scholarly journals PBL height estimation based on lidar depolarisation measurements (POLARIS)

2016 ◽  
Author(s):  
Juan Antonio Bravo-Aranda ◽  
Gregori de-Arruda-Moreira ◽  
Francisco Navas-Guzmán ◽  
María José Granados-Muñoz ◽  
Juan Luís Guerrero-Rascado ◽  
...  
Keyword(s):  
Weather Prediction ◽  
Microwave Radiometer ◽  
Numerical Weather Prediction Model ◽  
Saharan Dust ◽  
Night Time ◽  
Signal Ratio ◽  
Height Estimation ◽  
Boundary Layer Height ◽  
Lidar Measurements ◽  
Dust Events

Abstract. The automatic and non-supervised detection of the planetary boundary layer height (zPBL) by means of lidar measurements was widely investigated during the last years. Despite the considerable advances achieved the experimental detection still present difficulties either because the PBL is stratified (typically, during night-time) either because advected aerosol layers are coupled to the PBL. The coupling uses to produce an overestimation of the zPBL. To improve the detection even in these complex atmospheric situations, we present a new algorithm, called POLARIS (PBL height estimatiOn based on Lidar depolARISation). POLARIS applies the wavelet covariance transform (WCT) to the range corrected signal and to the perpendicular-to-parallel signal ratio (δ) profiles. Different candidates for zPBL are chosen and the attribution is done, based on the WCT applied to the RCS and the δ. We use two ChArMEx campaigns with lidar and microwave radiometer (MWR), conducted on 2012 and 2013, for the POLARIS' adjustment and validation. POLARIS improves the zPBL detection thanks to the consideration of the relative changes in the depolarization capabilities of the aerosol particles in the lower part of the atmospheric column. Taking the advantage of a proper determination of the zPBL determined by POLARIS and by MWR under Saharan dust events, we compare the POLARIS and MWR zPBL with the zPBL provided by the Weather Research and Forecasting (WRF) numerical weather prediction model. WRF underestimates the zPBL during daytime but agrees with the MWR during night-time. The zPBL provided by WRF showed a better temporal evolution during daytime than during night-time.

scholarly journals A new methodology for PBL height estimations based on lidar depolarization measurements: analysis and comparison against MWR and WRF model-based results

2017 ◽  
Vol 17 (11) ◽  
pp. 6839-6851 ◽  
Author(s):  
Juan Antonio Bravo-Aranda ◽  
Gregori de Arruda Moreira ◽  
Francisco Navas-Guzmán ◽  
María José Granados-Muñoz ◽  
Juan Luis Guerrero-Rascado ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Planetary Boundary Layer ◽  
Weather Prediction ◽  
Microwave Radiometer ◽  
Wrf Model ◽  
Saharan Dust ◽  
Aerosol Layer ◽  
Night Time ◽  
Signal Ratio ◽  
Lidar Measurements

Abstract. The automatic and non-supervised detection of the planetary boundary layer height (zPBL) by means of lidar measurements was widely investigated during the last several years. Despite considerable advances, the experimental detection still presents difficulties such as advected aerosol layers coupled to the planetary boundary layer (PBL) which usually produces an overestimation of the zPBL. To improve the detection of the zPBL in these complex atmospheric situations, we present a new algorithm, called POLARIS (PBL height estimation based on lidar depolarisation). POLARIS applies the wavelet covariance transform (WCT) to the range-corrected signal (RCS) and to the perpendicular-to-parallel signal ratio (δ) profiles. Different candidates for zPBL are chosen and the selection is done based on the WCT applied to the RCS and δ. We use two ChArMEx (Chemistry-Aerosol Mediterranean Experiment) campaigns with lidar and microwave radiometer (MWR) measurements, conducted in 2012 and 2013, for the POLARIS' adjustment and validation. POLARIS improves the zPBL detection compared to previous methods based on lidar measurements, especially when an aerosol layer is coupled to the PBL. We also compare the zPBL provided by the Weather Research and Forecasting (WRF) numerical weather prediction (NWP) model with respect to the zPBL determined with POLARIS and the MWR under Saharan dust events. WRF underestimates the zPBL during daytime but agrees with the MWR during night-time. The zPBL provided by WRF shows a better temporal evolution compared to the MWR during daytime than during night-time.

scholarly journals Tropospheric water vapour and relative humidity profiles from lidar and microwave radiometry

2014 ◽  
Vol 7 (5) ◽  
pp. 1201-1211 ◽  
Author(s):  
F. Navas-Guzmán ◽  
J. Fernández-Gálvez ◽  
M. J. Granados-Muñoz ◽  
J. L. Guerrero-Rascado ◽  
J. A. Bravo-Aranda ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Water Vapour ◽  
Microwave Radiometer ◽  
Radiosonde Data ◽  
Mixing Ratio ◽  
Raman Lidar ◽  
Night Time ◽  
New Approach ◽  
Lidar Measurements ◽  
Humidity Profiles

