Application of Cluster Analysis to Climate Model Performance Metrics

AbstractThe overall performance of general circulation models is often investigated on the basis of the synthesis of a number of scalar performance metrics of individual models that measure the reproducibility of diverse aspects of the climate. Because of physical and dynamic constraints governing the climate, a model’s performance in simulating a certain aspect of the climate is sometimes related closely to that in simulating another aspect, which results in significant intermodel correlation between performance metrics. Numerous metrics and intermodel correlations may cause a problem in understanding the evaluation and synthesizing the metrics. One possible way to alleviate this problem is to group the correlated metrics beforehand. This study attempts to use simple cluster analysis to group 43 performance metrics. Two clustering methods, the K-means and the Ward methods, yield considerably similar clustering results, and several aspects of the results are found to be physically and dynamically reasonable. Furthermore, the intermodel correlation between the cluster averages is considerably lower than that between the metrics. These results suggest that the cluster analysis is helpful in obtaining the appropriate grouping. Applications of the clustering results are also discussed.

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On the potential use of glacier and permafrost observations for verification of climate models

Annals of Glaciology ◽

10.1017/s026030550001435x ◽

1997 ◽

Vol 25 ◽

pp. 400-406 ◽

Cited By ~ 2

Author(s):

Martin Beniston ◽

Wilfried Haeberli ◽

Martin Hoelzle ◽

Alan Taylor

Keyword(s):

General Circulation ◽

Climate Models ◽

Climate Model ◽

Global Climate ◽

Regional Climate ◽

Model Performance ◽

Regional Climate Models ◽

General Circulation Models ◽

Model Verification ◽

Dominant Feature

While the capability of global and regional climate models in reproducing current climate has significantly improved over the past few years, the confidence in model results for remote regions, or those where complex orography is a dominant feature, is still relatively low. This is, in part, linked to the lack of observational data for model verification and intercomparison purposes.Glacier and permafrost observations are directly related to past and present energy flux patterns at the Earth-atmosphere interface and could be used as a proxy for air temperature and precipitation, particularly of value in remote mountain regions and boreal and Arctic zones where instrumental climate records are sparse or non-existent. It is particularly important to verify climate-model performance in these regions, as this is where most general circulation models (GCMs) predict the greatest changes in air temperatures in a warmer global climate.Existing datasets from glacier and permafrost monitoring sites in remote and high altitudes are described in this paper; the data could be used in model-verification studies, as a means to improving model performance in these regions.

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Projection of Future Heat Waves in the United States. Part I: Selecting a Climate Model Subset

Atmosphere ◽

10.3390/atmos11060587 ◽

2020 ◽

Vol 11 (6) ◽

pp. 587

Author(s):

Javad Shafiei Shiva ◽

David G. Chandler

Keyword(s):

United States ◽

General Circulation ◽

Climate Model ◽

Heat Waves ◽

Well Being ◽

General Circulation Models ◽

The United States ◽

Wide Range ◽

Overall Performance ◽

Impact Predictions

The widespread increase in global temperature is driving more frequent and more severe local heatwaves within the contiguous United States (CONUS). General circulation models (GCMs) show increasing, but spatially uneven trends in heatwave properties. However, the wide range of model outputs raises the question of the suitability of this method for indicating the future impacts of heatwaves on human health and well-being. This work examines the fitness of 32 models from CMIP5 and their ensemble median to predict a set of heatwave descriptors across the CONUS, by analyzing their capabilities in the simulation of historical heatwaves during 1950–2005. Then, we use a multi-criteria decision-making tool and rank the overall performance of each model for 10 locations with different climates. We found GCMs have different capabilities in the simulation of historical heatwave characteristics. In addition, we observed similar performances for GCMs over the areas with a partially similar climate. The ensemble model showed better performance in simulation of historical heatwave intensity in some locations, while other individual GCMs represented heatwave time-related components more similar to observations. These results are a step towards the use of contemporary weather models to guide heatwave impact predictions.

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On the potential use of glacier and permafrost observations for verification of climate models

Annals of Glaciology ◽

10.3189/s026030550001435x ◽

1997 ◽

Vol 25 ◽

pp. 400-406 ◽

Cited By ~ 4

Author(s):

Martin Beniston ◽

Wilfried Haeberli ◽

Martin Hoelzle ◽

Alan Taylor

Keyword(s):

General Circulation ◽

Climate Models ◽

Climate Model ◽

Global Climate ◽

Regional Climate ◽

Model Performance ◽

Regional Climate Models ◽

General Circulation Models ◽

Model Verification ◽

Dominant Feature

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Interhemispheric differences of mesosphere/lower thermosphere winds and tides investigated from three whole atmosphere models and meteor radar observations

10.5194/acp-2021-142 ◽

2021 ◽

Author(s):

Gunter Stober ◽

Ales Kuchar ◽

Dimitry Pokhotelov ◽

Huixin Liu ◽

Han-Li Liu ◽

...

