scholarly journals A model intercomparison analysing the link between column ozone and geopotential height anomalies in January

2008 ◽  
Vol 8 (9) ◽  
pp. 2519-2535 ◽  
Author(s):  
P. Braesicke ◽  
C. Brühl ◽  
M. Dameris ◽  
R. Deckert ◽  
V. Eyring ◽  
...  
Keyword(s):  
Geopotential Height ◽  
Climate Models ◽  
Horizontal Resolution ◽  
Empirical Orthogonal Functions ◽  
Orthogonal Functions ◽  
The Pacific ◽  
Column Ozone ◽  
Linear Correlations ◽  
Upper Boundary ◽  
Good Agreement

Abstract. A statistical framework to evaluate the performance of chemistry-climate models with respect to the interaction between meteorology and column ozone during northern hemisphere mid-winter, in particularly January, is used. Different statistical diagnostics from four chemistry-climate models (E39C, ME4C, UMUCAM, ULAQ) are compared with the ERA-40 re-analysis. First, we analyse vertical coherence in geopotential height anomalies as described by linear correlations between two different pressure levels (30 and 200 hPa) of the atmosphere. In addition, linear correlations between column ozone and geopotential height anomalies at 200 hPa are discussed to motivate a simple picture of the meteorological impacts on column ozone on interannual timescales. Secondly, we discuss characteristic spatial structures in geopotential height and column ozone anomalies as given by their first two empirical orthogonal functions. Finally, we describe the covariance patterns between reconstructed anomalies of geopotential height and column ozone. In general we find good agreement between the models with higher horizontal resolution (E39C, ME4C, UMUCAM) and ERA-40. The Pacific-North American (PNA) pattern emerges as a useful qualitative benchmark for the model performance. Models with higher horizontal resolution and high upper boundary (ME4C and UMUCAM) show good agreement with the PNA tripole derived from ERA-40 data, including the column ozone modulation over the Pacfic sector. The model with lowest horizontal resolution does not show a classic PNA pattern (ULAQ), and the model with the lowest upper boundary (E39C) does not capture the PNA related column ozone variations over the Pacific sector. Those discrepancies have to be taken into account when providing confidence intervals for climate change integrations.

scholarly journals A model intercomparison analysing the link between ozone and geopotential height anomalies in January

2007 ◽  
Vol 7 (6) ◽  
pp. 15409-15451 ◽  
Author(s):  
P. Braesicke ◽  
C. Brühl ◽  
M. Dameris ◽  
R. Deckert ◽  
V. Eyring ◽  
...  
Keyword(s):  
Geopotential Height ◽  
Climate Models ◽  
Horizontal Resolution ◽  
Empirical Orthogonal Functions ◽  
Orthogonal Functions ◽  
Modes Of Variability ◽  
Statistical Framework ◽  
Column Ozone ◽  
Linear Correlations ◽  
Upper Boundary

Abstract. A statistical framework to evaluate the performance of chemistry-climate models with respect to the interaction between meteorology and ozone during northern hemisphere mid-winter, in particularly January, is used. Different statistical diagnostics from four chemistry-climate models (E39C, ME4C, UMUCAM, ULAQ) are compared with the ERA-40 re-analysis. First, we analyse vertical coherence in geopotential height anomalies as described by linear correlations between two different pressure levels (30 and 200 hPa) of the atmosphere. In addition, linear correlations between (partial) column ozone and geopotential height anomalies at 200 hPa are discussed to motivate a simple picture of the meteorological impacts on ozone on interannual timescales. Secondly, we discuss characteristic spatial structures in geopotential height and (partial) column ozone anomalies as given by their first two empirical orthogonal functions. Finally, we describe the covariance patterns between reconstructed anomalies of geopotential height and (partial) column ozone. In general we find good agreement between the models with higher horizontal resolution (E39C, ME4C, UMUCAM) and ERA-40. Some diagnostics seem to be capable of picking up model similarities (either that the models use the same dynamical core (E39C, ME4C), or that they have a high upper boundary (ME4C, UMUCAM)). The methodology allows to identify the leading modes of variability contributing to the overall ozone-geopotential height correlations and points to interesting differences between the chemistry-climate models and ERA-40. Those discrepancies have to be taken into account when providing confidence intervals for climate change integrations.

