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Brockville – Scuba Diving Caribbean of the North December 20, 2008

Posted by Chris Sullivan in Miscellany.
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It’s amazing the amount of information that’s out there on the web that useful to divers. Two of the most important things to know when diving are the temperature of the water and the exposure protection that’s best for that temperature. For my first experience in Brockville I took my dry-suit just in case but ended up using a full length 3mm Henderson HyperStretch Wet Suit with my warm water fins – basically the same get-up as I use in the Caribbean. After my first dive I found it to be a little chilling afterwards, so I added my dry suit hood, which helped keep my core temperature in the right vicinity.

More recently, I’ve purchased a 6.5mm Scubapro wet suit which is better for the longer dives. This turns out to be perfect for those dives, so now my 3mm is reserved for the pool and tropical waters.

I’ve now found out that the water temperature question is easily answered for the St. Lawrence River diving around Brockville. NOAA has a National Data Buoy Center site at Alexandria Bay, where current (to the last half hour) and historical weather information and water temperatures can be found. Being a sucker for this stuff, I dumped all the 2007 data and plotted the water temperature in Excel. The months shown are numeric (1-12) but this gives you a good idea of what’s happening in the river. At this point in the river the water temperature is uniform from top to bottom (which is why us deep divers like it) so it’s likely that wherever you dive in the region is going to be pretty close to what’s reported. Temperatures are in Celsius.

2007 daily water temperatures at Alexandria Bay, NY.

2007 daily water temperatures at Alexandria Bay, NY.

If you want to plot this yourself in Excel, you’ll find a link to the historical and climatic summaries near the bottom of the page, and select the year you want, from 1993 to 2007. I expect that 2008 data will be available sometime after the end of the year. I noticed that a couple of observations were missing, with the temperature reported at 999C. These need to be eliminated to make the graph work. I used the autofilter feature of Excel for that.

The yearly information is presented as a text file. I used ctrl-A to select the entire text, ctrl-c to copy it to the clipboard, and ctrl-V to paste it into an Excel worksheet. The next trick is to use the text-to-columns feature (under the Data Menu) of Excel to separate the space-delimited data into seperate columns. That worked perfectly. Then use a custom autofilter to select observations where the water temperature is less than say 30, and you have a graphable data set.

To graph it, I selected the month and water temperature columns and clicked on the graph button. The default graph, whether you use a bar chart or a line chart like I did, assumes you are charting both the month and temperature on the Y axis. You need to go into the Series tab, then copy the values specification from the Y-axis onto the label specification for the X-axis, then delete the first data series. Presto, you have a fine graph of yearly water temperature. I’m sure it can be refined further to get the months from numeric into text and so forth.

It’s interesting to see that the water temperature at the beginning of 2007 was higher than it was at the end. It shows that there are variations from year-to-year in the temperature of the river. I’d like to compare the information from year-to-year so  I know on any given date what the average temperature has been and the range of temperatures (or even standard deviation from the mean) that occurs. It would also be interesting to see if one could improve the prediction from observations in the previous week, and to compare the recorded temperatures from the buoy with the temperatures recorded in my log book.



1. Chris Sullivan - August 9, 2010

Unfortunately the station has been decommissioned due to lack of funding.Blue foot diving posts a temp from time to time but that’s it. At the time of writing the last temperature was more than a month ago.


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