Mixing layer height retrievals by multichannel microwave radiometer observations

Abstract. The mixing layer height (MLH) is a key parameter for boundary layer studies, including meteorology, air quality, and climate. MLH estimates are inferred from in situ radiosonde measurements or remote sensing observations from instruments like lidar, wind profiling radar, or sodar. Methods used to estimate MLH from radiosonde profiles are also used with atmospheric temperature and humidity profiles retrieved by microwave radiometers (MWR). This paper proposes an alternative approach to estimate MLH from MWR data, based on direct observations (brightness temperatures, Tb) instead of retrieved profiles. To our knowledge, MLH estimates directly from Tb observations has never been attempted before. The method consists of a multivariate linear regression trained with an a priori set of collocated MWR Tb observations (multi-frequency and multi-angle) and MLH estimates from a state-of-the-art lidar system. Results show that the method is able to follow both the diurnal cycle and the day-to-day variability as suggested by the lidar measurements, and also it can detect low MLH values that are below the full overlap limit (~ 200 m) of the lidar system used. Statistics of the comparison between MWR- and reference lidar-based MLH retrievals show mean difference within 10 m, RMS within 340 m, and correlation coefficient higher than 0.77. Monthly mean analysis for day-time MLH from MWR, lidar, and radiosonde shows consistent seasonal variability, peaking at ~ 1200–1400 m in June and decreasing down to ~ 600 m in October. Conversely, night-time monthly mean MLH from all methods are within 300–500 m without any significant seasonal variability. The proposed method provides results that are more consistent with radiosonde estimates than MLH estimates from MWR retrieved profiles. MLH monthly mean values agree well within 1 std with bulk Richardson number method applied at radiosonde profiles at 11:00 and 23:00 UTC. The method described herewith operates continuously and it is expected to work with analogous performances for the entire diurnal cycle, except during considerable precipitation, demonstrating new potential for atmospheric observation by ground-based microwave radiometry.

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Mixing layer height retrievals by multichannel microwave radiometer observations

Atmospheric Measurement Techniques ◽

10.5194/amt-6-2941-2013 ◽

2013 ◽

Vol 6 (11) ◽

pp. 2941-2951 ◽

Cited By ~ 38

Author(s):

D. Cimini ◽

F. De Angelis ◽

J.-C. Dupont ◽

S. Pal ◽

M. Haeffelin

Keyword(s):

Diurnal Cycle ◽

Seasonal Variability ◽

Microwave Radiometer ◽

Mixing Layer ◽

Atmospheric Temperature ◽

Lidar System ◽

Data Set ◽

Mean Values ◽

Layer Height ◽

Mixing Layer Height

Abstract. The mixing layer height (MLH) is a key parameter for boundary layer studies, including meteorology, air quality, and climate. MLH estimates are inferred from in situ radiosonde measurements or remote sensing observations from instruments like lidar, wind profiling radar, or sodar. Methods used to estimate MLH from radiosonde profiles are also used with atmospheric temperature and humidity profiles retrieved by microwave radiometers (MWR). This paper proposes an alternative approach to estimate MLH from MWR data, based on direct observations (brightness temperatures, Tb) instead of retrieved profiles. To our knowledge, MLH estimates directly from Tb observations have never been attempted before. The method consists of a multivariate linear regression trained with an a priori set of collocated MWR Tb observations (multifrequency and multi-angle) and MLH estimates from a state-of-the-art lidar system. The proposed method was applied to a 7-month data set collected at a typical midlatitude site. Results show that the method is able to follow both the diurnal cycle and the day-to-day variability as suggested by the lidar measurements, and also it can detect low MLH values that are below the full overlap limit (~200 m) of the lidar system used. Statistics of the comparison between MWR- and reference lidar-based MLH retrievals show mean difference within 10 m, root mean square within 340 m, and correlation coefficient higher than 0.77. Monthly mean analysis for daytime MLH from MWR, lidar, and radiosonde shows consistent seasonal variability, peaking at ~1200–1400 m in June and decreasing down to ~600 m in October. Conversely, nighttime monthly mean MLH from all methods are within 300–500 m without any significant seasonal variability. The proposed method provides results that are more consistent with radiosonde estimates than MLH estimates from MWR-retrieved profiles. MLH monthly mean values agree well within 1 standard deviation with the bulk Richardson number method applied at radiosonde profiles at 11:00 and 23:00 UTC. The method described herewith operates continuously and is expected to work with analogous performances for the entire diurnal cycle, except during considerable precipitation, demonstrating new potential for atmospheric observation by ground-based microwave radiometry.