Keyword(s):

General Circulation ◽

Climate Models ◽

Climate Model ◽

Lower Thermosphere ◽

Winter Season ◽

General Circulation Models ◽

Meteor Radar ◽

Radar Observations ◽

Seasonal Characteristics

Abstract. Long-term and continuous observations of mesospheric/lower thermospheric winds are rare, but they are important to investigate climatological changes at these altitudes on time scales of several years, covering a solar cycle and longer. Such long time series are a natural heritage of the mesosphere/lower thermosphere climate, and they are valuable to compare climate models or long term runs of general circulation models (GCMs). Here we present a climatological comparison of wind observations from six meteor radars at two conjugate latitudes to validate the corresponding mean winds and atmospheric diurnal and semidiurnal tides from three GCMs, namely Ground-to-Topside Model of Atmosphere and Ionosphere for Aeronomy (GAIA), Whole Atmosphere Community Climate Model Extension (Specified Dynamics) (WACCM-X(SD)) and Upper Atmosphere ICOsahedral Non-hydrostatic (UA-ICON) model. Our results indicate that there are interhemispheric differences in the seasonal characteristics of the diurnal and semidiurnal tide. There also are some differences in the mean wind climatologies of the models and the observations. Our results indicate that GAIA shows a reasonable agreement with the meteor radar observations during the winter season, whereas WACCM-X(SD) shows a better agreement with the radars for the hemispheric zonal summer wind reversal, which is more consistent with the meteor radar observations. The free running UA-ICON tends to show similar winds and tides compared to WACCM-X(SD).

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Tracking Scheme Dependence of Simulated Tropical Cyclone Response to Idealized Climate Simulations

Journal of Climate ◽

10.1175/jcli-d-14-00200.1 ◽

2014 ◽

Vol 27 (24) ◽

pp. 9197-9213 ◽

Cited By ~ 53

Author(s):

Michael Horn ◽

Kevin Walsh ◽

Ming Zhao ◽

Suzana J. Camargo ◽

Enrico Scoccimarro ◽

...

Keyword(s):

Tropical Cyclone ◽

Tropical Cyclones ◽

General Circulation ◽

Climate Model ◽

Circulation Model ◽

General Circulation Models ◽

Tropical Cyclone Activity ◽

Model Data ◽

Cyclone Activity ◽

Sensitivity Testing

Abstract Future tropical cyclone activity is a topic of great scientific and societal interest. In the absence of a climate theory of tropical cyclogenesis, general circulation models are the primary tool available for investigating the issue. However, the identification of tropical cyclones in model data at moderate resolution is complex, and numerous schemes have been developed for their detection. The influence of different tracking schemes on detected tropical cyclone activity and responses in the Hurricane Working Group experiments is examined herein. These are idealized atmospheric general circulation model experiments aimed at determining and distinguishing the effects of increased sea surface temperature and other increased CO2 effects on tropical cyclone activity. Two tracking schemes are applied to these data and the tracks provided by each modeling group are analyzed. The results herein indicate moderate agreement between the different tracking methods, with some models and experiments showing better agreement across schemes than others. When comparing responses between experiments, it is found that much of the disagreement between schemes is due to differences in duration, wind speed, and formation-latitude thresholds. After homogenization in these thresholds, agreement between different tracking methods is improved. However, much disagreement remains, accountable for by more fundamental differences between the tracking schemes. The results indicate that sensitivity testing and selection of objective thresholds are the key factors in obtaining meaningful, reproducible results when tracking tropical cyclones in climate model data at these resolutions, but that more fundamental differences between tracking methods can also have a significant impact on the responses in activity detected.

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Evaluating the ability of NA-CORDEX to simulate the seasonal modes of precipitation variability across the Western United States: Does resolution matter?

10.5194/egusphere-egu21-6999 ◽

2021 ◽

Author(s):

Jonathan Meyer ◽

Shih-Yu (Simon) Wang ◽

Robert Gillies ◽

Jin-Ho Yoon

Keyword(s):

