scholarly journals CondiDiag1.0: A flexible online diagnostic tool for conditional sampling and budget analysis in the E3SM atmosphere model (EAM)

2021 ◽  
Author(s):  
Hui Wan ◽  
Kai Zhang ◽  
Philip J. Rasch ◽  
Vincent E. Larson ◽  
Xubin Zeng ◽  
...  
Keyword(s):  
Diagnostic Tool ◽  
Numerical Models ◽  
Time Integration ◽  
Life Cycles ◽  
Similar Data ◽  
Conditional Sampling ◽  
Atmospheric Processes ◽  
Aerosol Mass Concentration ◽  
Budget Analysis ◽  
Sampling Conditions

Abstract. Numerical models used in weather and climate prediction take into account a comprehensive set of atmospheric processes such as the resolved and unresolved fluid dynamics, radiative transfer, cloud and aerosol life cycles, and mass or energy exchanges with the Earth's surface. In order to identify model deficiencies and improve predictive skills, it is important to obtain process-level understanding of the interactions between different processes. Conditional sampling and budget analysis are powerful tools for process-oriented model evaluation, but they often require tedious ad hoc coding and large amounts of instantaneous model output, resulting in inefficient use of human and computing resources. This paper presents an online diagnostic tool that addresses this challenge by monitoring model variables in a generic manner as they evolve within the time integration cycle. The tool is convenient to use. It allows users to select sampling conditions and specify monitored variables at run time. Both the evolving values of the model variables and their increments caused by different atmospheric processes can be monitored and archived. Online calculation of vertical integrals is also supported. Multiple sampling conditions can be monitored in a single simulation in combination with unconditional sampling. The paper explains in detail the design and implementation of the tool in the Energy Exascale Earth System Model (E3SM) version 1. The usage is demonstrated through three examples: a global budget analysis of dust aerosol mass concentration, a composite analysis of sea salt emission and its dependency on surface wind speed, and a conditionally sampled relative humidity budget. The tool is expected to be easily portable to closely related atmospheric models that use the same or similar data structures and time integration methods.

Modelling rain heterogeneities within an urban neighbourhood

2021 ◽  
Author(s):  
Karolin S. Ferner ◽  
K. Heinke Schlünzen ◽  
Marita Boettcher
Keyword(s):  
Wind Speed ◽  
Urban Areas ◽  
Climate Model ◽  
Numerical Models ◽  
Urban Climate ◽  
Cloud Microphysics ◽  
In Situ Measurements ◽  
Small Scale ◽  
Atmospheric Processes

<p>Urbanisation locally modifies the regional climate: an urban climate develops. For example, the average wind speed in cities is reduced, while the gustiness is increased. Buildings induce vertical winds, which influence the falling of rain. All these processes lead to heterogeneous patterns of rain at ground and on building surfaces. The small-scale spatial rain heterogeneities may cause discomfort for people. Moreover, non-uniform wetting of buildings affects their hydrothermal performance and durability of their facades.</p><p>Measuring rain heterogeneities between buildings is, however, nearly impossible. Building induced wind gusts negatively influence the representativeness of in-situ measurements, especially in densely urbanised areas. Weather radars are usually too coarse and, more importantly, require an unobstructed view over the domain and thus do not measure ground precipitation in urban areas. Consequently, researchers turn to numerical modelling in order to investigate small-scale precipitation heterogeneities between buildings.</p><p>In building science, numerical models are used to investigate rain heterogeneities typically focussing on single buildings and vertical facades. Only few studies were performed for more than a single building or with inclusion of atmospheric processes such as radiation or condensation. In meteorology, increasing computational power now allows the use of small-scale obstacle-resolving models resolving atmospheric processes while covering neighbourhoods.</p><p>In order to assess rain heterogeneities between buildings we extended the micro-scale and obstacle-resolving transport- and stream model MITRAS (Salim et al. 2019). The same cloud microphysics parameterisation as in its mesoscale sister model METRAS (Schlünzen et al., 2018) was applied and boundary conditions for cloud and rain water content at obstacle surfaces were introduced. MITRAS results are checked for plausibility using radar and in-situ measurements (Ferner et al., 2021). To our knowledge MITRAS is the first numerical urban climate model that includes rain and simulates corresponding processes.</p><p>Model simulations were initialised for various wind speeds and mesoscale rain rates to assess their influence on the heterogeneity of falling rain in a domain of 1.9 x 1.7 km² around Hamburg City Hall. We investigated how wind speed or mesoscale rain rate influence the precipitation patterns at ground and at roof level. Based on these results we assessed the height dependence of precipitation. First analyses show that higher buildings receive more rain on their roofs than lower buildings; the results will be presented in detail in our talk.</p><p>Ferner, K.S., Boettcher, M., Schlünzen, K.H. (2021): Modelling the heterogeneity of rain in an urban neighbourhood. Publication in preparation</p><p>Salim, M.H., Schlünzen, K.H., Grawe, D., Boettcher, M., Gierisch, A.M.U., Fock B.H. (2018): The microscale obstacle-resolving meteorological model MITRAS v2.0: model theory. Geosci. Model Dev., 11, 3427–3445, https://doi.org/10.5194/gmd-11-3427-2018.</p><p>Schlünzen, K.H., Boettcher, M., Fock, B.H., Gierisch, A.M.U., Grawe, D., and Salim, M. (2018): Scientific Documentation of the Multiscale Model System M-SYS. Meteorological Institute, Universität Hamburg. MEMI Technical Report 4</p>

