In my previous post Dial “M” for mangled – Wikipedia and Environment Canada caught with temperature data errors. we identified some problems with temperature data from the Eureka Weather Station.
Today I’m starting what may be a two or three part series having a detailed look inside the Eureka Weather Station and the data it produces. Thanks to the manager of the station Rai LeCotey, we have a lot of new information that had not previously been available on the web. Mr. LeCotey has been most gracious and forthcoming and I commend his openness, which as we have seen in Climate Science, is a rare quality. Here’s an aerial view of the station.
click for a larger image
Ecotretas and I looked at a number of what we identified as errors in data from Eureka, Nunavut, Canada weather station. Some errors are real, such as the January 1st 2007 METAR error (caused by transcription error).
We identified what we thought were errors on July 13th and 14th. The Station Manager Mr. LeCotey says that the July 14th new record high temperature “error” was real (meaning meteorological data, not a transcription error), and a function of wind direction bringing air from the North that has been warmed by terrain. He also says he’s working to get the error on Jan 1 2007 corrected in the record. He’s sent along some photo documentation of the July 14th 2009, event. We’ll get to that in a subsequent post, but first some background on the station itself.
Here’s what the Meteorological Instrument Complex looks like:
Looking Southwest at Eureka Met Instrument Compound -7/24/2004 - click to enlarge
The truck is interesting. Note the blowers on top of the Stevenson Screens for continuous aspiration.
Mr. LeCotey provided this official visitors guide to Eureka, which I have posted as a PDF, link below
click for PDF
He also graciously answered a number of questions. His answers are in blue.
1) The sensors in the Stevenson Screens are electronic it appears. Am I correct in assuming they are cabled to the met office? Of what type are they? Thermistors, RTD? Thermocouple?
We use a remote temperature and dew point measuring system type 2. The dry bulb temperature is measured with a thermistor and the dew point is measured with a dew cell.
2) I notice fan aspirators on the screens. Are these run continuously for the electronic sensors, or are they a holdover of earlier times when wet bulb DP/humidty readings required aspiration?
The sensors are housed in a ventilated Stevenson screen that runs continuously. Psychrometer comparisons between the remote system and our mercury thermometers (in a second Stevenson Screen right next to the remote screen) are done once a week with an thorough calibration done once a year.
3) How far away, in meters, is the Met Instrument compound from the nearest structure, such as the bright blue HQ building?
The Stevenson screens are approx. 40 meters
4) Why are there no readings in the first two hours of the day (00 and 01)?
We only do a surface weather program for 22 hours a day. We have a contract with Nav Canada that only wants aviation weather between 06Z to 03Z inclusive.
Surface weather observations are done on the side (with NavCan funding). Our primary function is that we send up 2 weather balloons a day as our commitment to the WMO. We stay on EST all year (there is no point to go to daylight savings time as an extra hour of daylight does mean anything to us when we have 24 hours of daylight in the summer anyway). Therefore, our last observation is at 22:00 EST (local) and we start observing again at 01:00 EST (local). The 23:00 & 00:00 observations are missing as NavCan does not pay us for those two observations.
5) Do the electronic displays have max/min memories?
Yes, our AES remote temperature and dew point (1987) system (RTD-87) measure the max and min temperatures and stores them in memory until cleared by the observer every six hours on the syno. The RTD measures the temperature & dew point every minute.
6) How often are the meteorological instruments calibrated and how is this done?
Psychrometer comparisons between the remote system and our mercury thermometers (in a second Stevenson Screen right next to the remote screen) are done once a week with an thorough calibration done once a year.
7) How are the hourly METAR reports made. Are they transcribed from the paper form to teletype or Internet data, or some other method?
The METARS are transcribe from the 2322 form into a WinIDE quality assurance software system (WinIDE version 3.0, is used as the principle data input system for human METAR observations within EC) that automatically checks for errors/discrepancies and gives a warning to the observer to make a correction before the observation data will be sent out. The WinIDE system is very good and follows the observing criteria of MANOBS very well. It will not allow an observation to be sent out over the met circuit with any errors or unnatural trends as in the case of the temperature being entered in as +23.0°C when it was supposed to be -23.0°C.
There will be subsequent posts on Eureka coming in the next day or two.