The Regional UHI

Its fun to share new results and updates on progress. Today is one of those days. I have been busy putting together the first UHI chapter of my dissertation and getting it ready for publication. This is a sneak peak.

The figure above shows the distribution of the urban and rural land cover classes in Orange, Durham and Wake Counties of North Carolina. These distributions were found by aggregating 20 land cover types from the NLCD 2011 data product into two groups: urban (white) and rural (dark gray). Open water appears black. Using GIS software and a thermal image of the study area taken from the Landsat-8 satellite, I calculated the average temperature of the two different land classes for a hot summer afternoon earlier this year (June 21, 2015, 3:52pm). The temperature of the rural land cover in this image is 2.1 degrees Celsius cooler than the urban areas. Additional results and a detailed analysis will appear in the chapter and publication.

I also posted this image to the maps section of my website. Check it out!

Transecting

Looking for something fun to do on a Friday night? Maybe a beer with friends after work, grab a bite to eat, catch a show or a late night hang at the bar… movie night with the kiddos…¬†how about driving back and forth across Durham County collecting temperature data?! It’s all for the fun of science.

But I digress… Thursday night was build-out. The idea is to get an external temperature and relative humidity sensor attached to the car at approximately 2 m (6 ft) height and out of the slip-stream of the car so I can drive the sensor around measuring the ambient environment. The data will be correlated to GPS data collected at the same time so I can start to unravel the correlation of temperature with urban form.

The design required an old 2-by-4, in this case harvested from an old renovation project around the house, and a two foot section of 4″ PVC pipe, also left over from a house project. Using a circular saw and drill, a seat for the external HOBO sensor and a notch for the chord were created in the end of the 2-by-4. The sensor was installed in its home and the chord stapled down to the beam using chord staples. Of course we have a chord stapler. Who doesn’t?

image

The PVC pipe was installed over the sensor after a bit of electrical tape was wrapped around the sensor for good measure to make sure it didn’t move in the wind. Then I drilled out two sets of 4 holes in line with the location of the roof rack bars so zip ties could be used to attach the rig. In addition to the zip ties, I ended up using a ratchet strap to keep the whole thing in place, again, just for good measure. Once installed on the car, the sensor body drops through the sun roof so I can launch and download data inside the car.

The set up looks a little home-made, and it is. I was thinking I needed to create a hashtag: #NotAGoogleCar… but it’s probably pretty obvious.

image

With the mount ready, and the weather window open, it was time to get transecting! (Yes, I made a verb out of transect.) Starting at 6 am on Friday morning, I drove the predefined route every 4 hours (6 am, 10 am, 2 pm, 6 pm, 10 pm, 2 am). Each run to Durham and back took an average of 1:45, and was 46 miles. That totals up to some 280 miles and about 10 hours of driving. On each run, I collected temperature, relative humidity and GPS data every second. That’s a lot of data! That’s a lot of NPR.

image

With raw data in hand, its time to get processing, but first I have to rest up for the next round of transecting… possibly as soon as Monday. Because the fun doesn’t stop when science walks in…!

Weather Watch

Now that the sensors are out in the field happily logging away, it’s time to watch the weather so the next phase of the 2015 Summer Field Campaign can kick into gear.

I’m looking for ideal UHI conditions: calm winds, clear skies, no precipitation… for several days in a row. This weather pattern allows the thermodynamic processes that create the heat island to take shape without being obscured by additional, hard to model factors in the atmosphere. It’s the ideal time to take measurements, and I’m looking for a 48+ hour period of good weather to complete the transect phase of the campaign which will require driving the transect (see Maps Page) every 4 hours for 24 hours.

A window may be emerging…

2015_06_10_DurhamWeatherForecast

But it also maybe not… the forecast not only keeps changing, the wind profile is a bit high, and the threat of rain could put the whole thing off.

So for now, I wait, and watch the weather.

…Oh! And build a sensor mount for the car so I’m ready when the weather is!

Stay tuned.