Baroclinic Model Research Articles

Roles of vertical distributions of atmospheric transient eddy dynamical forcing and diabatic heating in midlatitude unstable air\u2013sea interaction

Atmospheric transient eddy dynamical forcing (TEDF)-driven midlatitude unstable air–sea interaction has recently been recognized as a crucial positive feedback for the maintenance of the extratropical decadal variabilities. Our recent theoretical work (Chen et al., Clim Dyn https://doi.org/10.1007/s00382-020-05405-0, 2020) has characterized such an interaction through building an analytical midlatitude barotropic atmospheric model coupled to a simplified upper oceanic model. This study extends the analytical model to including a two-layer quasi-geostrophic baroclinic atmospheric model and then identifies the roles of vertical distributions of atmospheric TEDF and diabatic heating in midlatitude unstable air–sea interaction. It is found that midlatitude air–sea coupling with more realistic vertical profiles of atmospheric TEDF and diabatic heating destabilizes oceanic Rossby wave modes over the entire range of zonal wavelengths, in which the most unstable coupled mode features an equivalent barotropic atmospheric low (high) pressure over a cold (warm) oceanic surface. Spatial structure and period of the most unstable mode are more consistent with the observation than those from in previous model. Although either TEDF or diabatic heating alone can lead to a destabilized coupled mode, the former makes a dominant contribution to the instability. The increase of low-layer TEDF stimulates the instability more effectively if the TEDF in upper layer is larger than in lower layer, while the TEDF in either high or low layers can individually cause the instability. The surface heating always destabilizes the air–sea interaction, while the mid-level heating always decays the coupled mode. The results of this study further confirm the TEDF-driven positive feedback mechanism in midlatitude air–sea interaction proposed by recent observational and numerical experiment studies.

Potential links between wintertime snow cover in central Europe and precipitation over the low‐latitude highlands of China in May

AbstractThis research describes a link between winter–springtime snow cover anomalies in central Europe and precipitation over the low‐latitude highlands of China (LLHC). Excessive snow cover over Europe and East Asia alters the meridional temperature gradient, which induces zonal wind anomalies at the 500 hPa level that impact the strength and position of subtropical streams. These anomalies persist until spring and result in a distinctive paired cyclonic–anticyclonic circulation pattern. Over Mongolia, the imposition of cyclonic circulation weakens the Mongolia High and reduces the potential southward flow of cold air that normally affects the LLHC during spring. Concurrently, the development of anticyclonic conditions over the LLHC weakens springtime precipitation in this area. This paired circulation system is verified by the linear baroclinic model, which also confirms that the observed linkage between snow cover and precipitation is not modulated by the El Niño–Southern Oscillation. This analysis affords new insight into the effects of snow cover on the subtropical stream and atmospheric circulations downwind.

Global large solution for the tropical climate model with diffusion

We study the d-dimensional (d=2,3) tropical climate model with only the dissipation of the first baroclinic model of the velocity −ηΔv. By choosing a class of special initial data (u0,v0,𝜃0) whose Hs(ℝd) norm can be arbitrarily large, we obtain the global smooth solution of d-dimensional tropical climate model.

Global large solution for the tropical climate model with diffusion

We study the d-dimensional (d=2,3) tropical climate model with only the dissipation of the first baroclinic model of the velocity −ηΔv. By choosing a class of special initial data (u0,v0,𝜃0) whose Hs(ℝd) norm can be arbitrarily large, we obtain the global smooth solution of d-dimensional tropical climate model.

Optimisation of Parameters in a German Bight Circulation Model by 4DVAR Assimilation of Current and Water Level Observations

Uncertain parameters in a 3D barotropic circulation model of the German Bight are estimated with a variational optimisation approach. Surface current measurements from a high frequency (HF) radar are used in combination with acoustic Doppler current profiler (ADCP) and tide gauge observations as input for a 4DVAR assimilation scheme. The required cost function gradients are estimated using an adjoint model code. The focus of the study is on systematic errors of the model with the control vector including parameters of the bathymetry, bottom roughness, open boundary forcing, meteorological forcing as well as the turbulence model. The model uses the same bathymetry, open boundary forcing, and metereological forcing as the operational model run at the Federal Maritime and Hydrographic Agency (BSH). The baroclinic BSH model is used as a reference to put the performance of the optimised model into perspective. It is shown that the optimised model has better agreement with HF radar data and tide gauge observations both within the fortnight training period and the test period 1 month later. Current profile measurements taken at two platforms indicate that both models have comparable error magnitudes at those locations. The optimised model was also compared with independent drifter data. In this case, drifter simulations based on the BSH model and the respective operational drift model including some surface wave effects were used as a reference. Again, these comparison showed very similar results overall, with some larger errors of the tuned model in very shallow areas, where no observations were used for the tuning and surface wave effects, which are only explicitly considered in the BSH model, play a more important role. The tuned model seems to be slightly more dissipative than the BSH model with more energy entering through the western boundary and less energy leaving toward the north. It also became evident that the 4DVAR cost function minimisation process is complicated by momentum advection, which leads to non-differentiable dependencies of the model with respect to the control vector. It turned out that the omission of momentum advection in the adjoint code still leads to robust estimates of descent directions.

