In search of the perfect tower

Instrument towers are not only the most visible part of eddy covariance flux sites, but are also the places where our experiences working as flux scientists are shaped and our memories are formed. The physical challenge of ascending to the top on an upright ladder versus a staired tower, the accessibility of instruments for maintenance, the frustration of dropping a tool or a nut, the difficulties of communication with ground support on a windy day, and yes, also the fear of heights – they all make up the fabric of our memories, and may decide whether we dread or look forward to the upcoming field day.

For nearly two decades, the NC Core Flux Sites (US-NC1 to US-NC4) relied on traditional construction scaffolds for flux measurements. Some, who had known different, were grateful for the horizontal catwalks where to rest the toolbag and perform a maintenance task. Others dreamt of a staired tower where the ascent would not be as breathtaking and the instrument mounting options not as challenging. Big and sincere was the joy when in 2012 we were able to upgrade the US-NC4 tower to just such a wonderful walkup tower. With the decommission of the Duke FACE site a few years prior, and the generosity of the Duke Forest site managers, we were given a chance to replace the scaffolding that in a salty seaside air had corroded faster than any of us expected with a nifty aluminum walk-up tower. Life became fun and easy, the horsefly bites were less painful, and the half-mile walk through the swamp to the tower could have been passed skipping and singing, if not for the deep cycle batteries on our back. Still, we took much delight and pride in the new (used) luxurious tower.

Until January 21^st, 2022. With strong winds and 0.25-0.5” ice accumulation documented in the area, one of the legs of our beloved tower buckled under the weight. We discovered it weeks later, resting on top of the trees.  Devastated though we were, quietly we thanked our stars that none of us had been on the tower or anywhere close to it when the disaster struck. Figuring out the way and obtaining necessary permits for removing the tower took nearly a year, and the request to rebuild at the same location was not approved. The land owners US Fish and Wildlife Service (USFWS) were as shaken by the experience as were we.

Nevertheless, ending the work at this site was never an option. With unwavering support from all involved (Ameriflux Management Project, USFWS, Duke Forest), the measurements were restored within a mile of the original tower location and with a partial footprint overlap. But this time, we decided to eliminate nearly every possible height-related risk and inconvenience. We opted for a folding telescoping tower (LINK). No more climbing or fear of heights, no more dropping tools and no more of wind carrying our voice away before it reaches the helper on the ground. Even with a lot more horseflies, instrument cleanup and maintenance goes a lot faster now. And it can done by a single person. In all, we liked the upside of the change so much that we also replaced our still functional 20-yr old scaffolding tower at US-NC2 with a folding and telescoping one. Although not flawless, we are glad to have transitioned both sites to this design, and recommend that other sites in need of a new tower consider this option, as the logistics have been greatly simplified, and the safety risks have been largely eliminated. (No, we are not getting a commission on the sale of these towers. We just want to share our joy.)

View our short demo video HERE.