scholarly journals Evaluation of convective boundary layer height estimates using radars operating at different frequency bands

2021 ◽  
Vol 14 (11) ◽  
pp. 7341-7353
Author(s):  
Anna Franck ◽  
Dmitri Moisseev ◽  
Ville Vakkari ◽  
Matti Leskinen ◽  
Janne Lampilahti ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Potential Temperature ◽  
Convective Boundary ◽  
Data Set ◽  
Layer Height ◽  
Frequency Bands ◽  
Boundary Layer Height ◽  
W Band ◽  
Water Vapour Concentration ◽  
5 Ghz

Abstract. Knowledge of the atmospheric boundary layer state and evolution is important for understanding air pollution and low-level cloud development, among other things. There are a number of instruments and methods that are currently used to estimate boundary layer height (BLH). However, no single instrument is capable of providing BLH measurements in all weather conditions. We proposed a method to derive a daytime convective BLH using clear air echoes in radar observations and investigated the consistency of these retrievals between different radar frequencies. We utilized data from three vertically pointing radars that are available at the SMEAR II station in Finland, i.e. the C band (5 GHz), Ka band (35 GHz) and W band (94 GHz). The Ka- or W-band cloud radars are an integral part of cloud profiling stations of pan-European Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS). Our method will be utilized at ACTRIS stations to serve as an additional estimate of the BLH during summer months. During this period, insects and Bragg scatter are often responsible for clear air echoes recorded by weather and cloud radars. To retrieve a BLH, we suggested a mechanism to separate passive and independently flying insects that works for all analysed frequency bands. At the lower frequency (the C band) insect scattering has been separated from Bragg scattering using a combination of the radar reflectivity factor and linear depolarization ratio. Retrieved values of the BLH from all radars are in a good agreement when compared to the BLH obtained with the co-located HALO Doppler lidar and ERA5 reanalysis data set. Our method showed some underestimation of the BLH after nighttime heavy precipitation yet demonstrated a potential to serve as a reliable method to obtain a BLH during clear-sky days. Additionally, the entrainment zone was observed by the C-band radar above the CBL in the form of a Bragg scatter layer. Aircraft observations of vertical profiles of potential temperature and water vapour concentration, collected in the vicinity of the radar, demonstrated some agreement with the Bragg scatter layer.

scholarly journals Evaluation of convective boundary layer height estimates using radars operating at different frequency bands

2021 ◽  
Author(s):  
Anna Franck ◽  
Dmitri Moisseev ◽  
Ville Vakkari ◽  
Matti Leskinen ◽  
Janne Lampilahti ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Potential Temperature ◽  
Night Time ◽  
Convective Boundary ◽  
Reanalysis Dataset ◽  
Layer Height ◽  
Frequency Bands ◽  
Boundary Layer Height ◽  
W Band ◽  
5 Ghz

Abstract. Knowledge of atmospheric boundary layer state and evolution is important for understanding air pollution and low level cloud development, among other things. There are a number of instruments and methods that are currently used to estimate boundary layer height (BLH). However, no single instrument is capable of providing BLH measurements in all weather conditions. We proposed a method to derive a daytime convective BLH using radar observations and investigated the consistency of these retrievals between different radars. We utilized data from three vertically-pointing radars that are available at the measurement station in Southern Finland: the C-band (5 GHz), Ka-band (35 GHz) and W-band (94 GHz). The Ka- or W- band cloud radars are an integral part of cloud profiling stations of pan-European Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS). Our method will be utilized at ACTRIS stations to serve as an additional estimate of the BLH during summer months. During this period, echoes from insects and Bragg scatter are often recorded by radars. To retrieve a BLH, we suggested a mechanism to separate small insects that follow air motion and independently flying insects that works for all analyzed frequency bands. At the lower frequency (the C-band) insect scattering was separated from Bragg scattering using a combination of radar reflectivity factor and linear depolarization ratio. Retrieved values of the BLH from all radars are in a good agreement when compared to the BLH obtained with the co-located lidar and reanalysis dataset. Our method showed some underestimation of the BLH after night-time heavy precipitation yet demonstrated a potential to serve as a reliable method to obtain a BLH during clear-sky days. Additionally, the entrainment zone was observed by the C-band radar above the CBL in a form of a Bragg scatter layer. Aircraft observations of vertical profiles of potential temperature and water vapor mixing ratio, collected in the vicinity of the radar, demonstrated some agreement with the Bragg scatter layer.