scholarly journals Generalized Z-Grid Model for Numerical Weather Prediction

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 179 ◽  
Author(s):  
Yuanfu Xie
Keyword(s):  
Shallow Water ◽  
Finite Volume ◽  
Numerical Models ◽  
Weather Prediction ◽  
Shallow Water Equation ◽  
Computing Time ◽  
Time Integration ◽  
Grid Model ◽  
Rotating Shallow Water ◽  
Volume Models

Z-grid finite volume models conserve all-scalar quantities as well as energy and potential enstrophy and yield better dispersion relations for shallow water equations than other finite volume models, such as C-grid and C-D grid models; however, they are more expensive to implement. During each time integration, a Z-grid model must solve Poisson equations to convert its vorticity and divergence to a stream function and velocity potential, respectively. To optimally utilize these conversions, we propose a model in which the stability and possibly accuracy on the sphere are improved by introducing more stencils, such that a generalized Z-grid model can utilize longer time-integration steps and reduce computing time. Further, we analyzed the proposed model’s dispersion relation and compared it to that of the original Z-grid model for a linearly rotating shallow water equation, an important property for numerical models solving primitive equations. The analysis results suggest a means of balancing stability and dispersion. Our numerical results also show that the proposed Z-grid model for a shallow water equation is more stable and efficient than the original Z-grid model, increasing the time steps by more than 1.4 times.

scholarly journals Potential vorticity dynamics of life cycles of blocked weather regimes in the Euro-Atlantic region: A diagnostic framework

2021 ◽  
Author(s):  
Seraphine Hauser ◽  
Christian M. Grams ◽  
Michael Riemer ◽  
Peter Knippertz ◽  
Franziska Teubler
Keyword(s):  
Potential Vorticity ◽  
Large Scale ◽  
Climate Models ◽  
Numerical Models ◽  
Weather Prediction ◽  
Life Cycles ◽  
Forecast Errors ◽  
Atlantic Region ◽  
Weather Regimes ◽  
Medium Range

<p>Quasi-stationary, persistent, and recurrent states of the large-scale extratropical circulation, so-called weather regimes, characterize the atmospheric variability on sub-seasonal timescales of several days to a few weeks. Weather regimes featuring a blocking anticyclone are of particular interest due to their long lifetime and potential for high-impact weather. However, state-of-the-art numerical weather prediction and climate models struggle to correctly represent blocking life cycles, which results in large forecast errors at the medium-range to sub-seasonal timescale. Despite progress in recent years, we are still lacking a process-based conceptual understanding of blocked regime dynamics, which hinders a better representation of blocks in numerical models. In particular the relative contributions of dry and moist processes in the onset and maintenance of a block remain unclear.</p><p>Here we aim to revisit the dynamics of blocking in the Euro-Atlantic region. To this end we investigate the life cycles of blocked weather regimes from a potential vorticity (PV) perspective in ERA5 reanalysis data (from 1979 to present) from the European Centre for Medium-Range Weather Forecasts. We develop a diagnostic PV framework that allows the tracking of negative PV anomalies associated with blocked weather regimes. Complemented by piecewise PV-tendencies - separated into advective and diabatic PV tendencies - we are able to disentangle different physical processes affecting the amplitude evolution of negative PV anomalies associated with blocked regimes. Most importantly, this approach newly enables us to distinguish between the roles of dry and moist dynamics in the initiation and maintenance of blocked weather regimes in a common framework. A first application demonstrates the functionality of the developed PV framework and corroborates the importance of moist-diabatic processes in the initiation and maintenance of a block in a regime life cycle. </p>

scholarly journals Numerical Study of Landslide-Generated Waves

2004 ◽  
Author(s):  
Gang Yang ◽  
Michael Isaacson
Keyword(s):  
Numerical Study ◽  
Numerical Models ◽  
Domain Boundary ◽  
Time Integration ◽  
Integral Equation Method ◽  
Three Dimensions ◽  
Time Step ◽  
Engineering Applications ◽  
Linear Waves ◽  
Quick Estimate

