Top PDF A new airborne Polar Nephelometer for the measurement of optical and microphysical cloud properties. Part II: Preliminary tests

A new airborne Polar Nephelometer for the measurement of optical and microphysical cloud properties. Part II: Preliminary tests

A new airborne Polar Nephelometer for the measurement of optical and microphysical cloud properties. Part II: Preliminary tests

discuss now results obtained in a cold chamber. Figure 14 displays a sketch of the apparatus. The cold chamber consists of a freezer in which the temperature can be lowered to about )30 °C near the ¯oor. Inside the cold chamber, the ASSP probe has been mounted and the Polar Nephelometer was installed with a special inlet on the roof of the chamber. An aspirator installed at the rear of the Polar Nephelometer provides the air circulation which is ®rst cooled in the cooling room. The cold air then reaches the cloud room and is sucked into the probe inlets. The experimental procedure is to put a source of hot water in the cloud room. This induces the condensation of water droplets which are monitored with the ASSP measurements. The hot-water source is then removed and the water droplet cloud is seeded by silver iodide nuclei which provokes a rapid glaciation of the cloud by Findeisen-Bergeron e€ect. At the same time the Polar Nephelometer is operated and the measure- ments are recorded at 10 Hz. The size and shape of the produced ice crystals are measured by capture on slides coated with a solution of Formvar plastic in chloroform. Then, photographs of the slides are taken. Figure 15 gives an example of such a slide photograph which exhibits the presence of hexagonal ice crystals with a mean size of 20±30 lm. The smallest particles sampled at the beginning of the seeding were about 5 lm diam- eter. Figure 16 displays a typical example of the scattering phase function measured during the sampling of ice crystals. The results evidence the 22° halo which characterizes the scattering phase function of hexagonal ice crystals as theoretically displayed in Fig. 16 (Liou, 1986). Compared to the theoretical curve, the measured phase function exhibits a halo which is less pronounced and a lower scattering near the forward and side di- rections, respectively. Several explanations can be hypothesized to explain these di€erences:
Mostrar mais

11 Ler mais

A new airborne polar Nephelometer for the measurements of optical and microphysical cloud properties. Part I: Theoretical design

A new airborne polar Nephelometer for the measurements of optical and microphysical cloud properties. Part I: Theoretical design

P3) operating at k ˆ 785 nm. The chip temperature of the laser diode is regulated by a Peltier element in order to maintain a constant wavelength. The laser beam is routed via an optic fibre to an optical system providing a collimated beam (5 mm diameter) with a divergence lower than 13 mrad and an output power of 1.0 W (the beam intensity can be varied by setting the laser power). The beam is not polarized in the present prototype version. The paraboloidal mirror (Melles Griot product number 02 RPM 017, focal distance: 33 mm) is drilled with holes (8 mm diameter) for laser-beam entrance and exit. The reflector surface is coated with electrolytically deposited rhodium which is particularly resistant to oxidation. Rhodium has a reflectance of 80% for visible wavelengths. A light trap is placed close to the beam exit hole to avoid reflection of the incident laser beam from any surface.
Mostrar mais

9 Ler mais

Microphysical and optical properties of Arctic mixed-phase clouds. The 9 April 2007 case study.

Microphysical and optical properties of Arctic mixed-phase clouds. The 9 April 2007 case study.

This paper focusses on observations obtained from a com- bination of instruments installed onboard the Polar-2 aircraft operated by the Alfred Wegener Institute for Polar and Ma- rine Research (AWI). These instruments include: a Polar Nephelometer (Gayet et al., 1997), a Cloud Particle Imager (CPI, Lawson et al., 2001) as well as standard Forward Scat- tering Spectrometer Probe (FSSP-100) to measure cloud par- ticle properties in terms of scattering, morphology and size, and in-cloud partitioning of ice/water content. Remote sens- ing measurements were obtained onboard the Polar-2 aircraft from the Airborne Mobile Aerosol Lidar (AMALi, Stach- lewska et al., 2004) and the Spectral Modular Airborne Radi- ation measurement sysTem (SMART, Wendisch et al., 2001). The paper describes in detail the microphysical and op- tical properties of a mixed-phase boundary-layer cloud ob- served on 9 April 2007. A unique set of concomitant obser- vations is used for this description, including detailed in situ measurements along with airborne remote sensing observa- tions and co-located spaceborne remote sensing data (Lidar on CALIPSO and radar on CloudSat satellites). Observations are then compared to European Centre for Medium-Range Weather Forecasts (ECMWF) analyses.
Mostrar mais

