Dangerous assumption. 12:00 51.74 With no other knowledge about the periods, we have no basis to inject additional information. How unique is the name Tobs? 8:00 50.90 USHCN TOBS correction attempts to Debias those changes. Also, while the operator made the change on the 18th, the Switching from an afternoon time of observation to a morning time of observation would result in minimum, maximum, and mean temperatures around 0.6 C colder previously measured. If max/min temps of successive days do not vary, TOB does not occur. I get to pass this on to a friend of mine to show that he was incorrect…. 0.5 below to 0.5 above. what is the Weather data can serve many business applications, such as evaluating the impact of weather on insurance claims, heating oil consumption, electricity load during summer months in hot weather areas, agricultural output, and clothing items purchased from retail outlets. JerryB took time series and emulated the proceedure required for observers at COOP sites. And that’s all in an idealized, perfect sensor world! Our interactive map allows you to see the local & national weather 1. the ISSUE at hand is MICROSITE BIAS. If you check the TREND of a 7AM OBS for this site it was .0004F day. to my IQ: If it is colder than the 11 am pseudo reading, then it’s correct. NC, add this noise and the sine wave temperature column. FILNET is not needed for JohnVs approach. 1. Tony and his band of merry moderators also suppress polite but adverse commentary. Most shelters had the thermometer mounted on a device with a crank that allowed the observer to reset the thermometer without touching the instrument. Feb 1: 24 samples, 320 degrees. Numbers of hourly observations of current 24 hour min temperature in 24 Obviously a bad idea to simply connect across the “gap”. http://www.john-daly.com/tob/TOBSUM.HTM, “I’m not convinced on outliers, do you have a link for the tables? prior and next day (if it happens to be the actual high/low of both 24 The reason that it matters, however, is that depending on the time of observation you will end up occasionally double counting either high or low days more than you should. For example, if its CO2, shouldn’t the night temperatures be rising FASTER than the daytime ones, not slower? The overall avg for the three periods is 20. We don’t know. Outside of the box take a fictitious site called FT. Hansen, TX. But in order to make this comparison, you have to know whether Joe was referring to July 14 or July 15. pairs would be sufficient for a 24 hour period. :-D) lastly ;level with the first row of your 24 hours max and min columns copy the time of day column across. Sort of (but not completely) answers my questions. Love it!) If the object is to proxy the 24-hour average temperature with the average of a 24-hour min and max, the ideal time to take the reading would be at the intersection of the two plateaus. In this case, the “vertical” axis of the grid is typically “snapped” (in graphics/drawing parlance) to whole degree units. In case the wording of “Numbers of hourly observations of current 24 hour To me, all of these recording delays, etc “ought” to result in non-recorded data. And, we have no basis to make use of measurements from the day before or after any given day, to modify that day’s high or low temperature. Let me be a bit clearer. Let me use the word spike(s) for brief changes of temperature up, then Rounds up 5/9 of the time (5,6,7,8,9) and down 4/9 of the time (1,2,3,4). Of the 8,756 hourly readings, twelve were missing and replaced using a linear approximation based on the surrounding temperatures. Karl et al’s Min graphs in Fig. 9 Yrs 50.71 -0.47 -0.19 0.12 0.39 1.62 1.26 0.89 0.64 0.48 0.34 One spike greater than 20 F removed The temperature persists through The tempeature at the moment between two consecutive time periods is This bias will apply to TMIN. The maximum (MAX.) NC, ‘MOD’ this hours column by 24 to get time of day. Here is the same graph for all USHCN stations. If you observed temp at 7AM you would see a TMEAN of 68.8 F. THAT IS NOT THE POINT OF TOBS ADJUSTMENTS FOLKS. 249 instances of 5 occurrences Annual Weather Averages Near Lansing. Furthermore, nearly all the MD stations observed at midnight. There is a whole new realm of questions when one changes instruments to types that measure hourly temperatures or even less. Silly isn’t the word for it. His data file will how you how shifting the the first day of the next month. Do we really need to align the different stations to be recording the exact same 24 hour sequences? (is there anywhere that temps are incredibly stable day and night? The only other possible explanation is automated recording is deliberately TOB biased, which I find hard to believe. If the hourly measurements were hourly high/low measurements, then 24 seem odd or rare. finer grained approach, you might have 1902 for some sites and 1904 for others. The challenge is how to properly handle the edges of the day.). Yet as I’ve shown, such rearrangements gives an average that varies from 16.7 to 23.3! A great shortcoming of how history is taught is the omission why and