scholarly journals Assessing the performance of 33 CMIP6 models in simulating the large-scale environmental fields of tropical cyclones

2021 ◽  
Author(s):  
Ying Han ◽  
Mengzhuo Zhang ◽  
Zhongfeng Xu ◽  
Weidong Guo
Keyword(s):  
Interannual Variability ◽  
Tropical Cyclones ◽  
General Circulation ◽  
Large Scale ◽  
Evaluation Method ◽  
Climate Models ◽  
Circulation Model ◽  
Horizontal Resolution ◽  
Vertical Shear ◽  
Multiple Variables

Abstract General circulation model (GCM) biases are one of the important sources of biases and uncertainty in dynamic downscaling–based simulations. The ability of regional climate models to simulate tropical cyclones (TCs) is strongly affected by the ability of GCMs to simulate the large-scale environmental field. Thus, in this work, we employ a recently developed multivariable integrated evaluation method to assess the performance of 33 CMIP6 (phase 6 of the Coupled Model Intercomparison Project) models in simulating multiple fields. The CMIP6 models are quantitatively evaluated against two reanalysis datasets over five ocean areas. The results show that most of the CMIP6 models overestimate the mid-level humidity in almost all tropical oceans. The multi-model ensemble mean overestimates the vertical shear of the horizontal winds in the Northeast Pacific and North Atlantic. An increase in model horizontal resolution appears to be helpful in improving the model simulations. For example, there are 6–8 models with higher resolution among the top 10 models in terms of overall model performance in simulating the climatology and interannual variability of multiple variables. Similarly, there are 7–8 models with lower resolution among the bottom 10 patterns. The model skill varies depending on the region and variable being evaluated. Although no model performs best in all regions and for all variables, some models do show relatively good capability in simulating the large-scale environmental field of TCs. For example, the MPI-ESM1-2-LR, MPI-ESM1-2-HR, and FIO-ESM-2-0 models show relatively good skill in simulating the climatology and interannual variability of the large-scale environmental field in the Northern and Southern Hemispheres.

scholarly journals Can Lagrangian Tracking Simulate Tracer Spreading in a High-Resolution Ocean General Circulation Model?

2019 ◽  
Vol 49 (5) ◽  
pp. 1141-1157 ◽  
Author(s):  
Patrick Wagner ◽  
Siren Rühs ◽  
Franziska U. Schwarzkopf ◽  
Inga Monika Koszalka ◽  
Arne Biastoch
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Eddy Diffusivity ◽  
Ocean General Circulation Model ◽  
Horizontal Resolution ◽  
Ocean Model ◽  
Time Step ◽  
Lagrangian Particles ◽  
Cape Basin

AbstractTo model tracer spreading in the ocean, Lagrangian simulations in an offline framework are a practical and efficient alternative to solving the advective–diffusive tracer equations online. Differences in both approaches raise the question of whether both methods are comparable. Lagrangian simulations usually use model output averaged in time, and trajectories are not subject to parameterized subgrid diffusion, which is included in the advection–diffusion equations of ocean models. Previous studies focused on diffusivity estimates in idealized models but could show that both methods yield similar results as long as the deformations-scale dynamics are resolved and a sufficient amount of Lagrangian particles is used. This study compares spreading of an Eulerian tracer simulated online and a cloud of Lagrangian particles simulated offline with velocities from the same ocean model. We use a global, eddy-resolving ocean model featuring 1/20° horizontal resolution in the Agulhas region around South Africa. Tracer and particles were released at one time step in the Cape Basin and below the mixed layer and integrated for 3 years. Large-scale diagnostics, like mean pathways of floats and tracer, are almost identical and 1D horizontal distributions show no significant differences. Differences in vertical distributions, seen in a reduced vertical spreading and downward displacement of particles, are due to the combined effect of unresolved subdaily variability of the vertical velocities and the spatial variation of vertical diffusivity. This, in turn, has a small impact on the horizontal spreading behavior. The estimates of eddy diffusivity from particles and tracer yield comparable results of about 4000 m2 s−1 in the Cape Basin.

