scholarly journals Mechanisms driving MJO teleconnection changes with warming in CMIP6

2021 ◽  
Author(s):  
Andrea M. Jenney ◽  
David A. Randall ◽  
Elizabeth A. Barnes
Keyword(s):  
North America ◽  
Rossby Wave ◽  
North Pacific ◽  
Static Stability ◽  
Future Climate ◽  
Extended Time ◽  
The North ◽  
The Mean ◽  
The North Pacific ◽  
Mean State

Abstract. Teleconnections from the Madden-Julian Oscillation (MJO) are a key source of predictability of weather on the extended time scale of about 10–40 days. The MJO teleconnection is sensitive to a number of factors, including the mean state dry static stability, the mean flow, and the propagation and intensity characteristics of the MJO itself, 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 potential predictability on extended time scales. Current state-of-the-art climate models do not agree on how MJO teleconnections 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 to separate and investigate alternate mechanisms explaining why and how MJO teleconnections over the North Pacific and North America will change in a future climate, and to identify key sources of inter-model uncertainty. We find that decreases to the MJO teleconnection due to increases in tropical dry static stability alone are robust, and that uncertainty in mean state winds are a key driver of uncertainty in future MJO teleconnections. We find no systematic relationship between changes in Rossby wave excitation and the MJO teleconnection. However, we find that models that predict increases (decreases) in the stationary Rossby wave number over the gulf of Alaska also predict stronger (weaker) teleconnections over North America. Uncertainty in future changes to the MJO's intensity, eastward propagation speed, and eastward propagation extent are other important sources of uncertainty in future MJO teleconnections, although to a lesser degree than uncertainty in the mean state. The overall outlook is a reduction of the boreal winter MJO teleconnection across the vast majority of CMIP6 models, especially over the North Pacific, but with some nuance over North America due to larger sensitivity to expansion of the MJO's eastward extent.

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

2021 ◽  
Vol 2 (3) ◽  
pp. 653-673
Author(s):  
Andrea M. Jenney ◽  
David A. Randall ◽  
Elizabeth A. Barnes
Keyword(s):  
North America ◽  
North Pacific ◽  
Static Stability ◽  
Boreal Winter ◽  
Madden Julian Oscillation ◽  
Future Projections ◽  
The North ◽  
The Mean ◽  
The North Pacific ◽  
Mean State

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.

Season-Dependent Forecast Skill of the Leading Forced Atmospheric Circulation Pattern over the North Pacific and North American Region*

2012 ◽  
Vol 25 (20) ◽  
pp. 7248-7265 ◽  
Author(s):  
XiaoJing Jia ◽  
Hai Lin ◽  
June-Yi Lee ◽  
Bin Wang
Keyword(s):  
Atmospheric Circulation ◽  
North Pacific ◽  
Circulation Pattern ◽  
Tropical Pacific ◽  
Atmospheric Circulation Pattern ◽  
Potential Predictability ◽  
The North ◽  
The Mean ◽  
The North Pacific ◽  
Mean State

Abstract Multimodel ensemble (MME) seasonal forecasts are analyzed to evaluate numerical model performance in predicting the leading forced atmospheric circulation pattern over the extratropical Northern Hemisphere (NH). Results show that the time evolution of the leading tropical Pacific sea surface temperature (SST)-coupled atmospheric pattern (MCA1), which is obtained by applying a maximum covariance analysis (MCA) between 500-hPa geopotential height (Z500) in the extratropical NH and SST in the tropical Pacific Ocean, can be predicted with a significant skill in March–May (MAM), June–August (JJA), and December–February (DJF) one month ahead. However, most models perform poorly in capturing the time variation of MCA1 in September–November (SON) with 1 August initial condition. Two possible reasons for the models’ low skill in SON are identified. First, the models have the most pronounced errors in the mean state of SST and precipitation along the central equatorial Pacific. Because of the link between the divergent circulation forced by tropical heating and the midlatitude atmospheric circulation, errors in the mean state of tropical SST and precipitation may lead to a degradation of midlatitude forecast skill. Second, examination of the potential predictability of the atmosphere, estimated by the ratio of the total variance to the variance of the model forecasts due to internal dynamics, shows that the atmospheric potential predictability over the North Pacific–North American (NPNA) region is the lowest in SON compared to the other three seasons. The low ratio in SON is due to a low variance associated with external forcing and a high variance related to atmospheric internal processes over this area.

Future Changes to El Niño Teleconnections over the North Pacific and North America

2021 ◽  
pp. 1-43
Author(s):  
Jonathan D. Beverley ◽  
Matthew Collins ◽  
F. Hugo Lambert ◽  
Robin Chadwick
Keyword(s):  
North America ◽  
El Niño ◽  
North Pacific ◽  
El Nino ◽  
Positive Temperature ◽  
Central Pacific ◽  
Wave Source ◽  
The North ◽  
Precipitation Anomalies ◽  
The North Pacific

AbstractThe El Niño-Southern Oscillation (ENSO) is the leading mode of interannual climate variability and it exerts a strong influence on many remote regions of the world, for example in northern North America. Here, we examine future changes to the positive-phase ENSO teleconnection to the North Pacific/North America sector and investigate the mechanisms involved. We find that the positive temperature anomalies over Alaska and northern North America that are associated with an El Niño event in the present day are much weaker, or of the opposite sign, in the CMIP6 abrupt 4×CO2 experiments for almost all models (22 out of 26, of which 15 are statistically significant differences). This is largely related to changes to the anomalous circulation over the North Pacific, rather than differences in the equator-to-pole temperature gradient. Using a barotropic model, run with different background circulation basic states and Rossby wave source forcing patterns from the individual CMIP6 models, we find that changes to the forcing from the equatorial central Pacific precipitation anomalies are more important than changes in the global basic state background circulation. By further decomposing this forcing change into changes associated with the longitude and magnitude of ENSO precipitation anomalies, we demonstrate that the projected overall eastward shift of ENSO precipitation is the main driver of the temperature teleconnection change, rather than the increase in magnitude of El Niño precipitation anomalies which are, nevertheless, seen in the majority of models.