Performance Metrics ◽

Climate Model ◽

Regional Climate ◽

Storm Track ◽

Model Performance ◽

Precipitation Variability ◽

Future Trend ◽

Spring Precipitation ◽

Precipitation Patterns ◽

The North

The western U.S. precipitation climatology simulated by the NA-CORDEX regional climate model ensembles are examined to evaluate the capability of the 0.44&#176; and 0.22&#176; resolutionensembles to reproduce 1) the annual and semi-annual precipitation cycle of several hydrologically important western U.S. regions and 2) localized seasonality in the amount and timing of precipitation. Collectively, when compared against observation-based gridded precipitation, NA-CORDEX RCMs driven by ERA-Interim reanalysis at the higher resolution 0.22&#176; domain resolution dramatically outperformed the 0.44&#176; ensemble over the 1950-2005 historical periods. Furthermore, the ability to capture the annual and semi-annual modes of variability was starkly improved in the higher resolution 0.22&#176; ensemble. The higher resolution members reproduced more consistent spatial patterns of variance featuring lower errors in magnitude&#8212;especially with respect to the winter-summer and spring-fall seasonality. A great deal of spread in model performance was found for the semi-annual cycles, although the higher-resolution ensemble exhibited a more coherent clustering of performance metrics. In general, model performance was a function of which RCM was used, while future trend scenarios seem to cluster around which GCM was downscaled. Future projections of precipitation patterns from the 0.22&#176; NA-CORDEX RCMs driven by the RCP4.5 &#8220;stabilization scenario&#8221; and the RCP8.5 &#8220;high emission&#8221; scenario were analyzed to examine trends to the &#8220;end of century&#8221; (i.e. 2050-2099) precipitation patterns. Except for the Desert Southwest&#8217;s spring season, the RCP4.5 and RCP8.5 scenarios show a consensus change towards an increase in winter and spring precipitation throughout all regions of interest with the RCP8.5 scenario containing a greater number of ensemble members simulating greater wetting trends. The future winter-summer mode of variability exhibited a general consensus towards increasing variability with greatest change found over the region&#8217;s terrain suggesting a greater year-to-year variability of the region&#8217;s orographic response to the strength and location of the mid-latitude jet streams and storm track. Increasing spring-fall precipitation variability suggests an expanding influence of tropical moisture advection associated with the North American Monsoon, although we note that like many future monsoon projections, a spring &#8220;convective barrier&#8221; was also apparent in the NA-CORDEX ensembles.

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An automatic and effective parameter optimization method for model tuning

Geoscientific Model Development ◽

10.5194/gmd-8-3579-2015 ◽

2015 ◽

Vol 8 (11) ◽

pp. 3579-3591 ◽

Cited By ~ 19

Author(s):

T. Zhang ◽

L. Li ◽

Y. Lin ◽

W. Xue ◽

F. Xie ◽

...

Keyword(s):

Simplex Method ◽

General Circulation ◽

Model Development ◽

Model Performance ◽

Parameter Tuning ◽

General Circulation Models ◽

Development Stage ◽

Optimum Combination ◽

Downhill Simplex Method ◽

Downhill Simplex

Abstract. Physical parameterizations in general circulation models (GCMs), having various uncertain parameters, greatly impact model performance and model climate sensitivity. Traditional manual and empirical tuning of these parameters is time-consuming and ineffective. In this study, a "three-step" methodology is proposed to automatically and effectively obtain the optimum combination of some key parameters in cloud and convective parameterizations according to a comprehensive objective evaluation metrics. Different from the traditional optimization methods, two extra steps, one determining the model's sensitivity to the parameters and the other choosing the optimum initial value for those sensitive parameters, are introduced before the downhill simplex method. This new method reduces the number of parameters to be tuned and accelerates the convergence of the downhill simplex method. Atmospheric GCM simulation results show that the optimum combination of these parameters determined using this method is able to improve the model's overall performance by 9 %. The proposed methodology and software framework can be easily applied to other GCMs to speed up the model development process, especially regarding unavoidable comprehensive parameter tuning during the model development stage.

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Alpine Younger Dryas glaciers as palaeo-precipitation gauges

Annals of Glaciology ◽

10.3189/172756400781820237 ◽

2000 ◽

Vol 31 ◽

pp. 80-84 ◽

Cited By ~ 60

Author(s):

Hanns Kerschner ◽

Georg Kaser ◽

Rudolf Sailer

Keyword(s):

General Circulation ◽

Climate Model ◽

Younger Dryas ◽

General Circulation Models ◽

Summer Temperature ◽

Equilibrium Line Altitude ◽

The West ◽

Temperature And Precipitation ◽

Data Points ◽

The Alps

AbstractMoraines of the Younger Dryas ˚Egesen Stadial", which are widespread features in the Alps, are a valuable terrestrial data source for quantitative palaeoclimatic studies. The depression of the early Younger Dryas (Egesen-I) equilibrium-line altitude (ELA) shows a distinct spatial pattern. It was greatest (about –450 to –500 m vs present day) m areas exposed towards the west and northwest. In the central, more sheltered valleys it was on the order of –300 m or less. Summer temperature depression, which can be derived from the Younger Dryas timberline depression, was on the order of –3.5 K. The stochastic glacier-climate model of Ohmura and others (1992), which relates summer temperature and precipitation at the ELA, is used to infer precipitation change. Results are compared with those obtained from the glacial-meteorological approach of Kuhn (1981a). The two models produce highly similar results. During the early Younger Dryas, climate in the central valleys of the Alps seems to have been considerably drier than today In areas open to the west and northwest, precipitation seems to have been the same as today or even slightly higher. These results, which are based on a rather dense network of data points, agree well with results from permafrost-climate studies and the more qualitative information from palaeobotanical research. They also support the results from atmospheric general circulation models for the Younger Dryas in Europe, which point towards a more zonal type of circulation.

