Here, we present investigations on the impact of absorbing aerosol particles on cloud and radiation fields over Germany. Using advanced high-resolution simulations with grid spacings of 312 and 625 m, numerical experiments with different aerosol optical properties are contrasted using purely-scattering aerosol as control case and realistic absorbing aerosol as perturbation. The combined effect of surface dimming and atmospheric heating induces positive temperature and negative moisture anomalies between 800 and 900 hPa impacting low-level cloud formation. Decreased relative humidity as well as increased atmospheric stability below clouds lead to a reduction of low-level cloud cover, liquid water path and precipitation. It is further found that direct and semi-direct effects of absorbing aerosol forcing have similar magnitudes and equally contribute to a reduction of net radiation at the top of the atmosphere .

Blazed gratings are of dedicated interest for the monochromatization of synchrotron radiation when a high photon flux is required, such as, for example, in resonant inelastic X-ray scattering experiments or when the use of laminar gratings is excluded due to too high flux densities and expected damage, for example at free-electron laser beamlines. Their availability became a bottleneck since the decommissioning of the grating manufacture facility at Carl Zeiss in Oberkochen. To resolve this situation a new technological laboratory was established at the Helmholtz Zentrum Berlin, including instrumentation from Carl Zeiss. Besides the upgraded ZEISS equipment, an advanced grating production line has been developed, including a new ultra-precise ruling machine, ion etching technology as well as laser interference lithography. While the old ZEISS ruling machine GTM-6 allows ruling for a grating length up to 170 mm, the new GTM-24 will have the capacity for 600 mm (24 inch) gratings with groove densities between 50 lines mm −1 and 1200 lines mm −1 . A new ion etching machine with a scanning radiofrequency excited ion beam (HF) source allows gratings to be etched into substrates of up to 500 mm length. For a final at-wavelength characterization, a new reflectometer at a new Optics beamline at the BESSY-II storage ring is under operation. This paper reports on the status of the grating fabrication, the measured quality of fabricated items by ex situ and in situ metrology, and future development goals.

The reliable detection of clouds that will develop into thunderstorms is of high interest in operational weather forecasting. Satellite based detection algorithms for convective initiation are considered a promising avenue to improve the nowcasting of thunderstorms. The thunderstorm detection indicators with the highest information content for convective growth in its early stage within these algorithms are the Lagrangian time trends of cloud properties. Reliable thunderstorm tracking techniques are needed to determine them properly. Hence, the tracking technique used has a large impact on the overall detection capability. Therefore, this study explores four different automatic cloud tracking techniques and their applicability to the task of quantifying the temporal evolution of cloud properties within the detection algorithms and reports preliminary results for a set of cases in Central Europe.

The interaction between locally monochromatic finite‐amplitude mesoscale waves, their nonlinearly induced higher harmonics, and a synoptic‐scale flow is reconsidered, both in the tropospheric regime of weak stratification and in the stratospheric regime of moderately strong stratification. A review of the basic assumptions of quasi‐geostrophic theory on an f‐plane yields all synoptic scales in terms of a minimal number of natural variables, i.e. two out of the speed of sound, gravitational acceleration and Coriolis parameter. The wave scaling is defined so that all spatial and temporal scales are shorter by one order in the Rossby number, and by assuming their buoyancy field to be close to static instability. WKB theory is applied, with the Rossby number as scale separation parameter, combined with a systematic Rossby‐number expansion of all fields. Classic results for synoptic‐scale‐flow balances and inertia‐gravity‐wave (IGW) dynamics are recovered. These are supplemented by explicit expressions for the interaction between mesoscale geostrophic modes (GMs), a possibly somewhat overlooked agent of horizontal coupling in the atmosphere, and the synoptic‐scale flow. It is shown that IGW higher harmonics are slaved to the basic IGW, and that their amplitude is one order of magnitude smaller than the basic‐wave amplitude. GM higher harmonics are not that weak and they are in intense nonlinear interaction between themselves and the basic GM. Compressible dynamics plays a significant role in the stratospheric stratification regime, where anelastic theory would yield insufficient results. Supplementing classic derivations, it is moreover shown that, in the absence of mesoscale waves, quasi‐geostrophic theory holds also in the stratospheric stratification regime.

