the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Atmospheric boundary layer structure over the Arctic Ocean during MOSAiC
Shijie Peng
Qinghua Yang
Matthew D. Shupe
Xingya Xi
Bo Han
Dake Chen
Abstract. The important roles of the atmospheric boundary layer (ABL) over the Arctic Ocean in the Arctic climate system have been recognized, but the atmospheric boundary layer height (ABLH), as a fundamental variable to characterize the vertical structure of ABL, has rarely been investigated. Analyzing a year-round radiosonde dataset during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC), we suggest the optimal critical value of 0.15 of bulk Richardson number to derive ABLH. Based on this algorithm, the hourly ABLH values are derived to analyze the characteristics and variability of ABLH over the Arctic Ocean. The results reveal that the annual cycle is clearly characterized by a distinct peak in May and an abrupt decrease in the following July and August, with a second minimum in December and January. The annual ABLH variation is primarily controlled by the evolution of ABL thermal structure. The temperature inversions in the winter and summer are intensified by seasonal radiative cooling and surface melting, respectively, leading to the low ABLH. The near-surface conditions can also play a significant role in ABLH variation, with turbulent parameters (e.g., friction velocity and turbulent dissipation rate) well correlated with the ABL development. In addition, the MOSAiC ABLH is more suppressed than the ABLH during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment in the summer, which indicates that there is large variability in the Arctic ABL structure during summer melting season.
Shijie Peng et al.
Status: open (until 19 Apr 2023)
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RC1: 'Comment on egusphere-2023-347', Anonymous Referee #1, 26 Mar 2023
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Review for Atmospheric boundary layer structure over the Arctic Ocean during MOSAiC
Summary: In this study, the authors performed analyses on data collected during the MOSAiC campaign, focusing on the atmospheric boundary layer height (ABLH). The authors first identified the ABLH manually and then calibrated the critical bulk Richardson number in the bulk Richardson number method for computing ABLH based on the manually labeled ABLH. The relations between ABLH and surface variables were examined, and two cases were examined in detail to investigate the controlling factors of the ABLH variations during the campaign. My overall impression of the paper is that the motivation was justified, the methodology was sound, and the results made sense. I have a few comments on the bulk Richardson number method and also the language needs to be improved (beyond what I pointed out in my comments bleow).
Major comments:
1, the bulk Richardson number method for computing the ABLH.
1.1 Some studies also considered a friction velocity in the definition of bulk Richardson number (see e.g., Zhang et al. 2020). It might be worth discussing this.
1.2 it is not clear whether Eq. 2 is exactly the formula used in the VAP. If so, please state it.
1.3 the authors mentioned that their results are different from Jozef et al. (2022). It would help the readers understand this by discussing a bit more of how exactly the formulations differ. Which formula did Jozef et al use?
2, an automated algorithm
By looking at Figure 3, why not use an automated algorithm that is based on the bulk Richardson number method for SBL and the Heffter algorithm for CBL?
3, line 318:
If the manually labeled ABLH didn’t include any data in transit, why did the authors think that the calibrated bulk Richardson number method using the manually labeled ABLH could be used to compute ABLH during transit?
Minor comments:
1, line 32: “has” should be “have”, and add “the” before “rapid changing”
2, line 37: “and the essential place for…” can be removed.
3, line 52: add “the” before “Atmospheric boundary layer height”, “referred to…” should be removed.
4, line 56: replace “literature” with “studies”
5, line 60: replace “surface mixed layer” with “surface layer”. Surface mixed layer is odd.
6, line 107: remove “special”
7, line 108: remove “fundamental”
8, line 211: I wouldn’t call this “multiple methods”. Maybe change it to “multiple profiles”.
9, line 161/182/221/260: I would not call this “subjective ABLHs”. Maybe “manually-labeled ABLHs”.
10, line 223: replace “applied” with “available”
11, line 257: add “a” before “better performance”.
12, line 302: “the smallest” should be “the best”. R is not the smallest clearly.
13, line 324-327: these sentences need to be re-worded.
14, line 382: I would probably not call this “where the annual cycle began”. Please reword.
15, line 392: how do you know a priori that it is the surface conditions that influence the ABLH, not the other way around? Please re-word.
16, line 397: I would not say this. The friction velocity and dissipation are affected by both shear and buoyancy.
17, line 408: turbulence intensity is different from turbulence kinetic energy. Do you mean turbulence intensity or turbulence kinetic energy?
18, line 412: replace “accorded” with “proposed”
19, line 427: add “the” before “highest”
20, line 468: I wonder what features on the figure led the authors to conclude “the cloud-mixed layer aloft does not interact with the near-surface environment”. The relative humidity is closer to saturation than figure 9 where the authors concluded “the near-saturated relative humidity indicates that the cloud-mixed layer couples with the surface-mixed layer, which facilitates the ABL development”. This needs to be clarified.
21, line 556-558: it’s unclear to me what the authors mean by “Coupling between the cloud mixed layer and surface mixed layer could also be recognized by the Rib algorithm”. Does the Rib method can really distinguish this?
References:
Zhang, Y. J., K. Sun, Z. Q. Gao, Z. T. Pan, M. A. Shook, and D. Li, 2020: Diurnal Climatology of Planetary Boundary Layer Height Over the Contiguous United States Derived From AMDAR and Reanalysis Data. J Geophys Res Atmos, 125.
Citation: https://doi.org/10.5194/egusphere-2023-347-RC1
Shijie Peng et al.
Shijie Peng et al.
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