scholarly journals Characterization of Boundary Layer Turbulent Processes by the Raman Lidar BASIL in the frame of HD(CP)<sup>2</sup>) Observational Prototype Experiment

2016 ◽  
Author(s):  
Paolo Di Girolamo ◽  
Marco Cacciani ◽  
Donato Summa ◽  
Andrea Scoccione ◽  
Benedetto De Rosa ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Vapour ◽  
Temporal Resolution ◽  
Fourth Order ◽  
Temperature Fluctuations ◽  
Temperature Measurements ◽  
Order Moment ◽  
Mixing Ratio ◽  
Raman Lidar ◽  
Turbulent Fluctuations

Abstract. Measurements carried out by the University of BASILicata Raman lidar system (BASIL) are reported to demonstrate the capability of this instrument to characterize turbulent processes within the convective boundary layer (CBL). In order to resolve the vertical profiles of turbulent variables, high resolution water vapour and temperature measurements, with a temporal resolution of 10 s and a vertical resolution of 90 m and 30 m, respectively, are considered. Measurements of higher-order moments of the turbulent fluctuations of water vapour mixing ratio and temperature are obtained based on the application of auto-covariance analyses to the water vapour mixing ratio and temperature time series. The algorithms are applied to a case study (11:30–13:30 UTC, 20 April 2013) from the High Definition Clouds and Precipitation for Climate Prediction (HD(CP)2) Observational Prototype Experiment (HOPE), held in Western Germany in the spring 2013. A new correction scheme for the elastic-signal leakage in the low-quantum number rotational Raman signal is applied. The noise errors are small enough to derive up to fourth-order moments for both water vapour mixing ratio and temperature fluctuations. To the best of our knowledge, BASIL is the first Raman lidar with a demonstrated capability to simultaneously retrieve daytime profiles of water vapour turbulent fluctuations up to the fourth order throughout the atmospheric CBL, this capability being combined with the one to also measure daytime profiles of temperature fluctuations up to the fourth order. For the considered case study, which represents a well-mixed and quasi-stationary CBL, the mean boundary layer height is found to be 1290 ± 77 m a.g.l. Values of the integral scale for water vapour and temperature fluctuations at the top of the CBL are in the range of 70–125 s and 75–225 s, respectively; these values are much larger than the temporal resolution of the measurements (10 s), which testifies that the temporal resolution considered for the measurements is sufficiently high to resolve turbulence processes down to the inertial sub-range and consequently resolve the major part of the turbulent fluctuations. Peak values of all moments are found in the interfacial layer in the proximity of the top of the CBL. Specifically, water vapour and temperature second-order moment (variance) has a maximum value of 0.29 g2 kg−2 and 0.26 K2, respectively, water vapour and temperature third-order moment has a peak value of 0.156 g3 kg−3 and −0.067 K3, respectively, while water vapour and temperature fourth-order moment has a maximum value of 0.28 g4 kg−4 and 0.24 K4, respectively. Water vapour and temperature kurtosis have values of ~ 3 in the entrainment zone, which indicate normally distributed humidity and temperature fluctuations. Reported values of the higher-order moments result to be in good agreement with previous measurements at different locations, thus providing confidence on the possibility to use them for turbulence parameterization in weather and climate models. In the determination of the temperature profiles, particular care was dedicated to minimize potential effects associated with elastic signal leakage in the rotational Raman signals. For this purpose, a specific algorithm was defined and tested to identify and remove signal leakages and to assess the residual systematic uncertainty affecting temperature measurements after correction. The application of this approach confirms that for the present Raman lidar system the leakage factor keeps constant with time, and consequently an appropriate assessment of its constant value allows for a complete removal of the leaking elastic signal from the rotational Raman lidar signals at any time (with a residual error on temperature measurements after correction not exceeding 0.16 K).

scholarly journals Characterisation of boundary layer turbulent processes by the Raman lidar BASIL in the frame of HD(CP)<sup>2</sup> Observational Prototype Experiment

