It is the purpose of this paper to provide a comprehensive documentation of the new NCAR (National Center for Atmospheric Research) version of the spectral element (SE) dynamical core as part of the Community Earth System Model (CESM2.0) release. This version differs from previous releases of the SE dynamical core in several ways. Most notably the hybrid sigma vertical coordinate is based on dry air mass, the condensates are dynamically active in the thermodynamic and momentum equations (also referred to as condensate loading), and the continuous equations of motion conserve a more comprehensive total energy that includes condensates. Not related to the vertical coordinate change, the hyperviscosity operators and the vertical remapping algorithms have been modified. The code base has been significantly reduced, sped up, and cleaned up as part of integrating SE as a dynamical core in the CAM (Community Atmosphere Model) repository rather than importing the SE dynamical core from High‐Order Methods Modeling environment as an external code.

The standard cross correlation technique frequently used in particle image velocimetry to extract velocity vectors necessitates the assumption that the velocity gradients inside the interrogation area are negligible. However, the procedure is generally video-based, so such an assumption may no longer be valid. This is particularly so in re-circulation zones, in which the distortion between images can be dramatic. A new iterative procedure for re-building the second image, based on velocity gradients of particles due to displacement, rotation and shear, has been proposed. This improved cross correlation algorithm has been shown to be considerably more accurate for simulated uniform, re-circulating and bi-axial shearing flows, and has been applied to the case of natural convection due to a heated horizontal cylinder.

Abstract. Solar climate intervention using stratospheric aerosol injection is a proposed method of reducing global mean temperatures to reduce the worst consequences of climate change. A detailed assessment of responses and impacts of such an intervention is needed with multiple global models to support societal decisions regarding the use of these approaches to help address climate change. We present a new modeling protocol aimed at simulating a plausible deployment of stratospheric aerosol injection and reproducibility of simulations using other Earth system models: Assessing Responses and Impacts of Solar climate intervention on the Earth system with stratospheric aerosol injection (ARISE-SAI). The protocol and simulations are aimed at enabling community assessment of responses of the Earth system to solar climate intervention. ARISE-SAI simulations are designed to be more policy-relevant than existing large ensembles or multi-model simulation sets. We describe in detail the first set of ARISE-SAI simulations, ARISE-SAI-1.5, which utilize a moderate emissions scenario, introduce stratospheric aerosol injection at ∼21.5 km in the year 2035, and keep global mean surface air temperature near 1.5 ∘C above the pre-industrial value utilizing a feedback or control algorithm. We present the detailed setup, aerosol injection strategy, and preliminary climate analysis from a 10-member ensemble of these simulations carried out with the Community Earth System Model version 2 with the Whole Atmosphere Community Climate Model version 6 as its atmospheric component.

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The approach of the next-generation computing platforms offers a tremendous opportunity to advance the state-of-the-art in global atmospheric dynamical models. We detail our incremental approach to utilize this emerging technology by enhancing concurrency within the High-Order Method Modeling Environment (HOMME) atmospheric dynamical model developed at the National Center for Atmospheric Research (NCAR). The study focused on improvements to the performance of HOMME which is a Fortran 90 code with a hybrid (MPIOpenMP) programming model. The article describes the changes made to the use of message passing interface (MPI) and OpenMP as well as single-core optimizations to achieve significant improvements in concurrency and overall code performance. For our optimization studies, we utilize the “Cori” system with an Intel Xeon Phi Knights Landing processor deployed at the National Energy Research Supercomputing Center and the “`Cheyenne” system with an Intel Xeon Broadwell processor installed at the NCAR. The results from the studies, using “workhorse” configurations performed at NCAR, show that these changes have a transformative impact on the computational performance of HOMME. Our improvements have shown that we can effectively increase potential concurrency by efficiently threading the vertical dimension. Further, we have seen a factor of two overall improvement in the computational performance of the code resulting from the single-core optimizations. Most notably from the work is that our incremental approach allows for high-impact changes without disrupting existing scientific productivity in the HOMME community.

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A BSTRACT Two methods of extracting velocity vectors from particle image patterns are described. The results are compared with Part Image Velocimetry (PIV) using the well established cross-correlation technique for a case of natural convection from a heated tube submerged in a water bath. In an endeavour to improve the accuracy of velocity extraction, velocity gradients have been introduced into the algorithm. The procedure is repeated to a chosen iterative limit. Results presented show the effect of the gradient operator on the velocities obtained in regions where the velocity gradient is large. INTROI)UCTIONSince Kinoshita1 first applied the Particle Image Velocimetry (PIV) technique to obtain two-dimensional information of velocity vectors on the surface of a flood floW lfl a river by the manual operation of a stereograph-image plotter, othersZ3 have used PIV intensively for measurement of fluid flow fields. Essentially there are two methods to record flow patterns of fluid fields, One utilizes film or plate and the other utilizes video records. The film method employs point by point analysisYoung's fringes2 or the auto-correlation method4 to investigate the double/multi-exposed film or plate to extract velocity data which has direction ambiguity. Adrian5 and Grant ci a!.6 tried to resolve directional ambiguity by using an image shifting technique. Goss" introduced two-colour PIV attempting to remove the directional ambiguity. The video method employs the cross-correlation method39 or other tracking melhods'°" to analyze two image frames, obtaining velocity data, removing directional ambiguity which is characteristic !r both Young's fringe and the auto-correlation techniques. An important advantage of the video method is its easy applicability for flow velocity measurements due to the absence of photographic and opto-mechanical processing steps inherent to non-video based PIV techniques. Yano'2 applied the correlation technique to a fairly simple steady how held without any reverse how and proved that the technique was effective. Kimura et al.9 used correlation techniques to analyze how around a circular cylinder, in an attempt to decrease erroneous velocity vectors.In this paper, two methods of extracting the velocity vectors from particle image patterns are described. The results are compared with the well established cross-correlation technique for a case of natural convection from a heated tube submerged in a water bath. The first, the subtraction method, is based on the minimisation of the absolute values, following subtraction, 478 /SPIE Vol. 2005 08194-1254-6/93/$6.0Q Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/23/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx