scholarly journals Decadal Transition of the Leading Mode of Interannual Moisture Circulation over East Asia–Western North Pacific: Bonding to Different Evolution of ENSO

2018 ◽  
Vol 32 (2) ◽  
pp. 289-308 ◽  
Author(s):  
Xiuzhen Li ◽  
Zhiping Wen ◽  
Deliang Chen ◽  
Zesheng Chen
Keyword(s):  
Indian Ocean ◽  
East Asia ◽  
North Pacific ◽  
Western North Pacific ◽  
Eastern Pacific ◽  
Enso Cycle ◽  
Central Pacific ◽  
Huai River ◽  
Leading Mode ◽  
The Impact

Abstract The El Niño–Southern Oscillation (ENSO) cycle has a great impact on the summer moisture circulation over East Asia (EA) and the western North Pacific [WNP (EA-WNP)] on an interannual time scale, and its modulation is mainly embedded in the leading mode. In contrast to the stable influence of the mature phase of ENSO, the impact of synchronous eastern Pacific sea surface temperature anomalies (SSTAs) on summer moisture circulation is negligible during the 1970s–80s, while it intensifies after 1991. In response, the interannual variation of moisture circulation exhibits a much more widespread anticyclonic/cyclonic pattern over the subtropical WNP and a weaker counterpart to the north after 1991. Abnormal moisture moves farther northward with the enhanced moisture convergence, and thus precipitation shifts from the Yangtze River to the Huai River valley. The decadal shift in the modulation of ENSO on moisture circulation arises from a more rapid evolution of the bonding ENSO cycle and its stronger coupling with circulation over the Indian Ocean after 1991. The rapid development of cooling SSTAs over the central-eastern Pacific, and warming SSTAs to the west over the eastern Indian Ocean–Maritime Continent (EIO-MC) in summer, stimulates abnormal descending motion over the western-central Pacific and ascending motion over the EIO-MC. The former excites an anticyclone over the WNP as a Rossby wave response, sustaining and intensifying the WNP anticyclone; the latter helps anchor the anticyclone over the tropical–subtropical WNP via an abnormal southwest–northeast vertical circulation between EIO-MC and WNP.

scholarly journals Intensified Impact of East Indian Ocean SST Anomaly on Tropical Cyclone Genesis Frequency over the Western North Pacific

2014 ◽  
Vol 27 (23) ◽  
pp. 8724-8739 ◽  
Author(s):  
Ruifen Zhan ◽  
Yuqing Wang ◽  
Li Tao
Keyword(s):  
Indian Ocean ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Tropical Cyclone Genesis ◽  
Central Pacific ◽  
East Indian ◽  
The Impact ◽  
East Indian Ocean ◽  
Genesis Frequency

Abstract A recent finding is the significant impact of the sea surface temperature anomaly (SSTA) over the east Indian Ocean (EIO) on the genesis frequency of tropical cyclones (TCs) over the western North Pacific (WNP). In this study it is shown that such an impact is significant only after the late 1970s. The results based on both data analysis and numerical model experiments demonstrate that prior to the late 1970s the EIO SSTA is positively correlated with the equatorial central Pacific SSTA and the latter produces an opposite atmospheric circulation response over the WNP to the former. As a result, the impact of the EIO SSTA on the TC genesis over the WNP is largely suppressed by the latter. After the late 1970s, the area coverage of the EIO SSTA is expanding. This considerably enhances the large-scale circulation response over the WNP to the EIO SSTA and significantly intensifies the impact of the EIO SSTA on TC genesis frequency over the WNP. The results from this study have great implications for seasonal prediction of TC activity over the WNP.

scholarly journals A Comparison of the Downstream Predictability Associated with ET and Baroclinic Cyclones

2017 ◽  
Vol 145 (11) ◽  
pp. 4651-4672 ◽  
Author(s):  
Ryan D. Torn
Keyword(s):  
Standard Deviation ◽  
Indian Ocean ◽  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Ensemble Forecast ◽  
Latent Heat Release ◽  
Propagation Characteristics ◽  
Forecast System ◽  
The Impact

The impact of the extratropical transition (ET) of tropical cyclones and baroclinic cyclogenesis in the western North Pacific (WNP), Atlantic, and southern Indian Ocean (SIO) basins on the predictability of the downstream midlatitude flow is assessed using 30 years of cases from the Global Ensemble Forecast System (GEFS) Reforecast, version 2. In all three basins, ET is associated with statistically larger 500-hPa geopotential height forecast standard deviation (SD) compared to the forecast climatology. The higher SD values originate from where the TC enters the midlatitudes and spread downstream at the group velocity of the associated wave packet. Of the three basins, WNP ET is associated with the largest amplitude and longest-lasting SD anomalies. Forecasts initialized 2–4 days prior to the onset of ET have larger SD anomalies compared to forecasts initialized during or after the onset of ET. By contrast, the region of positive SD anomaly associated with winter baroclinic cyclones is confined to the upstream trough, with fall cyclones exhibiting some downstream propagation characteristics similar to ET. The ET cases with the larger downstream SD anomaly are characterized by a more amplified ridge downstream of the TC as it enters the midlatitudes. By contrast, ET cases with an upstream trough, large TC position variability at the onset of ET, latent heat release, or upper-tropospheric PV advection by the irrotational wind are not characterized by significantly larger downstream SD compared to cases without an upstream trough or smaller values of these quantities.

scholarly journals Role of climate variability in the potential predictability of tropical cyclone formation in tropical and subtropical western North Pacific Ocean

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yu-Lin K. Chang ◽  
Yasumasa Miyazawa ◽  
Swadhin Behera
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Southern Oscillation ◽  
North Pacific Ocean ◽  
Eastern Pacific ◽  
Central Pacific ◽  
Potential Predictability ◽  
Vorticity Anomaly ◽  
Tropical Western North Pacific

AbstractThe out of phase tropical cyclone (TC) formation in the subtropical and tropical western North Pacific associated with local low-level wind vorticity anomaly, driven by the remote central and eastern equatorial Pacific warming/cooling, is investigated based on the reanalysis and observational data in the period of 1979−2017. TC frequencies in the subtropical and tropical western North Pacific appear to be connected to different remote heating/cooling sources and are linked to eastern and central Pacific warming/cooling, which are in turn related to canonical El Niño/Southern Oscillation (ENSO) and ENSO Modoki, respectively. TCs formed in subtropics (SfTC) are generally found to be associated with a dipole in wind vorticity anomaly, which is driven by the tropical eastern Pacific warming/cooling. Tropically formed TCs (TfTC) are seen to be triggered by the single-core of wind vorticity anomaly locally associated with the warming/cooling of central and eastern Pacific. The predicted ENSOs and ENSO Modokis, therefore, provide a potential source of seasonal predictability for SfTC and TfTC frequencies.

scholarly journals Impacts of MJO on the Intraseasonal Temperature Variation in East Asia

2020 ◽  
Vol 33 (20) ◽  
pp. 8903-8916
Author(s):  
Sunyong Kim ◽  
Jong-Seong Kug ◽  
Kyong-Hwan Seo
Keyword(s):  
Indian Ocean ◽  
East Asia ◽  
Eastern Europe ◽  
Rossby Wave ◽  
North Pacific ◽  
Western North Pacific ◽  
Phase 3 ◽  
Overturning Circulation ◽  
Cold Surface ◽  
Adiabatic Cooling

