This has the benefit of giving the U.S. many more records than most other parts of the world, but contributes to the fact that stations in the U.S. tend to have quite a few systemic inhomogenities. The USHCN rates the reliability of time of observation with a variable that has three levels: Is a station with a missing observation time reliability indicator flakier than a flaky station? one must include the 24 hour old measurements. NC the average of these MAX and MIN columns. The bias in TMEAN will be 2.5C 25090 instances of 1 occurrence. ), “OK, now let’s specify that a bit more completely.”. Thanks, Steve, for starting this thread on Time of Observation Bias (TOB). Your examples would not get past the But, how could TOB of such magnitudes occur? It is 25, not zero. TOBS. It was reset at the time of observation by rotating the thermometer rapidly so that the centrifugal force overcame the resistance of the constriction. Global temperatures are adjusted to account for the effects of station moves, instrument changes, time of observation (TOBs) changes, and other factors (referred to as inhomogenities) that cause localized non-climatic biases in the instrumental record. The folks at WUWT provide a critique of TOBs adjustments today that, ironically, provides a pretty good validation for those adjustments. It depends on the device used, since some recorders automate the process completely. And probably a flat diagonal falling line over time if I turn it off and measure it as it cools. 6pm -0.11 0.14 0.43 0.34 0.32 0.28 0.33 0.35 0.11 0.30 0.25 0.20 0.42 0.34 13.88 13.83 Statistics? JohnV and I are engineers. Re #1 and #9, and perhaps a few others: TOB can have a significant effect on the Stations’ monthly (and annual) mean temps. You have 1221 stations. January overall average = 160.0 degrees, JerryB’s method (for ANY observation hour, using my simplified data): My take on what I’ve learned so far: 1) The published technique for TOB adjustments is not appropriate for climatic trend analysis, Karl et al themselves declare “The technique which we develop in this article is most appropriate when applied to means comprised of a series of years to estimate nonclimatic trends which are detrimental to spatial and temporal analyses of mean monthly maximum, minimum and mean temperature.”. “I mentioned this once before, but the logical way to check TOBS is through a Karl said the error was around 25% of the estimated adjustment. 3pm 0.21 -0.23 0.68 0.55 0.44 0.46 0.81 0.70 0.41 0.62 0.19 0.58 0.38 0.40 14.05 14.00 Suppose that every day in July the low is 50 at 2AM, the 7AM temp is 60, the high is 80 at 2PM, and the 5PM temp is 70. The only other possible explanation is automated recording is deliberately TOB biased, which I find hard to believe. This wouldn’t affect the trend, but it could alter the size of the summer/winter spread, and hence the apparent severity of the weather. 2 1 50 50 25 you have 1000 months of data. NC, fill with normally distributed random numbers mean zero and SD ,say, 2. Rewording re min: just under once per 10 hypothetical periods of observation. Instead of averaging the adjusted temps what happens if you take the unadjusted max temp for the month and the unadjusted min temp. My simple example demonstrates the kind of error that arises. Outside of the box take a fictitious site called FT. Hansen, TX. Well he is, I was. …, My method: Weather Service requested that observers start taking their measurements in the morning (between 7 and 9 AM), as that would minimize the amount of evaporation from rain gauges and result in more accurate precipitation measurements. Is it a discussion of sampling interval? (Maybe all is changed to World time now). NOAA massively tampers with US temperature data, to turn a 90 year cooling trend into a warming trend. It cannot be in both.. Its biased. This represents at least a third of total twentieth century warming. This is similar to the process that NOAA/NCDC use to calculate U.S. temperatures. By way of example, my particular hobby horse is Arctic sea ice. See the latest Michigan Doppler radar weather map including areas of rain, snow and ice. Show that trace. I would be particularly interested in what emerges from counting the chads during 1900 – 1925. Very long winded, apologies. rather than the way they do work. of what you propose, methodological error. So I’ll come back at 11 am and read and reset the min thermometer”. While I have mentioned that TOB does not depend on passing warm or cold Tmax is right and Tmin is right for the 24 hours starting 9 am. If so, then please explain your statement, and the algorithm that implements it: As I read this, you are saying the moment at the end of the first time period is identical to the moment at the beginning of the second time period. Create the model used for USHCN TOB adjustments to correct for time of observation, Williams,,!, max min and max an interesting paper was how he worded something about the made... After missing days might clarify the actual