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 afternoon–evening 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)

The role of urban boundary layer investigated with high-resolution models and ground-based observations in Rome area: a step towards understanding parameterization potentialities

Abstract. The urban forcing on thermodynamical conditions can greatly influence the local evolution of the atmospheric boundary layer. Heat stored in an urban environment can produce noteworthy mesoscale perturbations of the lower atmosphere. The new generation of high-resolution numerical weather prediction models (NWP) is nowadays often applied also to urban areas. An accurate representation of cities is key role because of the cities' influence on wind, temperature and water vapor content of the planetary boundary layer (PBL). The Advanced Weather Research and Forecasting model WRF (ARW) has been used to reproduce the circulation in the urban area of Rome. A sensitivity study is performed using different PBL and surface schemes. The significant role of the surface forcing in the PBL evolution has been investigated by comparing model results with observations coming from many instruments (lidar, sodar, sonic anemometer and surface stations). The impact of different urban canopy models (UCMs) on the forecast has also been investigated. One meteorological event will be presented, chosen as statistically relevant for the area of interest. The WRF-ARW model shows a tendency to overestimate the vertical transport of horizontal momentum from upper levels to low atmosphere if strong large-scale forcing occurs. This overestimation is partially corrected by a local PBL scheme coupled with an advanced UCM. Moreover, a general underestimation of vertical motions has been verified

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

On the complexity of the boundary layer structure and aerosol vertical distribution in the coastal Mediterranean regions: a case study

The planetary boundary layer structure in the coastal areas, and particularly in complex orography regions such as the Mediterranean, is extremely intricate. In this study, we show the evolution of the planetary boundary layer based on in situ airborne measurements and ground-based remote sensing observations carried out during the MORE (Marine Ozone and Radiation Experiment) campaign in June 2010. The campaign was held in a rural coastal Mediterranean region in Southern Italy. The study focuses on the observations made on 17 June. Vertical profiles of meteorological parameters and aerosol size distribution were measured during two flights: in the morning and in the afternoon. Airborne observations were combined with ground-based LIDAR, SODAR, microwave and visible radiometer measurements, allowing a detailed description of the atmospheric vertical structure. The analysis was complemented with data from a regional atmospheric model run with horizontal resolutions of 12, 4 and 1 km, respectively; back-trajectories were calculated at these spatial resolutions. The observations show the simultaneous occurrence of dust transport, descent of mid-tropospheric air and sea breeze circulation on 17 June. Local pollution effects on the aerosol distribution, and a possible event of new particles formation were also observed. A large variability in the thermodynamical structure and aerosol distribution in the flight region, extending by approximately 30km along the coast, was found. Within this complex, environment-relevant differences in the back-trajectories calculated at different spatial resolutions are found, suggesting that the description of several dynamical processes, and in particular the sea breeze circulation, requires high-resolution meteorological analyses. The study also shows that the integration of different observational techniques is needed to describe these complex conditions; in particular, the availability of flights and their timing with respect to the occurring phenomena are crucial

Magnetoacoustic Portals and the Basal Heating of the Solar Chromosphere

We show that inclined magnetic field lines at the boundaries of large-scale convective cells (supergranules) provide "portals" through which low-frequency ( 5 mHz) acoustic waves, which are believed to provide the dominant source of wave heating of the chromosphere. This result opens up the possibility that low-frequency magnetoacoustic waves provide a significant source of energy for balancing the radiative losses of the ambient solar chromosphere

Oscillator strengths for transitions to Rydberg levels in 12C16O^{12}C^{16}O, 13C16O^{13}C^{16}O and 13C18O^{13}C^{18}O between 967 and 972 A

