Arctic amplification under greenhouse warming [6, 7]. In recent decades, the Arctic indeed has been experiencing rapid changes. Arctic sea ice extent, most prominently in September, has shrunk substantially since the beginning of the modern satellite record . Amplified warming in high northern latitudes has also been observed over the past decades, especially in winter [1, 3]. This warming has been observed to be surface intensified , with trends that can be discerned in observational records despite the large internal variability in high latitudes . Furthermore, significant increases in specific humidity have been observed, but relative humidity changes are more complex [2, 23]. Cloud feedbacks and the trapping of heat under the stable inversion are thought to contribute to Arctic amplification of global warming [7, 24–26]. However, the sign of any cloud feedback in high latitudes is uncertain . In GCMs, low clouds depends on parameterizations for turbulence and convection, which are developed mainly for lower latitudes. In fact, GCMs show large spread in the simulated seasonal cycle of Arctic cloud fraction [28, 29]. A key step towards constraining Arctic cloud feedbacks is to identify robust mechanisms of how the clouds respond to changes in temperature, inversion strength, and moisture content of the free troposphere.
Spin resolved spectroscopy of DQ Her was performed with the 4.2-m William Herschel Telescope on La Palma (Spain), on the nights of 8-10 July 1998. Approximately 3 orbital periods were observed using the double-armed ISIS spectro- graph. The CCDs were operated in low smear drift mode (Rutten et al. 1997) to limit the dead-time between two ex- posures to about 0.6 s. The blue arm spectra cover the spec- tral range 4200 − 5000 ˚ A and have a spectral resolution of 1.9 ˚ A. The spectral range covered by the red arm spectra is 6320 − 6710 ˚ A and their spectral resolution is 0.8 ˚ A. An overview of the observations is given in Table 1. The observ- ing conditions were generally good with a few cirrus clouds at times and some dust in the air during the first night.
When using a single polarized backscatter ratio or a total backscatter ratio (S01, M06, and P09/P11), two dis- tinct maxima appear in the occurrence rate of PSC types (see Figure 5). Both cases show a low to medium backscatter ratio, but one features a small particle depolarization ratio (STS) while the other comes with a medium to large particle depolarization ratio (NAT). Using backscatter ratios in both planes of polarization as in the case of B05 increases the contrast for observations with weakly backscattering and weakly depolar- izing particles. The now resolved third maximum in the occurrence rate represents a mixture of STS and NAT particles. Hence, both backscatter ratios should be used independently and not as a total backscatter ratio to better distinguish between STS, NAT, and MIX. Even though the diﬀerent MIX and NAT classes are quite similar regarding their optical properties, it is most likely that they show diﬀerent microphysical properties. MIX cases will show bimodal size distributions, while the size distribution of pure NAT can be expected to be monomodal. To distinguish optically between these subtypes is diﬃcult since a single PSC usually does not consist of only one particle type. Lidar observations of PSCs often reveal several layers of varying PSC types and external mixtures [Daneva and Shibata, 2003].
Despite these uncertainties, the SMR tomographic mea- surements provide a unique and useful complement to exist- ing data sets. As an example of the capabilities of the mea- surements, we compared the retrieved atmosphere to PMC extinction coefficients measured by OSIRIS for two of the recorded orbits. The results from the two instruments showed both depletion and enhancement of water vapour around the clouds as well as larger-scale horizontal variation in both wa- ter vapour and temperature. To explain the complete water vapour and temperature fields of the background atmosphere requires a more thorough analysis, taking into account both cloud microphysics as well as atmospheric dynamics. Future plans include using the data set to evaluate atmospheric and cloud models, and thus improve our understanding of PMCs and their effect on and response to the background atmo- sphere under which they form.