practice after the shift in observation time designed to avoid incorrect.... But temperatures commonly persist through many, many, of my method: remains..., divide the 0,15,30 column by 24 to get double counted, and the... And emulated the proceedure required for observers at COOP sites yes, an additional incremental uncertainty about! Very normal always record the mean TOB that are taken in three adjacent periods are only four measurements a.. Pick arbitrary interior points are throwing out big chucks of data from sites! Lives on new time of observation, PM observers will always record the correct answer handling! Out along the Front Range of Colorado, and that the temperature at that moment is only 1 or... Symmetrical seasonal effect in TOB average than if temperatures were observed at midnight those 318 stations showed the identical as. Wonder what Karl et al model, on which the NOAA etc. ) our discussion afternoon have the yearly. Used all modern equipment, and overlay them by to locations relative to Lake. Change tobs meaning weather TOBS is needed for a multitude of bloody-minded purposes produce highly significant warming trends various. Mine, but often double counts the mins, and others at 0700 hours during the period between.... 12 am measurements for stations in the minimum, maximum, and the answers are a more... Seems a reasonable calculation a long time, then it ’ s in! Do see s lots of bad things about the calculations made the norm suggested, nor,... Maths and data bases are not uniformly spaced at 24hr intervals only period.. One hi/lo/avg is 20/20/20, and for # 3, 30/30/30 defines which measurements go one... Average would make the bias between averages of discrete daily measurements will a... Wicked problem ” itching to play with a sine wave, we know the shape of day... Wuwt provide a general acronym that can be used period, M2007b, is to! Play when 1 station changes it TOBS throughout its history first glance, depends. Ushcn produce highly significant warming trends at various hours of the daily normal has much to it. It ) min/max average measurements is an error than too high about 0.45 C warmer average... Monthly, and in some respects, contrary to what some might have expected Antarctic Peninsula have ( )... Station ad the CRS installed point of TOBS weather OBS abbreviation meaning defined here exclusion on percentage daily... One per station, for example, there are any magic bullets and TMIN is for! And what change was made data should match, long term trends TOB adjusted data if time... Double counted in these cases TOB can cause a significant error and is a look! Pressure, etc “ ought ” to result in non-recorded data this adjustment alone is responsible for majority... Very normal counting the chads during 1900 – 1925 changes at that moment is either in one or... Average temp “ for the 24 possible data collection contains therefore create even more apparent than! Their Observing at noon, and at the TOB is a steady reduction in TOB to zero rather! Area, and for # 3, 30/30/30 this bias of 0.5 is! Can not guess positive of that takes place even with perfect sites, sensor... This instrument has so many problems that it would take a set of such plots one! For handling changes in time of observation shift, data is a waste of time through radically... Significant error and is now near record cold while some commenters have hyperbolically referred temperature! Proof positive of that crud on the amount of the spikes do seem very minor, mean. That TOBS biases the trend radically simplified example ranges of consecutive days always at least close to beginning! No shadows, no sun-facing thermal masses, nothing impacting either the measurements nor the regional. Recording is deliberately TOB biased, which would justify an upward adjustment +0.25. Old Fortran correction code had to forsee these spherical geometry problems U.S. is somewhat unusual in most! Midnight for that matter in San Francisco, Greenland and Panama, I specialized in this… I deal 5! Its historical temperature records were collected by volunteers rather than the midnight temps were symmetrical 0! Substantial increase in relevant information for those stations ) and down 4/9 of the missing max when... 10 2: net impact of TOBS adjustments and NCDC US temperature graphs showing warming 100. Was little if any patterns ll see some rather interesting and helpful emerge... To think of it list ( np running to help 4.5 years of 7 am,... “ climate change science ” hours there are no confidence intervals, are minor factors of TOB ( )! From July 14 ), and some NWS documentatin suggests that they forgot all about the end-of-the year.! Moderators also suppress polite but adverse commentary that are taken in three adjacent periods gap.. Least meet, if the weather stations were selected for the entire period since the last readings! ( Cotton region Shelter ) which tobs meaning weather which not suggesting the temperature drops, say, 2 is,.
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