how events occurred as precipitates of weather (pun intended) A great shortcoming of climate studies is the omission of the accurate history of weather. Astute observers will be aware that weather stations don’t take a single temperature measurement at the observation time. A hail storm turns the temperature curve upside down. before asking another TOBS question or proffering another TOBS opinion. temperature as the 24 hour old 24 hour min: 3554, just over once per high, and the first three of them are lower yet than the previous This is similar to the process that NOAA/NCDC use to calculate U.S. temperatures. This whole TOBS thing continues to feel like an exercise in learning to properly handle missing and invalid measurements. From above comment (trying to use photobucket): [IMG]http://i225.photobucket.com/albums/dd204/beach_040/TOB.jpg[/IMG]. 3: 30. moment, at the end of the first time period is identical to the variations of temperatures. I would hope that any future station surveys would include similar close-up photos of the MMTS sensor in order to see how pervasive this blackening problem is. My goal is not to fill in the gaps, but properly analyze the trend without allowing the gaps to bias the analysis. time to get some real work done and come back later. One used to reset it with a magnet, drawing the peg down from the max shown, to the top of the mercury again, each day. fronts, I had never quantified how much it does not depend on them. Or does it record the highest T reached, or the temp at the end of each hour? Contiguous U.S. monthly temperature anomalies from unbiased and synthetic TOBs-biased CRN data. It creeps up. He has presented very clear evidence in the Australian case that there is no significant temperature trend when temperatures are measured at midnight, 3am or 6 am but there is a positive trend at 9am and mid-day. As a result, by assuming 7 AM observation for all AM stations and 5 PM for all PM stations, a good estimate of the median bias is obtained for all AM or PM observations. sine this. This makes a big difference for how the gap should be interpolated. Notwithstanding the above, as re #1, if the station continues to use the same time of observation throughout its record, the trends at the station will not be affected provided that the trends are the same for both the max and min temps. Such thermometers as above, if used, would record the same max for several days in a row (unless mathematically corrected by guessing). If it’s warmer than the 11 am pseudo reading, then the minimum for the day has already been taken at 11 am. It’s different than that. Sorry, that would mean saying bad things about NASA GISS, and you definately aren’t going to do that, are you? In short, the Karl et al model, on which the NOAA etc. If the temperatures rose, the index would remain where it was as the fluid flowed past it. (The Nimbus records every 16 seconds, and reports the high, low and time of high/low within each 24 hour period! sure that I understand just what it is that you are suggesting be changed. Oct-10 Nov-10 Dec-10 Jan-11 Feb-11 Mar-11 Apr-11 May-11 Jun-11 Jul-11 Aug-11 Sep-11 Oct-11 Nov-11 Nov year Oct year So I’ll come back at 11 am and read and reset the min thermometer”. TOBs is irrelevant. January overall average = 165.0 degrees. observation the previous day.”. their procedures at the time that I initially wrote my code (summer 2002). Jan 31 hi/lo/avg = 20/10/15 Between 1960 and today, the majority of stations switched from a late afternoon to an early morning observation time, resulting a systemic change (and resulting bias) in temperature observations. But the same issue will arise if one uses more samples and deletes the edge values. Next thing is to consider the different monitoring and recording methods and how they should be properly analyzed. Yes, we can draw an imaginary continuous line between our measurements, but when we want to fix a given temp/time estimate along that curve, we recognize it will resolve to a spot on the grid, never in between grid points. Let me explain why. greater than the mean is 2 in 10000. This is attributed to the preponderance of AM observation times falling between 6 AM and 9 AM, and PM observation times falling between 4 PM and 7 PM. There’s lots of assumin’ goin’ on out there. I suppose it’s everywhere, just seems more so on ‘the alarmist’ sites than on ‘the denier’ sites. . Below is the station list used in the top graph. JerryB has 9 years of hour data from 190 sites. To get the tempeature a guy has to walk out and write down the MIN measurement time is lower than the day’s min, it replaces that min. Geography impacts climate! While some commenters have hyperbolically referred to temperature adjustments as “the biggest science scandal ever”, the reality is far more mundane. What means TOBS, SHAP, FILNET ? consectutive days. Select August 1991 that 1991-08. I see TOB being a further potential worry when daylight saving chages, coincidental with the thermometer reading being done by custom within an hour of max or min for a day. F, not because of their possible effects on TOB, but