RETRACTED ARTICLE: Seasonal variation of coastal circulation based on parameter grey estimation and evaluation of residents’ physical exercise behavior

In the past decades, global climate change has greatly changed the natural environment. Due to the lack of measurement data and technical means, there is no consensus on the structure and dynamic mechanism of the b-sea cycle. In this paper, based on ROMs model and grey estimation of parameters, a three-dimensional baroclinic model of thermodynamic coupling in b-ocean region under new background field is established by using high-quality data recently obtained. According to the simulation results and comparative experiments, the seasonal distribution characteristics of b-sea circulation and the water exchange form between b-sea and high seas are analyzed and explained. And many scientific problems of coastal circulation, such as education and mutation mechanism. However, good physical exercise is an important way to improve the physical quality of residents. As the basic requirement of residents’ physical exercise, the community sports environment affects and limits the residents’ physical exercise behavior. Environmental behavior studies show that the relationship between environment and behavior is not directly related to the individual’s response to environmental stimuli. The principle of “applicability” should be emphasized in the construction of sports environment in society. Therefore, the residents’ behavior evaluation of the school sports environment should become an important feedback information in the construction of community sports environment. The purpose of this paper is to analyze the correlation between residents’ sports environment evaluation and sports exercise behavior orientation, and to provide a theoretical basis for improving residents' sports exercise behavior and optimizing and perfecting the sports environment of the community.

Drivers of uncertainty in future projections of Madden–Julian Oscillation teleconnections

Abstract. Teleconnections from the Madden–Julian Oscillation (MJO) are a key source of predictability of weather on the extended timescale of about 10–40 d. The MJO teleconnection is sensitive to a number of factors, including the mean dry static stability, the mean flow, and the propagation and intensity characteristics of the MJO, which are traditionally difficult to separate across models. Each of these factors may evolve in response to increasing greenhouse gas emissions, which will impact MJO teleconnections and potentially impact predictability on extended timescales. Current state-of-the-art climate models do not agree on how MJO teleconnections over central and eastern North America will change in a future climate. Here, we use results from the Coupled Model Intercomparison Project Phase 6 (CMIP6) historical and SSP585 experiments in concert with a linear baroclinic model (LBM) to separate and investigate alternate mechanisms explaining why and how boreal winter (January) MJO teleconnections over the North Pacific and North America may change in a future climate and to identify key sources of inter-model uncertainty. LBM simulations suggest that a weakening teleconnection due to increases in tropical dry static stability alone is robust across CMIP6 models and that uncertainty in mean state winds is a key driver of uncertainty in future MJO teleconnections. Uncertainty in future changes to the MJO's intensity, eastward propagation speed, zonal wavenumber, and eastward propagation extent are other important sources of uncertainty in future MJO teleconnections. We find no systematic relationship between future changes in the Rossby wave source and the MJO teleconnection or between changes to the zonal wind or stationary Rossby wave number and the MJO teleconnection over the North Pacific and North America. LBM simulations suggest a reduction of the boreal winter MJO teleconnection over the North Pacific and an uncertain change over North America, with large spread over both regions that lends to weak confidence in the overall outlook. While quantitatively determining the relative importance of MJO versus mean state uncertainties in determining future teleconnections remains a challenge, the LBM simulations suggest that uncertainty in the mean state winds is a larger contributor to the uncertainty in future projections of the MJO teleconnection than the MJO.