The moisture budget of tropical cyclones: large scale environmental constraints and sensitivity to model horizontal resolution

2020 ◽  
Author(s):  
Benoit Vanniere ◽  
Malcolm Roberts ◽  
Pier Luigi Vidale ◽  
Kevin Hodges ◽  
Marie-Estelle Demory
Keyword(s):  
Tropical Cyclones ◽  
Large Scale ◽  
Climate Models ◽  
Potential Temperature ◽  
Large Change ◽  
Moisture Flux ◽  
Horizontal Resolution ◽  
Moisture Budget ◽  
High Resolution Models ◽  
The Impact

<p>Previous studies have shown that, the number, intensity and structure of simulated tropical cyclones (TC) in climate models get closer to the observations as the horizontal resolution is increased. However, the sensitivity of tropical cyclone precipitation and moisture budget to changes in resolution has received less attention. In this study, we use the five-model ensemble from project PRIMAVERA/HighResMIP to investigate the systematic changes associated with the water budget of tropical cyclones in a range of horizontal resolutions from 1º to 0.25º. Our results show that despite a large change in the distribution of TC intensity with resolution, the distribution of precipitation per TC does not change significantly. This result is explained by the large scale balance which characterises the moisture budget of TCs, i.e. radii of ~15º a scale that low and high resolution models represent equally well. The wind profile is found to converge between low and high resolutions for radii > 5º, resulting in a moisture flux convergence into the TC with similar magnitude at low and high resolutions. In contrast to precipitation per TC, the larger TC intensity at higher resolution is explained by the larger surface latent heat flux near the center of the storm, which leads to an increase in equivalent potential temperature and warmer core anomalies, despite representing a negligible contribution to the moisture budget. We discuss the complication arising from the choice of the tracking algorithm when assessing the impact of model resolution and the implications of such a constraint on the TC moisture budget in the context of climate change.</p>

Simulation of the Diurnal Cycle in Tropical Rainfall and Circulation during Boreal Summer with a High-Resolution GCM

2010 ◽  
Vol 138 (9) ◽  
pp. 3434-3453 ◽  
Author(s):  
Jeffrey J. Ploshay ◽  
Ngar-Cheung Lau
Keyword(s):  
Diurnal Cycle ◽  
General Circulation ◽  
Large Scale ◽  
Surface Wind ◽  
Circulation Model ◽  
Horizontal Resolution ◽  
Boreal Summer ◽  
Tropical Rainfall ◽  
Early Afternoon ◽  
Seaward Migration

Abstract The simulation of the diurnal cycle (DC) of precipitation and surface wind pattern by a general circulation model (GCM) with a uniform horizontal resolution of 50 km over the global domain is evaluated. The model output is compared with observational counterparts based on datasets provided by the Tropical Rainfall Measuring Mission and reanalysis products of the European Centre for Medium-Range Weather Forecasts. The summertime diurnal characteristics over tropical regions in Asia, the Americas, and Africa are portrayed using the amplitude and phase of the first harmonic of the 24-h cycle, departures of data fields during selected hours from the daily mean, and differences between extreme phases of the DC. There is general agreement between the model and observations with respect to the large-scale land–sea contrasts in the DC. Maximum land precipitation, onshore flows, and landward migration of rainfall signals from the coasts occur in the afternoon, whereas peak maritime rainfall and offshore flows prevail in the morning. Seaward migration of precipitation is discernible over the western Bay of Bengal and South China Sea during nocturnal and morning hours. The evolution from low-intensity rainfall in the morning/early afternoon to heavier precipitation several hours later is also evident over selected continental sites. However, the observed incidence of rainfall with very high intensity in midafternoon is not reproduced in the model atmosphere. Although the model provides an adequate simulation of the daytime upslope and nighttime downslope winds in the vicinity of mountain ranges, valleys, and basins, there are notable discrepancies between model and observations in the DC of precipitation near some of these orographic features. The model does not reproduce the observed seaward migration of precipitation from the western coasts of Myanmar (Burma) and India, and from individual islands of the Indonesian Archipelago at nighttime.

scholarly journals Effects of Tropical Cyclones on Ocean Heat Transport in a High-Resolution Coupled General Circulation Model