scholarly journals Relationship analysis of PM<sub>2.5</sub> and boundary layer height using an aerosol and turbulence detection lidar

2019 ◽  
Vol 12 (6) ◽  
pp. 3303-3315 ◽  
Author(s):  
Chong Wang ◽  
Mingjiao Jia ◽  
Haiyun Xia ◽  
Yunbin Wu ◽  
Tianwen Wei ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Weather Forecasting ◽  
Direct Detection ◽  
Vertical Wind ◽  
Precipitation Event ◽  
Cloud Base ◽  
Convective Boundary ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Relationship Analysis

Abstract. The atmospheric boundary layer height (BLH) is a key parameter in weather forecasting and air quality prediction. To investigate the relationship between BLH and air pollution under different conditions, a compact micro-pulse lidar integrating both direct-detection lidar (DDL) and coherent Doppler wind lidar (CDWL) has been built. This hybrid lidar is operated at 1.5 µm, which is eye-safe and made of all-fibre components. The BLH can be determined from aerosol density and vertical wind independently. During a 45 h continuous observation in June 2018, the stable boundary layer, residual layer and convective boundary layer are identified. The fine structure of the aerosol layers, drizzles and vertical wind near the cloud base are also detected. In comparison, the standard deviation between BLH values derived from DDL and CDWL is 0.06 km, indicating the accuracy of this work. The retrieved convective BLH is a little higher than that from ERA5 reanalysis due to different retrieval methods. Correlation between different BLH and PM2.5 is strongly negative before a precipitation event and becomes much weaker after the precipitation. Different relationships between PM2.5 and BLH may result from different BLH retrieval methods, pollutant sources and meteorological conditions.

Homogenized Variability of Radiosonde-Derived Atmospheric Boundary Layer Height over the Global Land Surface from 1973 to 2014

2016 ◽  
Vol 29 (19) ◽  
pp. 6893-6908 ◽  
Author(s):  
Xiaoyan Wang ◽  
Kaicun Wang
Keyword(s):  
United States ◽  
Boundary Layer ◽  
Time Series ◽  
Land Surface ◽  
Statistical Significance ◽  
Potential Temperature ◽  
The United States ◽  
Near Surface ◽  
Layer Height ◽  
Boundary Layer Height

Abstract Boundary layer height (BLH) significantly impacts near-surface air quality, and its determination is important for climate change studies. Integrated Global Radiosonde Archive data from 1973 to 2014 were used to estimate the long-term variability of the BLH based on profiles of potential temperature, relative humidity, and atmospheric refractivity. However, this study found that there was an obvious inhomogeneity in the radiosonde-derived BLH time series because of the presence of discontinuities in the raw radiosonde dataset. The penalized maximal F test and quantile-matching adjustment were used to detect the changepoints and to adjust the raw BLH series. The most significant inhomogeneity of the BLH time series was found over the United States from 1986 to 1992, which was mainly due to progress made in sonde models and processing procedures. The homogenization did not obviously change the magnitude of the daytime convective BLH (CBLH) tendency, but it improved the statistical significance of its linear trend. The trend of nighttime stable BLH (SBLH) is more dependent on the homogenization because the magnitude of SBLH is small, and SBLH is sensitive to the observational biases. The global daytime CBLH increased by about 1.6% decade−1 before and after homogenization from 1973 to 2014, and the nighttime homogenized SBLH decreased by −4.2% decade−1 compared to a decrease of −7.1% decade−1 based on the raw series. Regionally, the daytime CBLH increased by 2.8%, 0.9%, 1.6%, and 2.7% decade−1 and the nighttime SBLH decreased significantly by −2.7%, −6.9%, −7.7%, and −3.5% decade−1 over Europe, the United States, Japan, and Australia, respectively.

scholarly journals Assimilation of lidar planetary boundary layer height observations

2020 ◽  
Author(s):  
Andrew Tangborn ◽  
Belay Demoz ◽  
Brian J. Carroll ◽  
Joseph Santanello ◽  
Jeffrey L. Anderson
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Forecast Error ◽  
State Variables ◽  
Planetary Boundary Layer Height ◽  
Error Statistics ◽  
Convective Boundary ◽  
Layer Height ◽  
Late Afternoon ◽  
Boundary Layer Height