AbstractThe Madden–Julian oscillation (MJO) is closely related to the intraseasonal variability of surface temperature in East Asia. It has been shown that significant cold surface temperature anomalies are observed in East Asia during MJO phase 3. However, the cooling tendency develops prior to phase 3, suggesting that the cold surface anomalies in East Asia are a delayed and accumulated response to the MJO forcings prior to phase 3. Here, using a thermodynamic equation, it is shown that both meridional advection and adiabatic cooling terms associated with the MJO flow are the dominant contributors to the cooling tendency. The meridional cold advection initially manifests in East Asia in the form of northerly wind anomalies in the eastern part of anticyclonic circulation anomalies that are centered over eastern Europe and develop before the establishment of the cold anomalies. It is suggested that the enhanced convection in the western North Pacific Ocean is responsible for the anomalous anticyclonic flow over eastern Europe with about a 10-day lag via a meridionally propagating Rossby wave train. Further, cooling by the vertical wind component in East Asia is a result of adiabatic cooling interpreted as a reversed local overturning circulation, with downward motion in the tropics and upward motion in the subtropics. This anomalous meridional overturning circulation process initiated from suppressed convection spanning the tropical Indian Ocean to East Asia also takes about 10 days. Therefore, both the Rossby wave propagation and a local overturning circulation induced by the tropical convections play an important role in driving the lagged response of cold surface anomalies in East Asia. Interestingly, these tropical convection forcings are similar to the typical dipole pattern in convection during MJO phase 7, with suppressed Indian Ocean convection and enhanced western North Pacific convection. This implies that the dipole convective forcing during MJO phase 7 possibly leads to the cold anomalies in East Asia following phase 3.

scholarly journals Impact of Storm Size on Prediction of Storm Track and Intensity Using the 2016 Operational GFDL Hurricane Model

2017 ◽  
Vol 32 (4) ◽  
pp. 1491-1508 ◽  
Author(s):  
Morris A. Bender ◽  
Timothy P. Marchok ◽  
Charles R. Sampson ◽  
John A. Knaff ◽  
Matthew J. Morin
Keyword(s):  
Tropical Cyclones ◽  
North Pacific ◽  
Western North Pacific ◽  
Numerical Models ◽  
Storm Track ◽  
Eastern Pacific ◽  
Lead Times ◽  
Rapid Intensification ◽  
Forecast Lead Time ◽  
The Impact

Abstract The impact of storm size on the forecast of tropical cyclone storm track and intensity is investigated using the 2016 version of the operational GFDL hurricane model. Evaluation was made for 1529 forecasts in the Atlantic, eastern Pacific, and western North Pacific basins, during the 2014 and 2015 seasons. The track and intensity errors were computed from forecasts in which the 34-kt (where 1 kt = 0.514 m s−1) wind radii obtained from the operational TC vitals that are used to initialize TCs in the GFDL model were replaced with wind radii estimates derived using an equally weighted average of six objective estimates. It was found that modifying the radius of 34-kt winds had a significant positive impact on the intensity forecasts in the 1–2 day lead times. For example, at 48 h, the intensity error was reduced 10%, 5%, and 4% in the Atlantic, eastern Pacific, and western North Pacific, respectively. The largest improvements in intensity forecasts were for those tropical cyclones undergoing rapid intensification, with a maximum error reduction in the 1–2 day forecast lead time of 14% and 17% in the eastern and western North Pacific, respectively. The large negative intensity biases in the eastern and western North Pacific were also reduced 25% and 75% in the 12–72-h forecast lead times. Although the overall impact on the average track error was neutral, forecasts of recurving storms were improved and tracks of nonrecurving storms degraded. Results also suggest that objective specification of storm size may impact intensity forecasts in other high-resolution numerical models, particularly for tropical cyclones entering a rapid intensification phase.

scholarly journals What modulates the intensity of synoptic scale variability over the western North Pacific during boreal summer and fall?

2021 ◽  
pp. 1
Author(s):  
Renguang Wu ◽  
Yuqi Wang ◽  
Xi Cao
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Eastern Pacific ◽  
Propagation Path ◽  
Boreal Summer ◽  
Synoptic Scale ◽  
Mean Flow ◽  
Central Pacific ◽  
Background Fields ◽  
Sst Anomalies