Statistical description of the East Australian Current low-frequency variability from the WOCE PCM3 array

2006 ◽  
Vol 57 (3) ◽  
pp. 273 ◽  
Author(s):  
Mauricio M. Mata ◽  
Susan Wijffels ◽  
John A. Church ◽  
Matthias Tomczak
Keyword(s):  
Ocean Circulation ◽  
World Ocean ◽  
Low Frequency ◽  
General Rule ◽  
Empirical Orthogonal Functions ◽  
East Australian Current ◽  
Orthogonal Functions ◽  
The Pacific ◽  
Strong Surface ◽  
The Impact

The in situ dataset used in the current study consists of the Pacific Current Meter 3 (PCM3) array, which was a significant part of the Australian contribution to the World Ocean Circulation Experiment to study the variability of the East Australian Current (EAC), and was operational between September 1991 and March 1994. Area-preserving spectral analysis has been used to investigate the typical time scales observed by the current meters. As a general rule, the spectra from the top layers of the shallow (1, 2 and 3) and the deep (4, 5 and 6) moorings have a distinct peak in the temporal mesoscale band (periods between 70 and 170 days), with a general redistribution of energy towards the higher-frequencies near the ocean floor. This peak has been linked with eddy variability of the EAC system, which influences the fluctuations of the current main jet. The vertical modes of the velocity profile show that the strong surface-intensified baroclinic signal of the EAC dominated the variability at mooring 4 location. Further offshore the predominant configuration resembles more closely the barotropic mode. Ultimately, spatial empirical orthogonal functions (EOF) analysis point out the impact of the presence/absence of the EAC jet in the array.

scholarly journals Climatic Changes of Thermal Conditions in the Pacific Subarctic at the Modern Stage of Global Warming

2021 ◽  
Vol 37 (2) ◽  
Author(s):  
I. D. Rostov ◽  
E. V. Dmitrieva ◽  
N. I. Rudykh ◽  
◽  
◽  
...  
Keyword(s):  
Air Temperature ◽  
Climate Changes ◽  
Surface Air Temperature ◽  
Ocean Surface ◽  
Empirical Orthogonal Functions ◽  
Orthogonal Functions ◽  
The North ◽  
Regional Features ◽  
The Pacific ◽  
Warming Rate

Purpose. The study is aimed at identifying the regional features of the surface air temperature in the coastal zone and over the Pacific Ocean (to the north of 40° N) manifested as a result of global climate changes at the turn of the XX–XXI centuries, and at assessing their trends and possible causal relationships with the processes in the atmosphere and on the ocean surface. Methods and Results. Based on the Global Meteorological Network and NOAA reanalysis data, the regional features of interannual fluctuations of the surface air temperature and their relationship with variations in the fields of pressure, wind and water temperature on the ocean surface, and with climate indices over the past 4 decades were identified. In order to determine the temperature field spatialtemporal structure and to zone the water area according to the features of climate changes, the methods of cluster, correlation analysis and the apparatus of empirical orthogonal functions were used. The results obtained made it possible to characterize the degree of heterogeneity of the studied area response to the ongoing global changes, to identify different domains and to assess quantitatively the warming rate in these water areas. Conclusions. The tendencies of modern warming are manifested in the trends of interannual air temperature variability, on the average, by ~0.20°C/10 years in the subarctic, and indicate significant regional differences (1.5–2 times) in the ongoing changes. In the west of the region, the warming rate is higher than in the east, where the temperature trends are minimal or statistically insignificant. In the warm period of a year, their values are higher than those in the cold period. The alternation phases of the warm and cold periods are consistent with the variation tendencies in the characteristics both of the atmospheric action centers and various climatic parameters. The corresponding correlations are most widely manifested in variations in the empirical orthogonal functions modes of the H500 geopotential field, and the PDO, NP, SOI, PTW, AD and EP/NP indices. Stable anomalies and trends of the ocean surface temperature in the North Atlantic also play an important role in formation of the Та anomalies in the western subarctic.

scholarly journals Climatic Changes of Thermal Conditions in the Pacific Subarctic at the Modern Stage of Global Warming