Abstract. In this paper, we outline an iterative method to calibrate the water vapour mixing ratio profiles retrieved from Raman lidar measurements. Simultaneous and co-located radiosonde data are used for this purpose and the calibration results obtained during a radiosonde campaign in summer and autumn 2011 are presented. The water vapour profiles measured during night-time by the Raman lidar and radiosondes are compared and the differences between the methodologies are discussed. Then, a new approach to obtain relative humidity profiles by combination of simultaneous profiles of temperature (retrieved from a microwave radiometer) and water vapour mixing ratio (from a Raman lidar) is addressed. In the last part of this work, a statistical analysis of water vapour mixing ratio and relative humidity profiles obtained during 1 year of simultaneous measurements is presented.

scholarly journals Aircraft Icing Study Using Integrated Observations and Model Data

2019 ◽  
Vol 34 (3) ◽  
pp. 485-506 ◽  
Author(s):  
Faisal Boudala ◽  
George A. Isaac ◽  
Di Wu
Keyword(s):  
Accumulation Rate ◽  
Weather Prediction ◽  
Microwave Radiometer ◽  
Weather Conditions ◽  
Numerical Weather Prediction Model ◽  
Winter Period ◽  
Cylindrical Shape ◽  
Observation Data ◽  
Aircraft Icing ◽  
Cold Lake

Abstract Light (LGT) to moderate (MOD) aircraft icing (AI) is frequently reported at Cold Lake, Alberta, but forecasting AI has been a big challenge. The purpose of this study is to investigate and understand the weather conditions associated with AI based on observations in order to improve the icing forecast. To achieve this goal, Environment and Climate Change Canada in cooperation with the Department of National Defence deployed a number of ground-based instruments that include a microwave radiometer, a ceilometer, disdrometers, and conventional present weather sensors at the Cold Lake airport (CYOD). A number of pilot reports (PIREPs) of icing at Cold Lake during the 2016/17 winter period and associated observation data are examined. Most of the AI events were LGT (76%) followed by MOD (20%) and occurred during landing and takeoff at relatively warm temperatures. Two AI intensity algorithms have been tested based on an ice accumulation rate (IAR) assuming a cylindrical shape moving with airspeed υa of 60 and 89.4 m s−1, and the Canadian numerical weather prediction model forecasts. It was found that the algorithms IAR2 with υa = 89.4 m s−1 and IAR1 with υa = 60 m s−1 underestimated (overestimated) the LGT (MOD) icing events, respectively. The algorithm IAR2 with υa = 60 m s−1 appeared to be more suitable for forecasting LGT icing. Over all, the hit rate score was 0.33 for the 1200 UTC model run and 0.6 for 0000 UTC run for both algorithms, but based on the individual icing intensity scores, the IAR2 did better than IAR1 for forecasting LGT icing events.

scholarly journals Lidar measurement of planetary boundary layer height and comparison with microwave profiling radiometer observation

2012 ◽  
Vol 5 (8) ◽  
pp. 1965-1972 ◽  
Author(s):  
Z. Wang ◽  
X. Cao ◽  
L. Zhang ◽  
J. Notholt ◽  
B. Zhou ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Microwave Radiometer ◽  
Theoretical Models ◽  
Lidar Measurement ◽  
Layer Height ◽  
Boundary Layer Height ◽  
Lidar Measurements ◽  
Theoretical Predictions ◽  
Entrainment Zone ◽  
The City

Abstract. The atmospheric boundary layer height was derived at two locations in the city of Lanzhou (China) and its suburb rural area Yuzhong. The aerosol backscatter lidar measurements were analysed using a wavelet technology and the parcel method was applied to profiling microwave radiometer observations. For a few occasions the average boundary layer height and entrainment zone thickness was derived in convective situations at Yuzhong. Results from selected observation days show that both datasets agree in strong convective situations. However, for weak convective situations the lidar measurements reveal boundary layer heights that are higher compared to the microwave observations, because a decrease of the thermal boundary layer height does not directly lead to a change of aerosols in that altitude layer. Finally, the entrainment zone thicknesses are compared with theoretical predictions, and the results show that the measurements are compatible with theoretical models.

scholarly journals Representation of the grey zone of turbulence in the atmospheric boundary layer

2016 ◽  
Vol 13 ◽  
pp. 63-67 ◽  
Author(s):  
Rachel Honnert
Keyword(s):  
Boundary Layer ◽  
Weather Prediction ◽  
Numerical Weather Prediction Model ◽  
Grey Zone ◽  
Shallow Convection ◽  
Convective Boundary ◽  
Boundary Layer Height ◽  
Eddy Simulation ◽  
Layer Structures ◽  
Large Eddy

Abstract. Numerical weather prediction model forecasts at horizontal grid lengths in the range of 100 to 1 km are now possible. This range of scales is the "grey zone of turbulence". Previous studies, based on large-eddy simulation (LES) analysis from the MésoNH model, showed that some assumptions of some turbulence schemes on boundary-layer structures are not valid. Indeed, boundary-layer thermals are now partly resolved, and the subgrid remaining part of the thermals is possibly largely or completely absent from the model columns. First, some modifications of the equations of the shallow convection scheme have been tested in the MésoNH model and in an idealized version of the operational AROME model at resolutions coarser than 500 m. Secondly, although the turbulence is mainly vertical at mesoscale (>  2 km resolution), it is isotropic in LES (<  100 m resolution). It has been proved by LES analysis that, in convective boundary layers, the horizontal production of turbulence cannot be neglected at resolutions finer than half of the boundary-layer height. Thus, in the grey zone, fully unidirectional turbulence scheme should become tridirectional around 500 m resolution. At Météo-France, the dynamical turbulence is modelled by a K-gradient in LES as well as at mesoscale in both MésoNH and AROME, which needs mixing lengths in the formulation. Vertical and horizontal mixing lengths have been calculated from LES of neutral and convective cases at resolutions in the grey zone.

