scholarly journals The Mutual Interaction between External Rossby Waves and Thermal Forcing: The Subpolar Regions

2010 ◽  
Vol 67 (6) ◽  
pp. 2018-2038 ◽  
Author(s):  
Isidoro Orlanski ◽  
Silvina Solman
Keyword(s):  
Large Amplitude ◽  
Diabatic Heating ◽  
Rossby Waves ◽  
Feedback Mechanism ◽  
High Latitudes ◽  
Thermal Forcing ◽  
Global Spectral Model ◽  
Meridional Velocity ◽  
Series Of Experiments ◽  
Simple Feedback

Abstract The authors hypothesize a simple feedback mechanism between external Rossby waves and diabatic heating from convection. This mechanism could explain the large amplitude that external Rossby waves attain as they propagate to mid- and high latitudes. A series of experiments has been carried out with a core dynamic global spectral model. These simulations with the idealized atmospheric GCM and a simple parameterization of thermal forcing proportional to the low-level wave meridional velocity suggest that external Rossby waves can be enhanced by convection, which they themselves induce. It is shown that in the tropospheric upper levels the amplitude of the external waves can be twice as large with feedback as for a control simulation that does not allow feedback.

PMIP4/CMIP6 last interglacial simulations using three different versions of MIROC: importance of vegetation

2021 ◽  
Author(s):  
Ryouta O'ishi ◽  
Wing-Le Chan ◽  
Ayako Abe-Ouchi ◽  
Sam Sherriff-Tadano ◽  
Rumi Ohgaito ◽  
...  
Keyword(s):  
Feedback Mechanism ◽  
Climate Feedback ◽  
High Latitudes ◽  
Last Interglacial ◽  
Proxy Data ◽  
Area Index ◽  
Vegetation Feedback ◽  
Temperature Changes ◽  
Northern High Latitude ◽  
Series Of Experiments

<p>We carry out three sets of last interglacial (LIG) experiments, named lig127k, and of pre-industrial experiments, named piControl, both as part of PMIP4/CMIP6 using three versions of the MIROC model: MIROC4m, MIROC4m-LPJ, and MIROC-ES2L. The results are compared with reconstructions from climate proxy data. All models show summer warming over northern high-latitude land, reflecting the differences between the distributions of the LIG and present-day solar irradiance. Globally averaged temperature changes are −0.94 K (MIROC4m), −0.39 K (MIROC4m-LPJ), and −0.43 K (MIROC-ES2L).<br>Only MIROC4m-LPJ, which includes dynamical vegetation feedback from the change in vegetation distribution, shows annual mean warming signals at northern high latitudes, as indicated by proxy data. In contrast, the latest Earth system model (ESM) of MIROC, MIROC-ES2L, which considers only a partial vegetation effect through the leaf area index, shows no change or even annual cooling over large parts of the Northern Hemisphere. Results from the series of experiments show that the inclusion of full vegetation feedback is necessary for the reproduction of the strong annual warming over land at northern high latitudes. The LIG experimental results show that the warming predicted by models is still underestimated, even with dynamical vegetation, compared to reconstructions from proxy data, suggesting that further investigation and improvement to the climate feedback mechanism are needed.</p>

scholarly journals PMIP4/CMIP6 Last Interglacial simulations using different versions of MIROC, with and without vegetation feedback

2020 ◽  
Author(s):  
Ryouta O'ishi ◽  
Wing-Le Chan ◽  
Ayako Abe-Ouchi ◽  
Sam Sherriff-Tadano ◽  
Rumi Ohgaito
Keyword(s):  
Feedback Mechanism ◽  
Climate Feedback ◽  
High Latitudes ◽  
Last Interglacial ◽  
Proxy Data ◽  
Area Index ◽  
Vegetation Feedback ◽  
Summer Warming ◽  
Northern High Latitude ◽  
Series Of Experiments

Abstract. We carry out a Last Interglacial (LIG) experiment, named lig127k and a Tier1 experiment of PMIP4/CMIP6, using three versions of the MIROC model, MIROC4m, MIROC4m-LPJ and MIROC-ES2L. The results are compared with reconstructions from climate proxy data. All models show summer warming over northern high latitude land, reflecting the differences between the distributions of the LIG and present-day solar irradiance. Only MIROC4m-LPJ, which includes dynamical vegetation feedback from the change in vegetation distribution, shows warming signals, even for the annual mean, at northern high latitudes, as shown by proxy data. However, the latest Earth System Model (ESM) of MIROC, MIROC-ES2L, in which there is only a partial vegetation effect through the leaf area index, shows no change or even annual cooling over large parts of the northern hemisphere. Results from the series of experiments show that the inclusion of vegetation feedback is necessary for the reproduction of the strong annual warming over land at northern high latitudes. The LIG experimental results show that the warming predicted by models is still underestimated, even with dynamical vegetation, compared to reconstructions from proxy data, suggesting that further investigation and improvement to the climate feedback mechanism are needed.