Seasonality and Dynamics of Atmospheric Teleconnection from the Tropical Indian Ocean and the Western Pacific to West Antarctica

The global impact of the tropical Indian Ocean and the Western Pacific (IOWP) is expected to increase in the future because this area has been continuously warming due to global warming; however, the impact of the IOWP forcing on West Antarctica has not been clearly revealed. Recently, ice loss in West Antarctica has been accelerated due to the basal melting of ice shelves. This study examines the characteristics and formation mechanisms of the teleconnection between the IOWP and West Antarctica for each season using the Rossby wave theory. To explicitly understand the role of the background flow in the teleconnection process, we conduct linear baroclinic model (LBM) simulations in which the background flow is initialized differently depending on the season. During JJA/SON, the barotropic Rossby wave generated by the IOWP forcing propagates into the Southern Hemisphere through the climatological northerly wind and arrives in West Antarctica; meanwhile, during DJF/MAM, the wave can hardly penetrate the tropical region. This indicates that during the Austral winter and spring, the IOWP forcing and IOWP-region variabilities such as the Indian Ocean Dipole (IOD) and Indian Ocean Basin (IOB) modes should paid more attention to in order to investigate the ice change in West Antarctica.

A zonally-oriented teleconnection pattern induced by heating of the western Tibetan Plateau in boreal summer

The thermal effect of the Tibetan Plateau (TP) on the northern hemisphere climate has long been a hot topic of scientific research. However, the global effects of the TP heat source are still unclear. We investigate the teleconnection patterns coincident with the TP heat source in boreal summer using both observational data and numerical models including a linearized baroclinic model and an atmospheric general circulation model. The western TP shows the most intense variability in atmospheric heating and the most active connection to atmospheric circulations. The surface sensible heating component of the western TP heat source is associated with a high-latitude wave train propagating from North Japan to central North America through the Bering Sea and Canada. The radiative heating component is accompanied by a wavenumber-4 wave train over Eurasia. We focus on the global zonally-oriented pattern that is connected with the latent heat release from the western TP, referred to here as the TP–circumglobal teleconnection (TP-CGT). The TP-CGT pattern is triggered by the western TP latent heating in two parts starting from the TP: an eastward-propagating wave train trapped in the westerly jet stream and a westward Rossby wave response. The TP-CGT accounts for above 18% of the total variance of the circumglobal teleconnection pattern and modulates mid-latitude precipitation by superimposition. The western TP is the key region in which diabatic heating can initiate the two atmospheric responses concurrently, and the heating over northeastern Asia or the Indian Peninsula is unable to induce the circumglobal pattern directly. The unique geographical location and strong tropospheric heating also make the western TP as a “transit area” of transferring the indirect impact of the Indian summer monsoon (ISM) to the TP-CGT. These results enhance our understanding of the relationship between the circumglobal teleconnection and the ISM and is helpful for improving the prediction of the circumglobal teleconnection variability.

Interannual covariability of summer monsoon precipitation in Yunnan, China, and diabatic heating anomalies over the Arabian Sea–Bay of Bengal

Covariability of summer monsoon precipitation in Yunnan and diabatic heating anomalies over the Arabian Sea–Bay of Bengal (AS–BOB) is analyzed using ERA-Interim monthly reanalysis data and monthly mean precipitation data from 124 stations across Yunnan, China. Singular value decomposition analysis indicates a seesaw pattern associated with the diabatic heating over the AS–BOB and summer monsoon precipitation in Yunnan over interannual timescales. When the diabatic heating over the AS–BOB is weaker (stronger) than the climatology during the summer monsoon season, more (less) summer monsoon precipitation generally occurs in Yunnan. A significant correlation between the diabatic heating over the AS–BOB and summer monsoon precipitation in Yunnan begins in late spring–early summer and persists throughout the summer. The AS–BOB diabatic heating in late spring–early summer may thus have a prediction potential for summer monsoon precipitation in Yunnan. The anomalous low-level winds associated with the diabatic heating anomalies over the AS–BOB influence the Indian summer monsoon trough, the vertical motion in Yunnan, and then the summer monsoon precipitation. Numerical experiments based on a linear baroclinic model confirm the key physical process revealed in the observational diagnosis. These experiments also indicate that the diabatic heating over the AS–BOB has a greater impact on summer monsoon precipitation in Yunnan than does diabatic heating around Yunnan on the atmospheric circulation over the AS–BOB. The diabatic heating anomalies over the AS–BOB contributed to the severe summer droughts in Yunnan in 2010, 2011, and 2013 by influencing the circulation.

