40 research outputs found
Arctic biomass burning aerosol eventâmicrophysical property retrieval
An intense biomass-burning (BB) event from North America in July 2015 was observed over Ny-Ă
lesund (Spitsbergen, European Arctic). An extreme air pollution took place and aerosol optical depth (AOD) of more than 1 at 500nm occurs in middle and lower troposphere. We analyse data from the multi-wavelength Raman-lidar KARL of Alfred Wegener Institute to derive microphysical properties of the aerosol of one interesting layer from 3186 to 3306 m via regularization. We found credible and confidential microphysical parameters
Wind and Turbulence Statistics in the Urban Boundary Layer over a MountainâValley System in Granada, Spain
Urban boundary layer characterization is currently a challenging and relevant issue,
because of its role in weather and air quality modelling and forecast. In many cities, the effect of
complex topography at local scale makes this modelling even more complicated. This is the case of
mid-latitude urban areas located in typical basin topographies, which usually present low winds and
high turbulence within the atmospheric boundary layer (ABL). This study focuses on the analysis
of the first ever measurements of wind with high temporal and vertical resolution throughout the
ABL over a medium-sized city surrounded by mountains in southern Spain. These measurements
have been gathered with a scanning Doppler lidar system and analyzed using the Halo lidar toolbox
processing chain developed at the Finnish Meteorological Institute. We have used the horizontal
wind product and the ABL turbulence classification product to carry out a statistical study using a
two-year database. The data availability in terms of maximum analyzed altitudes for statistically
significant results was limited to around 1000â1500mabove ground level (a.g.l.) due to the decreasing
signal intensity with height that also depends on aerosol load. We have analyzed the differences
and similarities in the diurnal evolution of the horizontal wind profiles for different seasons and
their modelling with Weibull and von Mises probability distributions, finding a general trend of
mean daytime wind from the NW with mean speeds around 3â4 m/s at low altitudes and 6â10 m/s
at higher altitudes, and weaker mean nocturnal wind from the SE with similar height dependence.
The highest speeds were observed during spring, and the lowest during winter. Finally, we studied
the turbulent sources at the ABL with temporal (for each hour of the day) and height resolution.
The results show a clear convective activity during daytime at altitudes increasing with time, and a
significant wind-shear-driven turbulence during night-time.Spanish Government FPU14/03684Ministerio de Asusntos Economicos y Transformacion Digital CGL2016-81092-R
CGL2017-83538-C3-1-R
CGL2017-90884-REDT
PID2020-120015RB-I00
PID2020.117825GB.C21Junta de Andalucia A-RNM-430-UGR20
P18-RT-3820
P20-00136Horizon 2020 Framework Programme of the European Union 654109European Cooperation in Science and Technology (COST) ES1303
CA18235Erasmus + Programme of the European UnionFundacion Ramon ArecesPolish National Science Centre (NCN) 2021/40/C/ST10/00023Excellence Units Program of the University of Granada
'Programa 7' of 'Plan Propio' of the University of Granad
Methodology for deriving the telescope focus function and its uncertainty for a heterodyne pulsed Doppler lidar
Doppler lidars provide two measured parameters, radial velocity and signal-to-noise ratio, from which winds and turbulent properties are routinely derived. Attenuated backscatter, which gives quantitative information on aerosols, clouds, and precipitation in the atmosphere, can be used in conjunction with the winds and turbulent properties to create a sophisticated classification of the state of the atmospheric boundary layer. Calculating attenuated backscatter from the signal-to-noise ratio requires accurate knowledge of the telescope focus function, which is usually unavailable. Inaccurate assumptions of the telescope focus function can significantly deform attenuated backscatter profiles, even if the instrument is focused at infinity. Here, we present a methodology for deriving the telescope focus function using a co-located ceilometer for pulsed heterodyne Doppler lidars. The method was tested with Halo Photonics StreamLine and StreamLine XR Doppler lidars but should also be applicable to other pulsed heterodyne Doppler lidar systems. The method derives two parameters of the telescope focus function, the effective beam diameter and the effective focal length of the telescope. Additionally, the method provides uncertainty estimates for the retrieved attenuated backscatter profile arising from uncertainties in deriving the telescope function, together with standard measurement uncertainties from the signal-to-noise ratio. The method is best suited for locations where the absolute difference in aerosol extinction at the ceilometer and Doppler lidar wavelengths is small.Peer reviewe
