Revealing the Evolution and Small-Scale Variability of the Morning
Transition Phase in the atmospheric boundary layer using Distributed
Temperature Sensing
Abstract
During the morning transition, the nocturnal stable boundary layer, SBL,
turns into the daytime convective boundary layer, making it an important
phase for modelling and predicting temperature or pollutant
distributions. By applying distributed temperature sensing suspended
from a tethered balloon (0-200m height) and along a measurement tower
(0-11m), for the first time we observed the detailed evolution of three
complete morning transition phases with a high temporal (<10s)
and spatial (<0.25m) resolution. Using distributed
observations, the transition can be derived solely from a change in
spatially continuous observations of static stability. It was validated
that the transition occurs at the top and the bottom of the SBL
simultaneously and advection of heat was identified as a main driver in
addition to local surface warming. The transition is characterized by
complex structures and small-scale variability, highlighting how
distributed temperature sensing is a crucial tool for future research.