If you’re like me, there has been more than one occasion where you returned to your office from doing some field work and wished you had taken the time to document the outdoor air conditions better than you had. Maybe you thought the data was being captured by the facilities control system or data logger, only to discover that the data was bad or missing. Or, maybe you were trying to recall if it was sunny or cloudy or when it rained or exactly when the marine layer moved out one day and at best, you can only infer those events from the temperature and humidity data logged by the system. What ever the specifics, with out the data, while it may not be the end of the world, your analysis suffers because you have to make more assumptions than would be necessary if you had the data.
The good news is that the National Weather Service collects hourly data from countless sites across the country and makes this information available on line. Here is a screen shot of the current data for a little spot on the Oregon Coast, where I am writing this from.
Notice the 3 Day History link highlighted in red toward the middle bottom of the screen. If you click on this link, it will open a page that has three days worth of hourly data for the site. Most of the sites I have visited have a link on the 3 day history page that provides the past 7 days of hourly data, which is what I have illustrated below.
How much information is available is a function of the location of the site. For instance, the site above is pulling its data from instruments deployed at a location along the Oregon Coast, which is somewhat rural and less populated than one of the sites in Portland. So, it has basic data, but not as much data as might be available at a site near a population center or an airport. Still, there is information like dew point, wind speed and direction, barometric pressure. 24 hour precipitation summaries, etc. all of which provide more clues about what was going on than the typical temperature and relative humidity data logged by most control systems.
The screen shot below is from the site at Portland International Airport. As you can see, not only does it have the basics it also includes things like cloud cover, visibility, and when and how much precipitation occurred.
To top it all off, you can very easily extract this information from the website to you hard drive. You will notice in both of the screen shots shown above, there is a little green pop-up menu. The menu is accessed by moving your mouse over the data table and right-clicking. When you do that, the menu will open and you will notice that there is an “Export to Excel” option.
If you select that option, Excel will launch and in very short order, you will have a spreadsheet that is loaded with the website data for you to analyze and graph to your heart’s content. Here is what I captured from the Portland Airport web site using this technique.
Note that what I am describing above is how it works with Internet Explorer. You can do the same thing in Firefox by clicking into the table, right clicking, picking “Select All” and then right clicking again and picking “Copy”. Next, open a spread sheet, click into a cell, pick “Paste Special” and then “As HTML”.
Bottom line, when I’m out in the field working on a building, I’ve found it to be helpful to make it a habit of going to the closest NOAA website and downloading the data for the past week, just to have it for reference. It only takes a few minutes and if you discover you need it, after the fact, the information will be priceless, even though you obtained it for free.
Senior Engineer – Facility Dynamics Engineering