15 Ler mais

Chemical composition and sources of coastal marine aerosol particles during the 2008 VOCALS-REx campaign

Chemical composition and sources of coastal marine aerosol particles during the 2008 VOCALS-REx campaign

AC concentrations of these five species are plotted analo- gously, but with RH shown to identify recent contact with the surface (Fig. 5). All of the box plots in this work show the median and the inner quartiles by the center, bottom, and top cross bars of the rectangular boxes, and the 5 % and 95 % ranges by the whiskers. To present data patterns in a continu- ous fashion, to facilitate comparisons, we also include Lo- cally Weighted Scatter Smoothing (LOWESS) (Cleveland, 1979) lines as proxies for median values. The good agree- ment between these two approaches can be seen in Figs. 5 and 6 where the LOWESS lines are overlaid on the box plots. The LOWESS fits for BC concentrations of SO 2− 4 , NH + 4 , Org, and NO − 3 (Fig. 4) exhibit pronounced longitudinal gra- dients with concentrations lower offshore than near the coast. In contrast, the median of SSA represented by Na + , exhibits a rather uniform longitudinal distribution, increasing slightly offshore. These gradients are consistent with a continental source for SO 2− 4 , NH + 4 , Org, and NO − 3 . The median AC con- centrations of SO 2− 4 and NH + 4 (Fig. 5) also exhibited a land- to-sea gradient, showing the influence of nearby terrestrial sources, likely in Chile and Peru (Allen et al., 2011). Higher AC concentrations of SO 2− 4 , NH + 4 , as well as Org, near the coast (east of ∼ 73 ◦ W) were associated with moist air (RH
Mostrar mais

16 Ler mais

Theoretical study of solar light reflectance from vertical snow surfaces

Theoretical study of solar light reflectance from vertical snow surfaces

Optical measurements are commonly used to derive snow microphysical parameters from plane-parallel snow layers (Kokhanovsky et al., 2011). In particular, snow grain size is obtained from near-infrared (NIR) measurements (in the spectral range 865–1240 nm) of intensity of solar light re- flected from flat snow layers. The corresponding retrieval al- gorithms are based upon the physical phenomenon of the en- hancement of light absorption by larger ice grains (and as a consequence, a smaller light reflectance for snow layers with larger grains). The main problem with such a method is that only upper snow layers can be observed. The information on the snow microphysical parameters and snow pollution in deeper layers cannot be retrieved because of high absorp- tion of NIR radiation by snow grains. As a matter of fact, NIR
Mostrar mais

10 Ler mais

Polaritons in multilayer semiconductor structures

Polaritons in multilayer semiconductor structures

Polariton is a mixed quasiparticle formed by a photon and a crystal excitation, like, for ex- ample, phonons, plasmons or excitons. Polaritons can be formed in bulk crystals, at their surfaces, in quantum confined structures and microcavities [1]. Their characteristic feature is the strong coupling of an electromagnetic (EM) wave to the crystal excitation carrying an electric or magnetic dipole excitation. According to the type of this excitation one can distin- guish phonon-polaritons, plasmon-polaritons, exciton-polations, etc. The term "polariton" was proposed by J. Hopfield, [2], although the strong coupling between excitations and light in polar semiconductors had been considered earlier by K. B. Tolpygo [3], where the mixed quasiparticles were named "light-exciton". The exciton-polaritons are probably the most ex- tensively studied type of polaritons. Among their interesting properties is the experimentally observed Bose-Einstein condensation [1], due to the fact that it occurs at much higher tem- peratures than the same phenomenon in atomic vapors. Furthermore, a new type of laser, which is usually called polariton laser, has been demonstrated. Plasmon-polaritons, more specifically the surface plasmon-polaritons (SPPs), involve free electron oscillations instead of excitons. SPPs are evanescent EM waves coupled to the free electron plasma, propagating along the surface of a conductor. If the conductor is a metal with a typical free electron con- centration of the order of 10 22 cm −3 , the characteristic plasma frequency is the higher than
Mostrar mais