It is still difficult to determine zero velocity. The estimates most other experiments use are, (1) the average peak posi- tion from several opposing viewing directions, (2) the verti- cal peak position, (3) the peak position observed in cloudy nights, and (4) the average peak observed in long-term pe- riod. In using each baseline method, we are making certain assumptions about the winds in the thermosphere. Using (1) assumes that there is no horizontal divergence over the whole observing period. Using (2) assumes that the average vertical wind over the whole observing period is zero. For (3), it is as- sumed that the observing emission is well scattered by clouds particles and that the emission can be considered as summa- tion of emission from the whole sky. For (4), it is assumed that the averaged wind does not deflect to a certain direction. We use (1) for Doppler-imaging FPI. As mentioned before, the zero divergence assumption will be wrong at some times. The departure of the observed wind field from uniformity is estimated as a standard deviation. (the third panel of Figs. 2 and 5). The zonal and meridional component has meaning
Simulations of MSP growth and sedimentation have been carried out in a number of previous studies (Bardeen et al., 2008; Frankland et al., 2015; Neely et al., 2011). For this study we used atmospheric modelling data from Brooke et al. (2017). These were whole atmosphere community climate model (WACCM, e.g. Marsh et al., 2013) runs with specified dynamics using the modern-era retrospective analysis for re- search and applications (MERRA) reanalysis (Rienecker et al., 2011), an MSP input of 7.9 t day −1 (Carrillo-Sánchez et al., 2016), and included an interaction between MSP and sul- fate aerosol through condensation and heterogeneous nucle- ation (see Supplement for details). Aerosol microphysics cal- culations were performed using the community aerosol and radiation model for atmospheres (CARMA) model (Toon et al., 1979, 1988; Turco et al., 1979). The zonal mean MSP density at 67 ◦ N and 70 hPa during February, averaged over 2011–2014, is (1.5 ± 0.5) × 10 −15 g cm −3 .
The Albedo-Ice Regression (AIR) method was developed to fill the need to retrieve PMC IWC with only a single mea- surement of albedo. Based on the simple notions that both albedo and IWC depend linearly upon the ice particle col- umn density, multiple linear relationships are established be- tween IWC and cloud directional albedo, depending upon scattering angle. The regressions are derived from three data sources: (1) the Specified Dynamics version of the Whole At- mosphere Community Climate Model (SD-WACCM) com- bined with the Community Aerosol and Radiation Model for Atmospheres (CARMA); (2) CIPS data for the years 2007–2013, when multiple scattering angles were available to derive IWC; and (3) Solar Occultation For Ice Experiment (SOFIE), which provides IWC and particle sizes. These three sources provide many thousands of albedo–IWC–particle size combinations, from which the AIR regressions are de- rived. Although the AIR method may be inaccurate for a sin- gle retrieval of IWC, averages over many observations result in close agreement as the number of data points increases. The utility of AIR thus depends upon the availability of large data sets that apply to roughly the same atmospheric condi- tions. For example, we will show CIPS results for July and January averages for ascending and descending portions of the orbit.
In short, over the past few decades tremendous progress has been made in revealing the genes and their protein prod- ucts involved in PAT, and we observed an increasing number of computational models aimed at understanding the role of the distribution of auxin in time and space, during growth and developmental processes. These models rely largely on observed expression patterns of PAT genes instead of direct measurements of auxin fluxes (cf. Kramer, 2008). The prob- lem with these correlation studies is that it has still not been resolved in mechanistic terms how PAT proteins, for example members of the PIN family, might facilitate PAT (Luschnig and Vert, 2014). As a first step in contributing to solve this problem, we decided to develop an experimental system, sat- isfying the following requirements: (i) the system must allow
the injected power normalized to the power of the solitary VCSEL and the frequency detuning as the frequency difference between that of the externally injected signal and that of the resonance of the orthogonal polarization of the VCSEL. The VCSEL was biased five times above threshold to ensure that various strong dynamics can be found. Different types of nonlinear dynamic behaviors are found depending on the applied injection parameters. In particular, Fig. 2(a) shows the simultaneous occurrence of period one dynamics (P1, also referred as limit cycle) for both polarizations. In this case, as seen in Fig. 2(a), both time series exhibit periodic oscillations at a single frequency with both associated phase plots showing a characteristic open circular shape . Additionally, the radius of the circle is indicative of the amplitude of the periodic oscillations. In contrast, Fig. 2(b) shows a different situation where period doubling (P2) dynamics occur for the orthogonal polarization (in red) whereas very small power fluctuations, almost hidden within the instrument’s inherent noise background are observed for the output of the parallel polarization. In this latter case, the time series for the orthogonal polarization show oscillatory behavior at two different frequencies, the second frequency being half of the first, and the associated phase plot shows two distinct open circles . Finally, Fig. 2(c) and (d) illustrate a completely different situation where chaotic dynamics with similar amplitudes are obtained simultaneously for the output of both polarizations. Strongly aperiodic behavior is observed in the measured time series, and the phase plots show a very irregular and poorly defined closed shape.
