scholarly journals Signatures of universal characteristics of fractal fluctuations in global mean monthly temperature anomalies

2011 ◽  
Vol 24 (1) ◽  
pp. 14-38 ◽  
Author(s):  
A. M. Selvam
2021 ◽  
Author(s):  
Shruti Nath ◽  
Quentin Lejeune ◽  
Lea Beusch ◽  
Carl Schleussner ◽  
Lukas Gudmundsson ◽  
...  

<p>Emulators are computationally cheap statistical devices that derive simplified relationships from otherwise complex climate models. A recently developed Earth System Model (ESM) emulator, MESMER (Beusch et al. 2020), uses a combination of pattern scaling and a variability emulator to emulate ESM initial-condition ensembles. Linear scaling provides the spatially resolved yearly temperature trend projections from global mean temperature trend values. In addition, the variability emulator stochastically models spatio-temporally correlated local variability, yielding a convincing imitation of the internal climate variability displayed within a multi-model initial condition ensemble. The work presented here extends MESMER’s framework to have a monthly downscaling module, so as to provide spatially resolved monthly temperature values from spatially resolved yearly temperature values. For this purpose, a harmonic model is trained on monthly ESM output to capture monthly cycles and their evolution with changing temperature. Once the mean monthly cycle is sufficiently emulated, a process based understanding of the biases within the harmonic model is undertaken. Such entails employing a Gradient Boosting Regressor tree model (GBR) to explain the residuals from the harmonic model using biophysical climate variables such as albedo and thermal fluxes as explanatory variables. These variables can be rated according to their explanatory power when categorising residuals which furthermore elucidates the main physical processes driving biases in the harmonic model within seasons at the grid point level. Finally we add residual variability ontop of the harmonic model outputs to provide convincing imitations of ESM monthly temperature realisations. The residual variability is generated using an AR(1) process coupled to a multivariate trans-gaussian process so as to maintain spatio-temporal correlations and the non-stationarity in monthly variability with increasing yearly temperatures.</p><p>Beusch, L., Gudmundsson, L., & Seneviratne, S. I. (2020). Emulating Earth System Model temperatures: from global mean temperature trajectories to grid-point level realizations on land. Earth System Dynamics, 11(1), 139–159. https://doi.org/10.5194/esd-11-139-2020</p><p> </p><p> </p>


1993 ◽  
Vol 6 (7) ◽  
pp. 1368-1374 ◽  
Author(s):  
Richard F. Gunst ◽  
Sabyasachi Basu ◽  
Robert Brunell

2021 ◽  
Vol 64 (Vol 64 (2021)) ◽  
Author(s):  
Jouni Takalo

ract: Using detrended fluctuation analysis (DFA) we find that the all continents are persistent in temperature. The scaling exponents of the southern hemisphere (SH) continents, i.e., South America (α=0.78) and Oceania (0.75) are somewhat higher than scaling exponents of Europe (0.70), Asia (0.69) and North America (0.65), but the scaling  of Africa is by far the highest (0.89). The scaling exponents of the precipitation are much smaller, i.e., between 0.54 (Europe) and 0.67 (North America). The scaling exponent of Europe is near the exponent of random Brownian noise, which is 0.5. The other continents are slightly persistent in precipitation. The slopes of the logarithmic power spectra of the continents are in line with the scaling exponents confirming the DFA analysis results. We also show that the persistence is real and not the intrinsic property of the data itself. We find that scaling exponent α, i.e., persistence of the monthly temperature increases when going from local to larger area averages, at least in the case where climate type does not change much. The situation is not so obvious for the monthly precipitation. We also show that the three southernmost climate regions of USA, Ohio Valley, South and Southeast, have smaller scaling exponents for temperature anomalies, and are thus less persistent in temperature than other six climate regions. On the other hand they are slightly more persistent in precipitation that the other regions. The scaling exponents of the monthly temperature anomalies of the latitude zones of land area are 0.71 and 0.68 for the southern zones S44-S24, and S64-S44, respectively. For the northern zones N24-N44, N44-N64 and N64-N90, the scaling exponents are between 0.67-0.70.  Interestingly the scaling exponents are extremely high for the equatorial zones S24-EQ and EQ-N24, i. e., 1.02 and 0.95, respectively. The corresponding exponents of the monthly precipitation anomalies are between 0.55-0.61 for other zones than S24-EQ and EQ-N24, which have exponents 0.72 and 0.77, respectively.


1978 ◽  
Vol 39 (C6) ◽  
pp. C6-416-C6-417
Author(s):  
B. M. Klein ◽  
L. L. Boyer ◽  
D. A. Papaconstantopoulos

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