106 Ler mais

Assessing regional scale predictions of aerosols, marine stratocumulus, and their interactions during VOCALS-REx using WRF-Chem

Assessing regional scale predictions of aerosols, marine stratocumulus, and their interactions during VOCALS-REx using WRF-Chem

Reproducing CCN gradients and including coupled cloud- aerosol-radiation processes are important to properly sim- ulate the marine stratocumulus over the SEP. This pa- per shows the improvement gained in using an interactive aerosol-cloud-radiation module in the chemistry version of the Weather Research and Forecasting (WRF-Chem) model (Grell et al., 2005; Fast et al., 2006). Specifically, a new cou- pling between the double-moment Morrison microphysics scheme (Morrison et al., 2005, 2009) and the aerosol mod- ules is used; we implemented this coupling in the April 2011 v3.3 release of WRF-Chem. The VAMOS Ocean-Cloud- Atmosphere-Land Study Regional Experiment (VOCALS- REx) was a field campaign during October and November 2008 designed to improve the scientific understanding of model simulations and predictions of the coupled climate system over the SEP (Wood et al., 2011b). The campaign provided extensive measurements for evaluating the capabil- ity of our model with the aforementioned new coupling in predicting aerosol and marine stratus clouds over this region. A recent modeling exercise by Abel et al. (2010) using the UK Met Office Unified Model (MetUM) is parallel to this model evaluation study. MetUM simulated a good rep- resentation of synoptically induced variability in cloud cover and boundary layer depth during the VOCALS-REx (Abel et al., 2010). However, the exclusion of cloud-aerosol interac- tions and the model’s relatively simple parameterization of cloud-microphysical effects (Toniazzo et al., 2011) are likely to preclude better agreement with field observations.
Mostrar mais

25 Ler mais

Sky cover from MFRSR observations: cumulus clouds

Sky cover from MFRSR observations: cumulus clouds

servations by offering an opportunity to sample the fractional sky cover of optically thin clouds with small horizontal size, such as shallow cumulus clouds. Thus, the worldwide deployed MFRSRs can supply an integrated dataset of the water vapor, aerosol and cloud properties, and unique MFRSR-based datasets could be developed for different locations. Such datasets together with others from ground- and satellite-based ob-

21 Ler mais

The Impact of the Expansion of the Bolsa Familia Program on the Time Allocation of Youths And Their Parents Lia Chitolina Miguel Nathan Foguel Naercio Menezes-Filho

The Impact of the Expansion of the Bolsa Familia Program on the Time Allocation of Youths And Their Parents Lia Chitolina Miguel Nathan Foguel Naercio Menezes-Filho

As the multinomial model is non-linear, the marginal effect of the treatment in a DID model is not the marginal impact of the interaction between time and treatment, but the difference of the cross-differences, as described by Puhani (2012). The results of Table 7 (in terms of marginal effects) show that the BVJ has a significant effect on the probability studying and working at the same time, but not on the other outcome variables. The estimated marginal effects mean that the probability of a youngster studying and working increases by 4.2 percentage points with the BVJ, compared with a baseline of 30% in the control group in 2006. The estimated coefficients for the categories ‘studying only’ and ‘working only’ were negative but not statistically significant. It seems, therefore, that treated adolescents do not quit their jobs to study because of the program, but do both activities at the same time. This raises questions about the long run impacts of the program, since the quality of the night classes is notoriously low in Brazil.
Mostrar mais