The Impact of Abyssal Hill Roughness on the Benthic Tide

AbstractThe flow of tides over rough bathymetry in the deep ocean generates baroclinic motion including internal waves and bottom‐trapped tides. The stresses generated by this motion feedback on the amplitude and phase of the large‐scale tide. Quantifying the stresses associated with tidal flow over abyssal hills is especially important, as this scale of bathymetry is often unresolved in global baroclinic tide models, and the stresses must therefore be parameterized. Here, we extend the previous theoretical work of the authors to determine the amplitude, phasing, and vertical location of the stresses exerted on a flow driven by a time‐periodic body force when it encounters rough bathymetry. The theory compares favorably with a suite of fully nonlinear numerical simulations. It is shown that all topographic stresses are applied directly above the bathymetry, leading to a two‐layer baroclinic flow, with the near‐bottom spatial‐mean flow (the benthic tide) strongly modified by topographic stresses, and the flow at height unperturbed by the presence of topography. Our results provide a framework to improve baroclinic tide models by (i) providing a simple parameterization for the subinertial stress which is currently not included in any models, (ii) establishing that parameterized stresses should be applied in the diffusive boundary layer directly above the topography, independent of where internal tides may dissipate, and (iii) identifying a minimum resolution of ∼10 km for baroclinic tidal models to adequately capture wave resonance effects that can significantly impact the magnitude of the benthic tide.

Wet-to-dry climate shift of the Sichuan Basin during 1961–2010

The autumn precipitation over the Sichuan Basin (APSB) experienced a significant wet-to-dry shift around the mid-1980s during the 1961–2010 period. Thus, the dataset is divided into two subperiods, 1961–1985 (P1) and 1986–2010 (P2), which are denoted as the wet period and dry period, respectively. The possible mechanisms accounting for the wet-to-dry shift in the APSB are investigated using both observational data and a baroclinic atmospheric model. Analysis shows that the sea surface temperature (SST) in the tropical Indian-western Pacific (TIWP) regions displays continuous warming during the period under examination, which may intensify the ascent motion over the warm pool and favor the descent motion over the Sichuan Basin. Meanwhile, the Gill-type atmospheric response to anomalous TIWP warm SST is accompanied by anomalous northerly winds prevailing over central and Southwest China. Both the intensified descent motion and anomalous northerly winds over central and Southwest China favor the switch to dry conditions in the APSB. Further analysis shows that the decadal changes in the North Atlantic SST lead to an atmospheric wave pattern prevailing over the extratropical Eurasian continent. An anomalous cyclone over central-eastern Eurasia, which is one component of the wave pattern, is accompanied by significant northerly winds penetrating southward to central China. These northerly winds can cause more-than-normal snow cover around Lake Baikal, which may in turn modulate the atmospheric circulation through positive feedback and therefore result in intensified northerly winds, favorable for the switch to the anomalous dry state of the APSB.

Modeling the Influence of Upstream Land-atmosphere Coupling on the 2017 Persistent Drought over Northeast China

AbstractPersistent drought events that cause serious damages to economy and environment are usually intensified by the feedback between land surface and atmosphere. Therefore, reasonably modeling land-atmosphere coupling is critical for skillful prediction of persistent droughts. However, most high-resolution regional climate modeling focused on the amplification effect of land-atmosphere coupling on local anticyclonic circulation anomaly, while less attention was paid to the non-local influence through altering large-scale atmospheric circulation. Here we investigate how the antecedent land-atmosphere coupling over the area south to Lake Baikal (ASLB) influences the drought events occurred over its downstream region (Northeast China; NEC) by using Weather Research and Forecasting (WRF) model and linear baroclinic model (LBM). When the ASLB is artificially forced to be wet in the WRF simulations during March-May, the surface sensible heating is weakened and results in a cooling anomaly in low level atmosphere during May-July. Consequently, the anticyclonic circulation anomalies over ASLB and NEC are weakened, and the severity of NEC drought during May-July cannot be captured due to the upstream wetting in March-May. In the LBM experiments, idealized atmospheric heating anomaly that mimics the diabatic heating associated with surface wetness is imposed over ASLB, and the quasi-steady response pattern of 500-hPa geopotential height to the upstream wetting is highly consistent with that in the WRF simulation. In addition, the lower level heating instead of the upper level cooling makes a major contribution to the high pressure anomaly over NEC. This study implies the critical role of modeling upstream land-atmosphere coupling in capturing downstream persistent droughts.