2021 ◽  
Vol 28 (2) ◽  
Author(s):  
I. D. Rostov ◽  
E. V. Dmitrieva ◽  
N. I. Rudykh ◽  
◽  
◽  
...  
Keyword(s):  
Air Temperature ◽  
Climate Changes ◽  
Surface Air Temperature ◽  
Ocean Surface ◽  
Empirical Orthogonal Functions ◽  
Orthogonal Functions ◽  
The North ◽  
Regional Features ◽  
The Pacific ◽  
Warming Rate

Purpose. The study is aimed at identifying the regional features of the surface air temperature in the coastal zone and over the Pacific Ocean (to the north of 40° N) manifested as a result of global climate changes at the turn of the XX–XXI centuries, and at assessing their trends and possible causal relationships with the processes in the atmosphere and on the ocean surface. Methods and Results. Based on the Global Meteorological Network and NOAA reanalysis data, the regional features of interannual oscillations of the surface air temperature and their relationship with variations in the fields of pressure, wind and water temperature on the ocean surface, and with climate indices over the past 4 decades were identified. In order to determine the temperature field spatial-temporal structure and to zone the water area according to the features of climate changes, the methods of cluster, correlation analysis and the apparatus of empirical orthogonal functions were used. The results obtained made it possible to characterize the degree of heterogeneity of the studied area response to the ongoing global changes, to identify different domains and to assess quantitatively the warming rate in these water areas. Conclusions. The tendencies of modern warming are manifested in the trends of interannual air temperature variability, on the average, by ~0.20°C/10 years in the subarctic, and indicate significant regional differences (1.5–2 times) in the ongoing changes. In the west of the region, the warming rate is higher than in the east, where the temperature trends are minimal or statistically insignificant. In the warm period of a year, their values are higher than those in the cold period. The alternation phases of the warm and cold periods are consistent with the variation tendencies in the characteristics both of the atmospheric action centers and various climatic parameters. The corresponding correlations are most widely manifested in variations in the empirical orthogonal functions modes of the H500 geopotential field, and the PDO, NP, SOI, PTW, AD and EP/NP indices. Stable anomalies and trends of the ocean surface temperature in the North Atlantic also play an important role in formation of the Та anomalies in the western subarctic.

scholarly journals A pseudoproxy assessment of why climate field reconstruction methods perform the way they do in time and space

2021 ◽  
Author(s):  
Sooin Yun ◽  
Jason E. Smerdon ◽  
Bo Li ◽  
Xianyang Zhang
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
Ice Cores ◽  
Empirical Orthogonal Functions ◽  
Orthogonal Functions ◽  
Climate Conditions ◽  
Statistical Measures ◽  
Reconstruction Methods ◽  
Assessment Metrics ◽  
The Difference

Abstract. Spatiotemporal paleoclimate reconstructions that seek to estimate climate conditions over the last several millennia are derived from multiple climate proxy records (e.g. tree rings, ice cores, corals, and cave formations) that are heterogeneously distributed across land and marine environments. Assessing the skill of the methods used for these reconstructions is critical as a means of understanding the spatiotemporal uncertainties in the derived reconstruction products. Traditional statistical measures of skill have been applied in past applications, but they often lack formal null hypotheses that incorporate the spatiotemporal characteristics of the fields and allow for formal significance testing. More recent attempts have developed assessment metrics to evaluate the difference of the characteristics between two spatiotemporal fields. We apply these assessment metrics herein to results from synthetic reconstruction experiments based on multiple climate model simulations to assess the skill of four reconstruction methods. We further interpret the comparisons using analysis of Empirical Orthogonal Functions that represent the noise-filtered climate field. The features of climate models and reconstruction methods identified in this paper demonstrate more detailed assessments of reconstruction methods and point to important areas of testing and improving real-world reconstruction methods.

scholarly journals Using Enstrophy-Based Diagnostics in an Ensemble for Two Blocking Events

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Andrew D. Jensen ◽  
Anthony R. Lupo
Keyword(s):  
Geopotential Height ◽  
Climate Models ◽  
Reanalysis Data ◽  
Horizontal Resolution ◽  
Ensemble Forecast ◽  
Data Sets ◽  
Forecast System ◽  
Data Set ◽  
Using Data ◽  
Dynamical Control