For photon energies of 1 - 5 keV, blazed gratings with multilayer coating are ideally suited for the suppression of stray and higher orders light in grating monochromators. We developed and characterized a blazed 2000 lines/mm grating coated with a 20 period Cr/C- multilayer. The multilayer d-spacing of 7.3 nm has been adapted to the line distance of 500 nm and the blaze angle of 0.84° in order to provide highest efficiency in the photon energy range between 1.5 keV and 3 keV. Efficiency of the multilayer grating as well as the reflectance of a witness multilayer which were coated simultaneously have been measured. An efficiency of 35% was measured at 2 keV while a maximum efficiency of 55% was achieved at 4 keV. In addition, a strong suppression of higher orders was observed which makes blazed multilayer gratings a favorable dispersing element also for the low X-ray energy range.

At BESSY-II a new UV- and XUV optics beamline [1] has recently been setup with an in-house developed versatile reflectometer [2], [3], [4] for at-wavelength metrology on reflective and diffractive optical elements up to 4 kg mass. High precision measurements of the reflection and polarization properties are feasible by a 360 degrees azimuthal rotation of the sample around the beam of light, where samples can be adjusted reproducibly with a novel UHV-Tripod within arc sec and mu m precision. The azimuthal rotation requires an extremely high precision adjustment of the goniometer axis with respect to the incident light beam. Here we describe sophisticated methods with which we achieve nearly perfect agreement of the azimuthal rotation axis and the synchrotron beam in the 30 arc sec range. By using geodetic instruments (lasertracker, theodolite, autocollimator) the quality of the reflectometer UHV-mechanics has been characterized with respect to stiffness and radial run out with highest precision [5].

A new Optics Beamline coupled to a versatile UHV reflectometer is successfully operating at BESSY-II. It is used to carry out at-wavelength characterization and calibration of in-house produced gratings and novel nano-optical devices as well as mirrors and multilayer systems in the UV and XUV spectral region. This paper presents most recent commissioning data of the beamline and shows their correlation with initial beamline design calculations. Special attention is paid to beamline key parameters which determine the quality of the measurements such as high-order suppression and stray light behavior. The facility is open to user operation.

A technology center for the production of high-precision reflection gratings has been established. Within this project a new optics beamline and a versatile reflectometer for at-wavelength characterization of UV- and XUV-reflection gratings and other (nano-) optical elements has been set up at BESSY-II. The Plane Grating Monochromator beamline operated in collimated light (c-PGM) is equipped with an SX700 monochromator, of which the blazed gratings (600 and 1200 lines mm−1) have been recently exchanged for new ones of improved performance produced in-house. Over the operating range from 10 to 2000 eV this beamline has very high spectral purity achieved by (i) a four-mirror arrangement of different coatings which can be inserted into the beam at different angles and (ii) by absorber filters for high-order suppression. Stray light and scattered radiation is removed efficiently by double sets ofin situexchangeable apertures and slits. By use of in- and off-plane bending-magnet radiation the beamline can be adjusted to either linear or elliptical polarization. One of the main features of a novel 11-axes reflectometer is the possibility to incorporate real life-sized gratings. The samples are adjustable within six degrees of freedom by a newly developed UHV-tripod system carrying a load up to 4 kg, and the reflectivity can be measured between 0 and 90° incidence angle for boths- andp-polarization geometry. This novel powerful metrology facility has gone into operation recently and is now open for external users. First results on optical performance and measurements on multilayer gratings will be presented here.

The design for a new XUV-Optics Beamline is presented. The collimated plane grating monochromator (PGM-) beamline at a bending magnet is setup at the BESSY-II synchrotron radiation facility within the framework of the blazed-grating production facility. Coupled to a versatile four-circle (ten axes) UHV-reflectometer as a permanent end station the whole setup is dedicated to at-wavelength characterization and calibration of the in-house produced precision gratings and novel nano-optical devices as well as mirrors, multilayered systems etc. It is also open to external projects employing reflectometry, spectroscopy or scattering techniques. According to its purpose, this beamline has specific features, such as: very high spectral purity, provided by two independent high order suppression systems, an advanced aperture system for suppression of stray light and scattered radiation, a broad energy range between 10 eV and 2000 eV, small beam divergence and spot size on the sample. Thus this Optics Beamline will become a powerful metrology tool for reflectivity measurements in s-or p-polarisation geometry with linearly or elliptically polarized light on real optics up to 360 mm length and 4 kg weight.