First Ever Observations of Mineral Dust in Wintertime over Warsaw, Poland
The long-range transport of desert dust over the area of the temperate climate zone is associated with the influx of hot air masses due to the location of the sources of this aerosol in the tropical climate zone. Between 24â26 February 2021, such an aerosol outbreak took place and reached Central Europe. The mean temperature of +11.7 °C was recorded during the event. A comparison of this value to the 20-year (2000â2020) average February temperature for Warsaw (â0.2 °C) indicates the uniqueness of the meteorological conditions. It was the first wintertime inflow of Saharan dust over Warsaw, the presence of which was confirmed by lidar and sun-photometer measurements. The properties of the desert dust layers were obtained; the mean values of the particle depolarization for the fully developed mineral dust layer were 13 ± 3% and 22 ± 4% for 355 and 532 nm, respectively. The aerosol optical thickness was high with average values >0.36 for all wavelengths smaller than 500 nm. The three-modal, aerosol size distribution was dominated by coarse-mode particles, with a visible contribution of accumulation-mode particles. It suggests the possible presence of other aerosol types
Dynamics of the Atmospheric Boundary Layer over two middle-latitude rural sites with Doppler lidar
The Atmospheric Boundary Layer (ABL) over two middle-latitude rural sites was characterized in terms of mean
horizontal wind and turbulence sources using a standard classification methodology based on Doppler lidar. The
first location was an irrigated olive orchard in Ăbeda (Southern Spain), representing one of the most important
crops in the Mediterranean basin and a typical site with Mediterranean climate. The second location was PolWET
peatland site in Rzecin (Northwestern Poland), representing one of the largest natural terrestrial carbon storages
that have a strong interaction with the climate system. The results showed typical situations for non cloud-topped
ABL cases, where ABL is fully developed during daytime due to convection, with high turbulent activity and
strong positive skewness indicating frequent and powerful updrafts. The cloud-topped cases showed the strong
influence that clouds can have on ABL development, preventing it to reach the same maximum height and
introducing top-down movements as an important contribution to mixing. The statistical analysis of turbulent
sources allowed for finding a common diurnal cycle for convective mixing at both sites, but nocturnal wind shear
driven turbulence with marked differences in its vertical distribution. This analysis demonstrates the Doppler
lidar measurements and the classification algorithm strong potential to characterize the dynamics of ABL in its
full extent and with high temporal resolution. Moreover, some recommendations for future improvement of the
classification algorithm were provided on the basis of the experience gained.Fundacion Ramon ArecesEuropean Space Agency 4000119961/16/NL/FF/mgPolish National Science Centre (NCN) 2021/40/C/ST10/00023Spanish Government CGL2015-73250-JIN
CGL201681092-R
CGL2017-83538-C3-1-R
CGL2017-90884-REDT
PID2020117825GB-C21
PID2020-120015RB-100Andalusian Regional Government P18-RT-3820FEDER-UGR program ARNM-430-UGR20University of GranadaACTRIS-2 Research Infrastructure Project of the European Union's Horizon 2020 research and innovation program 654109European Cooperation in Science and Technology (COST) CA18235Universidad de Granada/CBU
Wind and Turbulence Statistics in the Urban Boundary Layer over a MountainâValley System in Granada, Spain