because of a concern weigh in on the decisions. Instead, we can use the summarize function. but No bias in trend. Hmmm…. midnight, observations like that occur often, even without passing storms, and Actually, come to think of it, it’s not just RC. read the min/max at Midnight in one ( and reset) Your method does not report what 24 hour max/min measurements would report for [Yeesh. To consider this in a bit more detail, consider the case where the precision of our timing is to the second, and our measurements are made hourly. days of data will not indicate the magnitude of the bias. 25% of the year. If the sensor is placed on a roof (or, to be extreme, near a wall of water barrels, in the exhaust plume of an A/C unit, etc et), the nearby thermal mass, thermal source or cooling source will have a massive effect on the daily temperature curve… potentially far more impact than the time of observation. it’s probably closer to the percentage of sunny days for pavement and summer days for AC and etc, Gregory et al 2019: Does climate feedback really vary in AOGCM historical simulations? a station ad the CRS installed? It’s already quite complete enough. It’s not too different from the adjustment built into my chicken coop automated seasonal light timer: we can turn the light on for a certain period before/after sunrise and sunset. Small wiggles are due to new stations entering the network between 2004 and 2014. Thanks! 7AM .146 F per year. Hu, while I agree that the TOB phenomena is real, and has potential to bias surface temperature measurements, I am unconvinced that NOAA’s execution of the adjustment for TOBS is either reasonable or accurate. Between 1-3 and 2-0, the temperature could have been anything in a wide range, certainly enough to impact the high/low for either day. This is all a matter of properly envisioning the two dimensional space, in this case of temperature vs time, with respect to the discrete point measurements. Differences between the Mohonk Lake record of mean annual temperatures and those of nearby stations in the USHCN (see map in Fig. it would appear that you have attempted to banish temperature. My question about TOB was if it was a part of the data for certain years, period.”. #120 Sorry, reposting to get rid of the pesky less than symbol: Differences of the biases were small ([less than] 0.3 Deg. Denver/Stapleton airport, which ranked #10 in the 5 F or more spike 70 Peter Hartley, Jonathan’s research is interesting but I don’t think it would be applicable to the data sets available for the GHCN/USHCN. Everything else is max/min only. , Next thing is to consider the different monitoring and recording methods and how they should be properly analyzed. I understand the reasoning behind their adjustments. Login via the left margin or if you're new, register here. I took a look at that, and at the “USHCN Daily” data, to see how it got Here is my first question for clarification: 1) Please articulate the definition of the moment at the end of the first time period, M2006e !=== M2007b, (My answer, for reference: for the purposes of this work, M2006e is one measurement interval before M2007b, e.g. The safe thing would be to regard the first reading after the gap as ambiguous, and not to resume the assumption of 24-hour periods until the second reading after the gap. NOW, what happens if halfway through the history of this site we SWITCH from Observing Please try to keep your images limited to 500px wide. Since the mins are not affected, this makes the average mean temperature about 1/12 = .08 degree too low, using these hypothetical numbers. A question that someone raised in one of my email spools about TOBS: If MMTS is an automated system that automatically records temperature then why would the TOBS trend increase as the amount of MMTS increased? Hmmmm, what a novel concept! I’ll only cover the simplest situation: the uncertainty of an initial measurement in “grid space.”, Suppose we see 10 degrees at 6am, presumably +/- 0.5 in an ideal world (hah… but let’s assume a perfectly accurate sensor for now!). TOBS. – Early 1910s personally, I’d write down 7AM no matter what time I visted the little wood box. I wonder what Karl et all think about how their numbers have been applied to the data. See more. F) will be replaced by a July 5 PM temperature (70 in the example), so that one daily reading for the year will be 60 degrees too high. The AT OBSN temperature is the temperature at the time you take your observation. Daily rain drains off afternoon heat potential and sets up the evening as the high of the day. It’s biased. I am saying (Jonathan Lowe is saying really) that we should move away from looking at trends in maximum and minimum temperatures and instead look at trends in temperatures recorded at 3am each day, trend in temperatures recorded at 6am each day, trends in temperatures recorded at 9am each day etc. (Talk about AGW! The problem is with the boundary definition and how it is handled. Sorry, I’ll have to come back to this later. Dictionary entry details • NOAA (noun) Sense 1. 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