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Performance test of the synergetic use of simulated lidar and microwave radiometer observations for mixing-layer height detection

10.1117/12.2195091 ◽

2015 ◽

Cited By ~ 1

Author(s):

Umar Saeed ◽

Francesc Rocadenbosch ◽

Susanne Crewell

Keyword(s):

Performance Test ◽

Microwave Radiometer ◽

Mixing Layer ◽

Layer Height ◽

Mixing Layer Height

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Determination and climatology of the diurnal cycle of the atmospheric mixing layer height over Beijing 2013–2018: lidar measurements and implications for air pollution

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-8839-2020 ◽

2020 ◽

Vol 20 (14) ◽

pp. 8839-8854 ◽

Cited By ~ 1

Author(s):

Haofei Wang ◽

Zhengqiang Li ◽

Yang Lv ◽

Ying Zhang ◽

Hua Xu ◽

...

Keyword(s):

Air Pollution ◽

Diurnal Cycle ◽

Mixing Layer ◽

Daily Maximum ◽

Layer Height ◽

Stable Conditions ◽

Lidar Measurements ◽

Significant Phenomenon ◽

Mixing Layer Height ◽

Convective Layer

Abstract. The atmospheric mixing layer height (MLH) determines the space in which pollutants diffuse and is thus conducive to the estimation of the pollutant concentration near the surface. The study evaluates the capability of lidar to describe the evolution of the atmospheric mixing layer and then presents a long-term observed climatology of the MLH diurnal cycle. Detection of the mixing layer heights (MLHL and MLHL′) using the wavelet method based on lidar observations was conducted from January 2013 to December 2018 in the Beijing urban area. The two dataset results are compared with radiosonde as case studies and statistical forms. MLHL shows good performance in calculating the convective layer height in the daytime and the residual layer height at night. While MLHL′ has the potential to describe the stable layer height at night, the performance is limited due to the high range gate of lidar. A nearly 6-year climatology for the diurnal cycle of the MLH is calculated for convective and stable conditions using the dataset of MLHL from lidar. The daily maximum MLHL characteristics of seasonal change in Beijing indicate that it is low in winter (1.404±0.751 km) and autumn (1.445±0.837 km) and high in spring (1.647±0.754 km) and summer (1.526±0.581 km). A significant phenomenon is found from 2014 to 2018: the magnitude of the diurnal cycle of MLHL increases year by year, with peak values of 1.291±0.646 km, 1.435±0.755 km, 1.577±0.739 km, 1.597±0.701 km and 1.629±0.751 km, respectively. It may partly benefit from the improvement of air quality. As to converting the column optical depth to surface pollution, the calculated PM2.5 using MLHL data from lidar shows better accuracy than that from radiosonde compared with observational PM2.5. Additionally, the accuracy of calculated PM2.5 using MLHL shows a diurnal cycle in the daytime, with the peak at 14:00 LST. The study provides a significant dataset of MLHL based on measurements and could be an effective reference for atmospheric models of surface air pollution calculation and analysis.

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Supplementary material to "Determination and climatology of diurnal cycle of atmospheric mixing layer height over Beijing 2013–2018: Lidar measurements and implication for airpollution"

10.5194/acp-2020-175-supplement ◽

2020 ◽

Author(s):

Haofei Wang ◽

Zhengqiang Li ◽

Yang Lv ◽

Ying Zhang ◽

Hua Xu ◽

...

Keyword(s):

Diurnal Cycle ◽

Mixing Layer ◽

Layer Height ◽

Lidar Measurements ◽

Mixing Layer Height ◽

Supplementary Material

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Investigation of the mixing layer height derived from ceilometer measurements in the Kathmandu Valley and implications for local air quality

10.5194/acp-2016-1002 ◽

2017 ◽

Author(s):

Andrea Mues ◽

Maheswar Rupakheti ◽

Christoph Münkel ◽

Axel Lauer ◽

Heiko Bozem ◽

...