39 Ler mais

The comparison of the structure and microhardness of the tool steel C90 and HS 6-5-2 remelted with the electric arc

The comparison of the structure and microhardness of the tool steel C90 and HS 6-5-2 remelted with the electric arc

The examination of the structure and microhardness of surface layer of C90 non-alloy steel and HS 6-5-2 high speed steel after electric arc treatment are presented in the paper. The comparison has been presented due to the similar content of the carbon in both steels. The structure of the remelted zone of the steel C90 before the conventional tempering consists of the cells, dendritic cells surrounded with the cementite, there is a plate martensite and retained austenite inside them, whereas the structure of the steel HS 6-5-2 is consistuted with cells, dendritic cells and dendrites surrounded with the eutectic system, inside of which there is a plate martensite and retained austenite. Such structure is characterized by the similar microhardness (790-800 HV0,065) and intensity of the tribiological wear. The tempering causes the decrease of the microhardness in non-alloy steel and the increase of the microhardness in high speed steel.
Mostrar mais

4 Ler mais

Development of prognostic aerosol–cloud interactions combining a chemistry transport model and a regional climate model

Development of prognostic aerosol–cloud interactions combining a chemistry transport model and a regional climate model

Hirtl, M., Joffre, S., Jorba, O., Kaas, E., Kaasik, M., Kallos, G., Kong, X., Korsholm, U., Kur- ganskiy, A., Kushta, J., Lohmann, U., Mahura, A., Manders-Groot, A., Maurizi, A., Mous- siopoulos, N., Rao, S. T., Savage, N., Seigneur, C., Sokhi, R. S., Solazzo, E., Solomos, S., Sørensen, B., Tsegas, G., Vignati, E., Vogel, B., and Zhang, Y.: Online coupled regional me- teorology chemistry models in Europe: current status and prospects, Atmos. Chem. Phys.,

37 Ler mais

Estimating cloud optical thickness and associated surface UV irradiance from SEVIRI by implementing a semi-analytical cloud retrieval algorithm

Estimating cloud optical thickness and associated surface UV irradiance from SEVIRI by implementing a semi-analytical cloud retrieval algorithm

(i.e., cloud-free) spectral albedo and the retrieval of the cloud water phase from re- flectance ratios in SEVIRI’s 0.6 µm and 1.6 µm spectral bands. The SACURA scheme is then applied to daytime SEVIRI imagery over Europe, for the month of June 2006, at 15-min time increments. The resulting SCOT fields are compared with values obtained by the CloudSat experimental satellite mission, yielding a negligible bias, correlation

31 Ler mais

Evaluation of cloud fraction and its radiative effect simulated by IPCC AR4 global models against ARM surface observations

Evaluation of cloud fraction and its radiative effect simulated by IPCC AR4 global models against ARM surface observations

Three dimensional general circulation models (GCMs) are probably the most powerful tools currently available to quan- titatively investigate the Earth’s climate system and to predict future climate change, which is affected by human activities that cause changes in greenhouse gases, aerosols, and land use and land cover (IPCC, 2007). From a physical point of view, anthropogenic climate change is first of all a perturba- tion of the Earth’s radiation balance (Wild, 2008). Realistic simulation by GCMs of the perturbations of radiative forc- ing is an important pre-requisite for projecting reliable fu- ture climate responses. As Webb et al. (2001) emphasize: “If we are to have confidence in predictions from climate mod- els, a necessary (although not sufficient) requirement is that they should be able to reproduce the observed present-day distribution of clouds and their associated radiative fluxes”. Many previous studies have evaluated GCMs’ performance in simulating shortwave (SW) and longwave (LW) radiation under cloudy and cloudless skies at the surface, where global ground radiation measurement networks are available, and/or at the top of atmosphere (TOA), where satellite observations can be used as constraints (e.g. Garratt, 1994; Wild et al., 1995, 1998, 2008; Li et al., 1997; Walsh et al., 2008). These studies found that GCMs were better at producing the mean TOA radiation budget than the surface radiation budget, al- though there were significant biases and inter-model vari- ability in estimating the SW and LW radiation in particular regions (Wild and Liepert, 1998; Wild et al., 1999, 2005; Walsh et al., 2008; Wild, 2008). Although in some cases good agreement was found between the observed and mod- eled cloud radiative forcing, that could be a result of compen- sating errors in either cloud vertical structure, cloud optical depth or cloud fraction (Potter and Cess, 2004).
Mostrar mais

