at Boston and Hartford to see if there is anything different.

[Jonger]

Out of curiosity, I ran the numbers for ORH on number of occurances of 50F temperatures in the December-February period...a definite increase from the minimum of the 1960s, but the overall trend back to the early 20th century is very noisy.

 

I'll have to run the numbers at Boston and Hartford to see if there is anything different.

 

My location is exactly the same, our statistics are all back to 1940's - 1960's numbers.

 

Winter warmth and cold... 2000-2010 is very close to 1960-1970.

[Jonger]

Out of curiosity, I ran the numbers for ORH on number of occurances of 50F temperatures in the December-February period...a definite increase from the minimum of the 1960s, but the overall trend back to the early 20th century is very noisy. The 1950s and 1930s were very high frequency for 50F days.

 

 

 

 

 

 

 

 

 

 

I'll have to run the numbers at Boston and Hartford to see if there is anything different.

 

What is that tool?

[ORH_wxman]

My location is exactly the same, our statistics are all back to 1940's - 1960's numbers.

 

Winter warmth and cold... 2000-2010 is very close to 1960-1970.

 

 

We don't come close to matching the 1960-1970 period here...for snowfall we do, but not for temps or occurance of 50F days. In fact, the 1960s had the fewest number of 50F occurances...a total of only 41 days the entire decade. In contrast, the 1990s had 98 days of such temperatures. The 1945-1955 period had more than 100 occurances. The decade of 2000-2009 had 73 such occruances.

What is that tool?

Excel 2010

[Jonger]

We don't come close to matching the 1960-1970 period here...for snowfall we do, but not for temps or occurance of 50F days. In fact, the 1960s had the fewest number of 50F occurances...a total of only 41 days the entire decade. In contrast, the 1990s had 98 days of such temperatures. The 1945-1955 period had more than 100 occurances. The decade of 2000-2009 had 73 such occruances.

 

There is a bit of a difference between my location and yours.

 

[Jonger]

 

Excel 2010

 

Nice... My skills with excel, don't excel.

[blizzard1024]

Out of curiosity, I ran the numbers for ORH on number of occurances of 50F temperatures in the December-February period...a definite increase from the minimum of the 1960s, but the overall trend back to the early 20th century is very noisy. The 1950s and 1930s were very high frequency for 50F days.

 

 

 

 

 

 

 

 

 

 

I'll have to run the numbers at Boston and Hartford to see if there is anything different.

nice. Make me wonder if the 1960s and 1970s (a benchmark for many of us) were unusually cold at least in the northeast U.S. Winters were not "normal", they were overall unusually cold.  It is interesting that the GISS normal period I believe is 1951-80 which is going to highlight this cold period. 

[The_Global_Warmer]

nice. Make me wonder if the 1960s and 1970s (a benchmark for many of us) were unusually cold at least in the northeast U.S. Winters were not "normal", they were overall unusually cold.  It is interesting that the GISS normal period I believe is 1951-80 which is going to highlight this cold period. 

 

Paranoid much? When do you think GISS was started?

 

 

 

 

[skierinvermont]

nice. Make me wonder if the 1960s and 1970s (a benchmark for many of us) were unusually cold at least in the northeast U.S. Winters were not "normal", they were overall unusually cold.  It is interesting that the GISS normal period I believe is 1951-80 which is going to highlight this cold period. 

 

1st of all, GISS was created in the 1980s and the 1951-80 base period was the standard climate base period at the time. 

 

2nd, GISS is a global source and the 1951-1980 period was not cool globally. The 40s might have been a hair warmer, but it is a much warmer base period than 1901-1930. Coincidentally, at the moment the 1951-1980 base period is also roughly equivalent to the 130+ year long-term average 1880-present. 

[skierinvermont]

Nice graph for Worcester. Looks like the long-term slope would be positive but lots of variability. Some other locations that have seen more warming like North Dakota might have a stronger trend. 

[Jonger]

1st of all, GISS was created in the 1980s and the 1951-80 base period was the standard climate base period at the time. 

 

2nd, GISS is a global source and the 1951-1980 period was not cool globally. The 40s might have been a hair warmer, but it is a much warmer base period than 1901-1930. Coincidentally, at the moment the 1951-1980 base period is also roughly equivalent to the 130+ year long-term average 1880-present. 

 

1950-1970 was clearly cooler than the 20 years preceding it, before that you have questionable data with quite a bit of pre-UHI and adjusted data.

 

Its amazing how ORH's graph is nearly a perfect pre 1998 GISS overlay, of course after 1998 they don't look the same anymore. 

 

[skierinvermont]

1950-1970 was clearly cooler than the 20 years preceding it, before that you have questionable data with quite a bit of pre-UHI and adjusted data.

 

Its amazing how ORH's graph is nearly a perfect pre 1998 GISS overlay, of course after 1998 they don't look the same anymore. 

 

giss.jpg

 

I said globally. 1951-1980 was warmer globally than the 30s and was even a hair warmer than the 1940s. 

 

Also, UHI is removed from the data, so that is a non-issue, and adjustments are made for necessary reasons like changing times of observation. 

