Aha!

Don't you just love that word? It has so much emotion behind it. I live for that feeling, that "AHA!" moment when something clicks, you thoroughly "get it". That's why I'm back in school. I like the clicking, the "getting it". Yesterday it was about an air parcel rising and falling, condensing and making a cloud....and then binary coding for computers (ever wonder what 100101010010001011101010 means?). It's like those connecting maps you make of where an airline flies. Some connect from major hubs, some connect from outlying airports...but pathways get put in. Turns out that's also how our neural network looks. Read a book about that last summer. Anyway, that's how I feel tying in information from math and GIS into computers and math into Meteorology and physics and chemistry, and so on.

Today, sitting at my desk and staring at my weather monitor again (see the long post from yesterday), it didn't make any sense to me that my weather station was right on with all the data of the more expensive weather station, with the exception of atmospheric pressure. I'm not close enough to a window to just sit and stare out of that, so I stare at my weather monitor. My atmospheric pressure has been consistently showing somewhere between 5-6 hPa off from what our weather observatory is posting on SJSU's Meteorology Website. When I looked closely at the website, the website reports it in "Sea Level Pressure". But the observatory is not at sea level, it's at 227 ft above sea level. How were they getting sea level data from a rooftop observatory? And if it was 1009 hPa at sea level, would it then make sense that mine, not accounting for a change in elevation, would read pressure at that point to be 1004 hPa?

Hmmm. I looked around the grad room. Everyone was wearing headphones. They looked busy, doing crazy calculations and trying to figure out why they can't get the Air Pollution section right from Atmospheric Dynamics class. Maybe I can go find a professor. No, don't go bugging the professors. They'll wonder why you didn't ask a room of grad students. It was about time for me to go to class so I packed up my stuff and slowly wandered out of the room.

On my way out, I said hi to one of the guys sitting at his desk. He looked up and we exchanged pleasantries. This opened it up for discussion. I brought up the question of our department posting pressure as "Sea Level Pressure" and he confirmed that there were codes in order to make a distinction between the actual pressure at your instrument and what that same air parcel (or column of air parcels rather) would weigh if your instrument was at zero feet. This is important for a few reasons, but none of you probably want to know why, so I'll move on.

How much difference then should I expect (under the same exact atmospheric conditions) there to be between the pressure at zero feet and the pressure at 227 ft? And no, it's not linear.(But did you know that dry air weighs more than wet/saturated air? Chew on that.)

At that time a professor walked in and the other grad student dragged him into the discussion. After a lengthy exchange which I mostly did not understand, it came out to a few key points. Number one, the coding involved in getting a computer to make the adjustments for sea level pressure is incredibly lengthy (not just something you do on your calculator with a formula). Number two, different areas (Denver as opposed to San Jose) use different calculations, but they cannot change those calculations because they would totally invalidate any existing weather data or there would have to be weird public documents annexed somewhere to make sure the entire world knew the exact date and time that Denver decided to change their calculations (which really makes me wonder how accurate any of this is if no one is using the same calculations).

And most importantly, number 3. So the difference in data collected between two points at about 227 ft apart (in elevation) should be around 4 or 5 hPa. No shit! So my little weather station is totally accurate! Sweet!

Then I went off into my GIS (Geographical Information Systems) class where we're learning to do crazy data things with maps and geographical information and my brain went...Whhaaa???