2017 ◽  
Vol 17 (1) ◽  
pp. 745-767 ◽  
Author(s):  
Paolo Di Girolamo ◽  
Marco Cacciani ◽  
Donato Summa ◽  
Andrea Scoccione ◽  
Benedetto De Rosa ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Vapour ◽  
Temporal Resolution ◽  
Fourth Order ◽  
Temperature Fluctuations ◽  
Temperature Measurements ◽  
Mixing Ratio ◽  
Raman Lidar ◽  
Turbulent Fluctuations ◽  
Signal Crosstalk

Abstract. Measurements carried out by the University of Basilicata Raman lidar system (BASIL) are reported to demonstrate the capability of this instrument to characterise turbulent processes within the convective boundary layer (CBL). In order to resolve the vertical profiles of turbulent variables, high-resolution water vapour and temperature measurements, with a temporal resolution of 10 s and vertical resolutions of 90 and 30 m, respectively, are considered. Measurements of higher-order moments of the turbulent fluctuations of water vapour mixing ratio and temperature are obtained based on the application of autocovariance analyses to the water vapour mixing ratio and temperature time series. The algorithms are applied to a case study (11:30–13:30 UTC, 20 April 2013) from the High Definition Clouds and Precipitation for Climate Prediction (HD(CP)2) Observational Prototype Experiment (HOPE), held in western Germany in the spring 2013. A new correction scheme for the removal of the elastic signal crosstalk into the low quantum number rotational Raman signal is applied. The noise errors are small enough to derive up to fourth-order moments for both water vapour mixing ratio and temperature fluctuations.To the best of our knowledge, BASIL is the first Raman lidar with a demonstrated capability to simultaneously retrieve daytime profiles of water vapour turbulent fluctuations up to the fourth order throughout the atmospheric CBL. This is combined with the capability of measuring daytime profiles of temperature fluctuations up to the fourth order. These measurements, in combination with measurements from other lidar and in situ systems, are important for verifying and possibly improving turbulence and convection parameterisation in weather and climate models at different scales down to the grey zone (grid increment  ∼  1 km; Wulfmeyer et al., 2016).For the considered case study, which represents a well-mixed and quasi-stationary CBL, the mean boundary layer height is found to be 1290 ± 75 m above ground level (a.g.l.). Values of the integral scale for water vapour and temperature fluctuations at the top of the CBL are in the range of 70–125 and 75–225 s, respectively; these values are much larger than the temporal resolution of the measurements (10 s), which testifies that the temporal resolution considered for the measurements is sufficiently high to resolve turbulent processes down to the inertial subrange and, consequently, to resolve the major part of the turbulent fluctuations. Peak values of all moments are found in the interfacial layer in the proximity of the top of the CBL. Specifically, water vapour and temperature second-order moments (variance) have maximum values of 0.29 g2 kg−2 and 0.26 K2; water vapour and temperature third-order moments have peak values of 0.156 g3 kg−3 and −0.067 K3, while water vapour and temperature fourth-order moments have maximum values of 0.28 g4 kg−4 and 0.24 K4. Water vapour and temperature kurtosis have values of  ∼  3 in the upper portion of the CBL, which indicate normally distributed humidity and temperature fluctuations. Reported values of the higher-order moments are in good agreement with previous measurements at different locations, thus providing confidence in the possibility of using these measurements for turbulence parameterisation in weather and climate models.In the determination of the temperature profiles, particular care was dedicated to minimise potential effects associated with elastic signal crosstalk on the rotational Raman signals. For this purpose, a specific algorithm was defined and tested to identify and remove the elastic signal crosstalk and to assess the residual systematic uncertainty affecting temperature measurements after correction. The application of this approach confirms that, for the present Raman lidar system, the crosstalk factor remains constant with time; consequently an appropriate assessment of its constant value allows for a complete removal of the leaking elastic signal from the rotational Raman lidar signals at any time (with a residual error on temperature measurements after correction not exceeding 0.18 K).

scholarly journals Profiles of second- to fourth-order moments of turbulent temperature fluctuations in the convective boundary layer: first measurements with rotational Raman lidar

