the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Improving the Estimate of Higher Order Moments from Lidar Observations Near the Top of the Convective Boundary Layer
Abstract. Ground-based lidar data have proven extremely useful for profiling the convective boundary layer (CBL). Many groups have derived higher order moments (e.g., variance, skewness, fluxes) from high temporal resolution lidar data using an autocovariance approach. However, these analyses are highly uncertain near the CBL top when the depth of the CBL (zi) is changing during the analysis period. This is because the autocovariance approach is usually applied to constant height levels and the character of the eddies are changing on either side of the changing CBL top. Here, a new approach is presented wherein the autocovariance analysis is performed on a normalized height grid, with a temporally smoothed zi. Output from a large eddy simulation model demonstrates that deriving higher order moments from time series on a normalized height grid has better agreement with the slab averaged quantities than the moments derived from the original height grid.
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CC1: 'Comment on egusphere-2024-868', Fleur Couvreux, 22 May 2024
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This manuscript proposes a methodology to improve the derivation of boundary-layer statistics from lidar observations. To do so, they propose to use the information derived from the observations but normalized by the boundary layer height before time-averaging. Although the subject is interesting, some modifications are needed before the manuscript is in the form for the definitive publication.
Introduction:
The introduction is well written, however a statement of the main objectives of the paper and the introduction of the outline are lacking.
Approach:
I suggest to repeat the same analysis, as shown in the paper, but for a certain amount of different locations sampled in the LES (instead of relying on outputs at only one given location) and then compute statistically the mean rmse of the difference between the computation over the regular grid and the one over the normalized grid to statistically demonstrate the improvement. The fact that the results rely on only one high-frequency time-serie is not completely convincing.
Results:
I propose to reduce slightly the number of figures. This can easily be done by combining Figures 2 and 3: you could just show the time-height variance for the slab and then only show the difference between the regular and slab and between the normalized and slab. Similarly for figures 4 and 5 and Figures 6 and 7.
Minor comments:
l 69: please change ‘derived three different ways’ to ‘derived through three different ways’
l 92: ‘Results’ should be a section and not a subsection
Citation: https://doi.org/10.5194/egusphere-2024-868-CC1 -
RC1: 'Comment on egusphere-2024-868', Anonymous Referee #1, 06 Jun 2024
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see attached PDF file
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