Three new mutants, each lacking a single gene from cluster 2 (pabA, pabB, or ETAE_RS10450) were generated and tested for their ability to produce an immune response protective against E. piscicida. Parallel assays were performed using existing vaccine strains (WED and the ΔaroC and ΔesrB mutants as positive controls) and with formalin-killed WT bacteria (FKC) and phosphate-buffered saline (PBS) treatment (neg- ative controls). The new candidate LAV strains and the previously tested LAV strains did not induce signiﬁcant mortality compared with controls following i.p. injection of naive ﬁsh (see Fig. S4A in the supplemental material). In general, all 6 of the vaccine strains colonized the turbot kidney more robustly than the liver and spleen: with one excep- tion (the ETAE_RS10450 mutant), the vaccine strains were still recoverable from the kidneys but not the spleens or livers of animals 45 dpi (Fig. 5A; Fig. S4C). New and previously validated vaccine candidates induced similar levels of IgM and serum bactericidal activity against E. piscicida (Fig. 5B and C), which markedly exceeded those of negative controls. Collectively, these analyses are consistent with the hypothesis that the characteristic ﬁtness dynamics of cluster 2 mutants are suitable for development of LAV strains.
Using the analysis technique of Paluch (1979), Blyth et al. (1988) examined more than 80 Montana cumuli and found that the source of entrained air was close to, or slightly above, the observation height of the aircraft at many different levels in the clouds. This result sug- gests that the entrainment process in growing clouds is modified cloud-top entrainment, where cloud top means the ascending cloud top (ACT) of the growing cloud. These and other considerations motivated Blyth et al. to propose a conceptual cloud model based on a shedding thermal. In this model, entrainment occurs near the ACT, and mixed parcels subsequently descend around the edge of the advancing thermal core into a trailing wake region driven by a toroidal circulation. While supporting the idea of ascending cloud-top en- trainment, Jonas (1990) presented a different picture in which the environmental air from near cloud top is transported in a thin, subsiding layer to lower levels and is then entrained laterally into the cloud. The cloud tracer experiments of Stith (1992) give some support to this latter picture. Although these in situ studies have provided insight into cumulus mixing dynamics, there is still no general agreement on the detailed mechanism
Abstract. Improvements to climate model results in po- lar regions require improved knowledge of cloud proper- ties. Surface-based infrared (IR) radiance spectrometers have been used to retrieve cloud properties in polar regions, but measurements are sparse. Reductions in cost and power re- quirements to allow more widespread measurements could be aided by reducing instrument resolution. Here we ex- plore the effects of errors and instrument resolution on cloud property retrievals from downwelling IR radiances for res- olutions of 0.1 to 20 cm −1 . Retrievals are tested on 336 radiance simulations characteristic of the Arctic, including mixed-phase, vertically inhomogeneous, and liquid-topped clouds and a variety of ice habits. Retrieval accuracy is found to be unaffected by resolution from 0.1 to 4 cm −1 , af- ter which it decreases slightly. When cloud heights are re- trieved, errors in retrieved cloud optical depth (COD) and ice fraction are considerably smaller for clouds with bases below 2 km than for higher clouds. For example, at a res- olution of 4 cm −1 , with errors imposed (noise and radia- tion bias of 0.2 mW/(m 2 sr cm −1 ) and biases in tempera- ture of 0.2 K and in water vapor of − 3 %), using retrieved cloud heights, root-mean-square errors decrease from 1.1 to 0.15 for COD, 0.3 to 0.18 for ice fraction (f ice ), and 10 to
We have investigated the relaxation kinetics of two small β-sheet peptides, H1a and H3, in an effort to distinguish the possible nucleation events, β-turn formation and hydrophobic core collapse. Both folding and unfolding processes can be studied using peptides that cold-denature such as H1 and H1a. The condition of cold-denaturation exists when a peptide is unfolded at low temperatures and folds as the temperature is increased. Heat-denaturation is more commonly encountered in protein folding and occurs when a peptide is folded at low temperatures and unfolds upon heating. H1 and H1a both cold-denature when small amounts (< 10%) of hexafluoroisopropanol (HFIP) are added to the aqueous solvent. The addition of an alcohol co-solvent such as HFIP lowers the solvent entropy by ordering solution molecules to create a hydrophobic efffect. 10 H3 was designed such that the hydrophobic core is next to the β-turn region. To our knowledge, the kinetics of such a design which deliberately moves the hydrophobic core next to the β-turn has not been previously characterized. Figure 1 shows the amino acid sequences and hydrophobic core placement for H1a and H3 peptides. Fourier transform infrared (FTIR) and time-resolved infrared spectroscopies were used to obtain dynamical information. The kinetic results of studies of multiple wavenumbers in the amide I′ region were further analyzed using singular value decomposition (SVD) and exponential fitting. SVD was found to be a valuable method for feature reduction to obtain a clear picture of the kinetic processes involved with the folding of H1a and H3 peptides.
