The Relationship Between Convective Adjustment Hadley Circulation and Normal Modes of the ANMRC Spectral Model

Abstract We find that part of the uncertainty in the amplitude and pattern of the modeled precipitation response to CO2 forcing traces to tropical condensation not directly involved with parameterized convection. The fraction of tropical rainfall associated with large-scale condensation can vary from a few percent to well over half depending on model details and parameter settings. In turn, because of the coupling between condensation and tropical circulation, the different ways model assumptions affect the large-scale rainfall fraction also affect the patterns of the response within individual models. In two single-model ensembles based on the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM), versions 3.1 and 5.3, we find strong correlations between the fraction of tropical large-scale rain and both climatological rainfall and circulation and the response to CO2 forcing. While the effects of an increasing tropical large-scale rain fraction are opposite in some ways in the two ensembles—for example, the Hadley circulation weakens with the large-scale rainfall fraction in the CAM3.1 ensemble while strengthening in the CAM5.3 ensemble—we can nonetheless understand these different effects in terms of the relationship between latent heating and circulation, and we propose explanations for each ensemble. We compare these results with data from phase 5 of the Coupled Model Intercomparison Project (CMIP5), for which some of the same patterns hold. Given the importance of this partitioning, there is a need for constraining this source of uncertainty using observations. However, since a “large-scale rainfall fraction” is a modeling construct, it is not clear how observations may be used to test various modeling assumptions determining this fraction.

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Deep Convective Adjustment of Temperature and Moisture

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-19-0227.1 ◽

2020 ◽

Vol 77 (6) ◽

pp. 2163-2186

Author(s):

Fiaz Ahmed ◽

Ángel F. Adames ◽

J. David Neelin

Keyword(s):

Boundary Layer ◽

Time Scale ◽

Climate Models ◽

Thick Layer ◽

Process Models ◽

Cumulus Parameterization ◽

Adjustment Process ◽

Convective Adjustment ◽

Static Energy ◽

The Relationship

Abstract Simple process models and complex climate models are remarkably sensitive to the time scale of convective adjustment τ, but this parameter remains poorly constrained and understood. This study uses the linear-range slope of a semiempirical relationship between precipitation and a lower-free-tropospheric buoyancy measure BL. The BL measure is a function of layer-averaged moist enthalpy in the boundary layer (150-hPa-thick layer above surface), and temperature and moisture in the lower free troposphere (boundary layer top to 500 hPa). Sensitivity parameters with units of time quantify the BL response to its component perturbations. In moist enthalpy units, BL is more sensitive to temperature than equivalent moisture perturbations. However, column-integrated moist static energy conservation ensures that temperature and moisture are equally altered during the adjustment process. Multiple adjusted states with different temperature–moisture combinations exist; the BL sensitivity parameters govern the relationship between adjusted states, and also combine to yield a time scale of convective adjustment ~2 h. This value is comparable to τ values used in cumulus parameterization closures. Disparities in previously reported values of τ are attributed to the neglect of the temperature contribution to precipitation, and to averaging operations that include data from both precipitating and nonprecipitating regimes. A stochastic model of tropical convection demonstrates how either averaging operations or neglected environmental influences on precipitation can yield τ estimates longer than the true τ value built into the model. The analysis here culminates in construction of a precipitation closure with both moisture and temperature adjustment (q–T closure), suitable for use in both linearized and nonlinear, intermediate-complexity models.

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Blind Visualization of Task-Related Networks From Visual Oddball Simultaneous EEG-fMRI Data: Spectral or Spatiospectral Model?

Frontiers in Neurology ◽

10.3389/fneur.2021.644874 ◽

2021 ◽

Vol 12 ◽

Author(s):

René Labounek ◽

Zhuolin Wu ◽

David A. Bridwell ◽

Milan Brázdil ◽

Jiří Jan ◽

...

Keyword(s):