A time-domain boundary element method is developed to simulate linear waves generated by a wave paddle or a horizontal-moving landslide of an arbitrary profile. In this approach, a time-integration procedure is used to apply the boundary conditions, and the wave field at each time step is solved by an integral equation method based on Green’s theorem. Numerical models in three dimensions are developed to simulate waves generated by landslides. The models were validated against theoretical and experimental results on comparative wavemaker problems. Numerical simulation results on landslide-generated waves demonstrate a number of features of interest. Design curves for engineering applications are also developed for quick estimate of magnitudes of landslide-generated waves in engineering applications.

A semi-implicit pseudo-incompressible flow solver for diabatic dynamics: Baroclinic-wave life cycles 

2021 ◽  
Author(s):  
Fabienne Schmid ◽  
Rupert Klein ◽  
Elena Gagarina ◽  
Ulrich Achatz
Keyword(s):  
Gravity Waves ◽  
Numerical Models ◽  
Life Cycles ◽  
Staggered Grid ◽  
Implicit Time ◽  
Baroclinic Wave ◽  
Modeling Framework ◽  
Flow Solver ◽  
Reference Atmosphere ◽  
Development And Validation

<p>This study introduces an efficient modeling framework for investigations of diabatic flows in the atmosphere. In particular, the spontaneous emission of inertia-gravity waves is addressed in idealized simulations of baroclinic-wave life cycles. Numerical simulations are perfomed using a finite-volume solver for the pseudo-incompressible equations on the f-plane with newly implemented semi-implicit time stepping scheme, adjusted to the staggered grid, which provides high stability and efficiency for long simulation runs with large domains. Furthermore, we have modified the entropy equation to include a heat source, allowing for a development of the vertically dependent reference atmosphere. Numerical experiments of several benchmarks are compared against an explicit third-order Runge-Kutta scheme as well as numerical models from the literature, verifying the accuracy and efficiency of the scheme. The proposed framework serves as a construction basis for an efficient simulation tool for the development and validation of a parameterization scheme for gravity-waves emitted from jets and fronts.</p>

scholarly journals Mesoscale Circulations and Organized Convection in African Easterly Waves

2018 ◽  
Vol 75 (12) ◽  
pp. 4357-4381 ◽  
Author(s):  
Lorenzo Tomassini
Keyword(s):  
Atmospheric Circulation ◽  
Numerical Models ◽  
Mesoscale Convective System ◽  
Leading Edge ◽  
Squall Line ◽  
Convective System ◽  
Dynamic Adjustment ◽  
Mesoscale Circulations ◽  
Budget Analysis ◽  
Organized Convection

Abstract Global convection-permitting model simulations and remote sensing observations are used to investigate the interaction between organized convection, both moist and dry, and the atmospheric circulation in the case of an African easterly wave (AEW). The wave disturbance is associated with a quadrupole structure of divergence, with two convergence centers slightly ahead of the trough. Moisture transport from southeast of the trough to the area in front and lower midtropospheric moisture convergence precondition and organize convection. The main inflow into the squall-line cluster is from behind. The moisture-abundant inflow collides at the low level with monsoon air with high moist static energy and establishes a frontal line of updrafts at the leading edge of the propagating mesoscale convective system. A mantle of moisture surrounds the convective core. A potential vorticity budget analysis reveals that convective latent heating is driving the evolution of the wave but not in a quasi-steady way. The wave propagation includes a succession of convective bursts and subsequent dynamic adjustment processes. Dry convection associated with the Saharan air layer (SAL) and SAL intrusions into the wave trough together with vorticity advection can play a role in intensifying AEWs dynamically as they move from the West African coast across the Atlantic Ocean. Our analysis demonstrates that the synoptic-scale wave and convection are interlinked through mesoscale circulations on a continuum of scales. This implies that the relation between organized convection and the atmospheric circulation is intrinsically dynamic, which poses a particular challenge to subgrid convection parameterizations in numerical models.

scholarly journals The urban heat budget derived from satellite data

2003 ◽  
Vol 58 (2) ◽  
pp. 99-111 ◽  
Author(s):  
E. Parlow
Keyword(s):  
Satellite Data ◽  
Urban Areas ◽  
Heat Budget ◽  
Numerical Models ◽  
Heat Fluxes ◽  
Landsat Tm ◽  
Net Radiation ◽  
Urban Climatology ◽  
Budget Analysis ◽  
Urban Heat