2015 ◽  
Vol 15 (10) ◽  
pp. 5485-5500 ◽  
Author(s):  
A. Behrendt ◽  
V. Wulfmeyer ◽  
E. Hammann ◽  
S. K. Muppa ◽  
S. Pal
Keyword(s):  
Boundary Layer ◽  
Fourth Order ◽  
Shot Noise ◽  
Temperature Fluctuations ◽  
Atmospheric Temperature ◽  
Order Moment ◽  
Statistical Uncertainty ◽  
Temperature Profiles ◽  
Raman Lidar ◽  
Noise Error

Abstract. The rotational Raman lidar (RRL) of the University of Hohenheim (UHOH) measures atmospheric temperature profiles with high resolution (10 s, 109 m). The data contain low-noise errors even in daytime due to the use of strong UV laser light (355 nm, 10 W, 50 Hz) and a very efficient interference-filter-based polychromator. In this paper, the first profiling of the second- to fourth-order moments of turbulent temperature fluctuations is presented. Furthermore, skewness profiles and kurtosis profiles in the convective planetary boundary layer (CBL) including the interfacial layer (IL) are discussed. The results demonstrate that the UHOH RRL resolves the vertical structure of these moments. The data set which is used for this case study was collected in western Germany (50°53'50.56'' N, 6°27'50.39'' E; 110 m a.s.l.) on 24 April 2013 during the Intensive Observations Period (IOP) 6 of the HD(CP)2 (High-Definition Clouds and Precipitation for advancing Climate Prediction) Observational Prototype Experiment (HOPE). We used the data between 11:00 and 12:00 UTC corresponding to 1 h around local noon (the highest position of the Sun was at 11:33 UTC). First, we investigated profiles of the total noise error of the temperature measurements and compared them with estimates of the temperature measurement uncertainty due to shot noise derived with Poisson statistics. The comparison confirms that the major contribution to the total statistical uncertainty of the temperature measurements originates from shot noise. The total statistical uncertainty of a 20 min temperature measurement is lower than 0.1 K up to 1050 m a.g.l. (above ground level) at noontime; even for single 10 s temperature profiles, it is smaller than 1 K up to 1020 m a.g.l. Autocovariance and spectral analyses of the atmospheric temperature fluctuations confirm that a temporal resolution of 10 s was sufficient to resolve the turbulence down to the inertial subrange. This is also indicated by the integral scale of the temperature fluctuations which had a mean value of about 80 s in the CBL with a tendency to decrease to smaller values towards the CBL top. Analyses of profiles of the second-, third-, and fourth-order moments show that all moments had peak values in the IL around the mean top of the CBL which was located at 1230 m a.g.l. The maximum of the variance profile in the IL was 0.39 K2 with 0.07 and 0.11 K2 for the sampling error and noise error, respectively. The third-order moment (TOM) was not significantly different from zero in the CBL but showed a negative peak in the IL with a minimum of −0.93 K3 and values of 0.05 and 0.16 K3 for the sampling and noise errors, respectively. The fourth-order moment (FOM) and kurtosis values throughout the CBL were not significantly different to those of a Gaussian distribution. Both showed also maxima in the IL but these were not statistically significant taking the measurement uncertainties into account. We conclude that these measurements permit the validation of large eddy simulation results and the direct investigation of turbulence parameterizations with respect to temperature.

End-to-end Simulator of a space-borne Raman Lidar for the thermodynamic profiling of the atmosphere

2021 ◽  
Author(s):  
Noemi Franco ◽  
Paolo Di Girolamo ◽  
Donato Summa ◽  
Benedetto De Rosa ◽  
Andreas Behrendt ◽  
...  
Keyword(s):  
Numerical Model ◽  
Water Vapour ◽  
Vertical Profile ◽  
Molecular Nitrogen ◽  
Reference Signal ◽  
Temperature Measurements ◽  
Mixing Ratio ◽  
Raman Lidar ◽  
Atmospheric Water ◽  
Atmospheric Water Vapour

&lt;p&gt;An end-to-end model has been developed in order to simulate the expected performance of a space-borne Raman Lidar, with a specific focus on the Atmospheric Thermodynamics LidAr in Space &amp;#8211; ATLAS proposed as a &amp;#8220;mission concept&amp;#8221; to the ESA in the frame of the &amp;#8220;Earth Explorer-11 Mission Ideas&amp;#8221; Call. The numerical model includes a forward module, which simulates the lidar signals with their statistical uncertainty, and a retrieval module able to provide vertical profiles of atmospheric water vapour mixing ratio and temperature based on the analyses of the simulated signals. Specifically, the forward module simulates the interaction mechanisms of laser radiation with the atmospheric constituents and the behavior of all the devices present in the experimental system(telescope, optical reflecting and transmitting components, avalanche photodiodes, ACCDs). An analytical expression of the lidar equation for the water vapour and molecular nitrogen roto-vibrational Raman signals and the pure rotational Raman signals from molecular oxygen and nitrogen is used. The analytically computed signals are perturbed by simulating their shot-noise through Poisson statistics. Perturbed signals thus take into account the fluctuations in the number of photons reaching the detector over a certain time interval.&amp;#160;The simulator also provides an estimation of the background due to the solar contribution. Daylight background includes three distinct terms: a cloud-free atmospheric contribution, a surface contribution and a cloud contribution[1]. Background is calculated as a function of the solar zenith angle. In order to better estimatethe background contribution, an integration on slant path is performed instead of a classical parallel-planes approximation. The proposed numerical model allows to better simulate solar background for high solar zenith angles, even higher than 90 degrees.&amp;#160;Signals simulated through the forward model are then fed into the retrieval module. A background subtraction scheme is used to remove the solar contribution and a vertical averaging is performed to smooth the signals. Based on the application of the roto-vibrational Raman lidar technique, the vertical profile of atmospheric water vapour mixing ratio is obtained from the power ratio of the water vapour to a reference signal, such as molecular nitrogen roto-vibrational Raman signal or an alternative temperature-independent reference signal. A vertical profile of temperature is then obtained through the ratio of high-to-low quantum number rotational Raman signals by the application of the pure rotational Raman lidar technique. Both atmospheric water vapour mixing ratio and temperature measurements require the determination of calibration constants, which can be obtained from the comparison with simultaneous and co-located measurements from a different sensor [2].&amp;#160;The simulator finally provides statistical (RMS) and systematic (bias) uncertainties. Estimates are provided in terms of percentage and absolute (g/kg) uncertainty for water vapour mixing ratio measurements and in terms of absolute uncertainty (K) for temperature measurements.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;1 - P.Di Girolamo et al., &quot;Spaceborne profiling of atmospheric temperature and particle extinction with pure rotational Raman lidar and of relative humidity in combination with differential absorption lidar: performance simulations&quot;Appl.Opt.&amp;#160;45, 2474-2494(2006)&lt;/p&gt;&lt;p&gt;2 - P.Di Girolamo et al., &quot;Space-borne profiling of atmospheric thermodynamic variables with Raman lidar: performance simulations,&quot;Opt.Express&amp;#160;26, 8125-8161(2018)&lt;/p&gt;

scholarly journals Water Vapour and Temperature Measurements by Raman Lidar in the Frame of the NDACC

2020 ◽  
Vol 237 ◽  
pp. 05012
Author(s):  
Benedetto De Rosa ◽  
Paolo Di Girolamo ◽  
Donato Summa
Keyword(s):  
Water Vapour ◽  
Temperature Measurements ◽  
Atmospheric Composition ◽  
Integration Time ◽  
Mixing Ratio ◽  
Raman Lidar ◽  
Model Data ◽  
Sensor Model ◽  
Paper Cover ◽  
Absolute Bias

In November 2012, the University of BASILicata Raman Lidar system (BASIL) was approved to enter the International Network for the Detection of Atmospheric Composition Change (NDACC). Since then measurements were routinely carried out on a once per week basis. This paper illustrates specific measurement examples from this effort, with a dedicated focus on temperature and water vapour measurements, with the ultimate goal to provide a characterization of the system performance. Case studies illustrated in this paper demonstrate the ability of BASIL to perform measurements of the temperature profile up to 50 km and of the water vapour mixing ratio profile up to 15 km, based on an integration time of 2 hours and a vertical resolution of 150 m, with measurement bias not exceeding 0.1 K and 0.1 g kg−1, respectively. Raman lidar measurements are compared with measurements from additional instruments, such as radiosondings and satellite sensors (IASI and AIRS), and with model re-analyses data (ECMWF and ECMWF-ERA). Comparisons in this paper cover the altitude interval up to 15 km for water vapour mixing ratio and up to 50 km for the temperature. Comparisons between BASIL and the different sensor/model data in terms of water vapour mixing ratio indicate a mean absolute/relative bias of -0.024 g kg−1(or -3.9 %), 0.342 g kg−1(or 36.8 %), 0.346 g kg−1 (or 37.5 %), -0.297 g kg−1 (or -25 %), -0.381 g kg−1 (or -31 %), when compared with radisondings, AIRS, IASI, ECMWF, ECMWF-ERA, respectively. For what concerns the comparisons in terms of temperature measurements, these indicate a mean absolute bias between BASIL and the radisondings, AIRS, IASI, ECMWF, ECMWF-ERA of -0.04, 1.99, 0.48, 0.14, 0.62 K, respectively. Based on the available dataset and benefiting from the circumstance that the Raman lidar BASIL could be compared with all other sensor/model data, it has been possible to estimate the absolute bias of all sensors/datasets, this being 0.004 g kg−1/0.30 K, 0.021 g kg−1/-0.34 K, -0.35 g kg−1/0.18 K, -0.346 g kg−1/-1.63 K, 0.293 g kg−1/-0.16 K and 0.377 g kg−1/0.32 K in terms of water vapour mixing ratio/temperature for BASIL, the radisondings, IASI, AIRS, ECMWF, ECMWF-ERA, respectively.

scholarly journals Profiles of second- to third-order moments of turbulent temperature fluctuations in the convective boundary layer: first measurements with Rotational Raman Lidar

2014 ◽  
Vol 14 (21) ◽  
pp. 29019-29055 ◽  
Author(s):  
A. Behrendt ◽  
V. Wulfmeyer ◽  
E. Hammann ◽  
S. K. Muppa ◽  
S. Pal
Keyword(s):  
Boundary Layer ◽  
Temperature Measurement ◽  
Convective Boundary Layer ◽  
Temperature Fluctuations ◽  
Atmospheric Temperature ◽  
Order Moment ◽  
Temperature Profiles ◽  
Raman Lidar ◽  
Third Order ◽  
Convective Boundary

Abstract. The rotational Raman lidar of the University of Hohenheim (UHOH) measures atmospheric temperature profiles during daytime with high resolution (10 s, 109 m). The data contain low noise errors even in daytime due to the use of strong UV laser light (355 nm, 10 W, 50 Hz) and a very efficient interference-filter-based polychromator. In this paper, we present the first profiling of the second- to forth-order moments of turbulent temperature fluctuations as well as of skewness and kurtosis in the convective boundary layer (CBL) including the interfacial layer (IL). The results demonstrate that the UHOH RRL resolves the vertical structure of these moments. The data set which is used for this case study was collected in western Germany (50°53'50.56′′ N, 6°27'50.39′′ E, 110 m a.s.l.) within one hour around local noon on 24 April 2013 during the Intensive Observations Period (IOP) 6 of the HD(CP)2 Observational Prototype Experiment (HOPE), which is embedded in the German project HD(CP)2 (High-Definition Clouds and Precipitation for advancing Climate Prediction). First, we investigated profiles of the noise variance and compared it with estimates of the statistical temperature measurement uncertainty Δ T based on Poisson statistics. The agreement confirms that photon count numbers obtained from extrapolated analog signal intensities provide a lower estimate of the statistical errors. The total statistical uncertainty of a 20 min temperature measurement is lower than 0.1 K up to 1050 m a.g.l. at noontime; even for single 10 s temperature profiles, it is smaller than 1 K up to 1000 m a.g.l.. Then we confirmed by autocovariance and spectral analyses of the atmospheric temperature fluctuations that a temporal resolution of 10 s was sufficient to resolve the turbulence down to the inertial subrange. This is also indicated by the profile of the integral scale of the temperature fluctuations, which was in the range of 40 to 120 s in the CBL. Analyzing then profiles of the second-, third-, and forth-order moments, we found the largest values of all moments in the IL around the mean top of the CBL which was located at 1230 m a.g.l. The maximum of the variance profile in the IL was 0.40 K2 with 0.06 and 0.08 K2 for the sampling error and noise error, respectively. The third-order moment was not significantly different from zero inside the CBL but showed a negative peak in the IL with a minimum of −0.72 K3 and values of 0.06 and 0.14 K3 for the sampling and noise errors, respectively. The forth-order moment and kurtosis values throughout the CBL were quasi-normal.

