Time of Observation Adjustment (TOBS)

It seems most of guys that stay involved with the Climate Change debate have Alzheimer like  memory issues.  Every now and again the same topic pops up just as fresh as it was a year ago, and the year before that, and the year before that.  Today for some reason its TOBS again.

I generally stay out of these debates because they are a waste of time.  All the players are entrenched in their positions and there is no way to reason with them.  Well, most of my blog posts are cut and paste ammo.  Someone brings up a topic for the old days I hit them with a link.

Steven Mosher pissed me off with a reference to the temperature record adjustments being required due to the incompetent "citizen scientist" volunteers that manned the surface stations.  Typical elitist BS, leadership or management is supposed to make the most out of their resources and accept any blame for defects.  That's why they get the big bucks.  When leadership passes the buck, time for new leadership.

So let me make this simple enough for even Mosher to follow.  These are the documented NOAA adjustments to the USHCN  There is a very small TOBS adjustment that increases with time into the modern era.  Those ignorant citizen scientists were replaced by educated and highly compensated scientists when the adjustments got out of hand.  Note the very small MMTS adjustment.

Next, the temperature data are adjusted for the time-of-observation bias (Karl, et al. 1986) which occurs when observing times are changed from midnight to some time earlier in the day. The TOB is the first of several adjustments. The ending time of the 24 hour climatological day varies from station to station and/or over a period of years at a given station. The TOB introduces a non climatic bias into the monthly means. The TOB software is an empirical model used to estimate the time of observation biases associated with different observation schedules and the routine computes the TOB with respect to daily readings taken at midnight. Details on the procedure are given in, "A Model to Estimate the Time of Observation Bias Associated with Monthly Mean Maximum, Minimum, and Mean Temperatures." by Karl, Williams, et al.1986, Journal of Climate and Applied Meteorology 15: 145-160.

TOBS adjustments came to be in roughly 1986 when Karl notice a quality issue.  He "ASSUMED" it was TOBS and created an adjustment that was only needed in special cases to correct that quality issue.  In actuality, the issue correlated with the change to Airport located weather stations, especially automated Airport weather stations.

Temperature data at stations that have the Maximum/Minimum Temperature System (MMTS) are adjusted for the bias introduced when the liquid-in-glass thermometers were replaced with the MMTS (Quayle, et al. 1991). The TOB debiased data are input into the MMTS program and is the second adjustment. The MMTS program debiases the data obtained from stations with MMTS sensors. The NWS has replaced a majority of the liquid-in-glass thermometers in wooden Cotton-Region shelters with thermistor based maximum-minimum temperature systems (MMTS) housed in smaller plastic shelters. This adjustment removes the MMTS bias for stations so equipped with this type of sensor. The adjustment factors are most appropriate for use when time series of states or larger areas are required. Specific details on the procedures used are given in, "Effects of Recent Thermometer Changes in the Cooperative Network" by Quayle, Easterling, et al. 1991, Bulletin of the American Meteorological Society 72:1718-1724.

Quayle noted that a correction was required for the new stations.  Now the TOBS adjustment could have been dropped and replaced with one MMTS/equipment adjustment.  I don't know who is higher up the food chain at NOAA, but it looks like Karl.  

So why are TOBS adjustments BS?  Because you don't need them.  Most of the record is based on LIG Tmax/Tmin thermometers that never cared what time a max/min occurred.  Changes in TOBS have minimal impact on most of the record.  There was a shift to Synoptic timing once overland communication became affordable.  Then stations, mainly manned by people that had the land line or telegraph, provided Universal Coordinated Time observations.  That way you could get your "national" forecast.  With the growth of private air travel in the US, stations where shifted to airports so pilots could call destinations for weather updates.  Those reading were taken more often.  Taking readings more often would mean more trips to the weather shack meaning weather shacks got located closer to the communications gear.  That means the adjustment required was a "TYPE" of observation adjustment or a "TYPE" of instrumentation adjustment.

To not step on toes, adjustments are added to existing fudges in order get the precision required, it has absolutely nothing to do with the volunteers that provided weather information as part of their day to day livelihoods.  

Does the Berkeley Earth Surface Temperature   project use TOBS adjustment? Nope, not required they just have instrumentation/break point adjustments since they didn't have any toes to avoid stepping on.  

The Quayley 1991 paper is a good place to start if you what to know the issues with each type of weather station, none are perfect.  Surfacestation.org has even more information on specific surface stations.  Thanks to TOBS and MMTS adjustments, other adjustments for things like station location are not included because they are already assumed away.