Power-over-tether aircraft is an effective tool for persistent spatiotemporal monitoring of environmental phenomena. This paper presents the design and evaluation of flight trajectories for the tethered aircraft unmanned system (TAUS) sensing a dynamic temperature field. TAUS is a novel power-over-tether-based unmanned aerial system (UAS) configured for long-term, high throughput atmospheric monitoring. It is unique in that it provides position control while measuring atmospheric properties on-board the aircraft and with sensors along the tether. We validated the robotic system by conducting outdoor experiments to characterize the sensor performance against a meteorological tower. We found minimal sensing error at the corresponding altitude relative to the ground truth installation. We then used the experimental data to simulate four trajectories (Lawn-mower, Spiral, Star, and Flower) on power-tethered and untethered system models to evaluate performance factors related to trajectory selection. The analysis of the simulated data indicated that the power-tethered Star trajectory performed well concerning key performance factors when measuring changing atmospheric fields.