Convergence of Daily GRACE Solutions and Models of Submonthly Ocean Bottom Pressure Variability

AbstractKnowledge of submonthly variability in ocean bottom pressure (pb) is an essential element in space‐geodetic analyses and global gravity field research. Estimates of these mass changes are typically drawn from numerical ocean models and, more recently, GRACE (Gravity Recovery and Climate Experiment) series at daily sampling. However, the quality of pb fields from either source has been difficult to assess and reservations persist as to the dependence of regularized GRACE solutions on their oceanographic priors. Here, we make headway on the subject by comparing two daily satellite gravimetry products (years 2007–2009) both with each other and with pb output from a diverse mix of ocean models, complemented by insights from bottom pressure gauges. Emphasis is given to large spatial scales and periods <60 days. Satellite‐based mass changes are in good agreement over basin interiors and point to excess pb signals (∼2 cm root‐mean‐square error) over Southern Ocean abyssal plains in the present GRACE de‐aliasing model. These and other imperfections in baroclinic models are especially apparent at periods <10 days, although none of the GRACE series presents a realistic ground truth on time scales of a few days. A barotropic model simulation with parameterized topographic wave drag is most commensurate with the GRACE fields over the entire submonthly band, allowing for first‐order inferences about error and noise in the gravimetric mass changes. Estimated pb errors vary with signal magnitude and location but are generally low enough (0.5–1.5 cm) to judge model skill in dynamically active regions.

Relationship between two types of heat waves in northern East Asia and temperature anomalies in Eastern Europe

In this study, the hierarchical clustering algorithm was used to cluster the summer heat waves (HWs) in northern East Asia (NEA) into wave-train HW and blocking HW. In the past 38 years, the wave-train HWs have increased significantly, while the blocking HWs have not shown a visible trend. The wave-train index and the blocking index are proposed to objectively identify the HW type after capturing the circulation characteristics of two kinds of HWs. When a wave-train HW occurs in NEA, simultaneous HW will occur in Eastern Europe. However, when a blocking HW occurs in NEA, a negative temperature anomaly will take place in Eastern Europe. The results of numerical simulations using the linear baroclinic model indicate that the wave-train HWs and the blocking HWs are related to the heating anomaly over southern Greenland and the cooling anomaly over the Barents Sea, respectively.

How Does Indian Monsoon Regulate the Northern Hemisphere Stationary Wave Pattern?

The Northern Hemisphere summer climate isstrongly affected by a circumglobal stationary Rossby wave train, which can be manifested by the first EOF mode of the geopotential height at 200 hPa. Interannual variation of this Northern Hemisphere wave (NHW) pattern has a significant impact on remarkably warm surface temperature anomalies over the North Atlantic, Northeast Europe, East Asia to Central-North Pacific, and America, particularly in 2018 and 2010. The NHW pattern is likely generated by atmospheric diabatic heating and vorticity forcing: diabatic heating is mainly confined in the Indian summer monsoon (ISM) precipitation region, whereas the anti-cyclonic vorticity forcing is distributed in the globe. The ISM is a well-known diabatic heat source; however, the main source of vorticity forcing has not been established. In general, the tropical vorticity anomaly comes from diabatic heating-induced atmospheric waves and randomly generated inherent internal waves. The linear baroclinic model experiment reveals that the NHW pattern can be generated by the westward propagating tropical waves generated by the ISM diabatic heat forcing.

Formation of the northern East Asian low: role of diabatic heating

The northern East Asian low (NEAL), characterized by a mid-latitude closed low (or trough) in the lower troposphere, is an important component of the East Asian summer monsoon system. This study investigates formation mechanism of the summer NEAL, with emphasis on the roles of diabatic heating and transient eddy forcing, using a linear baroclinic model (LBM) with prescribed forcing derived from the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) dataset during the 1979–2010 period. The LBM simulations show that the formation of NEAL is induced by the diabatic heating, and the effect of transient eddy forcing is negligible. Further investigation indicates that the diabatic heating over northern East Asia (NEA) is the key factor for the NEAL’s formation, in which the latent heating and radiative cooling in concert to play a major role and the vertical diffusion sensible heating plays a secondary role. In response to the NEA diabatic heating (latent and sensible heating), a local northerly is induced that advects cold air to partially balance the diabatic heat source and forms a low to the east. On the other hand, the radiative cooling induces a southerly anomaly over NEA, shaping the position and intensity of the low induced by the latent and sensible heating. The total effect of the diabatic heating and radiative cooling causes a closed NEAL. Results are similar for the NEAL’s formation in June, July, and August, respectively. Moreover, we further investigate sub-seasonal change of the NEAL in summer. The weakened intensity of the NEAL in August, relative to that in June and July, is contributed to mainly by the enhanced offset effect of the radiative cooling over NEA and partially by the weakened impact of the latent and diffusion sensible heating.