26 Ler mais

Model of knowledge representation about materials in the form of a relational database for CAPCAST system

Model of knowledge representation about materials in the form of a relational database for CAPCAST system

is the customer who gives the technical specification of the prod- uct and it is the customer who has to decide whether he can or cannot accept the price dictated by the manufacturer. Based on these restrictions, it is now the manufacturer who must decide whether he is able to execute the order (within the deadline ap- pointed and using the available facilities) and what will be the price of the product as dictated by the cost of production. Improv- ing the procedure of production costs estimation should improve the contract negotiations and make them more efficient. On the other hand, estimating the cost of production involves, among others, also the need to determine the type of material and treat- ment. The manufacturer can choose what materials he will use for the product and at what price, providing he can check which
Mostrar mais

6 Ler mais

The time-space exchangeability of satellite retrieved relations between cloud top temperature and particle effective radius

The time-space exchangeability of satellite retrieved relations between cloud top temperature and particle effective radius

Convective cloud development can be viewed as consecutive towers that dissipate or merge with previous cloud elements, and new towers replace them and develop some more, and so on until a fully-grown Cb cluster is formed in some cases, or in other cases the clouds dissipate before reaching that stature. The approach that was taken for the cloud tracking was to look for local minima of the temperature field in the cloudy pixels in each time step, and then to track these lo- cal minima from one time step to the next based on the cell
Mostrar mais

8 Ler mais

A statistical subgrid-scale algorithm for precipitation formation in stratiform clouds in the ECHAM5 single column model

A statistical subgrid-scale algorithm for precipitation formation in stratiform clouds in the ECHAM5 single column model

Cole, J. N. S., Del Genio, A. D., Falk, M., Foster, M. J., Fridlind, A., Golaz, J.-C., Hashino, T., Harrington, J. Y., Hoose, C., Khairoutdinov, M. F., Larson, V. E., Liu, X., Luo, Y., McFar- quhar, G. M., Menon, S., Neggers, R. A. J., Park, S., Poellot, M. R., Schmidt, J. M., Sednev, I., Shipway, B. J., Shupe, M. D., Spangenberg, D. A., Sud, Y. C., Turner, D. D., Veron, D. E., von Salzen, K., Walker, G. K., Wang, Z., Wolf, A. B., Xie, S., Xu, K.-M., Yang, F., and

40 Ler mais

The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI): a new tool for aerosol and cloud remote sensing

The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI): a new tool for aerosol and cloud remote sensing

Randall, D. A., Wood, R. A., Bony, S., Colman, R., Fichefet, T., Fyfe, J., Kattsov, V., Pitman, A., Shukla, J., Noda, A., Srinivasan, J., Stouffer, R. J., Sumi A., and Taylor, K. E.: Climate models and their evaluation, In Climate change 2007: The Physical Science Basis, Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Solomon, S., Qin, D., Manning, M., Chen, Z., Marquis, M., Averyt, K. B.,

53 Ler mais

The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI): a new tool for aerosol and cloud remote sensing

The Airborne Multiangle SpectroPolarimetric Imager (AirMSPI): a new tool for aerosol and cloud remote sensing