[ORH_wxman]

Nice graph for Worcester. Looks like the long-term slope would be positive but lots of variability. Some other locations that have seen more warming like North Dakota might have a stronger trend. 

 

 

Yes, the trend line for the data is positive...but I do not think it would be consdered statistically significant as the linear trend is 0.2 days per decade with a high standard dev. I agree the northern plains are probably the best area to find a statistically significant trend as the northern plains has the highest winter temperature trend of anywhere in the CONUS.

 

 

The "greater than X" temperature for highs would generally be the last component of temperatures to outrun the noise I would think, since the daytime maxes have seen the smaller trend. The night time mins have a much stronger positive trend. If we ran the inverse test of "number of days with low temps below 0F" or something, those would probably be much more robust.

[ORH_wxman]

I ran the BOS numbers this evening for # of days of 50F or greater during DJF...they look somewhat similar to ORH except a more pronounced spike in the late 40s/1950s

 

 

[The_Global_Warmer]

Every data set I have ever seen going back to the early 1900s or 1860s on become absurdly noisy and wild.  Does this have to do with measuring practices back then?

[donsutherland1]

nice. Make me wonder if the 1960s and 1970s (a benchmark for many of us) were unusually cold at least in the northeast U.S. Winters were not "normal", they were overall unusually cold.  It is interesting that the GISS normal period I believe is 1951-80 which is going to highlight this cold period. 

Both the GISS reference period and the NCDC reference period (1901-2000) are quite similar on a global basis.

[ORH_wxman]

Every data set I have ever seen going back to the early 1900s or 1860s on become absurdly noisy and wild.  Does this have to do with measuring practices back then?

 

 

For temperature at a given point if the station siting is up to par, then it shouldn't make a difference.

 

There is some question as to the station siting further back in time, but I haven't seen anything yet convincing me that so many stations were subpar as to greatly affect the data. An unshielded (or degraded shield) thermometer will be biased high for maximum temperatures and biased low for minimum temperatures. (it sort of acts like a thermometer on the moon so to speak)

[sokolow]

Put it into google scholar: I know it gets studied by DOTs because back in school we talked about regional frequencies & intensities of freeze thaw cycling in lifespan estimates for roads and bridges.

[blizzard1024]

Both the GISS reference period and the NCDC reference period (1901-2000) are quite similar on a global basis.

 

Why do both of these data sets cool the time period before the middle of the 20th century and warm the recent period? This gives plenty of fodder for skeptics, especially with UHI creeping into suburban areas from the 70s onward. Makes me wonder too as I lean skeptical on any extraordinary claims, like CAGW. 

[donsutherland1]

Why do both of these data sets cool the time period before the middle of the 20th century and warm the recent period? This gives plenty of fodder for skeptics, especially with UHI creeping into suburban areas from the 70s onward. Makes me wonder too as I lean skeptical on any extraordinary claims, like CAGW. 

The following paper explains the need for the adjustments and the kind of adjustments that were made:

 

ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2/monthly/menne-etal2009.pdf

[blizzard1024]

The following paper explains the need for the adjustments and the kind of adjustments that were made:

 

ftp://ftp.ncdc.noaa.gov/pub/data/ushcn/v2/monthly/menne-etal2009.pdf

thanks

[The_Global_Warmer]

For temperature at a given point if the station siting is up to par, then it shouldn't make a difference.

 

There is some question as to the station siting further back in time, but I haven't seen anything yet convincing me that so many stations were subpar as to greatly affect the data. An unshielded (or degraded shield) thermometer will be biased high for maximum temperatures and biased low for minimum temperatures. (it sort of acts like a thermometer on the moon so to speak)

 

 

Then I would say the answer would be during the colder period of the late 1800s early 1900s.  The max heat we see today was still possible not in terms of "length" or maybe likely but still attainable.  While it was easier to have prolonged cold periods.

 

We just had more wild swings from month to month, week to week, day to day.

 

From 1869-1929 the temp was taken on a roof in downtown STL.  I am not saying it's not legit.  But the wild swings quickly become less wild afterwards.

 

I will try to compile some data and see if there is a legit change around that time.

[The_Global_Warmer]

Why do both of these data sets cool the time period before the middle of the 20th century and warm the recent period? This gives plenty of fodder for skeptics, especially with UHI creeping into suburban areas from the 70s onward. Makes me wonder too as I lean skeptical on any extraordinary claims, like CAGW. 

 

Why would NASA and the NCDC commit fraud over this?

[michsnowfreak]

I ran the BOS numbers this evening for # of days of 50F or greater during DJF...they look somewhat similar to ORH except a more pronounced spike in the late 40s/1950s

 

 

Dont have the time to look up 50F+ days for all these years...but I do have the average # of times per winter the high temperature stayed at or below 32F.

1930s- 42.3 days per winter

1940s- 50.2 days per winter

1950s- 43.6 days per winter

1960s- 47.4 days per winter

1970s- 51.3 days per winter

1980s- 46.2 days per winter

1990s- 39.4 days per winter

2000s- 44.6 days per winter

2010s- 44.5 days per winter

 

This is an interesting idea though and I WILL be looking it up. Using days AOB 32F for highs can be contaminated by cold winters, but 50F seems like a good # to define a thaw.