Urban boundary layer characterization is currently a challenging and relevant issue, because of its role in weather and air quality modelling and forecast. In many cities, the effect of complex topography at local scale makes this modelling even more complicated. This is the case of mid-latitude urban areas located in typical basin topographies, which usually present low winds and high turbulence within the atmospheric boundary layer (ABL). This study focuses on the analysis of the first ever measurements of wind with high temporal and vertical resolution throughout the ABL over a medium-sized city surrounded by mountains in southern Spain. These measurements have been gathered with a scanning Doppler lidar system and analyzed using the Halo lidar toolbox processing chain developed at the Finnish Meteorological Institute. We have used the horizontal wind product and the ABL turbulence classification product to carry out a statistical study using a two-year database. The data availability in terms of maximum analyzed altitudes for statistically significant results was limited to around 1000â1500 m above ground level (a.g.l.) due to the decreasing signal intensity with height that also depends on aerosol load. We have analyzed the differences and similarities in the diurnal evolution of the horizontal wind profiles for different seasons and their modelling with Weibull and von Mises probability distributions, finding a general trend of mean daytime wind from the NW with mean speeds around 3â4 m/s at low altitudes and 6â10 m/s at higher altitudes, and weaker mean nocturnal wind from the SE with similar height dependence. The highest speeds were observed during spring, and the lowest during winter. Finally, we studied the turbulent sources at the ABL with temporal (for each hour of the day) and height resolution. The results show a clear convective activity during daytime at altitudes increasing with time, and a significant wind-shear-driven turbulence during night-time
Wind and Turbulence Statistics in the Urban Boundary Layer over a MountainâValley System in Granada, Spain
Urban boundary layer characterization is currently a challenging and relevant issue, because of its role in weather and air quality modelling and forecast. In many cities, the effect of complex topography at local scale makes this modelling even more complicated. This is the case of mid-latitude urban areas located in typical basin topographies, which usually present low winds and high turbulence within the atmospheric boundary layer (ABL). This study focuses on the analysis of the first ever measurements of wind with high temporal and vertical resolution throughout the ABL over a medium-sized city surrounded by mountains in southern Spain. These measurements have been gathered with a scanning Doppler lidar system and analyzed using the Halo lidar toolbox processing chain developed at the Finnish Meteorological Institute. We have used the horizontal wind product and the ABL turbulence classification product to carry out a statistical study using a two-year database. The data availability in terms of maximum analyzed altitudes for statistically significant results was limited to around 1000â1500 m above ground level (a.g.l.) due to the decreasing signal intensity with height that also depends on aerosol load. We have analyzed the differences and similarities in the diurnal evolution of the horizontal wind profiles for different seasons and their modelling with Weibull and von Mises probability distributions, finding a general trend of mean daytime wind from the NW with mean speeds around 3â4 m/s at low altitudes and 6â10 m/s at higher altitudes, and weaker mean nocturnal wind from the SE with similar height dependence. The highest speeds were observed during spring, and the lowest during winter. Finally, we studied the turbulent sources at the ABL with temporal (for each hour of the day) and height resolution. The results show a clear convective activity during daytime at altitudes increasing with time, and a significant wind-shear-driven turbulence during night-time
Comparative assessment of GRASP algorithm for a dust event over Granada (Spain) during ChArMEx-ADRIMED 2013 campaign
This work was supported by the Andalusia Regional
Government through project P12-RNM-2409, by the Spanish
Ministry of Economy and Competitiveness through project
CGL2013-45410-R and CGL2016-81092-R and through grant FPI
(BES-2014-068893), by the âJuan de la Cierva-FormaciĂłnâ program
(FJCI-2014-22052) and the Marie SkĆodowska-Curie Individual
Fellowships (IF) ACE_GFAT (grant agreement no. 659398), and
by the University of Granada through âPlan Propio. Programa 9
Convocatoria 2013â. The financial support for EARLINET in the
ACTRIS Research Infrastructure Project by the European Unionâs
Horizon 2020 research and innovation programme through project
ACTRIS-2 (grant agreement no. 654109). The authors thankfully
acknowledge the FEDER program for the instrumentation used in this work and the Sierra Nevada National Park, for its support for
the operation of Cerro Poyos station.