at this energy the photoelectron anisotropy parameter depends solely on the contribution from the l – 1 channel (s-type continuum in our case). For atomic photoionization from a p-orbital, the l – 1 channel possesses an isotropic angular distribution, corresponding to β = 0. Thus, in the vicinity of the Cooper minimum associated with the Cl 3p orbital, both the anisotropy parameter and the photoionization partial cross section (branching ratio) should exhibit a characteristic and easily recognisable behaviour. The degree to which these atomic properties are observable in the photoionization dynamics of molecular orbitals depends upon the extent to which the molecular orbitals retain their atomic properties.
The similarity of the cluster work reported here to the study in the liquid state of ammonia 23 is in the T-jump achieved on the ground s-state. For both cases, because the p→s conversion takes place in less than 100 fs, the population prepared is in a nonequilibrium state, which can be ascribed to an instant rise in temperature. Based on the change in density, Lindner et al. 23 estimated a solvent shell increase of 1 Å at the excitation used (1.4 µm). It is interesting that in our case an average speed of 1 Å ps –1 implies an angstrom expansion during the period. The self-diffusion coefficient in liquid ammonia is 1 Å 2 /ps, 41 implying a length scale of angstrom(s) during a picosecond dynamics. Finally, the electron diffusion of a Gaussian packet was calculated 30 to be 0.6 Å 2 ps –1 (in liquid it is 1.9 Å 2 ps –1 42 ). Thus, on the time scale of our experiments, the average length scale maintained is < 1 Å. Coherence in solvent cages is a reflection of the strength of solvent-solvent interactions, which control the degree of rigidity at finite temperatures. 43
of ATLAS and the third column the corresponding measure- ments of MLS. Figure 18 shows the same for the year 2006 and the Southern Hemisphere. The time evolution of ozone is reproduced well in both hemispheres. Since the long-term ozone climatology used for the initialization of Polar SWIFT is different from the actual measured values, some differ- ences show up in early winter. The evolution of HCl shows some differences, which are partly caused by the fact that the full ATLAS model has a parameterization that partitions a significant part of HCl into the liquid phase to overcome a discrepancy between modeled and measured HCl values (for a detailed discussion, see Wohltmann et al., 2017). Polar SWIFT is always fitted to the total HCl mixing ratios of AT- LAS and has no parameterization for HCl in the liquid phase. MLS measures HCl in the gas phase, and consequently, the
Here we present some initial results using the single-shot, time-resolved rear surface optical probe in order to demonstrate the applicability of the new technique. A number of Al target foils were irra- diated during the course of the experiment, with thicknesses varying from 100 nm to 150 µm. Each target foil was mounted in a 5 × 5 array, with a 1 mm clear circular aperture for each target position. Figure 3 illustrates the process of generating 2D reflectivity profiles. The left hand image shows the reference image of the target foil before the main interaction. The centre image shows the same foil, but imaged 5 ps after the main interaction at the target front surface, with a temporal resolution of 1.5 ps. The right hand image combines both images to generate a reflectivity map at that time, isolating the regions of the target where the reflectivity has changed, thus making it easier to analyse.