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Net effect of the QBO in a chemistry climate model

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-6505-2008 ◽

2008 ◽

Vol 8 (21) ◽

pp. 6505-6525 ◽

Cited By ~ 11

Author(s):

H. J. Punge ◽

M. A. Giorgetta

Keyword(s):

General Circulation ◽

Climate Models ◽

Climate Model ◽

Middle Atmosphere ◽

Meridional Circulation ◽

Vortex Formation ◽

General Circulation Models ◽

Quasi Biennial Oscillation ◽

The Mean ◽

The Tropics

Abstract. The quasi-biennial oscillation (QBO) of zonal wind is a prominent mode of variability in the tropical stratosphere. It affects not only the meridional circulation and temperature over a wide latitude range but also the transport and chemistry of trace gases such as ozone. Compared to a QBO less circulation, the long-term climatological means of these quantities are also different. These climatological net effects of the QBO can be studied in general circulation models that extend into the middle atmosphere and have a chemistry and transport component, so-called Chemistry Climate Models (CCMs). In this work we show that the CCM MAECHAM4-CHEM can reproduce the observed QBO variations in temperature and ozone mole fractions when nudged towards observed winds. In particular, it is shown that the QBO signal in transport of nitrogen oxides NOx plays an important role in reproducing the observed ozone QBO, which features a phase reversal slightly below the level of maximum of the ozone mole fraction in the tropics. We then compare two 20-year experiments with the MAECHAM4-CHEM model that differ by including or not including the QBO. The mean wind fields differ between the two model runs, especially during summer and fall seasons in both hemispheres. The differences in the wind field lead to differences in the meridional circulation, by the same mechanism that causes the QBO's secondary meridional circulation, and thereby affect mean temperatures and the mean transport of tracers. In the tropics, the net effect on ozone is mostly due to net differences in upwelling and, higher up, the associated temperature change. We show that a net surplus of up to 15% in NOx in the tropics above 10 hPa in the experiment that includes the QBO does not lead to significantly different volume mixing ratios of ozone. We also note a slight increase in the southern vortex strength as well as earlier vortex formation in northern winter. Polar temperatures differ accordingly. Differences in the strength of the Brewer-Dobson circulation and in further trace gas concentrations are analysed. Our findings underline the importance of a representation of the QBO in CCMs.

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The cloud–aerosol–radiation (CAR) ensemble modeling system

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-8335-2013 ◽

2013 ◽

Vol 13 (16) ◽

pp. 8335-8364 ◽

Cited By ~ 13

Author(s):

X.-Z. Liang ◽

F. Zhang

Keyword(s):

Radiative Forcing ◽

General Circulation ◽

Climate Model ◽

Climate Modeling ◽

General Circulation Models ◽

Climate Impacts ◽

Sensitivity Analyses ◽

General Description ◽

Ensemble Modeling ◽

Uncertainty Range

Abstract. A cloud–aerosol–radiation (CAR) ensemble modeling system has been developed to incorporate the largest choices of alternate parameterizations for cloud properties (cover, water, radius, optics, geometry), aerosol properties (type, profile, optics), radiation transfers (solar, infrared), and their interactions. These schemes form the most comprehensive collection currently available in the literature, including those used by the world's leading general circulation models (GCMs). CAR provides a unique framework to determine (via intercomparison across all schemes), reduce (via optimized ensemble simulations), and attribute specific key factors for (via physical process sensitivity analyses) the model discrepancies and uncertainties in representing greenhouse gas, aerosol, and cloud radiative forcing effects. This study presents a general description of the CAR system and illustrates its capabilities for climate modeling applications, especially in the context of estimating climate sensitivity and uncertainty range caused by cloud–aerosol–radiation interactions. For demonstration purposes, the evaluation is based on several CAR standalone and coupled climate model experiments, each comparing a limited subset of the full system ensemble with up to 896 members. It is shown that the quantification of radiative forcings and climate impacts strongly depends on the choices of the cloud, aerosol, and radiation schemes. The prevailing schemes used in current GCMs are likely insufficient in variety and physically biased in a significant way. There exists large room for improvement by optimally combining radiation transfer with cloud property schemes.

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