Impact of Sea Surface Temperature Anomalies in the Equatorial and North Pacific on the Arctic Stratosphere According to INMCM5 Climate Model Simulations

2021 ◽  
pp. 5-16
Author(s):  
P. N. Vargin ◽  
◽  
M. A. Kolennikova ◽  
S. V. Kostrykin ◽  
E. M. Volodin ◽  
...  

Five 50-year simulations with version 5 of the INM RAS coupled climate model revealed that the winters with El Nio are characterized by higher Arctic stratospheric temperature as compared to the seasons with La Nia. Lower stratospheric temperature in the Arctic regions as compared to the seasons with negative sea surface temperature (SST) anomalies corresponds to the winter seasons with positive SST anomalies in the North Pacific.

2021 ◽  
pp. 1-53
Author(s):  
Hua Li ◽  
Shengping He ◽  
Ke Fan ◽  
Yong Liu ◽  
Xing Yuan

AbstractThe Meiyu withdrawal date (MWD) is a crucial indicator of flood/drought conditions over East Asia. It is characterized by a strong interannual variability, but its underlying mechanism remains unknown. We investigated the possible effects of the winter sea surface temperature (SST) in the North Pacific Ocean on the MWD on interannual to interdecadal timescales. Both our observations and model results suggest that the winter SST anomalies associated with the MWD are mainly contributed by a combination of the first two leading modes of the winter SST in the North Pacific, which have a horseshoe shape (the NPSST). The statistical results indicate that the intimate linkage between the NPSST and the MWD has intensified since the early 1990s. During the time period 1990–2016, the NPSST-related SST anomalies persisted from winter to the following seasons and affected the SST over the tropical Pacific in July. Subsequently, the SST anomalies throughout the North Pacific strengthened the southward migration of the East Asian jet stream (EAJS) and the southward and westward replacement of the western North Pacific subtropical high (WPSH), leading to an increase in Meiyu rainfall from July 1 to 20. More convincingly, the anomalous EAJS and WPSH induced by the SST anomalies can be reproduced well by numerical simulations. By contrast, the influence of the NPSST on the EASJ and WPSH were not clear between 1961 and 1985. This study further illustrates that the enhanced interannual variability of the NPSST may be attributed to the more persistent SST anomalies during the time period 1990–2016.


2013 ◽  
Vol 26 (16) ◽  
pp. 6123-6136 ◽  
Author(s):  
Bolan Gan ◽  
Lixin Wu

Abstract In this study, a lagged maximum covariance analysis (MCA) of the wintertime storm-track and sea surface temperature (SST) anomalies derived from the reanalysis datasets shows significant seasonal and long-term relationships between storm tracks and SST variations in the North Pacific. At seasonal time scales, it is found that the midlatitude warm (cold) SST anomalies in the preceding fall, which are expected to change the tropospheric baroclinicity, can significantly reduce (enhance) the storm-track activities in early winter. The storm-track response pattern, however, is in sharp contrast to the forcing pattern, with warm (cold) SST anomalies in the western–central North Pacific corresponding to a poleward (equatorward) shift of storm tracks. At interannual-to-decadal time scales, it is found that the wintertime SST and storm-track anomalies are mutually reinforced up to 3 yr, which is characterized by PDO-like SST anomalies with warming in the western–central domain coupled with basin-scale positive storm-track anomalies extending along 50°N.


2021 ◽  
pp. 1-43
Author(s):  
TAO WANG ◽  
WENSHOU TIAN ◽  
TAO LIAN ◽  
CHENG SUN ◽  
FEI XIE ◽  
...  

AbstractChanges in the meridional position of the sea surface temperature (SST) anomalies (SSTAs) associated with the interannual component (PC1-I) of the principal component 1 (PC1) of the first leading mode of the North Pacific SST (referred here as PC1-I-related SSTAs) are investigated using reanalysis products and climate model output. It is found that the PC1-I-related SSTAs (or PC1-I anomaly) significantly shift southward at a rate of 1.04°/decade and have moved southward by 4.4 degrees since the 1960s. Our further analysis indicates that the southward shift of the PC1-I-related SSTAs is due to changes in ENSO teleconnections. Compared to the 1950–1975 period (PRE era), the meridional width of the ENSO-induced tropical positive geopotential height (GH) anomaly is narrower during the 1991–2016 period (POST era), inducing a southward shift of the subtropical westerly anomaly over the North Pacific through geostrophic wind relations. This southward shift of the westerly anomaly favors the southward shift of the ENSO-induced negative GH anomaly (cyclonic circulation anomaly) over the North Pacific by positive vorticity forcing of the zonal wind shear. The southward-shifting GH anomaly associated with ENSO further forces the PC1-I anomaly to shift southward. Furthermore, the contraction of the ENSO-induced tropical positive GH anomaly is related to the contraction of the meridional width of ENSO. The modeling results support that the decrease in the ENSO meridional width favors the contraction of the ENSO-induced tropical positive GH anomaly and the southward shift of ENSO teleconnections over the North Pacific, contributing to the southward shift of the PC1-I anomaly.


2008 ◽  
Vol 21 (7) ◽  
pp. 1569-1588 ◽  
Author(s):  
Takashi Mochizuki ◽  
Toshiyuki Awaji

Abstract To clarify the summertime evolution of decadal sea surface temperature (SST) anomalies and related physical processes in the midlatitudes of the North Pacific, numerical solutions of a three-dimensional bulk mixed layer model are analyzed, focusing on the contribution of the net shortwave radiative forcing at the sea surface. A quantitative heat budget analysis for the ocean mixed layer relating to late-1980s decadal SST change reveals that the decadal SST anomalies decay from late spring to early summer over the entire midlatitudes of the North Pacific. This quasi-seasonal decay of the decadal SST anomalies is controlled by an anomalous local thermal damping (i.e., anomalous surface heat fluxes). From midsummer to early autumn the anomalous net shortwave radiation flux associated with a meridional shift of the storm track acts to induce strong seasonal damping of the decadal SST anomaly in the northern Kuroshio–Oyashio Extension region. In contrast, in the north of the subtropical frontal region, the net shortwave radiation flux anomaly, which results from changes in low-level stratiform cloud cover, plays a major role in seasonally enhancing the decadal SST anomaly. Consequently, the SST anomalies formed by these radiative forcings cause significant variations in the local thermal damping rate at the sea surface over the period from late summer to early autumn.


2019 ◽  
Vol 32 (19) ◽  
pp. 6271-6284 ◽  
Author(s):  
Xiaofan Li ◽  
Zeng-Zhen Hu ◽  
Ping Liang ◽  
Jieshun Zhu

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.


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