Friday, March 8, 2013

Comment to and response from Env. Can.

I had noticed that Env. Can. observations at the Ottawa A/P were way off for the last storm so I provided the following feedback via their website:

There are some significant issues with the observation equipment at Ottawa INT'L.   For example, for February 27th, the hourly observations note only "Snow Showers" for the afternoon when heavy wet snow was the reality.  Secondly, the daily data shows a total snow amount of 14.2 cms while the reality was approx double that at 25-30cms (compare with Ottawa CDA station total snow of 29 cms).

This is the response:

----- Original Message -----
Sent: Thursday, March 07, 2013 4:36 PM
Subject: RE: Environment Canada Ser: C0306CZLEB NIRT:0005958

Hello Fred Nieuwenhuis,

Your request was forwarded to our office.  Thank you for your feedback.  In response to your comments, the weather conditions are reported by human observers.  For the amounts, we have received a lot of complaints indicating that the snowfall amount reported by Ottawa Int'l were too low for the February 27th storm.  You will find below an explanation of the differences.  I am unable to advise you on what information you will use, - maybe the official numbers with a reference to other reliable sources - these can be the weather summary (see link below) and the data from the Ottawa CDA site. 

The amount of snowfall recorded at Ottawa Int'l was 14.2 cm with a water equivalent of 25 mm.  This snow was very wet and there was a lot of compaction with the moisture.  In the hourly weather reports issued from the airport for this date, Ice pellets were reported, and this would definitely produce heavy solid snow.  There were high winds during the storm, and as in the past, the observation site at the airport probably did not capture the snow within its measuring area - snow may have blown elsewhere.

The other site in Ottawa at the CDA reported 29 cm.  This location may have a more protected snow measuring area.|2013-02-27&Year=2013&Month=2&Day=01

This was truly a very messy storm.  The amounts of snowfall were variable based on the location of measurement, and it may have depended on when the snow was measured.  The wetness and weight of the snow reduced the depth if it was not measured at the right time.  If the temperature was a bit colder, then the snow was less dense.  If the temperature was warmer, then the snow may have melted almost immediately. 

- link to weather summary bulletin issued after the storm, reporting 25-30 cm for the Ottawa area:

We have created a spreadsheet with the raw bulletins from Ottawa Int'l and we have posted it on our ftp site to assist clients looking for the missing data.  This information is in the files Ottawa 2012 and 2013.  Please note that this information is raw data, and is subject to corrections at a later date.

To access, link to:
Username: ontarioclimate
Password: 4climateData (case sensitive)

I hope the information provided will be helpful.  Do not hesitate to contact us if you have additional questions or comments.


I think I will provide further comment because there is several issues with the response:
- the human observers obviously need training to distinguish between snow showers and heavy snow.
- wet snow doesn't blow around.  Once it hits ground it sticks.
- the location dependency, while true in a general sense doesn't hold water in this case. I live just a few kms as the crow flies from the a/p and there was definitely close to 30cm of snow.  I shovelled it.

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