Abstract. The study of the interactions between urban surfaces and the urban boundary layer plays an important role in urban climatology, especially seen against the background of increasing urbanisation in most parts of the world. Measurements of radiation and heat fluxes suffer from the extreme heterogeneity of the urban landscape. It is therefore difficult to get accurate and representative measurements. To bridge the gap between accurate point measurements and their spatial representation, satellite data from Landsat-TM are used. Methods and results of the investigation of radiation properties, net radiation and heat fluxes of urban areas in the Basel Region, NW-Switzerland are presented. In addition to field measurements, satellite data from Landsat-TM were linked to numerical models to compute net radiation and heat fluxes of the whole region. By integrating the normalized difference Vegetation index (NDVI) from multi-spectral satellite data, storage heat fluxes could be estimated with high accuracy. The next step was to compute latent and sensible heat fluxes by using a Bowen-ratio approach attributed to a land use Classification. Of interest is the Observation that the idea of an «Urban Heat Island» (UHI) has to be defined very carefully. Very often an «Urban Cooling Island» may be found during daytime and under clear sky conditions. This feature could be explained using the results of the satellite based radiation and heat budget analysis.

scholarly journals Recharge Oscillator Mechanisms in Two Types of ENSO

2013 ◽  
Vol 26 (17) ◽  
pp. 6506-6523 ◽  
Author(s):  
Hong-Li Ren ◽  
Fei-Fei Jin
Keyword(s):  
Phase Transitions ◽  
Southern Oscillation ◽  
Heat Budget ◽  
Warm Pool ◽  
Life Cycles ◽  
Eastern Pacific ◽  
Cold Tongue ◽  
Central Pacific ◽  
Easterly Wind ◽  
Budget Analysis

Abstract The El Niño–Southern Oscillation (ENSO) tends to behave arguably as two different “types” or “flavors” in recent decades. One is the canonical cold-tongue-type ENSO with major sea surface temperature anomalies (SSTA) positioned over the eastern Pacific. The other is a warm-pool-type ENSO with SSTA centered in the central Pacific near the edge of the warm pool. In this study, the basic features and main feedback processes of these two types of ENSO are examined. It is shown that the interannual variability of upper-ocean heat content exhibits recharge–discharge processes throughout the life cycles of both the cold tongue (CT) and warm pool (WP) ENSO types. Through a heat budget analysis with focus on the interannual frequency band, the authors further demonstrate that the thermocline feedback plays a dominant role in contributing to the growth and phase transitions of both ENSO types, whereas the zonal advective feedback contributes mainly to their phase transitions. The westward shift of the SSTA center of the WP ENSO and the presence of significant surface easterly wind anomalies over the far eastern equatorial Pacific during its mature warm phase are the two main factors that lead to a reduced positive feedback for the eastern Pacific SSTA. Nevertheless, both the WP and CT ENSO can be understood to a large extent by the recharge oscillator mechanism.

scholarly journals Modelling thermomechanical ice deformation using a GPU-based implicit pseudo-transient method (FastICE v1.0)

2019 ◽  
Author(s):  
Ludovic Räss ◽  
Aleksandar Licul ◽  
Frédéric Herman ◽  
Yury Y. Podladchikov ◽  
Jenny Suckale
Keyword(s):  
Numerical Models ◽  
Time Integration ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Thermomechanical Coupling ◽  
Transition Zones ◽  
Distributed Memory Machines ◽  
Basal Sliding ◽  
Shear Heating ◽  
Matrix Free

Abstract. Accurate predictions of future sea level rise require numerical models that capture the complex thermomechanical feedbacks in rapidly deforming ice. Shear margins, grounding zones and the basal sliding interface are locations of particular interest where the stress-field is complex and fundamentally three-dimensional. These transition zones are prone to thermomechanical localisation, which can be captured numerically only with high temporal and spatial resolution. Thus, better understanding the coupled physical processes that govern these boundaries of localised strain necessitates a non-linear, full Stokes model that affords high resolution and scales well in three dimensions. This paper’s goal is to contribute to the growing toolbox for modelling thermomechanical deformation in ice by levering GPU accelerators’ parallel scalability. We propose a numerical model that relies on pseudo-transient iterations to solve the implicit thermomechanical coupling between ice motion and temperature involving shear-heating and a temperature-dependant ice viscosity. Our method is based on the finite-difference discretisation, and we implement the pseudo-time integration in a matrix-free way. We benchmark the mechanical Stokes solver against the finite-element code Elmer/Ice and report good agreement among the results. We showcase a parallel version of the solver to run on GPU-accelerated distributed memory machines, reaching a parallel efficiency of 93 %. We show that our model is particularly useful for improving our process-based understanding of flow localisation in the complex transition zones bounding rapidly moving ice.

Sign in / Sign up

Export Citation Format

Share Document