scholarly journals PMIP4/CMIP6 last interglacial simulations using three different versions of MIROC: importance of vegetation

2021 ◽  
Vol 17 (1) ◽  
pp. 21-36
Author(s):  
Ryouta O'ishi ◽  
Wing-Le Chan ◽  
Ayako Abe-Ouchi ◽  
Sam Sherriff-Tadano ◽  
Rumi Ohgaito ◽  
...  
Keyword(s):  
Feedback Mechanism ◽  
Climate Feedback ◽  
High Latitudes ◽  
Last Interglacial ◽  
Proxy Data ◽  
Area Index ◽  
Vegetation Feedback ◽  
Temperature Changes ◽  
Northern High Latitude ◽  
Series Of Experiments

Abstract. We carry out three sets of last interglacial (LIG) experiments, named lig127k, and of pre-industrial experiments, named piControl, both as part of PMIP4/CMIP6 using three versions of the MIROC model: MIROC4m, MIROC4m-LPJ, and MIROC-ES2L. The results are compared with reconstructions from climate proxy data. All models show summer warming over northern high-latitude land, reflecting the differences between the distributions of the LIG and present-day solar irradiance. Globally averaged temperature changes are −0.94 K (MIROC4m), −0.39 K (MIROC4m-LPJ), and −0.43 K (MIROC-ES2L). Only MIROC4m-LPJ, which includes dynamical vegetation feedback from the change in vegetation distribution, shows annual mean warming signals at northern high latitudes, as indicated by proxy data. In contrast, the latest Earth system model (ESM) of MIROC, MIROC-ES2L, which considers only a partial vegetation effect through the leaf area index, shows no change or even annual cooling over large parts of the Northern Hemisphere. Results from the series of experiments show that the inclusion of full vegetation feedback is necessary for the reproduction of the strong annual warming over land at northern high latitudes. The LIG experimental results show that the warming predicted by models is still underestimated, even with dynamical vegetation, compared to reconstructions from proxy data, suggesting that further investigation and improvement to the climate feedback mechanism are needed.

scholarly journals Potential Vorticity of the Madden–Julian Oscillation

2012 ◽  
Vol 69 (1) ◽  
pp. 65-78 ◽  
Author(s):  
Chidong Zhang ◽  
Jian Ling
Keyword(s):  
Potential Vorticity ◽  
Diabatic Heating ◽  
Rossby Waves ◽  
Early Stage ◽  
Relative Vorticity ◽  
Dynamical Structure ◽  
Madden Julian Oscillation ◽  
Convective Envelope ◽  
Convective Initiation ◽  
Pv Generation

Abstract This study explores the extent to which the dynamical structure of the Madden–Julian oscillation (MJO), its evolution, and its connection to diabatic heating can be described in terms of potential vorticity (PV). The signature PV structure of the MJO is an equatorial quadrupole of cyclonic and anticyclonic PV that tilts westward and poleward. This PV quadrupole is closely related to positive and negative anomalies in precipitation that are in a swallowtail pattern extending eastward along the equator and splitting into off-equatorial branches westward. Two processes dominate the generation of MJO PV. One is linear, involving MJO diabatic heating alone. The other is nonlinear, involving diabatic heating and relative vorticity of perturbations spectrally outside the MJO domain but spatially constrained to the MJO convective envelope. The MJO is thus partially a self-sustaining system and partially a consequence of scale interaction of MJO-constrained stochastic processes. Convective initiation of the MJO over the Indian Ocean features a swallowtail pattern of negative anomalous precipitation and associated anticyclonic PV anomalies at the early stage, and increasing cyclonic PV generation straddling the equator in the midtroposphere due to increasing positive anomalies in precipitation. These lead to the swallowtail pattern in positive anomalous precipitation and the associated PV quadrupole that signifies the fully developed MJO. The equatorial Kelvin and Rossby waves bear PV structures distinct from that of the MJO. They contribute insignificantly to the structure and generation of MJO PV. Solely based on the PV analysis, a hypothesis is proposed that the fundamental dynamics of the MJO depends on neither Kelvin nor Rossby waves.