scholarly journals Aerosol monitoring in Siberia using an 808 nm automatic compact lidar

2019 ◽  
Vol 12 (1) ◽  
pp. 147-168 ◽  
Author(s):  
Gerard Ancellet ◽  
Iogannes E. Penner ◽  
Jacques Pelon ◽  
Vincent Mariage ◽  
Antonin Zabukovec ◽  
...  
Keyword(s):  
Forest Fires ◽  
Lidar Data ◽  
Night Time ◽  
Lidar Measurements ◽  
Lidar Ratio ◽  
Aerosol Sources ◽  
Sun Photometer ◽  
Dust Events ◽  
Flexpart Model ◽  
Aerosol Type

Abstract. Our study provides new information on aerosol-type seasonal variability and sources in Siberia using observations (ground-based lidar and sun photometer combined with satellite measurements). A micropulse lidar emitting at 808 nm provided almost continuous aerosol backscatter measurements for 18 months (April 2015 to September 2016) in Siberia, near the city of Tomsk (56∘ N, 85∘ E). A total of 540 vertical profiles (300 daytime and 240 night-time) of backscatter ratio and aerosol extinction have been retrieved over periods of 30 min, after a careful calibration factor analysis. Lidar ratio and extinction profiles are constrained with sun-photometer aerosol optical depth at 808 nm (AOD808) for 70 % of the daytime lidar measurements, while 26 % of the night-time lidar ratio and AOD808 greater than 0.04 are constrained by direct lidar measurements at an altitude greater than 7.5 km and where a low aerosol concentration is found. An aerosol source apportionment using the Lagrangian FLEXPART model is used in order to determine the lidar ratio of the remaining 48 % of the lidar database. Backscatter ratio vertical profile, aerosol type and AOD808 derived from micropulse lidar data are compared with sun-photometer AOD808 and satellite observations (CALIOP space-borne lidar backscatter and extinction profiles, Moderate Resolution Imaging Spectroradiometer (MODIS) AOD550 and Infrared Atmospheric Sounding Interferometer (IASI) CO column) for three case studies corresponding to the main aerosol sources with AOD808>0.2 in Siberia. Aerosol typing using the FLEXPART model is consistent with the detailed analysis of the three case studies. According to the analysis of aerosol sources, the occurrence of layers linked to natural emissions (vegetation, forest fires and dust) is high (56 %), but anthropogenic emissions still contribute to 44 % of the detected layers (one-third from flaring and two-thirds from urban emissions). The frequency of dust events is very low (5 %). When only looking at AOD808>0.1, contributions from taiga emissions, forest fires and urban pollution become equivalent (25 %), while those from flaring and dust are lower (10 %–13 %). The lidar data can also be used to assess the contribution of different altitude ranges to the large AOD. For example, aerosols related to the urban and flaring emissions remain confined below 2.5 km, while aerosols from dust events are mainly observed above 2.5 km. Aerosols from forest fire emissions are observed to be the opposite, both within and above the planetary boundary layer (PBL).

scholarly journals Seventeen-year systematic measurements of dust aerosol optical properties using the eole ntua lidar system (2000-2016)

2018 ◽  
Vol 176 ◽  
pp. 05029
Author(s):  
Ourania Soupiona ◽  
Maria Mylonaki ◽  
Alexandros Papayannis ◽  
Athina Argyrouli ◽  
Panayotis Kokkalis ◽  
...  
Keyword(s):  
Optical Properties ◽  
Mean Value ◽  
Saharan Dust ◽  
Aerosol Optical Properties ◽  
Mean Values ◽  
Time Period ◽  
Lidar Measurements ◽  
Multi Wavelength ◽  
Lidar Ratio ◽  
Dust Events

A comprehensive analysis of the seasonal variability of the optical properties of Saharan dust aerosols over Athens, Greece, is presented for a 17-year time period (2000-2016), as derived from multi-wavelength Raman lidar measurements (57 dust events with more than 80 hours of measurements). The profiles of the derived aerosol optical properties (aerosol backscatter and extinction coefficients, lidar ratio and aerosol Ångström exponent) at 355 nm are presented. For these dust events we found a mean value of the lidar ratio of ~52±13 sr at 355 nm and of ~58±8 sr (not shown) at 532 nm (2-4 km a.s.l. height). For our statistical analysis, presented here, we used monthly-mean values and time periods under cloud-free conditions. The number of dust events was greatest in late spring, summer, and early autumn periods. In this paper we also present a selected case study (04 April 2016) of desert dust long-range transport from the Saharan desert.

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