Abstract. Lidar backscatter and wind retrievals of the planetary boundary layer height (PBLH) are assimilated into 22 hourly forecasts from the NASA Unified – Weather and Research Forecast (NU-WRF) model during the Plains Elevated Convection Convection at Night (PECAN) campaign on 11 July 2015 in Greensburg, Kansas, using error statistics collected from the model profiles to compute the necessary covariance matrices. Two separate forecast runs using different PBL physics schemes were employed, and comparisons with 5 independent sonde profiles were made for each run. Both of the forecast runs accurately predicted the PBLH and the state variable profiles within the planetary boundary layer during the early morning, and the assimilation had little impact during this time. In the late afternoon, the forecast runs showed decreased accuracy as the convective boundary layer developed. However, assimilation of the doppler lidar PBLH observations were found to improve the temperature, water vapor and velocity profiles relative to independent sonde profiles. The computed forecast error covariances between the PBLH and state variables were found to rise in the late afternoon, leading to the larger improvements in the afternoon. This work represents the first effort to assimilate PBLH into forecast states using ensemble methods.

scholarly journals Assimilation of lidar planetary boundary layer height observations

2021 ◽  
Vol 14 (2) ◽  
pp. 1099-1110
Author(s):  
Andrew Tangborn ◽  
Belay Demoz ◽  
Brian J. Carroll ◽  
Joseph Santanello ◽  
Jeffrey L. Anderson
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Forecast Error ◽  
State Variables ◽  
Planetary Boundary Layer Height ◽  
Error Statistics ◽  
Convective Boundary ◽  
Layer Height ◽  
Late Afternoon ◽  
Boundary Layer Height

Abstract. Lidar backscatter and wind retrievals of the planetary boundary layer height (PBLH) are assimilated into 22-hourly forecasts from the NASA Unified – Weather and Research Forecast (NU-WRF) model during the Plains Elevated Convection at Night (PECAN) campaign on 11 July 2015 in Greensburg, Kansas, using error statistics collected from the model profiles to compute the necessary covariance matrices. Two separate forecast runs using different PBL physics schemes were employed, and comparisons with six independent radiosonde profiles were made for each run. Both of the forecast runs accurately predicted the PBLH and the state variable profiles within the planetary boundary layer during the early morning, and the assimilation had a small impact during this time. In the late afternoon, the forecast runs showed decreased accuracy as the convective boundary layer developed. However, assimilation of the Doppler lidar PBLH observations was found to improve the temperature and V-velocity profiles relative to independent radiosonde profiles. Water vapor was overcorrected, leading to increased differences with independent data. Errors in the U velocity were made slightly larger. The computed forecast error covariances between the PBLH and state variables were found to rise in the late afternoon, leading to the larger improvements in the afternoon. This work represents the first effort to assimilate PBLH into forecast states using ensemble methods.

scholarly journals Marine boundary layer structure as observed by A-train satellites

2016 ◽  
Vol 16 (9) ◽  
pp. 5891-5903 ◽  
Author(s):  
Tao Luo ◽  
Zhien Wang ◽  
Damao Zhang ◽  
Bing Chen
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Layer Structure ◽  
Mixing Layer ◽  
Eastern Pacific ◽  
Data Set ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Ocean Region ◽  
Low Cloud

Abstract. The marine boundary layer (MBL) structure is important to the marine low cloud processes, and the exchange of heat, momentum, and moisture between oceans and the low atmosphere. This study examines the MBL structure over the eastern Pacific region and further explores the controlling factors of MBL structure over the global oceans with a new 4-year satellite-based data set. The MBL top (boundary layer height, BLH) and the mixing layer height (MLH) were identified using the MBL aerosol lidar backscattering from the CALIPSO (Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations). Results showed that the MBL is generally decoupled with MLH ∕ BLH ratio ranging from  ∼  0.5 to  ∼  0.8 over the eastern Pacific Ocean region. The MBL decoupling magnitude is mainly controlled by estimated inversion strength (EIS), which in turn controls the cloud top entrainment process. The systematic differences between drizzling and non-drizzling stratocumulus tops also show dependence on EIS. This may be related to the meso-scale circulations or gravity wave in the MBL. Further analysis indicates that the MBL shows a similar decoupled structure for clear-sky and cumulus-cloud-topped conditions, but is better mixed under stratiform cloud breakup and overcast conditions.

scholarly journals Study of a prototypical convective boundary layer observed during BLLAST: contributions by large-scale forcings

