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01-04-2021, 16:10   #16
Oneiric 3
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Originally Posted by M.T. Cranium View Post
Those co-ordinates are not carved in stone, what's the grid tolerance, nearest degree or 0.1 degree? The exact lat long as given in the EC source is 43.67N and 79.4W.

What exactly is re-analysis, estimates from maps? The maps from before 1945 would have no upper air measurements and any recreated maps showing that are based partly on actual temperatures; my data base has probably the only actual temperatures near the grid point before the airport opened in 1938, so really this is just a sort of estimate of what my data base applied to estimated maps comes out as after the fact. But I do think it correlates at a very high level from what I checked so far, mainly the January month by month and the more extreme values of other months, don't see any outliers. It's all a bit on the cold side of the actual or even urban-adjusted numbers.
I've attached data from the 'ERA 4th Generation' for the coordinates you specified for Toronto in an early post. The data only goes from 1950 up to the present year (on a monthly basis) and the resolution is stated as being 0.5 by 0.5 degrees.

And I really wish this platform would sort out its idioitic attachment system. Far too fiddly and unnecessarily complicated for my already very limited patience to endure.
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01-04-2021, 21:52   #17
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M.T. I was looking through your Toronto data sheet and just want to confirm something with you, and that is, is this section here there actual 'raw' daily readings?



I just want to be sure before I tidy it up (those God foresaken leap days should be completely abolished imo) and run it through some code to compare it with the data I posted up above just earlier.
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03-04-2021, 21:29   #18
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Yes those are raw daily means, but the monthly averages derived from them can be found in another part of the spreadsheet, they were averaged by EC and should all be within 0.1 rounded of what you would get from the work on those daily numbers. Also my tables for Toronto run top to bottom without a space for missing 29 Feb (the NYC tables have that feature) so that formulae for some columns would be different than others. Here's the grid references (range) for the monthly averages in the spreadsheet.

They are located in rows 1840 to 2021 to make it easier to figure out to which year the data belong. The columns in play are HW to II. That gives you Jan to Dec and annual means. Unfortunately I did not block the data to convert to one decimal for round numbers, e.g. you'll see April 1842 says 7 which is 7.0.

Let me know if you find this data section and have any questions. The website data are derived from their (EC) averages of monthly mean max and mean min rather than directly from averages of mean daily. It won't make much difference but some of these data would be 0.1 different from what you would get by taking the average of daily means. Once again, my table of daily means is derived from their conversions of the original F data whereas the tables above (the ones that are in F deg) are calculated by me from the entries in the original grids.

If you still wanted to average my data rather than using this table, be aware then that each column runs unbroken from 1 Jan to 31 Dec so that leap years will run from (a) days 1232-1260 for February and (b) days 1261-1291 for March compared to 1260-1290 for non-leap years (incl 1900), etc to end of columns.

My averages at the end of each row for dates have the formulae worked out for that. I suppose I should standardize this work with the NYC tables which I altered for missing leap year dates so that all similar dates of the year after Feb 28 are in the same row. Maybe the next version will have that built in. I'm nervous about throwing off formulae although they should convert along with the shifts.

Also minor point but the -7 and -3 for Jan and Feb 1840 are just rough guesses based on data from Providence RI, there was no weather station at Toronto until 1st of March 1840.

By the way, if you're transcribing these numbers into an excel file, then they also exist in print in the net-weather thread, in the second post of the thread.

You asked if they were raw data and the answer is yes, including those monthly means I mentioned.

For comparison with other data sets, I would recommend applying the urban heat island correction as follows: data 1840 to 1880 is okay as is. Data 1881 to 1890 reduce by 0.1 (to colder values), data 1891 to 1900 reduce 0.2, etc until you reach 1971 to 1980 which would reduce by 1.0 (C deg). After that 1981 to present all reduce by 1.1 C.

If it would save you some work, I could post an excel file of those conversions, that does not yet exist in the excel file but it does exist in print in the net-weather thread, this time on page two after the data on dry spells is tabulated (go to page two of the thread, second post).