Recent research has used enstrophy-based diagnostics to identify the development and dissipation stages of blocking events. These previous studies made use of reanalysis data sets in the calculations of the enstrophy-based diagnostics, such as the NCEP-NCAR reanalysis (2.5° × 2.5°) of geopotential height and horizontal winds. However, none of these studies has explored the use of the enstrophy-based diagnostics in weather or climate models with higher horizontal resolution. In this paper, the enstrophy-based diagnostics are used to analyze two blocking events, using data from the ERA-Interim reanalysis data set (0.75° × 0.75°) and also the Global Ensemble Forecast System (GEFS) (1° × 1°). The results of this work indicate that using an ensemble may be more effective than a single dynamical control forecast in evaluating the enstrophy-based diagnostic quantities, and that the results are similar to those obtained with coarser resolution.

scholarly journals Patterns of Precipitation Change and Climatological Uncertainty among CMIP5 Models, with a Focus on the Midlatitude Pacific Storm Track*

2015 ◽  
Vol 28 (19) ◽  
pp. 7857-7872 ◽  
Author(s):  
Baird Langenbrunner ◽  
J. David Neelin ◽  
Benjamin R. Lintner ◽  
Bruce T. Anderson
Keyword(s):  
Radiative Forcing ◽  
Storm Track ◽  
Coupled Model ◽  
Internal Variability ◽  
Empirical Orthogonal Functions ◽  
Cmip5 Models ◽  
Orthogonal Functions ◽  
Maximum Covariance Analysis ◽  
The Pacific ◽  
The Tropics

Abstract Projections of modeled precipitation (P) change in global warming scenarios demonstrate marked intermodel disagreement at regional scales. Empirical orthogonal functions (EOFs) and maximum covariance analysis (MCA) are used to diagnose spatial patterns of disagreement in the simulated climatology and end-of-century P changes in phase 5 of the Coupled Model Intercomparison Project (CMIP5) archive. The term principal uncertainty pattern (PUP) is used for any robust mode calculated when applying these techniques to a multimodel ensemble. For selected domains in the tropics, leading PUPs highlight features at the margins of convection zones and in the Pacific cold tongue. The midlatitude Pacific storm track is emphasized given its relevance to wintertime P projections over western North America. The first storm-track PUP identifies a sensitive region of disagreement in P increases over the eastern midlatitude Pacific where the storm track terminates, related to uncertainty in an eastward extension of the climatological jet. The second PUP portrays uncertainty in a zonally asymmetric meridional shift of storm-track P, related to uncertainty in the extent of a poleward jet shift in the western Pacific. Both modes appear to arise primarily from intermodel differences in the response to radiative forcing, distinct from sampling of internal variability. The leading storm-track PUPs for P and zonal wind change exhibit similarities to the leading uncertainty patterns for the historical climatology, indicating important and parallel sensitivities in the eastern Pacific storm-track terminus region. However, expansion coefficients for climatological uncertainties tend to be weakly correlated with those for end-of-century change.

From Model-Based Parameterizations to Lookup Tables: An EOF Approach

2008 ◽  
Vol 23 (6) ◽  
pp. 1127-1145 ◽  
Author(s):  
Giovanni Leoncini ◽  
Roger A. Pielke ◽  
Philip Gabriel
Keyword(s):  
Computational Cost ◽  
Empirical Orthogonal Functions ◽  
Lookup Table ◽  
Transfer Scheme ◽  
Orthogonal Functions ◽  
Mixing Ratios ◽  
The Difference ◽  
Input Variables ◽  
Rate Profile ◽  
Good Agreement

Abstract The goal of this study is to transform the Harrington radiation parameterization into a transfer scheme or lookup table, which provides essentially the same output (heating rate profile and short- and longwave fluxes at the surface) at a fraction of the computational cost. The methodology put forth here does not introduce a new parameterization simply derived from the Harrington scheme but, rather, shows that given a generic parameterization it is possible to build an algorithm, largely not based on the physics, that mimics the outcome of the parent parameterization. The core concept is to compute the empirical orthogonal functions (EOFs) of all of the input variables of the parent scheme, run the scheme on the EOFs, and express the output of a generic input sounding exploiting the input–output pairs associated with the EOFs. The weights are based on the difference between the input and EOFs water vapor mixing ratios. A detailed overview of the algorithm and the development of a few transfer schemes are also presented. Results show very good agreement (r > 0.91) between the different transfer schemes and the Harrington radiation parameterization with a very significant reduction in computational cost (at least 95%).