2011 ◽  
Vol 24 (16) ◽  
pp. 4368-4384 ◽  
Author(s):  
Enrico Scoccimarro ◽  
Silvio Gualdi ◽  
Alessio Bellucci ◽  
Antonella Sanna ◽  
Pier Giuseppe Fogli ◽  
...  
Keyword(s):  
Twentieth Century ◽  
High Resolution ◽  
Heat Transport ◽  
Tropical Cyclones ◽  
General Circulation Model ◽  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Ocean Heat Transport ◽  
Coupled General Circulation Model

Abstract In this paper the interplay between tropical cyclones (TCs) and the Northern Hemispheric ocean heat transport (OHT) is investigated. In particular, results from a numerical simulation of the twentieth-century and twenty-first-century climates, following the Intergovernmental Panel on Climate Change (IPCC) twentieth-century run (20C3M) and A1B scenario protocols, respectively, have been analyzed. The numerical simulations have been performed using a state-of-the-art global atmosphere–ocean–sea ice coupled general circulation model (CGCM) with relatively high-resolution (T159) in the atmosphere. The CGCM skill in reproducing a realistic TC climatology has been assessed by comparing the model results from the simulation of the twentieth century with available observations. The model simulates tropical cyclone–like vortices with many features similar to the observed TCs. Specifically, the simulated TCs exhibit realistic structure, geographical distribution, and interannual variability, indicating that the model is able to capture the basic mechanisms linking the TC activity with the large-scale circulation. The cooling of the surface ocean observed in correspondence of the TCs is well simulated by the model. TC activity is shown to significantly increase the poleward OHT out of the tropics and decrease the poleward OHT from the deep tropics on short time scales. This effect, investigated by looking at the 100 most intense Northern Hemisphere TCs, is strongly correlated with the TC-induced momentum flux at the ocean surface, where the winds associated with the TCs significantly weaken (strengthen) the trade winds in the 5°–18°N (18°–30°N) latitude belt. However, the induced perturbation does not impact the yearly averaged OHT. The frequency and intensity of the TCs appear to be substantially stationary through the entire 1950–2069 simulated period, as does the effect of the TCs on the OHT.

scholarly journals Simulation of winter and summer climates with PRL Atmospheric General Circulation Model

MAUSAM ◽  
2021 ◽  
Vol 50 (4) ◽  
pp. 391-400
Author(s):  
BIJU THOMAS ◽  
S.V. KASTURE ◽  
S. V. SATYAN
Keyword(s):  
General Circulation Model ◽  
General Circulation ◽  
Large Scale ◽  
Atmospheric General Circulation Model ◽  
Initial Conditions ◽  
Circulation Model ◽  
Horizontal Resolution ◽  
Hemispheric Differences ◽  
Physical Research Laboratory ◽  
Atmospheric General Circulation

A global, spectral Atmospheric General Circulation Model (AGCM) has been developed indigenously at Physical Research Laboratory (PRL) for climate studies. The model has six a levels in the vertical and has horizontal resolution of 21 waves with rhomboidal truncation. The model includes smooth topography, planetary boundary layer, deep convection, large scale condensation, interactive hydrology, radiation with interactive clouds and diurnal cycle. Sea surface temperature and sea ice values were fixed based on climatological data for different calender months.   The model was integrated for six years starting with an isothermal atmosphere (2400K), zero winds initial conditions and forcing from incoming solar radiation. After one year the model stabilizes. The seasonal averages of various fields of the last five years are discussed in this paper. It is found that the model reproduces reasonably well the seasonal features of atmospheric circulation, seasonal variability and hemispheric differences.

scholarly journals Quantitative Sensitivity Analysis of Physical Parameterizations for Cases of Deep Convection in the NASA GEOS-5

2016 ◽  
Vol 29 (2) ◽  
pp. 455-479 ◽  
Author(s):  
Derek J. Posselt ◽  
Bruce Fryxell ◽  
Andrea Molod ◽  
Brian Williams
Keyword(s):  
General Circulation ◽  
Process Model ◽  
Large Scale ◽  
Climate Models ◽  
Deep Convection ◽  
Input Parameter ◽  
Circulation Model ◽  
Parameter Sensitivity ◽  
Global Climate Models ◽  
Simulation Code

