202 research outputs found
Characterization of the planetary boundary layer height and structure by Raman lidar: comparison of different approaches
Abstract. The planetary boundary layer (PBL) 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 the boundary-layer vertical structure and time variability. As a result of this, elastic backscatter signals collected by lidar systems can be used to determine the height and the internal structure of the PBL. The present analysis considers three different methods to estimate the PBL height. The first method is based on the determination of the first-order derivative of the logarithm of the range-corrected elastic lidar signals. Estimates of the PBL height for specific case studies obtained through this approach are compared with simultaneous estimates from the potential temperature profiles measured by radiosondes launched simultaneously to lidar operation. Additional estimates of the boundary layer height are based on the determination of the first-order derivative of the range-corrected rotational Raman lidar signals. This latter approach results to be successfully applicable also in the afternoonâevening decaying phase of the PBL, when the effectiveness of the approach based on the elastic lidar signals may be compromised or altered by the presence of the residual layer. Results from these different approaches are compared and discussed in the paper, with a specific focus on selected case studies collected by the University of Basilicata Raman lidar system BASIL during the Convective and Orographically-induced Precipitation Study (COPS)
Helioseismic Mapping of the Magnetic Canopy in the Solar Chromosphere
We determine the three-dimensional topography of the magnetic canopy in and around active regions by mapping the propagation behavior of high-frequency acoustic waves in the solar chromosphere
Enrichment of CH3F nuclear spin isomers by resonant microwave radiation
Theoretical model of the coherent control of nuclear spin isomers by
microwave radiation has been developed. Model accounts the M-degeneracy of
molecular states and molecular center-of-mass motion. The model has been
applied to the 13CH3F molecules. Microwave radiation excites the para state
(J=11,K=1) which is mixed by the nuclear spin-spin interaction with the ortho
state (9,3). Dependencies of the isomer enrichment and conversion rates on the
radiation frequency have been calculated. Both spectra consist of two
resonances situated at the centers of allowed and forbidden (by nuclear spin)
transitions in the molecule. Larger enrichment, up to 7%, can be produced by
strong radiation resonant to the forbidden transition. The spin conversion rate
can be increased by 2 orders of magnitude at this resonance.Comment: REVTEX, 14 pages + 6 eps figure
Lidar in Space Technology Experiment correlative measurements by lidar in Potenza, southern Italy.
An intensive lidar measurement campaign was carried out in Potenza (40°36âČN-15°44âČE, 820 m above sea level (asl)) in conjunction with the Lidar in Space Technology Experiment (LITE) mission and primarily aimed at the validation of LITE stratospheric aerosol measurements. Potenza lidar measurements in coincidence with all five nighttime overpasses near southern Italy (September 11, 12, 17, and 18, 1994) are compared with simultaneous LITE data. Potenza lidar data appear to be highly correlated with LITE data both at 355 and 532 nm. Potenza lidar versus LITE measurements of the aerosol-scattering ratio show a correlation coefficient of 0.72â0.81 at 355 nm and 0.88â0.93 at 532 nm, with an average calibration coefficient of 0.92 ± 0.19 at 355 nm and 1.02 ± 0.07 at 532 nm. Comparisons are also made in terms of the average Angstrom coefficient, whose values are consistent with submicrometer aerosol particles. Finally, Potenza lidar measurements of the aerosol layer base and top heights, the peak aerosol-scattering ratio and peak height, as well as of the aerosol scattering ratio at the cloud base appear to be consistent with measurements performed by other ground lidar stations in Europe during the LITE campaign as well as with the LITE data
Observations of surface radiation and stratospheric processes at Thule Air Base, Greenland, during the IPY
Ground-based measurements of atmospheric parameters have been carried
out for more than 20 years at the Network for the Detection of Atmospheric
Composition Change (NDACC) station at Thule Air Base
(76.5°N, 68.8°W), on the north-western coast of Greenland. Various instruments
dedicated to the study of the lower and middle polar atmosphere
are installed at Thule in the framework of a long standing
collaboration among Danish, Italian, and US research institutes and universities.