AbstractThe present study investigates the factors that affect the year-to-year change in the intensity of synoptic scale variability (SSV) over the tropical western North Pacific (TWNP) during boreal summer and fall. It is found that the intensity of the TWNP SSV in summer is associated with the equatorial central-eastern Pacific sea surface temperature (SST) anomalies that modulates the background fields through a Rossby wave response both in the source region and along the propagation path of the synoptic scale disturbances. In fall, the intensity of the TWNP SSV is related to an SST anomaly pattern with opposite anomalies in the equatorial central Pacific and TWNP that modulates the background fields from the equatorial central Pacific to TWNP. However, the equatorial central Pacific SST anomalies alone fail to change the intensity of the TWNP SSV as the induced background field changes are limited to the equatorial central Pacific. It is shown that tropical western Pacific SST anomalies may induce notable changes in the intensity of the TWNP SSV. The relation of the TWNP SSV to the equatorial eastern Pacific SST is weak due to opposite SST anomalies in different types of years. Both seasonal mean and intraseasonal flows provide source of barotropic energy for the change in the intensity of the TWNP synoptic scale disturbances in summer. Seasonal mean flow has a main contribution to the barotropic energy conversion for the change in the intensity of the TWNP synoptic scale disturbances in fall.

Contrasting Relationship between Tropical Western North Pacific Convection and Rainfall over East Asia during Indian Ocean Warm and Cold Summers

2014 ◽  
Vol 27 (7) ◽  
pp. 2562-2576 ◽  
Author(s):  
Jie Song ◽  
Chongyin Li
Keyword(s):  
Indian Ocean ◽  
East Asia ◽  
North Pacific ◽  
Western North Pacific ◽  
Eastern China ◽  
Vertical Motion ◽  
Daily Data ◽  
Central Eastern ◽  
Action Center ◽  
Tropical Western North Pacific

Abstract Using daily data, this study compares the subseasonal seesaw relationship between anomalous tropical western North Pacific (WNP) convection and anomalous rainfall over subtropical East Asia during boreal summers (June–August) in which the Indian Ocean (IO) sea surface temperature is either warmer or colder than normal. It is found that the precipitation anomalies over central-eastern China (25°–35°N, 110°–120°E) associated with the anomalous tropical WNP convection activities during the IO cold summers are weaker and less evident compared to that in the IO warm summers, indicating the seesaw relationship in the IO cold summers becomes obscure. This contrasting seesaw relationship between the IO warm and cold summers is attributed to different patterns of anomalous moisture transportation and vertical motion over central-eastern China. The anomalous circulations associated with the anomalous tropical WNP convection [the Pacific–Japan (PJ) pattern] during the IO warm and cold summers show that, relative to the IO warm summers, the Japan action center of the PJ pattern has an evident northwestward displacement in the IO cold summers. It is argued that this northwestward displacement of the Japan action center plays a key role in the formation of the distinct seesaw relationship through modifying the anomalous moisture transportation and vertical motion.

scholarly journals Intraseasonal Variability of the East Asia-Pacific Teleconnection and Its Impacts on Multiple Tropical Cyclone Genesis Over the Western North Pacific

2021 ◽  
Vol 8 ◽  
Author(s):  
Xin Lin ◽  
Lan Wang ◽  
Jianyun Gao ◽  
Xiaoxiao Chen ◽  
Wei Zhang
Keyword(s):  
East Asia ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
El Nino ◽  
Intraseasonal Variability ◽  
Asia Pacific ◽  
Boreal Summer ◽  
Relative Role ◽  
The Impact

A daily East Asia–Pacific teleconnection (EAP) index was constructed to investigate the impact of the intraseasonal variability (ISV) of this index on the genesis of multiple tropical cyclones (MTC) in boreal summer over the western North Pacific (WNP). The result indicates that the EAP index has dominant intraseasonal periods of 10–20 days, 20–40 days and 50–70 days, respectively. The ISV of the EAP during 1979–2019 can be classified into three types, a single-period-domination type (37%), a multiple period coexistence type (24%) and a transition type (39%). It is found that during El Niño (La Niña) summers, the ISV of the EAP is dominated by a higher-frequency (lower-frequency) oscillation with a period of around 20–30 (50–70) days. The distinctive ISV characteristics during the different ENSO years were accompanied with different dynamic and thermodynamic background conditions over the WNP and the South China Sea, which modulated the frequency and location of MTC genesis. By examining the relative contributions of individual environmental variables of the Genesis Potential Index, we found that the low-level absolute vorticity and mid-level relative humidity are two important environmental factors modulating MTC genesis. However, the relative role of these variables tends to change with the EAP ISV phase. The environmental condition over the SCS appears less influenced by ENSO. A more southern location of MTC genesis during El Niño is attributed to the change of the environmental humidity.