This work is part of the ChArMEx project supported by
ADEME, CEA, CNRS-INSU and Météo- France through the multidisciplinary
programme MISTRALS (Mediterranean Integrated
STudies at Regional And Local Scales). We thank the instrument
scientists, pilots and ground crew of SAFIRE for facilitating the
instrument integration and conducting flight operations. Finally,
the authors would like to acknowledge the use of GRASP inversion
algorithm software (http://www.grasp-open.com) in this work.In this study, vertical profiles and column-integrated aerosol properties retrieved by the GRASP (Generalized Retrieval of Atmosphere and Surface Properties) algorithm are evaluated with in situ airborne measurements made during the ChArMEx-ADRIMED field campaign in summer 2013. In the framework of this campaign, two different flights took place over Granada (Spain) during a desert dust episode on 16 and 17 June. The GRASP algorithm, which combines lidar and sunâsky photometer data measured at Granada, was used to retrieve aerosol properties. Two sun-photometer datasets are used: one co-located with the lidar system and the other in the Cerro Poyos station, approximately 1200 m higher than the lidar system but at a short horizontal distance.
Column-integrated aerosol microphysical properties retrieved by GRASP are compared with AERONET products showing a good agreement. Differences between GRASP retrievals and airborne extinction profiles are in the range of 15 to 30âŻ%, depending on the instrument on board the aircraft used as reference. On 16 June, a case where the dust layer was coupled to the aerosol layer close to surface, the total volume concentration differences between in situ data and GRASP retrieval are 15 and 36âŻ% for Granada and Cerro Poyos retrievals, respectively. In contrast, on 17 June the dust layer was decoupled from the aerosol layer close to the surface, and the differences are around 17âŻ% for both retrievals. In general, all the discrepancies found are within the uncertainly limits, showing the robustness and reliability of the GRASP algorithm. However, the better agreement found for the Cerro Poyos retrieval with the aircraft data and the vertical homogeneity of certain properties retrieved with GRASP, such as the scattering Ă
ngström exponent, for cases with aerosol layers characterized by different aerosol types, shows that uncertainties in the vertical distribution of the aerosol properties have to be considered.
The comparison presented here between GRASP and other algorithms (i.e. AERONET and LIRIC) and with airborne in situ measurements shows the potential to retrieve the optical and microphysical profiles of the atmospheric aerosol properties. Also, the advantage of GRASP versus LIRIC is that GRASP does not assume the results of the AERONET inversion as a starting point
Study of the planetary boundary layer by microwave radiometer, elastic lidar and Doppler lidar estimations in Southern Iberian Peninsula
The Planetary Boundary Layer (PBL) is a relevant part of the atmosphere with a variable extension that clearly plays an important role in fields like air quality or weather forecasting. Passive and active remote sensing systems have been widely applied to analyze PBL characteristics. The combination of different remote sensing techniques allows obtaining a complete picture on the PBL dynamic. In this study, we analyze the PBL using microwave radiometer, elastic lidar and Doppler lidar data. We use co-located data simultaneously gathered in the framework of SLOPE-I (Sierra Nevada Lidar aerOsol Profiling Experiment) campaign at Granada (Spain) during a 90- day period in summer 2016. Firstly, the PBL height (PBLH) obtained from microwave radiometer data is validated against PBLH provided by analyzing co-located radiosondes, showing a good agreement. In a second stage, active remote sensing systems are used for deriving the PBLH. Thus, an extended Kalman filter method is applied to data obtained by the elastic lidar while the vertical wind speed variance method is applied to the Doppler lidar. PBLH's derived by these approaches are compared to PBLH retrieved by the microwave radiometer. The results show a good agreement among these retrievals based on active remote sensing in most of the cases, although some discrepancies appear in instances of intense PBL changes (either growth and/or decrease)
Implementation of UV rotational Raman channel to improve aerosol retrievals from multiwavelength lidar
Vibrational Raman effect is widely used in atmospheric lidar systems, but rotational Raman present several advantages. We have implemented a new setup in the ultraviolet branch of an existing multiwavelength lidar system to collect signal from rotational Raman lines of Oxygen and Nitrogen. We showed that, with an appropriate filter wavelength selection, the systematic error introduced in the particle optical properties due to temperature dependence was less than 4%. With this new setup, we have been able to retrieve aerosol extinction and backscatter coefficients profiles at 355 nm with 1-h time resolution during daytime and up to 1-min time resolution during nighttime.Grupo de FĂsica de la AtmĂłsfera (RNM119