The Structure and Maintenance of Stationary Waves in the Winter Northern Hemisphere

2005 ◽  
Vol 62 (10) ◽  
pp. 3637-3660 ◽  
Author(s):  
Tsing-Chang Chen
Keyword(s):  
Northern Hemisphere ◽  
Diabatic Heating ◽  
Velocity Potential ◽  
Stationary Waves ◽  
High Latitudes ◽  
Research Attention ◽  
Budget Analysis ◽  
The Tropics ◽  
Distinct Features ◽  
East West

Abstract Previous studies of extratropical stationary waves in the winter Northern Hemisphere (NH) often focused on effects of orography and land–ocean thermal contrast on the formation, structure, and maintenance of these waves. In contrast, research attention to tropical stationary waves was attracted by the summer monsoon circulations and the ENSO-related climate variability. Consequently, the structure and basic dynamics of tropical stationary waves and the relationship of these waves with those in mid–high latitudes have long been neglected. Thus, the following several distinct features of observed winter NH stationary waves have not been explained: 1) an abrupt change in the longitudinal phase across 30°N; 2) a transition from the vertical phase reversal of tropical stationary waves to the vertically westward tilt of extratropical stationary waves; and 3) a longitudinally quarter-phase relationship between stationary waves and east–west circulations, and a reversal of this relationship across 30°N. It is inferred from a spectral streamfunction budget analysis with the NCEP–NCAR reanalyses that these wave features are caused by the transition of wave dynamics from the Sverdrup regime in the Tropics to the Rossby regime in the mid–high latitudes. Based on the simplified vorticity equations of these two dynamic regimes, analytic solutions obtained with observed velocity potential fields (which were used to portray the global divergent circulation) confirm that the aforementioned distinct features of stationary waves are attributed to the dynamics transition across 30°N. Since east–west circulations are part of the global divergent circulation, it is revealed from a diagnosis of the velocity potential maintenance equation that this circulation component is maintained in the Tropics primarily by diabatic heating and in the mid–high latitudes by both horizontal heat advection and diabatic heating. Evidently, stationary waves are maintained by diabatic heating through the divergent circulation and the dynamics transition of these waves from the Sverdrup regime to the Rossby regime is attributed to strong midlatitude westerlies.

scholarly journals The problem of diagnosing jet waveguidability in the presence of large-amplitude eddies

2021 ◽  
Author(s):  
Volkmar Wirth ◽  
Christopher Polster
Keyword(s):  
Large Amplitude ◽  
Rossby Waves ◽  
Extreme Weather ◽  
Large Wave ◽  
Barotropic Model ◽  
Flow Configuration ◽  
Straightforward Computation ◽  
Zonal Average ◽  
Background State

AbstractThe waveguidability of an upper tropospheric zonal jet quantifies its propensity to duct Rossby waves in the zonal direction. This property has played a central role in previous attempts to explain large wave amplitudes and the subsequent occurrence of extreme weather. In these studies, waveguidability was diagnosed with the help of ray tracing arguments using the zonal average of the observed flow as the relevant background state. Here, it is argued that this method is problematic both conceptually and mathematically. The issue is investigated in the framework of the non-divergent barotropic model. This model allows the straightforward computation of an alternative “zonalized” background state, which is obtained through conservative symmetrization of potential vorticity contours and which is argued to be superior to the zonal average. Using an idealized prototypical flow configuration with large-amplitude eddies, it is shown that the two different choices for the background state yield very different results; in particular, the zonal-mean background state diagnoses a zonal waveguide, while the zonalized background state does not. This result suggests that the existence of a waveguide in the zonal mean background state is a consequence of, rather than a precondition for large wave amplitudes, and it would mean that the direction of causality is opposite to the usual argument. The analysis is applied to two heatwave episodes from summer 2003 and 2010, yielding essentially the same result. It is concluded that previous arguments about the role of waveguidability for extreme weather need to be carefully re-evaluated to prevent misinterpretation in the future.

scholarly journals A forced 3-D time fractional ZK-Burgers model for Rossby solitary waves with dissipation and thermal forcing