The butcher-block filter assembly makes use of high opti- cal density black epoxy between the spectral filters for stray light reduction. This assembly was bonded to a fused sil- ica substrate containing patterned WGPs in the polarization channels. Moxtek, Inc. supplied the WGPs. Application of a cement bond to the WGPs results in reduced transmittance T and polarization extinction ratio ε (ratio of transmittance of the polarization state aligned with polarizer to the transmit- tance for the orthogonal state) relative to their pre-bond val- ues. The use of high-contrast WGP stock results in post-bond T exceeding 75 % and ε values between 40 and 100, depend- ing on channel. These parameters affect the magnitude of the modulation pattern from the PEMs. As discussed in Diner et al. (2010), the systematic reduction in magnitude of the mod- ulation pattern due to imperfect T and ε is corrected by in- strument polarimetric calibration, though with increased sen- sitivity to random noise. For the worst-case values of T and ε relevant to AirMSPI, the corresponding reduction in signal- to-noise ratio (SNR) introduces a random error in DOLP of less than ±0.0009. A Mueller Matrix Imaging Polarimeter (MMIP) at the University of Arizona was used for inspection and characterization of the spectropolarimetric filter compo- nents. Alignment and bonding of the filter to the silicon com- plementary metal oxide semiconductor (Si-CMOS) imager was done at the Jet Propulsion Laboratory (JPL). The com- posite filter assembly is situated above the detector array in the camera focal plane. The precision positioning equipment used to accomplish this step is able to ensure alignment to within ±2 µm over the 17 mm length of the filter.
Mostrar mais

19 Ler mais

First correlated measurements of the shape and light scattering properties of cloud particles using the new Particle Habit Imaging and Polar Scattering (PHIPS) probe

First correlated measurements of the shape and light scattering properties of cloud particles using the new Particle Habit Imaging and Polar Scattering (PHIPS) probe

Abstract. Studying the radiative impact of cirrus clouds re- quires knowledge of the relationship between their micro- physics and the single scattering properties of cloud parti- cles. Usually, this relationship is obtained by modeling the optical scattering properties from in situ measurements of ice crystal size distributions. The measured size distribution and the assumed particle shape might be erroneous in case of non-spherical ice particles. We present here a novel op- tical sensor (the Particle Habit Imaging and Polar Scattering probe, PHIPS) designed to measure simultaneously the 3-D morphology and the corresponding optical and microphys- ical parameters of individual cloud particles. Clouds con- taining particles ranging from a few micrometers to about 800 µm diameter in size can be characterized systematically with an optical resolution power of 2 µm and polar scattering resolution of 1 ◦ for forward scattering directions (from 1 ◦ to 10 ◦ ) and 8 ◦ for side and backscattering directions (from 18 ◦ to 170 ◦ ). The maximum acquisition rates for scattering phase functions and images are 262 KHz and 10 Hz, respec- tively. Some preliminary results collected in two ice cloud campaigns conducted in the AIDA cloud simulation cham- ber are presented. PHIPS showed reliability in operation and produced size distributions and images comparable to those given by other certified cloud particles instruments. A 3-D model of a hexagonal ice plate is constructed and the corresponding scattering phase function is compared to that
Mostrar mais

18 Ler mais

Effect of Annealing Time for Quenching CuAl7Fe5Ni5W2Si2 Bronze on the Microstructure and Mechanical Properties

Effect of Annealing Time for Quenching CuAl7Fe5Ni5W2Si2 Bronze on the Microstructure and Mechanical Properties

At this scale of temperature and time (Fig. 9) it is difficult to identify the characteristic changes of the sample temperature, respectively, during the annealing (stage T2 - isothermal annealing), hyperquenching and quenching bronze (stage T3 - cooling in ambient air and T4 stage - cooling in 10% NaCl solution in water). Figure 10 shows representative characteristics of temperature changes during the isothermal annealing bronze sample at a constant temperature of t=1000 °C for 3600 s. There was a decrease of the temperature characteristic bronze samples during the annealing process in the studied range of isothermal annealing time (30, 60 and 120 min.). The presented characteristics t=f(τ) for a sample of bronze in the furnace that, after heating the furnace and the sample to a temperature of 1000 °C, there was a gradual decrease in temperature of the sample to about 996°C. Decrease of the temperature of the sample is associated with absorption of heat by the phase existing in bronze at 1000 °C, necessary for the occurrence of the following diffusion processes:
Mostrar mais

18 Ler mais

Show all 10000 documents...

temas relacionados