scholarly journals Proof in climatology for circulation effect of stalagmite δ<sup>18</sup>O in East Asia: analysis on the ratios among water vapor transport passageway intensities in East Asia

2013 ◽  
Vol 9 (4) ◽  
pp. 4263-4291
Author(s):  
S. Nan ◽  
M. Tan ◽  
P. Zhao
Keyword(s):  
Water Vapor ◽  
Indian Ocean ◽  
East Asia ◽  
North Pacific ◽  
El Nino ◽  
East Asian ◽  
Tropical Indian Ocean ◽  
Vapor Transport ◽  
Eastern Pacific ◽  
Water Vapor Transport

Abstract. Further verification about the circulation effect of stalagmite δ18O in East Asian monsoon region needs the quantitative description for the proportion of water vapor transport (WVT) from different source regions. WVT passageway intensities are defined as regionally averaged WVT flux modes in this paper. The ratio between two WVT passageways' intensities represents relative intensity of the two WVT passageways. Using the NCEP-NCAR reanalysis data for 1948–2011, the ratios of the intensities of three WVT passageways from low latitudes (the intensity of WVT from Bay of Bengal (IBOB), the intensity of WVT from South China Sea (ISCS) and the intensity of WVT from western North Pacific (IWNP) in summer are calculated. SB is for the ISCS-IBOB ratio, WB for the IWNP-IBOB ratio, and WS for the IWNP-ISCS ratio. The decadal increase occurs in the time series of WB and WS, with higher values in 1976–1995 and lower values in 1950–1975, probably resulting from the strengthening of WVT from WNP in the midterm of 1970s. East Asian atmospheric circulations, WVTs and previous SST characters corresponding to the ratios are analyzed. The result indicates that SB, WB and WS may properly reflect the relative intensities between ISCS and IBOB, between IWNP and IBOB, and between IWNP and ISCS, respectively. For high SB years, the Asian Low and the western Pacific subtropical high (WPSH) weaken. The southwesterly winds from BOB to the Yangtze River valley by the southeast of the Tibetan Plateau weaken and the WVT from BOB to East Asia weakens. The southwesterly winds from SCS to East Asia strengthen and the WVT from SCS to East Asia strengthens. In high WB years, the Asian Low weakens and the WPSH shifts westwards, enhances and enlarges. The WVT from WNP to East Asia increases because of the strengthening of the easterly winds on the south of the WPSH. The westerly winds from BOB to East Asia by Indo-China Peninsula decrease and the WVT from BOB to East Asia weakens. The atmospheric circulation and WVT associated with WS are similar with those associated with WB. There are close relationships between WB (and WS) and the WPSH area, position and intensity. In high WB (and WS) years, the WPSH shifts westwards, enlarges and enhances. There is no obvious anomalous previous SST signal in tropical Indian Ocean and equatorial central and eastern Pacific for anomalous SB years. WB and WS are closely related to previous SST signal. When the equatorial central and eastern Pacific is in El Niño phase, SST in the tropical Indian Ocean, BOB and SCS is high and SST at middle latitudes in North Pacific is low, WB and WS tend to be high. After the midterm of 1970s, the equatorial central and eastern Pacific is often in El Niño phase. It is in agreement with higher WB in 1976–1995 than that in 1950–1975. In light of circulation effect of stalagmite δ18O in East Asia, high WB implies high stalagmite δ18O. Therefore, the interdecadal increase of WB in 1976–1995 than in 1950–1975 provides the proof using the conception of circulation effect to explain the interdecadal change of stalagmite δ18O at most regions in East Asia.

Sign in / Sign up

Export Citation Format

Share Document