scholarly journals Climate Dependence in Empirical Parameters of Subgrid-Scale Parameterizations using the Fluctuation–Dissipation Theorem

2018 ◽  
Vol 75 (11) ◽  
pp. 3843-3860 ◽  
Author(s):  
Martin Pieroth ◽  
Stamen I. Dolaptchiev ◽  
Matthias Zacharuk ◽  
Tobias Heppelmann ◽  
Andrey Gritsun ◽  
...  
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
External Perturbation ◽  
Empirical Orthogonal Functions ◽  
Subgrid Scale ◽  
Orthogonal Functions ◽  
Fluctuation Dissipation ◽  
Fluctuation Dissipation Theorem ◽  
Marginal Improvement ◽  
Low Order

Abstract Many subgrid-scale (SGS) parameterizations in climate models contain empirical parameters and are thus data dependent. In particular, it is not guaranteed that the SGS parameterization still helps the model to produce the correct climate projection in the presence of an external perturbation (e.g., because of climate change). Therefore, a climate dependence of tuning parameters is proposed, using the fluctuation–dissipation theorem (FDT). The FDT provides an estimation of the changes in the statistics of a system, caused by a small external forcing. These estimations are then used to update the SGS parameterization. This procedure is tested for a toy atmosphere given by a quasigeostrophic three-layer model (QG3LM). We construct a low-order climate model for this toy atmosphere, based on a reduced number of its empirical orthogonal functions (EOFs), equipped with either an empirical deterministic or an empirical stochastic SGS parameterization. External forcings are considered that are either a local anomalous heat source in the extratropics or a global dynamical forcing represented by individual EOF patterns. A quasi-Gaussian variant of the FDT is able to successfully update the SGS parameterization leading to an improvement in both amplitude and correlation between the low-order climate model and the QG3LM, in case of a perturbed system. The stochastic closure exhibits nearly no improvement compared to the deterministic parameterization. The application of a more sophisticated non-Gaussian FDT algorithm (i.e., the blended short-time/quasi-Gaussian FDT) yields only marginal improvement over the simple quasi-Gaussian FDT.

Benchmarking performance changes in the simulation of extratropical modes of variability across CMIP generations

2021 ◽  
pp. 1-70
Author(s):  
Jiwoo Lee ◽  
Kenneth R. Sperber ◽  
Peter J. Gleckler ◽  
Karl E. Taylor ◽  
Céline J. W. Bonfils
Keyword(s):  
North Pacific ◽  
Climate Models ◽  
Southern Annular Mode ◽  
Empirical Orthogonal Functions ◽  
Orthogonal Functions ◽  
Gradual Improvement ◽  
Annular Mode ◽  
Vertical Coordinate ◽  
Mode Amplitude ◽  
Modes Of Variability

AbstractWe evaluate extratropical modes of variability in the three most recent phases of the Coupled Model Intercomparison Project (CMIP3, 5, and 6) to gauge improvement of climate models over time. A suite of high-level metrics is employed to objectively evaluate how well climate models simulate the qobserved Northern Annular Mode (NAM), North Atlantic Oscillation (NAO), Pacific North America pattern (PNA), Southern Annular Mode (SAM), Pacific Decadal Oscillation (PDO), North Pacific Oscillation (NPO), and North Pacific Gyre Oscillation (NPGO). We apply a Common Basis Function (CBF) approach that projects model anomalies onto observed empirical orthogonal functions (EOFs), together with the traditional EOF approach, to CMIP Historical and AMIP models. We find simulated spatial patterns of those modes have been significantly improved in the newer models, although the skill improvement is sensitive to the mode and season considered. We identify some potential contributions to the pattern improvement of certain modes (e.g., the Southern Hemisphere jet and High-top vertical coordinate), however the performance changes are likely attributed to gradual improvement of the base climate and multiple relevant processes. Less performance improvement is evident in the mode amplitude of these modes and systematic overestimation of the mode amplitude in spring remains in the newer climate models. We find that the post-dominant season amplitude errors in atmospheric modes are not limited to coupled runs but are often already evident in AMIP simulations. This suggests that rectifying the egregious post-dominant season amplitude errors found in many models can be addressed in an atmospheric-only framework making it more tractable to address in the model development process.

Sign in / Sign up

Export Citation Format

Share Document