Circulation typing with fuzzy rotated T-mode principal component analysis: methodological considerations

Ibebuchi, Chibuike Chiedozie; Richman, Michael B.

doi:10.1007/s00704-023-04474-5

Cited by 9 publications

(9 citation statements)

References 71 publications

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“…We assessed the degree of non-linearity of the autoencoder patterns by comparing them to SST patterns derived from rotated PCA, using the congruence coefficient. Only the first two encoded summer and winter patterns in figure 2 were identified to have limited similarity with the rotated PCA patterns, given their congruence matches in the range of 0.70-0.78 (figures S1(a) and (b)), values associated with a poor match [41]. This indicates that when the constraint of linearity is removed, these encoder patterns change from their linear counterparts.…”

Section: Resultsmentioning

confidence: 99%

“…Additionally, the encoded SST patterns were compared to the patterns derived from PCA using the congruence coefficient (Ibebuchi and Richman [41]) to observe if the autoencoder reproduced the linear patterns, or captured new non-linear patterns, altering linear patterns that PCA might have failed to resolve properly. Congruence coefficients values that range from 0.98 to 1.00 represent an excellent match; 0.92 to <0.98 represent a good match; 0.82 to <0.92 represent a borderline match; 0.68 to <0.82 represent a poor match and values <0.68 represent a terrible match [41,42].…”

Section: Methodsmentioning

confidence: 99%

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Non-linear modes of global sea surface temperature variability and their relationships with global precipitation and temperature

Ibebuchi,

Richman

2024

Environ. Res. Lett.

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Sea surface temperature (SST) modes are comprised of variability that arises from inherently nonlinear processes. Historically, a limitation arises from applying linear statistics to define these modes. Accurate depiction of the complex, non-linear nature of SST modes of variability necessitates the specification of a model capable of producing nonlinear patterns. In this study, we apply an artificial neural network algorithm integrated with autoencoders to analyze the seasonal non-linear global SST modes allowing for improved characterization of the modes and their large-scale temperature and precipitation teleconnections. Our results show that during boreal summer, SST cooling over the central to eastern tropical Pacific co-occurs with the Arctic amplification. In recent decades, the negative SST trend in the central to eastern tropical Pacific, combined with the positive trend in the western tropical Pacific is linked to an increase in the amplitude of SST modes associated with the Arctic warming, resulting in warmer temperatures over large portions of the global land, particularly over Greenland. In boreal winter, El Niño Southern Oscillation (ENSO) is the prominent global SST mode. The distinct spatiotemporal patterns of ENSO modes are associated with unique effects on regional land temperature and precipitation. The central Pacific El Niño is more associated with the combination of warm and dry conditions over western Australia, and the northern part of South America. Conversely, the central to eastern El Niño is more associated with the combination of warm and dry conditions over parts of Southern Africa, and the northern part of South America. The spatiotemporal patterns and trends in the amplitude of the analyzed non-linear global SST modes alongside their regional influences on temperature and precipitation are discussed. The broader impact of this study is on the potential of neural networks in effectively delineating non-linear global SST modes and their associations with regional climates.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Non-linear modes of global sea surface temperature variability and their relationships with global precipitation and temperature

Ibebuchi,

Richman

2024

Environ. Res. Lett.

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Section: Methodsmentioning

confidence: 99%

“…Principal component analysis (PCA) is a widely used multivariate tool in climatology for removing noise in climate data and identifying (asymmetric) climatic modes of variability 56 . This is achieved through its variance maximization property and by post-processing the PCs with a suitable simple structure rotation algorithm 56 . In this study, we apply the rotated S-mode PCA 57 to regionalize temperature in North America during boreal summer (JJA: July to August) and identify distinct temperature variability patterns.…”

Section: Methodsmentioning

confidence: 99%

“…6 , the correlation matrix is utilized to obtain the relationship between the temperature field at the grid points in the study domain. Further, we applied the singular value decomposition to diagonalize the correlation matrix 56 , resulting in the PC scores, eigenvectors, and eigenvalues. The eigenvectors are spatial variability patterns, while the PC scores (time series) are the amplitude of the spatial variability patterns at a given time.…”

Section: Methodsmentioning

confidence: 99%

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Circulation patterns associated with trends in summer temperature variability patterns in North America

Ibebuchi

Lee

2023

Sci Rep

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This study improves the understanding of circulation patterns associated with regional temperature trends by characterizing boreal summer temperature variability patterns in North America using rotated S-mode principal component analysis. We analyzed gridded observational 2-m temperature datasets and the ERA5 reanalysis temperature dataset to examine the climate patterns associated with long-term trends and inter-annual variability of temperature variability patterns in North America. Our analysis revealed significant trends among some classified temperature variability patterns from 1979 to 2022 summers, with inter-annual amplitudes (i.e., a departure from the mean state) signaling toward the warm regime. The anticyclonic circulation anomaly over the temperature coherent regions associated with Greenland/northeastern Canada, and Alaska, respectively, is linked to an increase in warm air advection and above-average temperatures, while cyclonic circulation over the northeast Pacific coast enhanced warm air advection and temperature increases in the coherent region comprising the northwestern portion of North America. The increase in global mean land and ocean temperatures is strongly associated with the long-term increase in the amplitude of atmospheric circulations associated with warm regimes in parts of North America. At the interannual time scale, temperature increase over Greenland/northeastern Canada is strongly associated with the negative phase of the Arctic Oscillation. These findings highlight the modulating effects of global temperature increase and warming of the western tropical Pacific Ocean on the increasing amplitude of circulations associated with warm regimes in North America. Our results further indicate that the enhancement of anticyclonic circulations over the Arctic contributes to nearly 68% of the observed reduction in sea ice extent.

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The impact of horizontal resolution on the representation of atmospheric circulation types in Western Europe using the MPI‐ESM model

Ibebuchi

2023

Intl Journal of Climatology

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In this study, the added value in using the sea level pressure field from the coupled higher‐resolution version of the Max Planck Institute Earth System Model (MPI‐ESM‐HR), compared to the lower‐resolution version (MPI‐ESM‐LR) for circulation typing, within the regional context of Western Europe was examined. The results show that the MPI‐ESM‐HR and the MPI‐ESM‐LR simulations can produce the classified circulation types (CTs) and their long‐term statistical characteristics as obtained from the ERA5 reanalysis. Overall, there are improvements in the composite maps, probability of occurrence and annual cycle of the simulated CTs in the MPI‐ESM‐HR compared to the MPI‐ESM‐LR. The model bias in simulating the structure of anticyclonic circulations over the Western European landmass was reduced by 14% under MPI‐ESM‐HR. Furthermore, under the shared socio‐economic pathways (SSP2‐4.5 and SSP5‐8.5) future emission scenarios, the historical CTs in the region of assessment were classified, suggesting that in Western Europe, the same historical CTs are present under future climate change scenarios. However, the frequency distribution and geographical structure of some of the CTs in Western Europe are projected to change by the MPI‐ESM model, especially under the higher future emission scenario.

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Circulation typing with fuzzy rotated T-mode principal component analysis: methodological considerations

Cited by 9 publications

References 71 publications

Non-linear modes of global sea surface temperature variability and their relationships with global precipitation and temperature

Non-linear modes of global sea surface temperature variability and their relationships with global precipitation and temperature

Circulation patterns associated with trends in summer temperature variability patterns in North America

The impact of horizontal resolution on the representation of atmospheric circulation types in Western Europe using the MPI‐ESM model

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