Keyword(s):

Black Carbon ◽

Diurnal Cycle ◽

Monsoon Season ◽

Mixing Layer ◽

Kathmandu Valley ◽

Mixing Height ◽

Layer Height ◽

Emission Fluxes ◽

Mixing Layer Height ◽

Carbon Concentrations

Abstract. In this study one year of ceilometer measurements taken in the Kathmandu Valley, Nepal, in the framework of the SusKat project (A Sustainable Atmosphere for the Kathmandu Valley) were analyzed to investigate the diurnal variation of the mixing layer height and its dependency on the meteorological conditions. In addition, the impact of the mixing layer height on the temporal variation and the magnitude of the measured black carbon concentrations are analysed for each season. Based on the assumption that black carbon aerosols are vertically well mixed within the mixing layer and the finding that the mixing layer varies only little during night time and morning hours, black carbon emission fluxes are estimated for these hours and per month. Even though this method is relatively simple, it can give an observationally based first estimate of the black carbon emissions in this region, especially illuminating the seasonal cycle of the emission fluxes. In all seasons the diurnal cycle of the mixing layer height is typically characterized by low heights during the night and maximum values during in the afternoon. Seasonal differences are found in the absolute mixing layer height values and the duration of the typical daytime maximum. During the monsoon season a diurnal cycle has been observed with the smallest amplitude, with the lowest daytime mixing height of all seasons, and also the highest nighttime and early morning mixing height of all seasons. These characteristics can mainly be explained with the frequently present clouds and the associated reduction in incoming solar radiation and outgoing longwave radiation. In general, the black carbon concentrations show a clear anticorrelation with mixing layer height measurements, although this relation is less pronounced in the monsoon season. The daily evolution of the black carbon diurnal cycle differs between the seasons, partly due to the different meteorological conditions including the mixing layer height. Other important reasons are the different main emission sources and their diurnal variations in the individual seasons. The estimation of the black carbon emission flux for the morning hours show a clear seasonal cycle with maximum values in December to April. Compared to the emission flux values provided by different emission databases for this region, the here estimated values are considerably higher. Several possible sources of uncertainty are considered, and even the absolute lower bound of the emissions based on our methodology is higher than in most emissions datasets, providing strong evidence that the black carbon emissions for this region have likely been underestimated in modelling studies thus far.

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Inter-comparison of lidar and ceilometer retrievals for aerosol and Planetary Boundary Layer profiling over Athens, Greece

Atmospheric Measurement Techniques ◽

10.5194/amt-4-1261-2011 ◽

2011 ◽

Vol 4 (6) ◽

pp. 1261-1273 ◽

Cited By ~ 66

Author(s):

G. Tsaknakis ◽

A. Papayannis ◽

P. Kokkalis ◽

V. Amiridis ◽

H. D. Kambezidis ◽

...

Keyword(s):

Boundary Layer ◽

Planetary Boundary Layer ◽

Mixing Layer ◽

Radiosonde Data ◽

Lidar System ◽

Height Range ◽

Layer Height ◽

Tropospheric Aerosol ◽

Filter Radiometer ◽

Mixing Layer Height

Abstract. This study presents an inter-comparison of two active remote sensors (lidar and ceilometer) to determine the mixing layer height and structure of the Planetary Boundary Layer (PBL) and to retrieve tropospheric aerosol vertical profiles over Athens, Greece. This inter-comparison was performed under various strongly different aerosol loads/types (urban air pollution, biomass burning and Saharan dust event), implementing two different lidar systems (one portable Raymetrics S.A. lidar system running at 355 nm and one multi-wavelength Raman lidar system running at 355 nm, 532 nm and 1064 nm) and one CL31 Vaisala S.A. ceilometer (running at 910 nm). Spectral conversions of the ceilometer's data were performed using the Ångström exponent estimated by ultraviolet multi-filter radiometer (UV-MFR) measurements. The inter-comparison was based on two parameters: the mixing layer height determined by the presence of the suspended aerosols and the attenuated backscatter coefficient. Additionally, radiosonde data were used to derive the PBL height. In general, a good agreement was found between the ceilometer and the lidar techniques in both inter-compared parameters in the height range from 500 m to 5000 m, while the limitations of each instrument are also examined.

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Determination and climatology of diurnal cycle of atmospheric mixing layer height over Beijing 2013–2018: Lidar measurements and implication for airpollution

10.5194/acp-2020-175 ◽

2020 ◽

Author(s):

Haofei Wang ◽

Zhengqiang Li ◽

Yang Lv ◽

Ying Zhang ◽

Hua Xu ◽

...

