1,721,202 research outputs found
Assessment of the potential role of atmospheric particulate pollution and airborne transmission in intensifying the first wave pandemic impact of SARS-CoV-2/COVID-19 in Northern Italy
Full text linkWater vapor measurements by lidar: Raman and DIAL campaigns
No full textGround-based water vapor measurements by lidar have been performed in Potenza, Southern Italy, by the application of the Raman and the DIAL techniques. Raman measurements have been accomplished through the simultaneous detection of the backscattered radiation in the vibrational Raman bands of water vapor and molecular nitrogen as stimulated by a 355 nm beam, while DIAL measurements at 720 nm have been accomplished by means of a dye laser transmitter. Water vapor measurements in the troposphere up to approximately 10 km above station level have been obtained through the simultaneous application of the Raman and DIAL techniques. Reported measurements have been performed on 18 February 1997, both in the early evening and at night-time. The deviation between DIAL and Raman measurements is found not to exceed 25% up to 7.5 km, while the deviation between Raman and radiosonde data keeps smaller than 20% up to 7 km. The large deviation between Raman and radiosonde data above 7 km is to be attributed to the limited accuracy (dry bias) of the Vaisala humicap sensor at low humidity levels for temperatures below -30°C. A further goal of the presentation is to define a calibration procedure for Raman measurements based on the comparison with simultaneous DIAL measurements. The estimate of the Raman calibration coefficient on the basis of simultaneous and independent water vapor DIAL measurements is more reliable than the traditional approach based on the comparison with radiosonde dat
Principal component analysis approach to evaluate instrument performances in developing a cost-effective reliable instrument network for atmospheric measurements
No full textDeveloping a reliable cost-effective instrument network for data measurement is a challenging task for
agency decisionmakers. A simple way to fully characterize the performances of an instrument that also
considers economical and operational factors—price, maintenance cost, lifetime, etc.—currently does not
exist. Through principal component analysis, a method is developed to build a composite index that assigns a
single score to each instrument, taking into account all the scientific, economic, and operational aspects. This
index will then represent solid help in building and optimizing a cost-effective network, bridging the gap
between two very different worlds: the scientific need for precision and economic constraints
RAMAN LIDAR CHARACTERIZATION OF PBL HEIGHT AND STRUCTURE DURING COPS: COMPARISON BETWEEN DIFFERENT APPROACHES
No full textThe planetary boundary layer includes the portion of the
atmosphere which is directly influenced by the
presence of the Earth's surface. Aerosol particles
trapped within the PBL can be used as tracers to study
boundary-layer vertical structure and time variability.
The PBL height and structure can be estimated based on
the use of Raman lidar data. The method is based on the
first order derivative of the range-corrected elastic
signal (RCS), which is a modified version of the method
defined by Seibert et al. [1] and Sicard et al. [2].
Estimates of the PBL height and structure are obtained
from the above mentioned approach are compared with
simultaneous estimates obtained from potential
temperature profiles determined from the radiosondes
launched simultaneously to lidar operation. Additional
estimates of the boundary layer height are obtained from
rotational Raman lidar signals, used for temperature
measurements signals. Preliminary results and
correlation are illustrated and discussed
Rotational Raman Lidar measurements for the characterization of stratosphere-troposphere exchange mechanisms
No full textA UV Raman lidar system (BASIL) is operational at DIFA-Univ. of Basilicata (Potenza-Italy). The system
was recently involved in LAUNCH 2005 the International Lindenberg campaign for assessment of
humidity and cloud profiling systems and its impact on high-resolution modelling - held from 12
September to 31 October 2005. During this period BASIL collected approx. 250 hours of measurements
distributed over 13 Intensive Observation Periods (IOPs) and 25 days. One specific IOP was
continuously run between 1-3 October 2005, covering a dry stratospheric intrusion episode associated
with a tropopause folding event and the subsequent onset of perturbed weather conditions that leaded
to the development of clouds and precipitations. Tropopause folds are the dominant and most efficient
mechanism of stratosphere-troposphere exchange (STE) in the middle latitudes [1]. Intruding
stratospheric air forms filamentary features in ozone and water vapour profiles [2]. The use of water
vapour to trace intruded stratospheric air allows to clearly identify a dry structure (approx. 1 km thick)
originated in the stratosphere and descending in the free troposphere down to ~ 3 km. A similar feature
is present in the temperature field, with lower temperature values observed within the dry air tongue.
Relative humidity measurements reveal values as small as 0.5-1 % within the intruded air. The
stratospheric origin of the observed dry layer has been verified by the application of a Lagrangian
trajectory model. The subsidence of the intruding heavy dry air is most probably responsible for the
gravity wave activity observed beneath the dry layer. Lidar measurements have been compared with
forecasts from a MM5 mesoscale model. Comparisons in term of water vapour reveal the capability of
the model to forecast the deep penetration into the troposphere of the dry intruded layer. Global and
mesoscale forecasts of potential temperature and potential vorticity are compared with those estimated
from lidar measurements. Comparisons of lidar and model data will be discussed in detail at the
conference. References 1. Holton, J. R., et al., Stratosphere-troposphere exchange, Rev. Geophys., 33,
403439, 1995. 2. Appenzeller, C., and H. C. Davies, Structure of stratospheric intrusions into the
troposphere, Nature, 358, 570 572, 1992
UV Raman lidar measurements of relative humidity for the characterization of aerosol hygroscopicity and cloud microphysical properties
No full textA UV Raman lidar system (BASIL) is operational at DIFA-Univ. of Basilicata (Potenza-Italy). The major feature of
BASIL is its capability to perform high-resolution and accurate measurements of atmospheric temperature, both in
daytime and night-time, based on the application of the rotational Raman lidar technique in the UV [1]. Besides
temperature, BASIL is capable to provide measurements of particle backscatter at 355 and 532 nm, particle extinction at
355 nm, particle depolarization at 355 and water vapour mixing ratio. Relative humidity (RH) measurements are
obtained from simultaneous water vapour mixing ratio and temperature measurements. These parameters represents a
suitable ensemble of measurements for the study of meteorological processes.