If the purpose is to compare with CET or Irish data, I would prefer that these adjusted values would be compared, otherwise there will appear to be a spurious warming trend in the Toronto data over the 20th century into recent decades. If it's to compare with the re-analysis, I don't know what to recommend because I don't know if they factored into their numbers any result of the change in the environment from small city (in 1900) to metropolis (after 1960). By 1900 Toronto was already about a quarter million people with the weather station near the centre of the core, so an urban heat island would already be in place then. It would have grown approximately as suggested by my corrections thereafter. By about 1960 Toronto had surpassed two million population and had spread out a good 20-25 miles beyond its 1900 extent. Changes since then have been relatively minor with most of the growth out beyond the 1960 suburban belt, and tending to cluster rather than run out unbroken, due to greenbelt and river valley intrusions. So I don't think the urban heat island grew very much after about 1950-1960 and the data suggest that also. I used to run my own backyard weather station in a perfect spot for urban-rural comparisons (30 miles west of the downtown station) so I had about ten years of data for comparison, although the location where Toronto downtown is located would be a bit warmer than my location anyway due to lower elevation and closer proximity in winter to Lake Ontario. A sample of some very cold clear night readings would average about 6-8 F deg colder at the MTC-jr location. And that was in a small heat island of a smaller town, really rural settings might be another 4-6 F deg colder again. Most daytime readings were 1-2 deg lower there. However that was complicated by cooling lake breezes that would be just about extinct at my location inland, so some days in March to June in particular would run cooler in the city. It looked to me like that season extended into July more frequently in the 1840s and 1850s before there was any real urban development to weaken the lake breezes (and probably after some of those winters the lake was pretty cold into the middle of summer too).

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03-04-2021, 21:52   #19
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By the way the main reason why I didn't convert daily data to the same system as the monthly/annual data would be that I don't believe the differentials would apply unbroken to all days, the cool, cloudy and wet days would be reduced less than the warm, dry days especially those in modified polar air masses in warm seasons. So it would be a complicated process to change all the daily data. It would probably result in a more variable adjustment with the cooler, wetter months adjusting less than warm, dry ones.

It's unfortunate that no particular weather station in the nearby rural areas has an unbroken data set for any long interval, they just came and went with various decades covered. So there's nothing absolute that I can use for a comparison. There is a long record at Kingston, Ontario at the east end of the lake, but it's probably too far from Toronto to provide the right kind of corrections, with the chance of anomaly regime differences; also that's a very lake-influenced location and despite being on the lake, Toronto only has limited intrusions of cooler air when winds are southeast to east. Kingston is open to southwest winds (which prevail in these climates) off the lake.
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03-04-2021, 22:25   #20
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Maybe then to save you some work just specify what time interval you want to have monthly means, and whether or not they should be raw data or adjusted to urban heat island reductions. I could post the file of just that information probably within an hour as it would not require much work here. Presumably if the data are in a dedicated excel file, you could then import said block of data into another file where you have the other data for comparison?

(later developments ...)

I created this file for you and anyone else who wants to use it, only the Celsius monthly means for Toronto are in this one, two sets of data, first the raw data as recorded, and second set, adjusted for urban heat island (so progressively larger amounts subtracted as explained).

This should save you some work. If you do happen to average out my daily C numbers, you'll likely find them similar but occasionally off by 0.1 for the reasons outlined above. I am making up a table of that parameter to compare.
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Last edited by M.T. Cranium; 04-04-2021 at 06:36.
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06-04-2021, 07:23   #21
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Originally Posted by M.T. Cranium View Post
Yes those are raw daily means, but the monthly averages derived from them can be found in another part of the spreadsheet, they were averaged by EC and should all be within 0.1 rounded of what you would get from the work on those daily numbers. Also my tables for Toronto run top to bottom without a space for missing 29 Feb (the NYC tables have that feature) so that formulae for some columns would be different than others. Here's the grid references (range) for the monthly averages in the spreadsheet.

They are located in rows 1840 to 2021 to make it easier to figure out to which year the data belong. The columns in play are HW to II. That gives you Jan to Dec and annual means. Unfortunately I did not block the data to convert to one decimal for round numbers, e.g. you'll see April 1842 says 7 which is 7.0.

Let me know if you find this data section and have any questions. The website data are derived from their (EC) averages of monthly mean max and mean min rather than directly from averages of mean daily. It won't make much difference but some of these data would be 0.1 different from what you would get by taking the average of daily means. Once again, my table of daily means is derived from their conversions of the original F data whereas the tables above (the ones that are in F deg) are calculated by me from the entries in the original grids.

If you still wanted to average my data rather than using this table, be aware then that each column runs unbroken from 1 Jan to 31 Dec so that leap years will run from (a) days 1232-1260 for February and (b) days 1261-1291 for March compared to 1260-1290 for non-leap years (incl 1900), etc to end of columns.

