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2013,

Description

In daily data set files, following level 2 products are included: 1) mixing layer height from vertical wind (zmlaw) based on std threshold (0.4 m/s), 2) mixing layer height uncertainties based on +/- 25 % std threshold (i.e. 0.5 and 0.3 m/s respectively), and 3) flag for mixing layer height retrieval status. Mixing layer height (zmlaw) from vertical wind speeds found in HD(CP)2 data base. Retrieval is based on standard deviation of vertical wind (w_sdev) and threshold w_sdev_ts. Also provided is uncertainty as lower and upper bound when increasing / decreasing threshold by 25% (zmlaw_uncty). Vertical wind is only available if backscattering targets like aerosol particles and cloud droplets are present with sufficient quantity. Therefore, vertical range of accurate Doppler velocity observations are limited to sensitivity of sensor.

Limitations: Measurements only available if backscattering targets like aerosol particles and cloud droplets are present with sufficient quantity. Therefore, vertical range of accurate Doppler velocity observations are limited to sensitivity of sensor. When clouds were present, zmlaw was forced to just below cloud if std values were higher than threshold throughout the height between ground and cloud base. In clear sky cases, when all std values were higher than threshold, last height with finite std was set as zmlaw.
Provenance: Data of JOYCE, processed by IMGK, University of Cologne
Comments: Status of retrieval is documented in variable zmlaw_flag: If there is no w_sdev data or all w_sdev values are below w_sdev_ts no zmlaw is returned (zmlaw_flag=0 or 1, respectively). If there is a region directly above the ground with w_sdev >= w_sdev_ts and at least one point with w_sdev < w_sdev_ts the height of this point is returned (zmlaw_flag=2). In clear sky cases, when all w_sdev values are higher than threshold, last height with finite w_sdev was set to zmlaw (zmlaw_flag=3). When clouds were present, zmlaw is forced to just below cloud if std values were higher than threshold throughout the height between ground and cloud base (zmlaw_flag=4). For details of retrieval see Schween et al. 2014, doi:10.5194/amtd-7-4275-2014.

• Source: Doppler lidar (no 17), HALO Photonics
• Descriptive Instrument location: The Doppler lidar is installed at the JOYCE; on the roof of the Institute for Climate and Energy Research, Research Center Juelich.

• PID: de.koeln.rrzk/amd.de.sups/joy.dlidST00.l2.zmlaw
• Project: HD(CP)2
• Level: 2
• Updated version: 00
• File format: NETCDF3_CLASSIC
• Convention: CF-1.6 where applicable
• Average File Size Uncompressed: 1 Mb
• File name: sups_joy_dlidST00_l2_zmlaw_v[VV]_[YYYYMMDDhhmmss].nc
• Start: 2013-01-01
• End: 2013-12-31

Name	Dimension	CF standard_name	long_name	Unit
beta	time, height	volume_attenuated_backwards_scattering_function_in_air	mean of backscatter coefficient	m-1 sr-1
beta_cloud_ts			threshold for cloudbase from beta_mean	m-1 sr-1
w	time, height	upward_air_velocity	mean of w	m s-1
w_sdev	time, height		standard deviation of w	m s-1
w_sdev_ts			threshold for standard deviation of vertical wind speed to determine zmlaw	m s-1
w_skew	time, height		skewness of w	1
zmlaw	time,	atmosphere_boundary_layer_thickness	mixing layer height from vertical wind	m
zmlaw_flag	time,		status of zmlaw retrieval	missing
zmlaw_uncty	time, bounds			m
zsl		altitude	altitude above mean sea level	m

Research Center Juelich, Institute for Energy and Climate research (IEK-8)

Ulrich Loehnert (loehnert@meteo.uni-koeln.de)

J. H. Schween, A. Hirsikko, U. Loehnert, and S. Crewell,Mixing layer height retrieval with ceilometer and Doppler lidar: from case studies to long-term assessment

For non-commercial use only. This data is subject to the HD(CP)2/SAMD data policy to be found at https://doi.org/10.25592/uhhfdm.9823  and in the HD(CP)2/SAMD Observation Data Product Standard https://doi.org/10.5281/zenodo.1741363 .