Basal Ganglia ◽

Power Spectra ◽

Spectral Model ◽

Dorsal Part ◽

Frontal Part ◽

Sensory Motor ◽

Spectral Patterns ◽

The Relationship ◽

Visual Oddball ◽

F Statistics

Various disease conditions can alter EEG event-related responses and fMRI-BOLD signals. We hypothesized that event-related responses and their clinical alterations are imprinted in the EEG spectral domain as event-related (spatio)spectral patterns (ERSPat). We tested four EEG-fMRI fusion models utilizing EEG power spectra fluctuations (i.e., absolute spectral model - ASM; relative spectral model - RSM; absolute spatiospectral model - ASSM; and relative spatiospectral model - RSSM) for fully automated and blind visualization of task-related neural networks. Two (spatio)spectral patterns (high δ4 band and low β1 band) demonstrated significant negative linear relationship (pFWE < 0.05) to the frequent stimulus and three patterns (two low δ2 and δ3 bands, and narrow θ1 band) demonstrated significant positive relationship (p < 0.05) to the target stimulus. These patterns were identified as ERSPats. EEG-fMRI F-map of each δ4 model showed strong engagement of insula, cuneus, precuneus, basal ganglia, sensory-motor, motor and dorsal part of fronto-parietal control (FPCN) networks with fast HRF peak and noticeable trough. ASM and RSSM emphasized spatial statistics, and the relative power amplified the relationship to the frequent stimulus. For the δ4 model, we detected a reduced HRF peak amplitude and a magnified HRF trough amplitude in the frontal part of the FPCN, default mode network (DMN) and in the frontal white matter. The frequent-related β1 patterns visualized less significant and distinct suprathreshold spatial associations. Each θ1 model showed strong involvement of lateralized left-sided sensory-motor and motor networks with simultaneous basal ganglia co-activations and reduced HRF peak and amplified HRF trough in the frontal part of the FPCN and DMN. The ASM θ1 model preserved target-related EEG-fMRI associations in the dorsal part of the FPCN. For δ4, β1, and θ1 bands, all models provided high local F-statistics in expected regions. The most robust EEG-fMRI associations were observed for ASM and RSSM.

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On the Sensitivity of the Relationship Between Hadley Circulation Asymmetry and ENSO in CMIP5 Models

Geophysical Research Letters ◽

10.1029/2018gl079515 ◽

2018 ◽

Vol 45 (17) ◽

pp. 9253-9259 ◽

Cited By ~ 2

Author(s):

Yi-Peng Guo ◽

Zhe-Min Tan

Keyword(s):

Hadley Circulation ◽

Cmip5 Models ◽

The Relationship

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Change in Relationship between the East Asian Winter Monsoon and the East Asian Jet Stream during the 1998–99 Regime Shift

Journal of Climate ◽

10.1175/jcli-d-18-0844.1 ◽

2019 ◽

Vol 32 (18) ◽

pp. 6163-6175 ◽

Cited By ~ 4

Author(s):

Se-Yong Song ◽

Sang-Wook Yeh ◽

Jae-Heung Park

Keyword(s):

East Asian Winter Monsoon ◽

East Asian ◽

Hadley Circulation ◽

Winter Monsoon ◽

Jet Stream ◽

Decadal Change ◽

Reanalysis Dataset ◽

Asian Winter Monsoon ◽

East Asian Jet Stream ◽

The Relationship

Abstract A composite analysis was conducted on the reanalysis dataset for 1979–2016, along with an idealized model experiment to show that the relationship between the East Asian jet stream (EAJS) and the East Asian winter monsoon (EAWM) is nonstationary. The relationship between EAWM and the EAJS weakened during the late 1990s. This decadal change in the EAJS–EAWM relationship was mainly due to a change in the secondary circulation across the EAJS between two contrasting periods, induced by the northward shift of the EAJS. A possible mechanism associated with the decadal change in meridional displacement of the EAJS is proposed. The enhanced convective activity in the western tropical Pacific after the late 1990s results in stronger Hadley circulation that could have contributed to the northward displacement of the Hadley circulation boundary latitude. Subsequently, this leads to the northward shift of the EAJS. Therefore, it is necessary to define a new EAJS index to account for the EAWM variability based on the change in the oceanic and atmospheric mean state across the late 1990s.

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Effects of Forward/Backward Whirl Mechanism on Nonlinear Normal Modes of a Rotor/Stator Rubbing System

Journal of Vibration and Acoustics ◽

10.1115/1.4030347 ◽

2015 ◽

Vol 137 (5) ◽

Cited By ~ 2

Author(s):

Yanhua Chen ◽

Jun Jiang

Keyword(s):

Response Spectrum ◽

Normal Modes ◽

Nonlinear Normal Modes ◽

Frequency Component ◽

Harmonic Response ◽

Backward Whirl ◽

Coupling Stiffness ◽

Nonlinear Normal ◽

The Stability ◽

The Relationship

In this paper, the effects of forward and backward whirl mechanism on the existence and the stability of multiple nonlinear normal modes (NNMs) in a four degree-of-freedom (DOF) rotor/stator rubbing system with cross-coupling stiffness and dry friction are investigated analytically. The NNMs may possess either positive or negative modal frequencies, corresponding, respectively, to the inherent motions of forward or backward whirl, and can be either stable or unstable. The relationship between the NNMs, regarding to their stability, and the forced system responses of the system is of great interest. It is found that a stable NNM corresponds to a forced harmonic response with the same whirl direction and frequency as the NNM, and an unstable NNM may still influence some forced system responses by contributing a frequency component equal to the modal frequency to the response spectrum.

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