My averages at the end of each row for dates have the formulae worked out for that. I suppose I should standardize this work with the NYC tables which I altered for missing leap year dates so that all similar dates of the year after Feb 28 are in the same row. Maybe the next version will have that built in. I'm nervous about throwing off formulae although they should convert along with the shifts.

Also minor point but the -7 and -3 for Jan and Feb 1840 are just rough guesses based on data from Providence RI, there was no weather station at Toronto until 1st of March 1840.

By the way, if you're transcribing these numbers into an excel file, then they also exist in print in the net-weather thread, in the second post of the thread.

You asked if they were raw data and the answer is yes, including those monthly means I mentioned.

For comparison with other data sets, I would recommend applying the urban heat island correction as follows: data 1840 to 1880 is okay as is. Data 1881 to 1890 reduce by 0.1 (to colder values), data 1891 to 1900 reduce 0.2, etc until you reach 1971 to 1980 which would reduce by 1.0 (C deg). After that 1981 to present all reduce by 1.1 C.

If it would save you some work, I could post an excel file of those conversions, that does not yet exist in the excel file but it does exist in print in the net-weather thread, this time on page two after the data on dry spells is tabulated (go to page two of the thread, second post).

If the purpose is to compare with CET or Irish data, I would prefer that these adjusted values would be compared, otherwise there will appear to be a spurious warming trend in the Toronto data over the 20th century into recent decades. If it's to compare with the re-analysis, I don't know what to recommend because I don't know if they factored into their numbers any result of the change in the environment from small city (in 1900) to metropolis (after 1960). By 1900 Toronto was already about a quarter million people with the weather station near the centre of the core, so an urban heat island would already be in place then. It would have grown approximately as suggested by my corrections thereafter. By about 1960 Toronto had surpassed two million population and had spread out a good 20-25 miles beyond its 1900 extent. Changes since then have been relatively minor with most of the growth out beyond the 1960 suburban belt, and tending to cluster rather than run out unbroken, due to greenbelt and river valley intrusions. So I don't think the urban heat island grew very much after about 1950-1960 and the data suggest that also. I used to run my own backyard weather station in a perfect spot for urban-rural comparisons (30 miles west of the downtown station) so I had about ten years of data for comparison, although the location where Toronto downtown is located would be a bit warmer than my location anyway due to lower elevation and closer proximity in winter to Lake Ontario. A sample of some very cold clear night readings would average about 6-8 F deg colder at the MTC-jr location. And that was in a small heat island of a smaller town, really rural settings might be another 4-6 F deg colder again. Most daytime readings were 1-2 deg lower there. However that was complicated by cooling lake breezes that would be just about extinct at my location inland, so some days in March to June in particular would run cooler in the city. It looked to me like that season extended into July more frequently in the 1840s and 1850s before there was any real urban development to weaken the lake breezes (and probably after some of those winters the lake was pretty cold into the middle of summer too).
Thanks for this and the others well detailed info MT. I was eventually going to compare this Toronto data with that of the CET, but my priority for now is to compare it with its model reanalysis equivalent just to see how well the reanalysis (EC 4th Gen) has done in capturing the relatively recent (since 1950) historic temperature trends in that region. I did, a number of years ago, do similar for the 'IMT' series and while general broad scale trends from the EC grib data were more or less similar with the raw data, actual values rarely were, particularly regarding daily and monthly extremes (Max/Min/wind/pressure etc)
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06-04-2021, 07:32   #22
M.T. Cranium
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Okay, so in that case I would suggest comparing the second data table generated (urban heat island adjusted) with the CET, and both with the reanalysis to see what you think of each of them.

I did construct a table of my file means in C and found the expected slight scatter within 0.1 from the official means, with about 80% overlap. However, there were no outliers at all 1991-2010 which made me wonder if they switched their methodology in 1991 (as they would get the same values as me assuming I had no typos from their tables which are the sources of the C data).

On the annual scale there is already a comparison graph available in the excel file for annual means and CET annuals, GL produced a graphic from that. Since it compares raw data it shows the Toronto means catching up to the CET, nowadays there is little difference, back before the city was very large, it was often 1 to 2 C deg colder than CET. The urban adjusted data (on a 5 yr rm basis) follow the CET fairly closely and remain in that range of 1 to 2 deg colder.

The peaks of warmth around 1921 and 1948-53 are similar, as is the warming from about 1987 to 2012. A few minor differences can be seen also, the rise in the 1890s is a bit more prominent for Toronto.

I have not gotten around to comparing months yet, that might reveal relationships which we don't see from just the annual data.
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