Specific case studies are considered and discussed to assess RH lidar measurement capability in presence of aerosols and
clouds. Measurements of aerosol backscatter as a function of relative humidity are illustrated, highlighting the swelling
tendency of hygroscopic aerosol for large relative humidity values (in excess of 80 %). Relative humidity measurements
in the proximity and within cirrus clouds are also illustrated and discussed. Both ice super-saturation and undersaturation
conditions are found inside these clouds, but air is observed to be always under-saturated with respect to water.
The sublimation of the precipitating ice crystals in cirrus clouds is found to cause upper tropospheric humidification, and
lead to increased relative humidity values beneath the clouds
UV Raman Lidar Mesurements of relative Humidity for the Characterization of Aerosol and Cloud Microphysical Properties
No full textThe lidar measurements discussed in this paper were
performed in Potenza (40o38’45”N, 15o48’32” -
Southern Italy) by the DIFA-Univ. of BASILicata
Raman lidar system (BASIL). The major feature of
BASIL is its capability to perform high-resolution and
accurate measurements of atmospheric temperature,
both in daytime and night-time, based on the
application of the rotational Raman lidar technique in
the UV [1]. Besides temperature, BASIL is capable to
provide measurements of particle backscatter at 355
and 532 nm, particle extinction at 355 nm, particle
depolarization at 355 and water vapour mixing ratio
both in daytime and night-time. Relative humidity
measurements are obtained from simultaneous water
vapour and temperature measurements. These
parameters represents a suitable ensemble of
measurements for the study of meteorological
processes.
Specific case studies are considered and discussed to
assess relative humidity lidar measurement capability
in presence of aerosols and clouds. Measurements of
aerosol backscatter as a function of relative humidity
are reported and discussed, highlighting the swelling
tendency of hygroscopic aerosol for large relative
humidity values
Characterization of atmospheric thermodynamic variables by Raman lidar in the frame of the International Network for the Detection of Atmospheric Composition Change - NDACC
Full text linkIn November 2012 the Raman Lidar system BASIL, located at the Univ. of Basilicata (Potenza), was approved to enter in NDACC, with the goal of providing accurate routine measurements of the vertical profiles of atmospheric temperature and water vapour mixing ratio. In this presentation we illustrate and discuss water vapour mixing ratio and temperature measurements carried out during these four years and their comparisons with the radiosondes launched from nearby Institute IMAA-CNR (7 km away)
The Use of Raman Lidar for the Characterization of Convection-related Parameters: Analysis of Selected Case Studies from COPS
No full textAn approach to determine the convective available
potential energy (CAPE) and the convective inhibition
(CIN) based on the use of data from a Raman lidar
system is illustrated in this work. The use of Raman
lidar data allows to provide high temporal resolution
measurements (5 min) of CAPE and CIN and follow
their evolution over extended time periods covering the
full cycle of convective activity. Lidar-based
measurements of CAPE and CIN are obtained from
Raman lidar measurements of the temperature and water
vapour mixing ratio profiles and the surface
measurements of temperature, pressure and dew point
temperature provided by a surface weather station.
The approach is applied to the data collected by the
Raman lidar system BASIL in the frame of COPS.
Attention was focused on 15 July and 25-26 July 2007.
Lidar-based measurements are in good agreement with
simultaneous measurements from radiosondes and with
estimates from different mesoscale models
Multiparameter Raman Lidar Measurements for the Characterization of a Dry Stratospheric Intrusion Event
No full textThe UV Raman lidar system (BASIL), operational at University of Basilicata (Potenza-Italy) and capable to perform high-resolution and accurate measurements of atmospheric temperature and water vapour based on the application of the rotational and vibrational Raman lidar techniques in the UV, was recently involved in the LAUNCH 2005 experiment (International Lindenberg campaign for assessment of humidity and cloud profiling systems and its impact on high-resolution modelling) held from 12 September to 31 October 2005. A thorough description of technical characteristics, measurements capabilities and performances of BASIL is given in the paper. Measurements were continuously run between 1 and 3 October 2005, covering a dry stratospheric intrusion episode associated with a tropopause folding event. The measurements in this paper represent the first simultaneous Raman Lidar measurements of atmospheric temperature and water vapour mixing ratio, and consequently relative humidity, reported for an extensive observation period (32 hours).
The use of water vapour to trace intruded stratospheric air allows to clearly identify a dry structure (approx. 1 km thick) originated in the stratosphere and descending in the free troposphere down to ~ 3 km. A similar feature is present in the temperature field, with lower temperature values detected within the dry air tongue. Relative humidity measurements reveal values as small as 0.5-1 % within the intruded air. The stratospheric origin of the observed dry layer has been verified by the application of a Lagrangian trajectory model. The subsidence of the intruding heavy dry air may be responsible for the gravity wave activity observed beneath the dry layer.
Lidar measurements have been compared with the output of both the PSU/NCAR Mesoscale Model (MM5) and the European Center for Medium range Weather Forecasting (ECMWF) global model. Comparisons in term of water vapour reveal the capability of MM5 to reproduce the dynamical structures associated with the stratospheric intrusion episode and simulate the deep penetration into the troposphere of the dry intruded layer. Moreover, lidar measurements of potential temperature are compared with MM5 output, while potential vorticity from both ECMWF and MM5 is compared with estimates obtained combining MM5 model vorticity and lidar measurements of potential temperature
- …
