Kilometer-scale climate models: Prospects and challenges

Currently major efforts are underway toward refining the horizontal resolution (or grid spacing) of climate models to about 1 km, using both global and regional climate models (GCMs and RCMs). Several groups have succeeded in conducting kilometer-scale multiweek GCM simulations and decadelong continental-scale RCM simulations. There is the well-founded hope that this increase in resolution represents a quantum jump in climate modeling, as it enables replacing the parameterization of moist convection by an explicit treatment. It is expected that this will improve the simulation of the water cycle and extreme events and reduce uncertainties in climate change projections. While kilometer-scale resolution is commonly employed in limited-area numerical weather prediction, enabling it on global scales for extended climate simulations requires a concerted effort. In this paper, we exploit an RCM that runs entirely on graphics processing units (GPUs) and show examples that highlight the prospects of this approach. A particular challenge addressed in this paper relates to the growth in output volumes. It is argued that the data avalanche of high-resolution simulations will make it impractical or impossible to store the data. Rather, repeating the simulation and conducting online analysis will become more efficient. A prototype of this methodology is presented. It makes use of a bit-reproducible model version that ensures reproducible simulations across hardware architectures, in conjunction with a data virtualization layer as a common interface for output analyses. An assessment of the potential of these novel approaches will be provided

Carbon buffer layers for smoothing superpolished glass surfaces as substrates for molybdenum/silicon multilayer soft-x-ray mirrors

Stock HJ, Hamelmann F, Kleineberg U, et al. Carbon buffer layers for smoothing superpolished glass surfaces as substrates for molybdenum/silicon multilayer soft-x-ray mirrors. APPLIED OPTICS. 1997;36(7):1650-1654.Zerodur and BK7 glass substrates (developed by Fa. Glaswerke Schott, D-55014 Mainz, Germany) from Carl Zeiss Oberkochen polished to a standard surface roughness of sigma = 0.8 nm rms were coated with a C layer by electron-beam evaporation in the UHV. The roughness of the C-layer surfaces is reduced to 0.6 nm rms. A normal-incidence reflectance of 50% at a wavelength of 13 nm was measured for a Mo/Si multilayer soft-x-ray mirror with 30 double layers (N = 30) deposited onto the BK7/C substrate, whereas a similar Mo/Si multilayer (N = 30) evaporated directly onto the bare BK7 surface turned out to show a reflectance of only 42%. (C) 1997 Optical Society of America

Multilayer-coated soft x-ray diffraction gratings for synchrotron radiation applications

Kleineberg U, Stock HJ, Menke D, et al. Multilayer-coated soft x-ray diffraction gratings for synchrotron radiation applications. Proc. SPIE. 1997;3150:18

Efficiency of a multilayer-coated, ion-etched laminar holographic grating in the 14.5-16.0-nm wavelength region

Kowalski MP, Cruddace RG, Seely JF, et al. Efficiency of a multilayer-coated, ion-etched laminar holographic grating in the 14.5-16.0-nm wavelength region. OPTICS LETTERS. 1997;22(11):834-836.The efficiency of an ion-etched laminar holographic grating was measured at near-normal incidence in the 14.5-16.0-nm wavelength range. The grating had an electron-beam-evaporated Mo/Si multilayer coating matched to the grating groove depth. The efficiency peaked at 16.3% in the first inside order at 15.12 nm and 15.0% in the first outside order at 14.94 nm. These are believed to be the highest efficiencies obtained to date from a multilayer-coated laminar grating at near-normal incidence in the EUV (lambda < 30.0 nm). Zero and even orders were almost completely suppressed. The grating groove efficiency in the first order approached the theoretical limit of 40.5%. (C) 1997 Optical Society of America

Multilayer reflection-type zone plate and blazed gratings for the normal-incidence soft X-ray region

Kleineberg U, Stock HJ, Menke D, et al. Multilayer reflection-type zone plate and blazed gratings for the normal-incidence soft X-ray region. Proc. SPIE. 1994;2279:269

Mo/Si multilayer coated laminar phase and ruled blaze gratings for the soft x-ray region

Kleineberg U, Stock HJ, Kloidt A, et al. Mo/Si multilayer coated laminar phase and ruled blaze gratings for the soft x-ray region. In: Journal of Electron Spectroscopy and Related Phenomena. JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA. Vol 80. ELSEVIER SCIENCE BV; 1996: 389-392.Mo-Si multilayer coated laminar and blase gratings with about 1200 L/mm have been manufactured for near normal incidence operation at soft x-ray wavelengths above the Si L-edge lambda greater than or equal to 12.4 nm. Higher diffraction efficiencies (up to 11% at lambda = 13.6 nm), as opposed to simple amplitude gratings, are achieved for a soft x-ray laminar phase grating coated with 24 Mo/Si bilayers. Two mechanically ruled blaze gratings have been coated with Mo/Si multilayers. The maximum Ist order efficiency of 32% at lambda = 13.8 nm has been achieved for one of them due to a refined groove forming technique and an optimum matching of the blaze angle (0.8 degrees) and the bilayer thickness (10.5 nm)