2014 ◽  
Vol 14 (13) ◽  
pp. 19247-19291 ◽  
Author(s):  
H. Pietersen ◽  
J. Vilà-Guerau de Arellano ◽  
P. Augustin ◽  
O. de Coster ◽  
H. Delbarre ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Surface Heterogeneity ◽  
Small Scale ◽  
Mountain Range ◽  
Convective Boundary ◽  
Good Correspondence ◽  
Data Set ◽  
Boundary Layer Height ◽  
Boundary Layer Dynamics

Abstract. We study the disturbances of CBL dynamics due to large-scale atmospheric contributions for a representative day observed during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) campaign. We first reproduce the observed boundary-layer dynamics by combining the Dutch Atmospheric Large-Eddy Simulation (DALES) model with a mixed-layer theory based model. We find that by only taking surface and entrainment fluxes into account, the boundary-layer height is overestimated by 70%. If we constrain our numerical experiments with the BLLAST comprehensive data set, we are able to quantify the contributions of advection of heat and moisture, and subsidence. We find that subsidence has a clear diurnal pattern. Supported by the presence of a nearby mountain range, this pattern suggests that not only synoptic scales exert their influence on the boundary layer, but also mesoscale circulations. Finally, we study whether the vertical and temporal evolution of turbulent variables are influenced by these large-scale forcings. Our model results show good correspondence of the vertical structure of turbulent variables with observations. Our findings further indicate that when large-scale advection and subsidence are applied, the values for turbulent kinetic are lower than without these large-scale forcings. We conclude that the prototypical CBL can still be used as a valid representation of the boundary-layer dynamics near regions characterized by complex topography and small-scale surface heterogeneity, provided that surface- and large-scale forcings are well characterized.

scholarly journals Application of Convective Condensation Level Limiter in Convective Boundary Layer Height Retrieval Based on Lidar Data

Atmosphere ◽  
2017 ◽  
Vol 8 (12) ◽  
pp. 79 ◽  
Author(s):  
Hong Li ◽  
Yi Yang ◽  
Xiao-Ming Hu ◽  
Zhongwei Huang ◽  
Guoyin Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Convective Boundary Layer ◽  
Lidar Data ◽  
Convective Boundary ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Convective Condensation

Investigation of inter-annual and seasonal variations of the Martian convective PBL by GCM simulations

2020 ◽  
Author(s):  
Cem Berk Senel ◽  
Orkun Temel ◽  
Sara Porchetta ◽  
Hakan Sert ◽  
Ozgur Karatekin ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Seasonal Variations ◽  
Potential Temperature ◽  
Dust Storms ◽  
Planetary Boundary Layer Height ◽  
Geophysical Research ◽  
Layer Potential ◽  
Layer Height ◽  
Boundary Layer Height

&lt;p&gt;The Martian planetary boundary layer (PBL) is an important component of the Martian climate. It is the lowest portion of the atmosphere where the strong buoyant and shear forces influence the interaction between surface and atmosphere &lt;strong&gt;[1]&lt;/strong&gt;. The Martian PBL exhibits extreme events compared to the Earth's PBL, such as global dust storms, local dust devils, turbulent gusts and strong updraughts. Due to the thinner atmosphere of Mars and lower surface thermal inertia, the Martian planetary boundary layer shows stronger diurnal variations compared to its terrestrial counterpart. Moreover, as a result of the thinner atmosphere, radiative heat forcing is stronger, such that the Martian planetary boundary layer height can reach up to 10 km. Radiative forcing on Mars is affected by the atmospheric cycles, i.e. CO&lt;sub&gt;2&lt;/sub&gt;, water and dust cycles. In this study, we perform GCM simulations, using dust climatologies corresponding to the last 10 Mars years and present the inter-annual and seasonal variations in the planetary boundary layer height, mixed-layer potential temperature, convective velocity scale, friction velocity and Richardson number. To perform these GCM simulations, the Mars version of planetWRF (MarsWRF) model &lt;strong&gt;[2]&lt;/strong&gt; is utilized, that solves the fully-compressible, non-hydrostatic Euler equations in a finite difference framework.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;[1]&lt;/strong&gt; Hinson, D. P., P&amp;#228;tzold, M., Tellmann, S., H&amp;#228;usler, B., &amp; Tyler, G. L. (2008). The depth of the convective boundary layer on Mars. Icarus, 198(1), 57-66.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;[2]&lt;/strong&gt; Richardson, M. I., Toigo, A. D., &amp; Newman, C. E. (2007). PlanetWRF: A general purpose, local to global numerical model for planetary atmospheric and climate dynamics. Journal of Geophysical Research: Planets, 112(E9).&lt;/p&gt;

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