scholarly journals Assessment of Mixed-Layer Height Estimation from Single-wavelength Ceilometer Profiles

2017 ◽  
Author(s):  
Travis N. Knepp ◽  
James S. Szykman ◽  
Russell Long ◽  
Rachelle M. Duvall ◽  
Jonathan Krug ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Data Collection ◽  
Mixed Layer ◽  
A Priori ◽  
Processing Algorithm ◽  
Height Measurement ◽  
Layer Height ◽  
Network Operation ◽  
Mixed Layer Height ◽  
The Impact

Abstract. Differing boundary/mixed-layer height measurement methods were assessed in moderately-polluted and clean environments, with a focus on the Vaisala CL51 ceilometer. This intercomparison was performed as part of ongoing measurements at the Chemistry And Physics of the Atmospheric Boundary Layer Experiment (CAPABLE) site in Hampton, Virginia and during the 2014 Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field campaign that took place in and around Denver, Colorado. We analyzed CL51 data that were collected via two different methods (BLView software, which applied correction factors, and simple terminal emulation logging) to determine the impact of data collection methodology. Further, we evaluated the STRucture of the ATmosphere (STRAT) algorithm as an open-source alternative to BLView (note that the current work presents an evaluation of the BLView and STRAT algorithms and does not intend to act as a validation of either). Filtering criteria were defined according to the change in mixed-layer height (MLH) distributions for each instrument and algorithm and were applied throughout the analysis to remove high-frequency fluctuations from the MLH retrievals. Of primary interest was determining how the different data-collection methodologies and algorithms compare to each other and to radiosonde-derived boundary-layer heights when deployed as part of a larger instrument network. We determined that data-collection methodology is not as important as the processing algorithm and that much of the algorithm differences might be driven by local meteorology and precipitation events that pose algorithm difficulties. The results of this study show that a common processing algorithm is necessary for LIght Detection And Ranging (LIDAR)-based MLH intercomparisons, and ceilometer-network operation and that sonde-derived boundary layer heights are higher (10–15 % at mid-day) than LIDAR-derived mixed-layer heights. We show that averaging the retrieved MLH to 1-hour resolution (as necessary for a priori data model initialization) significantly improved correlation between differing instruments and differing algorithms.

scholarly journals Assessment of mixed-layer height estimation from single-wavelength ceilometer profiles

2017 ◽  
Vol 10 (10) ◽  
pp. 3963-3983 ◽  
Author(s):  
Travis N. Knepp ◽  
James J. Szykman ◽  
Russell Long ◽  
Rachelle M. Duvall ◽  
Jonathan Krug ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Data Collection ◽  
Mixed Layer ◽  
A Priori ◽  
Processing Algorithm ◽  
Height Measurement ◽  
Layer Height ◽  
Network Operation ◽  
Mixed Layer Height ◽  
The Impact

Abstract. Differing boundary/mixed-layer height measurement methods were assessed in moderately polluted and clean environments, with a focus on the Vaisala CL51 ceilometer. This intercomparison was performed as part of ongoing measurements at the Chemistry And Physics of the Atmospheric Boundary Layer Experiment (CAPABLE) site in Hampton, Virginia and during the 2014 Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field campaign that took place in and around Denver, Colorado. We analyzed CL51 data that were collected via two different methods (BLView software, which applied correction factors, and simple terminal emulation logging) to determine the impact of data collection methodology. Further, we evaluated the STRucture of the ATmosphere (STRAT) algorithm as an open-source alternative to BLView (note that the current work presents an evaluation of the BLView and STRAT algorithms and does not intend to act as a validation of either). Filtering criteria were defined according to the change in mixed-layer height (MLH) distributions for each instrument and algorithm and were applied throughout the analysis to remove high-frequency fluctuations from the MLH retrievals. Of primary interest was determining how the different data-collection methodologies and algorithms compare to each other and to radiosonde-derived boundary-layer heights when deployed as part of a larger instrument network. We determined that data-collection methodology is not as important as the processing algorithm and that much of the algorithm differences might be driven by impacts of local meteorology and precipitation events that pose algorithm difficulties. The results of this study show that a common processing algorithm is necessary for light detection and ranging (lidar)-based MLH intercomparisons and ceilometer-network operation, and that sonde-derived boundary layer heights are higher (10–15 % at midday) than lidar-derived mixed-layer heights. We show that averaging the retrieved MLH to 1 h resolution (an appropriate timescale for a priori data model initialization) significantly improved the correlation between differing instruments and differing algorithms.

scholarly journals Atmospheric boundary layer dynamics from balloon soundings worldwide: CLASS4GL v1.0

2019 ◽  
Vol 12 (5) ◽  
pp. 2139-2153 ◽  
Author(s):  
Hendrik Wouters ◽  
Irina Y. Petrova ◽  
Chiel C. van Heerwaarden ◽  
Jordi Vilà-Guerau de Arellano ◽  
Adriaan J. Teuling ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Mixed Layer ◽  
Weather Prediction ◽  
Potential Temperature ◽  
Specific Humidity ◽  
Weather Extremes ◽  
Coupled Models ◽  
Layer Height ◽  
Mixed Layer Height