Abstract Parameterization of processes that occur on length scales too small to resolve on a computational grid is a major source of uncertainty in global climate models. This study investigates the relative importance of a number of parameters used in the Goddard Earth Observing System Model, version 5 (GEOS-5), atmospheric general circulation model, focusing on cloud, convection, and boundary layer parameterizations. Latin hypercube sampling is used to generate a few hundred sets of 19 candidate physics parameters, which are subsequently used to generate ensembles of single-column model realizations of cloud content, precipitation, and radiative fluxes for four different field campaigns. A Gaussian process model is then used to create a computationally inexpensive emulator for the simulation code that can be used to determine a measure of relative parameter sensitivity by sampling the response surface for a very large number of input parameter sets. Parameter sensitivities are computed for different geographic locations and seasons to determine whether the intrinsic sensitivity of the model parameterizations changes with season and location. The results indicate the same subset of parameters collectively control the model output across all experiments, independent of changes in the environment. These are the threshold relative humidity for cloud formation, the ice fall speeds, convective and large-scale autoconversion, deep convection relaxation time scale, maximum convective updraft diameter, and minimum ice effective radius. However, there are differences in the degree of parameter sensitivity between continental and tropical convective cases, as well as systematic changes in the degree of parameter influence and parameter–parameter interaction.

scholarly journals The Moisture Budget of Tropical Cyclones in HighResMIP Models: Large-Scale Environmental Balance and Sensitivity to Horizontal Resolution

2020 ◽  
Vol 33 (19) ◽  
pp. 8457-8474
Author(s):  
Benoît Vannière ◽  
Malcolm Roberts ◽  
Pier Luigi Vidale ◽  
Kevin Hodges ◽  
Marie-Estelle Demory ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Latent Heat ◽  
Large Scale ◽  
Climate Models ◽  
Potential Temperature ◽  
Large Change ◽  
Moisture Flux ◽  
Horizontal Resolution ◽  
Moisture Budget ◽  
The Impact

AbstractPrevious studies have shown that the number, intensity, and structure of simulated tropical cyclones (TCs) in climate models get closer to the observations as the horizontal resolution is increased. However, the sensitivity of tropical cyclone precipitation and moisture budget to changes in resolution has received less attention. In this study, we use the five-model ensemble from project PRIMAVERA/HighResMIP to investigate the systematic changes of the water budget of tropical cyclones in a range of horizontal resolutions from 1° to 0.25°. Our results show that, despite a large change in the distribution of TC intensity with resolution, the distribution of precipitation per TC (i.e., averaged in a 5° radial cap) does not change significantly. This result is explained by the fact that low- and high-resolution models represent equally well the large-scale balance that characterizes the moisture budget of TCs, with the radius of the moisture source extending to ~15° from the center of the TC (i.e. well beyond the TC edge). The wind profile is found to converge in the low and high resolutions for radii > 5°, resulting in a moisture flux convergence into the TC of similar magnitude at low and high resolutions. In contrast to precipitation per TC, TC intensity does increase at higher resolution and this is explained by the larger surface latent heat flux near the center of the storm, which leads to an increase in equivalent potential temperature and warmer core anomalies, although this extra latent heat represents a negligible contribution to the overall moisture budget. We discuss the complication arising from the choice of the tracking algorithm when assessing the impact of model resolution.

scholarly journals Relationships between South Atlantic SST Variability and Atmospheric Circulation over the South African Region during Austral Winter

2005 ◽  
Vol 18 (16) ◽  
pp. 3339-3355 ◽  
Author(s):  
C. J. C. Reason ◽  
D. Jagadheesha
Keyword(s):  
Interannual Variability ◽  
General Circulation ◽  
Large Scale ◽  
Rainfall Variability ◽  
Circulation Model ◽  
South Atlantic ◽  
The South ◽  
Winter Rainfall ◽  
Southwest Atlantic ◽  
Sst Anomalies

Abstract The Southwestern Cape (SWC) region of South Africa is characterized by winter rainfall brought mainly via cold fronts and by substantial interannual variability. Previous work has found evidence that the interannual variability in SWC winter rainfall may be related to sea surface temperature (SST) in the South Atlantic Ocean and to large-scale ocean–atmosphere interaction in this region. During wet winters, SST tends to be anomalously warm (cool) in the southwest Atlantic and southeast Atlantic (central South Atlantic). Atmospheric general circulation model experiments with various idealized SST anomalies in the South Atlantic are used to explore mechanisms potentially associated with the rainfall variability. The model results suggest that the atmosphere is sensitive to subtropical–midlatitude SST anomalies in the South Atlantic during winter. Locally, there are changes to the jet position and strength, low-level relative vorticity, and convergence of moisture and latent heat flux that lead to changes in rainfall over the SWC. The model response to the SST forcing also shows large-scale anomalies in the midlatitude Southern Hemisphere circulation, namely, an Antarctic Oscillation–type mode and wavenumber-3 changes, similar to those observed during anomalous winters in the region.