2019 ◽  
Vol 23 (3 Part A) ◽  
pp. 1689-1695 ◽  
Author(s):  
Lei Fu ◽  
Zheyuan Yu ◽  
Huanhe Dong ◽  
Yuqing Li ◽  
Hongwei Yang
Keyword(s):  
Fractional Derivative ◽  
Solitary Waves ◽  
Rossby Waves ◽  
Burgers Equation ◽  
Expansion Method ◽  
Scale Analysis ◽  
Thermal Forcing ◽  
Multi Scale ◽  
Rossby Solitary Waves ◽  
Multi Scale Analysis

In the paper, beginning from the quasi-geostrophic potential vorticity equation with the dissipation and thermal forcing in stratified fluid, by employing multi-scale analysis and perturbation method, we derive a forced 3-D Zakharov Kuznetsor (ZK)-Burgers equation describe the propagation of the Rossby solitary waves within the fractional derivative. The exact solutions are given by virtue of the (G?/G)-expansion method to analyze the excitation effect of thermal forcing on the Rossby waves.

scholarly journals Association between regional monsoon onset in South Asia and Tibetan Plateau thermal forcing

2021 ◽  
Author(s):  
Die Hu ◽  
Anmin Duan ◽  
Ping Zhang
Keyword(s):  
Tibetan Plateau ◽  
South Asian ◽  
Summer Monsoon ◽  
General Circulation ◽  
Diabatic Heating ◽  
Monsoon Onset ◽  
South Asian High ◽  
The Tibetan Plateau ◽  
South Asian Summer Monsoon ◽  
Thermal Forcing

Abstract By using multiple data sources and two sensitivity experiments using the atmospheric general circulation model of CAM4.0, we investigated the effect of thermal forcing over the Tibetan Plateau (TP) on the onset of the South Asian summer monsoon, including over the Arabian Sea (AS) and India. Results indicate that the seesaw pattern of diabatic heating over the TP, with a southeastern–northwestern inverse distribution in May, shows a robust relationship with the date of monsoon onset over the AS and India, which is independent of the influences from ocean signals. A positive diabatic heating seesaw pattern can enhance the ascending (descending) motion over the southeastern (northwestern) TP, corresponding to above (below) normal in- situ precipitation. Temperature budget diagnosis reveals that the adiabatic heating by the anomalous vertical motion and relevant horizontal advection of temperature convergence in the mid-upper troposphere are contributors to the warming over the TP. Consequently, the transition of the meridional temperature gradient over South Asian regions occurs earlier. Furthermore, the diabatic heating over the TP induces an enhanced and westward-extended South Asian high (SAH), which together with the easterly along the southern flank of the SAH superimpose on the low-level westerly flow over the AS and India, resulting in intensive upper-level divergence-pumping and upward motion. This anomalous circulation configuration in lower and upper levels further facilitates an earlier onset of summer monsoon in these two regions. These findings are corroborated in the sensitivity runs based on CAM4.0.

Diagnosing jet waveguidability in the presence of large-amplitude eddies

2021 ◽  
Author(s):  
Volkmar Wirth ◽  
Christopher Polster
Keyword(s):  
Large Amplitude ◽  
Rossby Waves ◽  
Extreme Weather ◽  
Large Wave ◽  
Barotropic Model ◽  
Flow Configuration ◽  
Straightforward Computation ◽  
Zonal Average ◽  
Background State

<p>The waveguidability of an upper tropospheric zonal jet quantifies its propensity to duct Rossby waves in the zonal direction. This property has played a central role in previous attempts to explain large wave amplitudes and the subsequent occurrence of extreme weather. In these studies, waveguidability was diagnosed with the help of the refractive index using the zonal average of the observed flow as the relevant background state. Here, it is argued that this method is problematic both conceptually and mathematically.</p><p>The issue is investigated in the framework of the non-divergent barotropic model. This model allows the straightforward computation of an alternative "zonalized" background state, which is obtained through conservative symmetrisation of potential vorticity contours and which is argued to be superior to the zonal average. Using an idealized prototypical flow configuration with large-amplitude eddies, it is shown that the two different choices for the background state yield very different results; in particular, the zonal-mean background state diagnoses a zonal waveguide, while the zonalized background state does not. This result suggests that the existence of a waveguide in the zonal mean background state is a consequence of, rather than a precondition for large wave amplitudes, and it would mean that the direction of causality is opposite to the usual argument.</p><p>The analysis is applied to two heatwave episodes from summer 2003 and 2010, yielding essentially the same result. It is concluded that previous arguments about the role of waveguidability for extreme weather need to be carefully re-evaluated to prevent misinterpretation in the future.</p>

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