scholarly journals Potential of Raman Lidar for Profiling of Methane Mixing Ratio in the Lower Troposphere

2020 ◽  
Vol 237 ◽  
pp. 03024
Author(s):  
Igor Veselovskii ◽  
Philippe Goloub ◽  
Qiaoyun Hu ◽  
Thierry Podvin ◽  
Mikhail Korenskiy
Keyword(s):  
Boundary Layer ◽  
Temporal Resolution ◽  
Nd:Yag Laser ◽  
Resolution Enhancement ◽  
Lower Troposphere ◽  
Free Troposphere ◽  
Mixing Ratio ◽  
Raman Lidar ◽  
Night Time

The results of methane profiling in the lower troposphere by Raman lidar from Lille University observatory platform (France), are presented. The use of powerful DPSS tripled Nd:YAG laser allowed profiling of methane background mixing ratio of 2 ppm in the night time up to 4000 m with 100 m height and 1 hour temporal resolution. Enhancement of CH4 mixing ratio inside the boundary layer comparing to the free troposphere values was observed.

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.

Characterization of the time evolution of the PBL structure and dry-layers based on the us of Raman Lidar measurements collected during HYMEX-SOP1

2021 ◽  
Author(s):  
Donato Summa ◽  
Paolo Di Girolamo ◽  
Noemi Franco ◽  
Benedetto De Rosa ◽  
Fabio Madonna ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Boundary Layer ◽  
Water Vapour ◽  
Planetary Boundary Layer ◽  
Grid Point ◽  
Laser Source ◽  
Raman Lidar ◽  
Water Vapour Concentration ◽  
Vapour Concentration

&lt;p&gt;The exchange processes between the Earth and the atmosphere play a crucial role in the development of the Planetary Boundary Layer (PBL). Different remote sensing techniques can provide PBL measurement with different spatial and temporal resolutions. Vertical profiles of atmospheric thermodynamic variables, i.e. &amp;#160;temperature and humidity, or wind speed, clouds and aerosols can be used as proxy to retrieve PBL height from active and passive remote sensing instruments. The University of BASILicata ground-based Raman Lidar system (BASIL) was deployed in the North-Western Mediterranean basin in the C&amp;#233;vennes-Vivarais site (Candillargues, Southern France, Lat: 43&amp;#176;37' N, Long: 4&amp;#176; 4' E, Elev: 1 m) and operated between 5 September and 5 November 2012, collecting more than 600 hours of measurements, distributed over 51 days and 19 intensive observation periods (IOPs). BASIL is capable to provide high-resolution and accurate measurements of atmospheric temperature and water vapour, both in daytime and night-time, based on the application of the rotational and vibrational Raman lidar techniques in the UV. This measurement capability makes BASIL a key instrument for the characterization of the water vapour concentration. BASIL makes use of a Nd:YAG laser source capable of emitting pulses at 355, 532 and 1064 nm, with a single pulse energy at 355nm of 500 mJ [1] .In the presented research effort, water vapour concentration was &amp;#160;computed and used to determine the PBL height. [2]. A dynamic index&amp;#160; included in the European Centre for Medium-range Weather Forecasts (ECMWF) ERA5 atmospheric reanalysis (CAPE, Friction velocity, etc.) is also considered and compared with BASIL resutls. ERA5 provides hourly data on regular latitude-longitude grids at 0.25&amp;#176; x 0.25&amp;#176; resolution at 37 pressure levels [3]. ERA5 is publicly available through the Copernicus Climate Data Store (CDS, https://cds.climate.copernicus.eu). &amp;#160;In order to properly carry out the comparison, the nearest ERA5 grid point to the lidar site has been considered assuming the representativeness uncertainty due to the use of the nearest grid-point comparable with other methods (e.g. kriging, bilinear interpolation, etc.). More results from this&amp;#160; measurement&amp;#160; effort will&amp;#160; be reported and discussed at the Conference.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Reference&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;[1] Di Girolamo, Paolo, De Rosa, Benedetto, Flamant, Cyrille, Summa, Donato, Bousquet, Olivier, Chazette, Patrick, Totems, Julien, Cacciani, Marco. Water vapor mixing ratio and temperature inter-comparison results in the framework of the Hydrological Cycle in the Mediterranean Experiment&amp;#8212;Special Observation Period 1. BULLETIN OF ATMOSPHERIC SCIENCE AND TECHNOLOGY, ISSN: 2662-1495, doi: 10.1007/s42865-020-00008-3&lt;/p&gt;&lt;p&gt;[2] D. Summa, P. Di Girolamo, D. Stelitano, and M. Cacciani. Characterization of the planetary boundary layer height and structure by Raman lidar: comparison of different approaches&amp;#160; Atmos. Meas. Tech., 6, 3515&amp;#8211;3525, 2013 www.atmos-meas-tech.net/6/3515/2013/doi:10.5194/amt-6-3515-2013&lt;/p&gt;&lt;p&gt;[3] Hersbach et al. The ERA5 global reanalysis Hans&amp;#160; https://doi.org/10.1002/qj.3803[3]&lt;/p&gt;