Keyword(s):

Diurnal Cycle ◽

Mixing Layer ◽

Layer Height ◽

Stable Conditions ◽

Lidar Measurements ◽

Significant Phenomenon ◽

Mixing Layer Height ◽

Convective Layer ◽

Wavelet Methods

Abstract. The atmospheric mixing layer height (MLH) determines the volume available for the dispersion of pollutants and thus contributes to the assessment of the pollutant concentration near the surface. The study evaluates the capability of lidar to describe the evolution of atmospheric mixing layer and then presents a long term observed climatology of MLH diurnal cycle. A system for automatic detection of the mixing layer height based on two wavelet methods (MLH and MLH') applied to lidar observations was operated from January 2013 to December 2018 in the Beijing urban area. The two dataset results are compared with radiosonde as case studies and statistical form. MLH shows good performance to calculate the convective layer height at daytime and the residual layer height at night. While MLH' has the potential to describe the stable layer height as radiosonde at night, the performance is limited due to the high range gate of lidar. A nearly six year climatology for diurnal cycle of MLH is calculated for convective and stable conditions using the dataset of MLH from lidar. The MLH characteristics of seasonal change in Beijing indicate that it is low in winter and autumn, and high in spring and summer. A significant phenomenon is found that from 2013 to 2018, the diurnal cycle of MLH increase year by year. It may partly benefit from the improvement of air quality. As to converting the column optical depth to the surface pollution, MLH from lidar shows better accuracy than that from radiosonde. Additionally, the accuracy with lidar MLH shows a diurnal cycle, with the peak at time of 14:00 LST. The study provides a significant dataset of MLH based on measurement and could be an effective reference to atmospheric models for surface air pollution calculation and analysis.

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Boundary Layer Characteristics over Aindanda Low-Mountain Pass of Kathmandu Valley, Nepal

Journal of Institute of Science and Technology ◽

10.3126/jist.v20i2.13944 ◽

2015 ◽

Vol 20 (2) ◽

pp. 22-30 ◽

Cited By ~ 1

Author(s):

Saraswati Shrestha ◽

Sajan Shrestha ◽

Sangeeta Maharjan ◽

Ram P. Regmi

Keyword(s):

Boundary Layer ◽

Mixing Layer ◽

Central Area ◽

Mountain Pass ◽

Kathmandu Valley ◽

Night Time ◽

Air Mass ◽

Layer Height ◽

Late Afternoon ◽

Mixing Layer Height

The early monsoon time boundary layer characteristics prevailing over Aindanda low-mountain pass of Kathmandu valley has been continuously monitored for the period of 11 to 24 June 2013. The study reveals that the Aindanda pass channels regional air masses from the western neighboring valley up into the Kathmandu valley as westerly/ northwesterly winds during the daytime whereas it drains air mass out of the valley during night-time. The speed of the westerly/northwesterly wind over the pass often exceeds 6.5 ms-1 during the late afternoon. Nighttime mixing layer height (MLH) was highly fluctuating with an average around 300m whereas daytime MLH was suppressed limiting it in between 290-450m above the ground in early part of the day but reduced to 210-270m during the late afternoon. Comparison of diurnal variation of mixing layer height at Aindanda with that of the central area of the valley floor strongly suggests that air mass intruding into the Kathmandu valley through this pass is a cool density flow over the weakly stratified mixed layer of valley. The structure of the wind channeled through this pass indicates the possibility of making hydraulic jump in the western part of the Kathmandu valley, particularly, during the late afternoon time.Journal of Institute of Science and Technology, 2015, 20(2): 22-30

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Lidar-based remote sensing of atmospheric boundary layer height over land and ocean

Atmospheric Measurement Techniques ◽

10.5194/amt-7-173-2014 ◽

2014 ◽

Vol 7 (1) ◽

pp. 173-182 ◽

Cited By ~ 37

Author(s):

T. Luo ◽

R. Yuan ◽

Z. Wang

Keyword(s):

Boundary Layer ◽

Atmospheric Boundary Layer ◽

Marine Boundary Layer ◽

Mixing Layer ◽

Layer Height ◽

Boundary Layer Height ◽

Lidar Measurements ◽

Mixing Layer Height ◽

Atmospheric Radiation Measurement ◽

Atmospheric Boundary Layer Height

Abstract. Atmospheric boundary layer (ABL) processes are important in climate, weather and air quality. A better understanding of the structure and the behavior of the ABL is required for understanding and modeling of the chemistry and dynamics of the atmosphere on all scales. Based on the systematic variations of the ABL structures over different surfaces, different lidar-based methods were developed and evaluated to determine the boundary layer height and mixing layer height over land and ocean. With Atmospheric Radiation Measurement Program (ARM) Climate Research Facility (ACRF) micropulse lidar (MPL) and radiosonde measurements, diurnal and season cycles of atmospheric boundary layer depth and the ABL vertical structure over ocean and land are analyzed. The new methods are then applied to satellite lidar measurements. The aerosol-derived global marine boundary layer heights are evaluated with marine ABL stratiform cloud top heights and results show a good agreement between them.

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