This effort aims at monitoring the composition, structure and
dynamics of the polar stratosphere, and at studying the Arctic energy
budget and the role played by different factors, such as aerosols, water
vapour, and surface albedo. During the International Polar Year (IPY),
in winter 2008-2009, an intensive measurement campaign was conducted
at Thule within the framework of the IPY project âOzone layer and UV
radiation in a changing climate evaluated during IPYâ (ORACLE-O3)
which sought to improve our understanding of the complex mechanisms
that lead to the Arctic stratospheric O3 depletion. The campaign involved
a lidar system, measuring aerosol backscatter and depolarization ratios
up to 35 km and atmospheric temperature profiles from 25 to 70 km altitude,
a ground-based millimeter-wave spectrometer (GBMS) used to derive
stratospheric mixing ratio profiles of different chemical species
involved in the stratospheric ozone depletion cycle, and then ground-based
radiometers and a Cimel sunphotometer to study the Arctic radiative
budget at the surface. The observations show that the surface radiation
budget is mainly regulated by the longwave component throughout most
of the year. Clouds have a significant impact contributing to enhance the
role of longwave radiation. Besides clouds, water vapour seasonal changes produce the largest modification in the shortwave component at the surface,
followed by changes in surface albedo and in aerosol amounts. For
what concerns the middle atmosphere, during the first part of winter
2008-2009 the cold polar vortex allowed for the formation of polar stratospheric
clouds (PSCs) which were observed above Thule by means of the
lidar. This period was also characterized by GBMS measurements of low
values of O3 due to the catalytic reactions prompted by the PSCs. In mid-
January, as the most intense Sudden Stratospheric Warming event ever
observed in the Arctic occurred, GBMS and lidar measurements of O3,
N2O, CO and temperature described its evolution as it propagated from
the upper atmosphere to the lower stratosphere
Characterization of atmospheric aerosol optical properties based on the combined use of a ground-based Raman lidar and an airborne optical particle counter in the framework of the Hydrological Cycle in the Mediterranean Experiment â Special Observation Period 1
Vertical profiles of the particle backscattering coefficient
at 355, 532 and 1064 nm measured by the University of Basilicata Raman
lidar system (BASIL) have been compared with simulated particle backscatter profiles obtained through a Mie
scattering code based on the use of simultaneous and almost co-located
profiles provided by an airborne optical particle counter. Measurements
were carried out during dedicated flights of the French research aircraft
ATR42 in the framework of the European Facility for Airborne Research (EUFAR)
project âWaLiTempâ, as part of the Hydrological Cycle in the Mediterranean
Experiment â Special Observation Period 1 (HyMeX-SOP1). Results from two
selected case studies are reported and discussed in the paper, and a dedicated analysis approach is illustrated and applied to the
dataset. Results reveal a good agreement between measured and simulated
multi-wavelength particle backscattering profiles. Specifically, simulated
and measured particle backscattering profiles at 355 and 532 nm for the second case study are found to
deviate less than 15 % (mean value =5.9 %) and 50 % (mean
value =25.9 %), respectively, when considering the presence of a
continentalâurban aerosol component, while slightly larger deviation values are found for the first study. The reported good agreement between
measured and simulated multi-wavelength particle backscatter profiles
testifies to the ability of multi-wavelength Raman lidar systems to infer
aerosol types at different altitudes.</p
Inflammatory cells and mediators in bronchial lavage of patients with chronic obstructive pulmonary disease
Cigarette smoking is the most important cause of chronic obstructive pulmonary disease (COPD). Although the precise sequence of events that leads a smoker to experience airway obstruction is not completely clear, airway inflammation is a relevant factor. To investigate airway inflammation, 12 nonatopic smoking COPD patients with a forced expiratory volume in one second (FEV1
A realistic example of chaotic tunneling: The hydrogen atom in parallel static electric and magnetic fields
Statistics of tunneling rates in the presence of chaotic classical dynamics
is discussed on a realistic example: a hydrogen atom placed in parallel uniform
static electric and magnetic fields, where tunneling is followed by ionization
along the fields direction. Depending on the magnetic quantum number, one may
observe either a standard Porter-Thomas distribution of tunneling rates or, for
strong scarring by a periodic orbit parallel to the external fields, strong
deviations from it. For the latter case, a simple model based on random matrix
theory gives the correct distribution.Comment: Submitted to Phys. Rev.
Spectrally resolved observations of atmospheric emitted radiance in the H2O rotation band
This paper presents the project Earth Cooling by Water
Vapor Radiation, an observational programme, which aims at
developing a database of spectrally resolved far infrared
observations, in atmospheric dry conditions, in order to
validate radiative transfer models and test the quality of water
vapor continuum and line parameters. The project provides
the very first set of far-infrared spectral downwelling
radiance measurements, in dry atmospheric conditions,
which are complemented with Raman Lidar-derived
temperature and water vapor profiles
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