Global attractors of two layer baroclinic quasi-geostrophic model

<p style='text-indent:20px;'>We study the dynamics of a two-layer baroclinic quasi-geostrophic model. We prove that the semigroup <inline-formula><tex-math id="M1">\begin{document}$ \{S(t)\}_{t\geq 0} $\end{document}</tex-math></inline-formula> associated with the solutions of the model has a global attractor in both <inline-formula><tex-math id="M2">\begin{document}$ {{\dot H}_{p}}^1(\Omega) $\end{document}</tex-math></inline-formula> and <inline-formula><tex-math id="M3">\begin{document}$ {{\dot H}_{p}}^2(\Omega) $\end{document}</tex-math></inline-formula>. Also we show that for any viscosity <inline-formula><tex-math id="M4">\begin{document}$ \mu>0 $\end{document}</tex-math></inline-formula>, there is an open and dense set of forcing <inline-formula><tex-math id="M5">\begin{document}$ \mathcal G\subset{{\dot H}_{p}}^0(\Omega) $\end{document}</tex-math></inline-formula> such that for each <inline-formula><tex-math id="M6">\begin{document}$ G = (g_1, g_2)\in \mathcal G $\end{document}</tex-math></inline-formula>, the set <inline-formula><tex-math id="M7">\begin{document}$ S(G, \mu) \subset {{\dot H}_{p}}^4(\Omega) $\end{document}</tex-math></inline-formula> of the steady state problem is non–empty and finite.</p>

Anomalous Warm Winter 2019/2020 over East Asia Associated with Trans-basin Indo-Pacific Connections

The anomalous warm winter from December 2019 to February 2020 over East Asia, particularly the anticyclonic anomaly around Japan, was examined from the teleconnection perspective anchored by a warmed Indian Ocean and the El Niño Modoki. In the upper troposphere, high–low–high wave patterns progressing from the Arabian Sea toward Japan via the southern region of China, coupled with the wave-activity flux diagnosis, implicate the propagation of stationary Rossby waves caused by enhanced convection in the western Indian Ocean and suppressed convection around the Maritime Continent. These anomalous convective activities could be responsible for the northward displacement of the subtropical jet and the ensuing warm conditions over East Asia. The atmospheric response to the observed diabatic heating by means of the linear baroclinic model well reproduced the observations. Moreover, sensitivity experiments of the atmospheric general circulation model to sea surface temperature (SST) anomalies, especially in the warmed western Indian and central Pacific oceans, can help understand the anomalous subsidence over the Maritime Continent sector and subsequently weakened convection. The warmer SST observed around the Maritime Continent alone reproduces the enhancement of rainfall and subsequent cold anomalies around Japan, suggesting the importance of trans-basin interaction for teleconnection towards East Asia.

Diversity of the Global Teleconnections Associated with the Madden–Julian Oscillation

AbstractA recent study has revealed that the Madden–Julian oscillation (MJO) during boreal winter exhibits diverse propagation patterns that consist of four archetypes: standing MJO, jumping MJO, slow eastward propagating MJO, and fast eastward propagating MJO. This study has explored the diversity of teleconnection associated with these four MJO groups. The results reveal that each MJO group corresponds to distinct global teleconnections, manifested as diverse upper-tropospheric Rossby wave train patterns. Overall, the teleconnections in the fast and slow MJO are similar to those in the canonical MJO constructed by the real-time multivariate MJO (RMM) indices, while the teleconnections in the jumping and standing MJO generally lose similarities to those in the canonical MJO. The causes of this diversity are investigated using a linearized potential vorticity equation. The various MJO tropical heating patterns in different MJO groups are the main cause of the diverse MJO teleconnections, as they induce assorted upper-level divergent flows that act as Rossby-wave sources through advecting the background potential vorticity. The variation of the Asian jet could affect the teleconnections over the Pacific jet exit region, but it plays an insignificant role in causing the diversity of global teleconnections. The numerical investigation with a linear baroclinic model shows that the teleconnections can be interpreted as linear responses to the MJO’s diabatic heating to various degrees for different MJO groups, with the fast and slow MJO having higher linear skill than the jumping and standing MJO. The results have broad implications in the MJO’s tropical–extratropical interactions and the associated impacts on global weather and climate.