Absorption oscillator strengths have been determined from high-resolution spectra in the 967-972 \AA region of three CO isotopomers for transitions to the Rydberg levels 4{\it p$\pi$}(0), 3{\it d$\pi$}(1) and 4{\it p$\sigma$}(0), as well as to the mixed {\it E(6)} level recently characterized by Eidelsberg et al. (2004). Synchrotron radiation from the Super-ACO electron storage ring at Orsay (LURE) was used as a light source. Oscillator strengths were extracted from the recorded spectra by least-squares fitting of the experimental profiles with synthetic spectra taking into account the homogeneous and heterogeneous interactions of the four levels. Column densities were derived from fits to the 3{\it p$\pi$}(0) absorption band whose oscillator strength is well established. These are the first reported measurements for $^{13}$C$^{18}$O. For $^{12}$C$^{16}$O, our results are consistent with the larger values obtained in the most recent laboratory and astronomical studies.Comment: 9 pages 7 figures 3 tables. Accepted in A&A, date of acceptance 11/05/200

The impact of the mixing properties within the Antarctic stratospheric vortex on ozone loss in spring

Calculations of equivalent length from an artificial advected tracer provide new insight into the isentropic transport processes occurring within the Antarctic stratospheric vortex. These calculations show two distinct regions of approximately equal area: a strongly mixed vortex core and a broad ring of weakly mixed air extending out to the vortex boundary. This broad ring of vortex air remains isolated from the core between late winter and midspring. Satellite measurements of stratospheric H2O confirm that the isolation lasts until at least mid-October. A three-dimensional chemical transport model simulation of the Antarctic ozone hole quantifies the ozone loss within this ring and demonstrates its isolation. In contrast to the vortex core, ozone loss in the weakly mixed broad ring is not complete. The reasons are twofold. First, warmer temperatures in the broad ring prevent continuous polar stratospheric cloud (PSC) formation and the associated chemical processing (i.e., the conversion of unreactive chlorine into reactive forms). Second, the isolation prevents ozone-rich air from the broad ring mixing with chemically processed air from the vortex core. If the stratosphere continues to cool, this will lead to increased PSC formation and more complete chemical processing in the broad ring. Despite the expected decline in halocarbons, sensitivity studies suggest that this mechanism will lead to enhanced ozone loss in the weakly mixed region, delaying the future recovery of the ozone hole

Lidar in Space Technology Experiment correlative measurements by lidar in Potenza, southern Italy.

An intensive lidar measurement campaign was carried out in Potenza (40°36′N-15°44′E, 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 0.72–0.81 at 355 nm and 0.88–0.93 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

Cobalt oxide nanoparticles induce oxidative stress and alter electromechanical function in rat ventricular myocytes

Background: Nanotoxicology is an increasingly relevant field and sound paradigms on how inhaled nanoparticles (NPs) interact with organs at the cellular level, causing harmful conditions, have yet to be established. This is particularly true in the case of the cardiovascular system, where experimental and clinical evidence shows morphological and functional damage associated with NP exposure. Giving the increasing interest on cobalt oxide (Co3O4) NPs applications in industrial and bio-medical fields, a detailed knowledge of the involved toxicological effects is required, in view of assessing health risk for subjects/workers daily exposed to nanomaterials. Specifically, it is of interest to evaluate whether NPs enter cardiac cells and interact with cell function. We addressed this issue by investigating the effect of acute exposure to Co3O4-NPs on excitation-contraction coupling in freshly isolated rat ventricular myocytes. Results: Patch clamp analysis showed instability of resting membrane potential, decrease in membrane electrical capacitance, and dose-dependent decrease in action potential duration in cardiomyocytes acutely exposed to Co3O4-NPs. Motion detection and intracellular calcium fluorescence highlighted a parallel impairment of cell contractility in comparison with controls. Specifically, NP-treated cardiomyocytes exhibited a dose-dependent decrease in the fraction of shortening and in the maximal rate of shortening and re-lengthening, as well as a less efficient cytosolic calcium clearing and an increased tendency to develop spontaneous twitches. In addition, treatment with Co3O4-NPs strongly increased ROS accumulation and induced nuclear DNA damage in a dose dependent manner. Finally, transmission electron microscopy analysis demonstrated that acute exposure did lead to cellular internalization of NPs. Conclusions: Taken together, our observations indicate that Co3O4-NPs alter cardiomyocyte electromechanical efficiency and intracellular calcium handling, and induce ROS production resulting in oxidative stress that can be related to DNA damage and adverse effects on cardiomyocyte functionality

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