Combined use of Raman lidar and DIAL measurements and MESO-NH model simulations for the characterization of complex water vapour field structures and their genesis: a case study from HyMeX-SOP 1

2020 ◽  
Author(s):  
Paolo Di Girolamo ◽  
Marie-Noelle Bouin ◽  
Cyrille Flamant ◽  
Donato Summa ◽  
Benedetto De Rosa
Keyword(s):  
Water Vapour ◽  
Heavy Precipitation ◽  
Time Interval ◽  
Mixing Ratio ◽  
Raman Lidar ◽  
Model Simulations ◽  
Combined Use ◽  
Geographical Regions ◽  
Lidar Measurements ◽  
Precipitation Events

&lt;p&gt;As part of the Cevennes-Vivarais site, the University of Basilicata Raman lidar system BASIL was deployed in Candillargues and operated throughout the duration of HyMeX-SOP 1 (September-November 2012), providing high-resolution and accurate measurements, both in daytime and night-time, of atmospheric temperature, water vapour mixing ratio and particle backscattering and extinction coefficient at three wavelengths.&lt;/p&gt;&lt;p&gt;Measurements carried out by BASIL on 28 September 2012 reveal a water vapour field characterized by a quite complex vertical structure. Reported measurements were run in the time interval between two consecutive heavy precipitation events, from 15:30 UTC on 28 September to 03:30 UTC on 29 September 2012. Throughout most of this observation period, lidar measurements reveal the presence of four distinct humidity layers.&lt;/p&gt;&lt;p&gt;The present research effort aims at assessing the origin and transport path of the different humidity filaments observed by BASIL on this day. The analysis approach relies on the comparison between Raman lidar measurements and MESO-NH and NOAA-HYSPLIT model simulations. Back-trajectory analyses from MESO-NH reveal that air masses ending in Candillargues at different altitudes levels are coming and are originated from different geographical regions.&lt;/p&gt;&lt;p&gt;The four distinct humidity layers observed by BASIL are also identified in the water vapour mixing ratio profiles collected by the air-borne DIAL LEANDRE 2 on-board of the French research aircraft ATR42. The exact correspondence, in terms of back-trajectories computation and water budget, between the humidity layers observed by BASIL and those identified in LEANDRE2 measurements has been verified based on a dedicated simulation effort.&lt;/p&gt;&lt;p&gt;In the paper we also try to identify the presence of dry layers and cold pools and assess their role in the genesis of the mesoscale convective systems and the heavy precipitation events observed on 29 September 2012 based on the combined use of water vapour mixing ratio and temperature profile measurements from BASIL and water vapour mixing ratio profile measurements from LEANDRE 2, again supported by MESO-NH simulations.&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document