Notes From the Picarro Roof: Intern Jeff's Perspective

日期: October 14, 2011

Greetings, Picarro Community!   My name is Jeff Forgeron, and I am a meteorology major at San Jose State University. I am currently interning for Picarro, and was recently asked to design and implement a weather station on the rooftop using an All-In-One Climatronics instrument. We have been using both the Picarro methane, acetylene analyzer and the CO, CO2, H20 analyzer to continuously measure green house gases (G.H.G.) for several weeks.

The reason behind this is to  better understand the local urban emissions. Adding a localized weather station allows us to accumulate wind data (speed and direction as well as temperature and relative humidity) to be paired up with the G.H.G. data. By doing so, it will inform us of where these G.H.G.’s may be coming from(i.e. active landfills such as Superior Disposal and Hauling in Sunnyvale,CA or inactive landfills near Great America Amusement Park). This is much better than relying on other weather stations around the south bay to supply our wind data because the location of Picarro has slightly different wind speeds and directions compared to other regions. The difference is due to local topography, as well as surface roughness(i.e. trees).

Setting up this station was a perfect task for me because it allowed me to apply the skill-set I learned in my meteorological instrumentation's course (last semester). Before setting up the instrument, there were a few steps I had to take to prepare for the installation. Placement of the instrument is very important. Obstructions such as buildings, trees, or even something as simple as an A.C. unit can have negative effects on wind data. A building across the street may stir or deflect wind, creating a localized turbulent pattern. In order to avoid the influences of obstructions, it is vital to place an instrument a certain distance away from the obstruction (specifically, 20x the height of the obstruction).  Instruments that measure wind vectors must also be raised a minimum of 10 meters off of the ground (~33 feet). This allows the instrument to record free flowing winds that are not affected by objects at ground level.

Although these rules are very important, I was challenged to come up with the best set-up that could be implemented within a week’s time.  We were in a time crunch, and needed enough wind data to present at an upcoming meeting.  Instead of installing a 33 foot tower, I compromised and used a 5 foot tall tripod on the edge of the roof. There are still a few A.C. units near the instrument, which may have a small affect on the data, but they are not in the path of the prevailing wind. Wind speeds should stay pretty accurate, but wind directions may read several degrees off of the actual values. If wind is advected from the south-east (which doesn’t happen too often considering the consistent northerly bay breeze), this wind will have to travel across the entire roof before it reaches the All-In-One. Due to this, A.C. units and other obstructions may deflect the wind before it is read into the system. Here is a link to the S.J.S.U. Meteorology website, which allows you to observe animations of the current wind patterns in the San Francisco Bay.

The instrument is located on the North-West corner of the roof, which should allow us to capture majority of  the wind data before they travel across the roof. The weather station is connected to a laptop and measurements are recorded every 3 seconds. The instrument has been recording data since Tuesday, October 4th.  I extract the data via USB and we analyze the data every 2-3 days.

In the future, we'd like to have a 33 foot tower on the roof, along with the All-In-One attached to the top. We also hope to purchase or make our own data logging system. This will allow us to store mass amounts of data at a time, while having the capability of extracting the data in a wireless fashion.  

I look forward to seeing what the data tells us and on keeping everyone updated.