scholarly journals Investigation of Intense Precipitation from Tropical Cyclones during the 21st Century by Dynamical Downscaling of CCSM4 RCP 4.5

2019 ◽  
Vol 16 (5) ◽  
pp. 687
Author(s):  
Mathieu Mure-Ravaud ◽  
M. Kavvas ◽  
Alain Dib
Keyword(s):  
Tropical Cyclones ◽  
General Circulation ◽  
Large Scale ◽  
Dynamical Downscaling ◽  
Circulation Model ◽  
Small Scale ◽  
Climate Projections ◽  
Modeling Framework ◽  
Climate System Model ◽  
Intense Precipitation

In this article, a dynamical downscaling (DD) procedure is proposed to downscale tropical cyclones (TCs) from a general circulation model, with the goal of investigating inland intense precipitation from these storms in the future. This DD procedure is sequential as it is performed from the large scale to the small scale within a one-way nesting modeling framework with the Weather Research and Forecasting (WRF) model. Furthermore, it involves a two-step validation process to ensure that the model produces realistic TCs, both in terms of their general properties and in terms of their intense precipitation statistics. In addition, this procedure makes use of several algorithms such as for the detection and tracking of TCs, with the objective of automatizing the DD process as much as possible so that this approach could be used to downscale massively many climate projections with several sets of model options. The DD approach was applied to the Community Climate System Model (CCSM) version 4 using Representative Concentration Pathway (RCP) 4.5 during the period 2005–2100, and the resulting TCs and their intense precipitation were examined.

Different Climatological Characteristics, Inner-Core Structures, and Intensification Processes of Simulated Intense Tropical Cyclones between 20-km Global and 5-km Regional Models

2017 ◽  
Vol 30 (5) ◽  
pp. 1583-1603 ◽  
Author(s):  
Sachie Kanada ◽  
Akiyoshi Wada
Keyword(s):  
Tropical Cyclones ◽  
General Circulation ◽  
Large Scale ◽  
Atmospheric General Circulation Model ◽  
Inner Core ◽  
Circulation Model ◽  
Maximum Intensity ◽  
Rapid Intensification ◽  
Nonhydrostatic Model ◽  
Before And After

Abstract Climatological characteristics of simulated intense tropical cyclones (TCs) in the western North Pacific were explored with a 20-km-mesh atmospheric general circulation model (AGCM20) and a 5-km-mesh regional atmospheric nonhydrostatic model (ANHM5). From the AGCM20 climate runs, 34 intense TCs with a minimum central pressure (MCP) less than or equal to 900 hPa were sampled. Downscaling experiments were conducted with the ANHM5 for each intense TC simulated by the AGCM20. Only 23 developed into TCs with MCP ≤ 900 hPa. Most of the best-track TCs with an MCP ≤ 900 hPa underwent rapid intensification (RI) and attained maximum intensities south of 25°N. The AGCM20 simulated a similar number of intense TCs as the best-track datasets. However, the intense AGCM20 TCs tended to intensify longer and more gradually; only half of them underwent RI. The prolonged gradual intensification resulted in significant northward shifts of the location of maximum intensity compared with the location derived from two best-track datasets. The inner-core structure of AGCM20 TCs exhibited weak and shallow eyewall updrafts with maxima below an altitude of 6 km, while downscaling experiments revealed that most of the intense ANHM5 TCs underwent RI with deep and intense eyewall updrafts and attained their maximum intensity at lower latitudes. The altitudes of updraft maxima simulated by the AGCM20 descended rapidly during the phase of greatest intensification as midlevel warming markedly developed. The change in major processes responsible for precipitation in AGCM20 TCs before and after maximum intensification suggests close relationships between the large-scale cloud scheme and midlevel warming and prolonged gradual intensification.

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