Abstract. The coupling between soil, vegetation and atmosphere is thought to be crucial in the development and intensification of weather extremes, especially meteorological droughts, heat waves and severe storms. Therefore, understanding the evolution of the atmospheric boundary layer (ABL) and the role of land–atmosphere feedbacks is necessary for earlier warnings, better climate projection and timely societal adaptation. However, this understanding is hampered by the difficulties of attributing cause–effect relationships from complex coupled models and the irregular space–time distribution of in situ observations of the land–atmosphere system. As such, there is a need for simple deterministic appraisals that systematically discriminate land–atmosphere interactions from observed weather phenomena over large domains and climatological time spans. Here, we present a new interactive data platform to study the behavior of the ABL and land–atmosphere interactions based on worldwide weather balloon soundings and an ABL model. This software tool – referred to as CLASS4GL (http://class4gl.eu, last access: 27 May 2018) – is developed with the objectives of (a) mining appropriate global observational data from ∼15 million weather balloon soundings since 1981 and combining them with satellite and reanalysis data and (b) constraining and initializing a numerical model of the daytime evolution of the ABL that serves as a tool to interpret these observations mechanistically and deterministically. As a result, it fully automizes extensive global model experiments to assess the effects of land and atmospheric conditions on the ABL evolution as observed in different climate regions around the world. The suitability of the set of observations, model formulations and global parameters employed by CLASS4GL is extensively validated. In most cases, the framework is able to realistically reproduce the observed daytime response of the mixed-layer height, potential temperature and specific humidity from the balloon soundings. In this extensive global validation exercise, a bias of 10.1 m h−1, −0.036 K h−1 and 0.06 g kg−1 h−1 is found for the morning-to-afternoon evolution of the mixed-layer height, potential temperature and specific humidity. The virtual tool is in continuous development and aims to foster a better process understanding of the drivers of the ABL evolution and their global distribution, particularly during the onset and amplification of weather extremes. Finally, it can also be used to scrutinize the representation of land–atmosphere feedbacks and ABL dynamics in Earth system models, numerical weather prediction models, atmospheric reanalysis and satellite retrievals, with the ultimate goal of improving local climate projections, providing earlier warning of extreme weather and fostering a more effective development of climate adaptation strategies. The tool can be easily downloaded via http://class4gl.eu (last access: 27 May 2018) and is open source.

Simulation of Structural Features of Atmospheric Boundary Layer of Chengdu Urban Agglomeration

2012 ◽  
Vol 599 ◽  
pp. 192-201
Author(s):  
Wen Yong Wang ◽  
Xiao Juan Ma ◽  
Gao Ping Fu
Keyword(s):  
Boundary Layer ◽  
Mixed Layer ◽  
Ground Surface ◽  
Urban Agglomeration ◽  
Heat Island ◽  
Isobaric Surface ◽  
Layer Height ◽  
Maximum Value ◽  
Mixed Layer Height ◽  
Humidity Field

In the present paper, features of the atmospheric boundary layer of Chengdu urban agglomeration were identified and transfer, diffusion and conversion rules of atmospheric pollutants in the boundary layer were analyzed by using the mesoscale meteorological model, WRF(Weather Research & Forecasting)to simulate the temporal and spatial distribution and features of the flow field, temperature field, humidity field, and atmospheric mixed layer height of Chengdu urban agglomeration. As a result, basic data were provided for developing the plan for the coordinated development of the urban agglomeration economy and environment. The simulation show that, in Sichuan Basin, south wind and east wind prevail on the near-ground surface and 850 hPa isobaric surface while west wind and southwest wind prevail on the 700 hPa isobaric surface. Under the influence of the mountains around the basin, the flow field on the near-ground surface forms circulation in the south of the basin. The atmosphere strongly exchanges in the vertical direction below 1500 m and the exchange becomes weaker upwards. The ground temperature field distribution is low in northwest and high in southeast. The urban heat island effect is obvious, and especially the “big heat island” occurs in the urban agglomeration. In winter, temperature inversion frequently happens. In terms of ground humidity field, in winter and spring, it is low in northwest and high in southeast, which is opposite in summer; in autumn, humidity is low in west and high in east. Regarding the mixed layer height of the study area, it reaches the minimum value in winter and the maximum value in summer; the daily mixed layer height reaches the maximum value between 14:00 and 15:00 and reaches the minimum value in the small hours.

scholarly journals Technical note: Boundary layer height determination from Lidar for improving air pollution episode modelling: development of new algorithm and evaluation

2017 ◽  
Author(s):  
Ting Yang ◽  
Zifa Wang ◽  
Wei Zhang ◽  
Alex Gbaguidi ◽  
Nubuo Sugimoto ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
High Performance ◽  
Accurate Determination ◽  
Technical Note ◽  
Strong Increase ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Retrieval Algorithms ◽  
The Impact

