Planetary Boundary Layer Heights from Cruises in Spring to Autumn Chukchi-Beaufort Sea Compared with ERA5

Abstract

The planetary boundary layer height (PBLH) is a diagnostic field related to the effective heat capacity of the lower atmosphere, both stable and convective, and it constrains motion in this layer as well as impacts surface warming. Here, we used radiosonde data from five icebreaker cruises to the Chukchi and Beaufort Seas during both spring and fall to derive PBLH using the bulk Ri method, which were then compared with results from ERA5 reanalysis. The ERA5 PBLH was similar to but slightly lower than the ship observations. Clear and consistent seasonal changes were found in both the observations and the reanalysis: PBLH decreased from mid-May to mid-June and subsequently increased after August. The comparison with ERA5 shows that, besides surface temperature, biases in PBLH are also a function of wind direction, suggesting that the availability of upwind observations is also important in representing processes active in the boundary layer over the Arctic Ocean.