scholarly journals Contrastive Influence of ENSO and PNA on Variability and Predictability of North American Winter Precipitation

2019 ◽  
Vol 32 (19) ◽  
pp. 6271-6284 ◽  
Author(s):  
Xiaofan Li ◽  
Zeng-Zhen Hu ◽  
Ping Liang ◽  
Jieshun Zhu
Keyword(s):  
North America ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
North American ◽  
North Pacific ◽  
Winter Precipitation ◽  
Sea Surface ◽  
The North ◽  
Remote Forcing ◽  
The North Pacific

Abstract In this work, the roles of El Niño–Southern Oscillation (ENSO) in the variability and predictability of the Pacific–North American (PNA) pattern and precipitation in North America in winter are examined. It is noted that statistically about 29% of the variance of PNA is linearly linked to ENSO, while the remaining 71% of the variance of PNA might be explained by other processes, including atmospheric internal dynamics and sea surface temperature variations in the North Pacific. The ENSO impact is mainly meridional from the tropics to the mid–high latitudes, while a major fraction of the non-ENSO variability associated with PNA is confined in the zonal direction from the North Pacific to the North American continent. Such interferential connection on PNA as well as on North American climate variability may reflect a competition between local internal dynamical processes (unpredictable fraction) and remote forcing (predictable fraction). Model responses to observed sea surface temperature and model forecasts confirm that the remote forcing is mainly associated with ENSO and it is the major source of predictability of PNA and winter precipitation in North America.

scholarly journals Near-Global Atmospheric Responses to Observed Springtime Tibetan Plateau Snow Anomalies

2020 ◽  
Vol 33 (5) ◽  
pp. 1691-1706 ◽  
Author(s):  
Shizuo Liu ◽  
Qigang Wu ◽  
Steven R. Schroeder ◽  
Yonghong Yao ◽  
Yang Zhang ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
North America ◽  
Tibetan Plateau ◽  
North Pacific ◽  
Snow Water Equivalent ◽  
North Pacific Ocean ◽  
Surface Cooling ◽  
The North ◽  
Snow Cover Extent ◽  
The North Pacific

AbstractPrevious studies show that there are substantial influences of winter–spring Tibetan Plateau (TP) snow anomalies on the Asian summer monsoon and that autumn–winter TP heavy snow can lead to persisting hemispheric Pacific–North America-like responses. This study further investigates global atmospheric responses to realistic extensive spring TP snow anomalies using observations and ensemble transient model integrations. Model ensemble simulations are forced by satellite-derived observed March–May TP snow cover extent and snow water equivalent in years with heavy or light TP snow. Heavy spring TP snow causes simultaneous significant local surface cooling and precipitation decreases over and near the TP snow anomaly. Distant responses include weaker surface cooling over most Asian areas surrounding the TP, a weaker drying band extending east and northeast into the North Pacific Ocean, and increased precipitation in a region surrounding this drying band. Also, there is tropospheric cooling from the TP into the North Pacific and over most of North America and the North Atlantic Ocean. The TP snow anomaly induces a negative North Pacific Oscillation/western Pacific–like teleconnection response throughout the troposphere and stratosphere. Atmospheric responses also include significantly increased Pacific trade winds, a strengthened intertropical convergence zone over the equatorial Pacific Ocean, and an enhanced local Hadley circulation. This result suggests a near-global impact of the TP snow anomaly in nearly all seasons.

scholarly journals The mean meridional circulation and midlatitude ozone buildup

2005 ◽  
Vol 5 (3) ◽  
pp. 4223-4256
Author(s):  
G. Nikulin ◽  
A. Karpechko
Keyword(s):  
Heat Flux ◽  
North Pacific ◽  
Meridional Circulation ◽  
Residual Velocity ◽  
The North ◽  
Eddy Heat Flux ◽  
Mean Meridional Circulation ◽  
The Mean ◽  
Temperature Tendency ◽  
The North Pacific

Abstract. The development of wintertime ozone buildup over the Northern Hemisphere (NH) midlatitudes and its connection with the mean meridional circulation in the stratosphere are examined statistically on a monthly basis from October to March (1980–2002). The ozone buildup begins locally in October with positive ozone tendencies over the North Pacific, which spread eastward and westward in November and finally cover all midlatitudes in December. During October–January a longitudinal distribution of the ozone tendencies mirrors a structure of quasi-stationary planetary waves in the lower stratosphere and has less similarity with this structure in February–March when chemistry begins to play a more important role. From November to March, zonal mean ozone tendencies (50°–60° N) show strong correlation (|r|=0.7) with different parameters used as proxies of the mean meridional circulation, namely: eddy heat flux, the vertical residual velocity (diabatically-derived) and temperature tendency. The correlation patterns between ozone tendency and the vertical residual velocity or temperature tendency are more homogeneous from month to month than ones for eddy heat flux. A partial exception is December when correlation is strong only for the vertical residual velocity. In October zonal mean ozone tendencies have no coupling with the proxies. However, positive tendencies averaged over the North Pacific correlate well, with all of them suggesting that intensification of northward ozone transport starts locally over the Pacific already in October. We show that the NH midlatitude ozone buildup has stable statistical relation with the mean meridional circulation in all months from October to March and half of the interannual variability in monthly ozone tendencies can be explained by applying different proxies of the mean meridional circulation.

Sign in / Sign up

Export Citation Format

Share Document