In 2009 Carl Zeiss stopped the manufacture of precision gratings. All users of precision gratings were very concerned about this decision, since they all need such gratings for their experiments. One of the institutes of the HZB, the Institute for Nanometer Optics and Technology (INT), has extensive experience in micro fabrication (technology group). In spring 2010, HZB decided to take over the old C. Zeiss grating fabrication and build up its own technology center for grating fabrication. Using governmental support, HZB has installed all necessary equipment and processes to fabricate high quality gratings for the synchrotron radiation community.

Within our technology center for production of highly efficient precision gratings a versatile 4-circle UHV-reflectometer for synchrotron radiation based at-wavelength characterization has been fabricated. The main feature is the possibility to incorporate real live-sized gratings. The samples are adjustable within six degrees of freedom by a novel UHV-tripod system, and the reflectivity can be measured at all incidence angles for both s-and p-polarization geometry. The reflectometer has been setup in a clean room hutch and it is coupled permanently to the optics beamline PM-1 for the UV and XUV range with the polarization adjustable to either linear or elliptical. The setup will be open to users by the end of 2014.

In 2009 Carl Zeiss stopped the manufacture of precision gratings. All users of their gratings were very concerned about this decision, since they all need precision gratings for their experiments. One of the institutes of the HZB, the Institute for Nanometer Optics and Technology (INT), has extensive experience in micro fabrication (technology group). In spring 2010, HZB decided to take over the old C. Zeiss grating fabrication and build up its own technology center for grating fabrication. In March 2010, the INT applied to the Senate of Berlin for funding for our project from the European Regional Development Fund (ERDF). In October 2010, HZB received an approval of its application from the Senate of Berlin (contract No 20072013 2/43). Using this governmental support, HZB will install all necessary equipment and processes to fulfill these demands until end of 2013.

At BESSY II a confocal plane grating spectrometer for resonant inelastic X-ray scattering (RIXS) is currently under commissioning. The new endstation operates with a source size of 4 x 1 mu m(2) provided by its dedicated beamline. The RIXS-spectrometer covers an energy range from 50 eV to 1000 eV, providing a resolving power E/Delta E of 5000-15,000. The beamline allows full polarization control and gives a photon flux of up to 7 x 10(14) photons/s/0.1 A/0.1%bandwidth by offering a resolving power E/Delta E of 4000-12,000. (C) 2012 Elsevier B.V. All rights reserved.

A new spectrometer, utilizing a reflection zone plate based grating, for the Mn L fluorescence line was recently designed, manufactured and tested at Helmholtz Zentrum Berlin. The angular acceptance of the grating is ~0.011 rad2 the absolute efficiency at 640 eV is 16%, and the energy resolution, for a detector slit size of 120 μm and in simultaneous spectra registration mode, is about λ/Δλ ~ 100 FWHM.

The design for an UHV-reflectometer for XUV-radiation is presented, which is dedicated to at-wavelength characterisation on high precision gratings. At-Wavelength Metrology is a powerful and necessary characterisation tool for the development and characterisation of optical elements. Since the optical constants of the coating materials involved are dependent on wavelength, information on e.g. reflectivity can only be obtained at-wavelength and cannot be provided by ex-situ methods.In our institute a technology centre for production and characterisation of highly efficient precision gratings is established. Within this project a reflectometer for at-wavelength characterisation of the fabricated blazed gratings is developed and manufactured. This reflectometer complements the SXR-metrology instrumentation at BESSY-II: the existing reflectometer and the polarimeter/ellipsometer chamber for polarisation studies on magneto-optical samples or non-magnetic multilayers.The main feature of the reflectometer is the possibility to incorporate real gratings with a length up to 600 mm, adjustable in six degrees of freedom by a custom designed tripod system. The reflectivity is measured between -180 degrees and +180 degrees incidence angle for both s- and p-polarisation geometry. A variety of detectors with a high dynamic range is accessible.The reflectometer is coupled permanently to the new optics beamline on a BESSY-II bending magnet operating in the UV, EUV and soft x-ray range with the polarisation adjustable to either linear or elliptical. The station will be available by the end of 2013. (C) 2013 Published by Elsevier B.V.