Abstract. Predicting air pollution events in low atmosphere over megacities requires thorough understanding of the tropospheric dynamic and chemical processes, involving notably, continuous and accurate determination of the boundary layer height (BLH). Through intensive observations experimented over Beijing (China), and an exhaustive evaluation existing algorithms applied to the BLH determination, persistent critical limitations are noticed, in particular over polluted episodes. Basically, under weak thermal convection with high aerosol loading, none of the retrieval algorithms is able to fully capture the diurnal cycle of the BLH due to pollutant insufficient vertical mixing in the boundary layer associated with the impact of gravity waves on the tropospheric structure. Subsequently, a new approach based on gravity wave theory (the cubic root gradient method: CRGM), is developed to overcome such weakness and accurately reproduce the fluctuations of the BLH under various atmospheric pollution conditions. Comprehensive evaluation of CRGM highlights its high performance in determining BLH from Lidar. In comparison with the existing retrieval algorithms, the CRGM potentially reduces related computational uncertainties and errors from BLH determination (strong increase of correlation coefficient from 0.44 to 0.91 and significant decrease of the root mean square error from 643 m to 142 m). Such newly developed technique is undoubtedly expected to contribute to improve the accuracy of air quality modelling and forecasting systems.

scholarly journals Entrainment and Mixing of Transported Ozone Layers: Implications for Surface Air Quality in the Western U.S.

2020 ◽  
Vol 237 ◽  
pp. 03012
Author(s):  
Christoph Senff ◽  
Andrew Langford ◽  
Raul Alvarez ◽  
Tim Bonin ◽  
Alan Brewer ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Quality ◽  
Mixed Layer ◽  
Las Vegas ◽  
Surface Ozone ◽  
Ground Level ◽  
San Joaquin Valley ◽  
Fire Emissions ◽  
Ozone Transport ◽  
The Impact

Recently, two air quality campaigns were conducted in the southwestern United States to study the impact of transported ozone, stratospheric intrusions, and fire emissions on ground-level ozone concentrations. The California Baseline Ozone Transport Study (CABOTS) took place in May – August 2016 covering the central California coast and San Joaquin Valley, and the Fires, Asian, and Stratospheric Transport Las Vegas Ozone Study (FAST-LVOS) was conducted in the greater Las Vegas, Nevada area in May – June 2017. During these studies, nearly 1000 hours of ozone and aerosol profile data were collected with the NOAA TOPAZ lidar. A Doppler wind lidar and a radar wind profiler provided continuous observations of atmospheric turbulence, horizontal winds, and mixed layer height. These measurements allowed us to directly observe the degree to which ozone transport layers aloft were entrained into the boundary layer and to quantify the resulting impact on surface ozone levels. Mixed layer heights in the San Joaquin Valley during CABOTS were generally below 1 km above ground level (AGL), while boundary layer heights in Las Vegas during FAST-LVOS routinely exceeded 3 km AGL and occasionally reached up to 4.5 km AGL. Consequently, boundary layer entrainment was more often observed during FAST-LVOS, while most elevated ozone layers passed untapped over the San Joaquin Valley during CABOTS.

scholarly journals Nature of the Mesoscale Boundary Layer Height and Water Vapor Variability Observed 14 June 2002 during the IHOP_2002 Campaign

2009 ◽  
Vol 137 (1) ◽  
pp. 414-432 ◽  
Author(s):  
F. Couvreux ◽  
F. Guichard ◽  
P. H. Austin ◽  
F. Chen
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Mesoscale Model ◽  
Surface Flux ◽  
Early Morning ◽  
Surface Fluxes ◽  
Layer Height ◽  
Horizontal Advection ◽  
Boundary Layer Height ◽  
The Impact

Abstract Mesoscale water vapor heterogeneities in the boundary layer are studied within the context of the International H2O Project (IHOP_2002). A significant portion of the water vapor variability in the IHOP_2002 occurs at the mesoscale, with the spatial pattern and the magnitude of the variability changing from day to day. On 14 June 2002, an atypical mesoscale gradient is observed, which is the reverse of the climatological gradient over this area. The factors causing this water vapor variability are investigated using complementary platforms (e.g., aircraft, satellite, and in situ) and models. The impact of surface flux heterogeneities and atmospheric variability are evaluated separately using a 1D boundary layer model, which uses surface fluxes from the High-Resolution Land Data Assimilation System (HRLDAS) and early-morning atmospheric temperature and moisture profiles from a mesoscale model. This methodology, based on the use of robust modeling components, allows the authors to tackle the question of the nature of the observed mesoscale variability. The impact of horizontal advection is inferred from a careful analysis of available observations. By isolating the individual contributions to mesoscale water vapor variability, it is shown that the observed moisture variability cannot be explained by a single process, but rather involves a combination of different factors: the boundary layer height, which is strongly controlled by the surface buoyancy flux, the surface latent heat flux, the early-morning heterogeneity of the atmosphere, horizontal advection, and the radiative impact of clouds.

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