Novel instrumentation developments in X-ray spectroscopy for parallel spectral measurements with soft X-rays are described. The significant performance improvements are achieved utilising Fresnel diffraction from structures built onto the surface of a total external reflection mirror. An array of reflection zone plates was tested as a wavelength-dispersive fluorescence spectrometer for soft X-rays in the energy range of 100–550 eV.

In the middle atmosphere, solar thermal tides cause large variations in the background conditions for gravity-wave propagation. The induced modulation of gravity-wave pseudo-momentum fluxes is responsible for a diurnal force. In past studies, this forcing was derived from gravity-wave parameterizations which neglect time-dependence and horizontal inhomogeneities of the background flow. In our study, we evaluate these assumptions using a highly simplified gravity-wave ensemble. With the help of a global ray-tracing model, a small number of different gravity-wave fields is transported through a time-changing background which is composed of a climatological mean and tidal fields from a general circulation model. Within three off-line experiments, assumptions on horizontal and temporal dependence of the background conditions have been successively omitted. Time-dependence leads to a modulation of gravity-wave observed frequencies and its phase velocities. Transient critical layers disappear. The amplitude of the diurnal forcing is reduced. Horizontal inhomogeneities induce a refraction of the gravity waves into the jet stream cores. Horizontal propagation can lead to large meridional displacements and an inter-hemispheric exchange of gravity-wave energy. With equivalent Rayleigh friction coefficients, it is shown that for the gravity-wave ensemble in use the damping of tidal amplitudes is reduced when horizontal and time dependence of tidal background conditions are taken into account.

Multiple-scale asymptotics is used to analyse the Euler equations for the dynamical situation of a gravity wave (GW) near breaking level. A simple saturation argument in combination with linear theory is used to obtain the relevant dynamical scales. As a small expansion parameter, the ratio of the inverse of the vertical wavenumber and potential temperature and pressure scale heights is used, which we allow to be of the same order of magnitude here. It is shown that the resulting equation hierarchy is consistent with that obtained from the pseudo-incompressible equations, both for non-hydrostatic and hydrostatic GWs, while this is not the case for the anelastic equations unless the additional assumption of sufficiently weak stratification is adopted. To describe vertical propagation of wavepackets over several atmospheric-scale heights, Wentzel–Kramers–Brillouin (WKB) theory is used to show that the pseudo-incompressible flow divergence generates the same amplitude equation that also obtains from the full Euler equations. This gives a mathematical justification for the use of the pseudo-incompressible equations in the study of GW breaking in the atmosphere for arbitrary background stratification. The WKB theory interestingly even holds at wave amplitudes close to static instability. In the mean-flow equations, we obtain in addition to the classic wave-induced momentum-flux divergences a wave-induced correction of hydrostatic balance in the vertical momentum equation, which cannot be obtained from Boussinesq or anelastic dynamics.

We present design and implementation details of the Diamond-NOM (nanometre optical metrology)—a non-contact profiler capable of measuring the surface topography of large (up to 1500mm long) and heavy (up to 150kg) optical assemblies with sub-nanometre resolution and repeatability. These levels of performance are essential to fabricate and optimize next generation optics. The capabilities of the Diamond-NOM have already enabled collaborations with optic manufacturers, including production of a preferentially deposited, large (1.2m), synchrotron mirror with a slope error of ∼0.44μrad rms and using bimorph technology to reduce figure error of a super-polished (elastic emission machining) optic to <1nm peak to valley. We demonstrate that the BESSY-NOM scanning pentaprism and autocollimator concept is robust, easily transferable, and repeatable.