scholarly journals Impact of Indo-Pacific warm pool Hadley circulation on the seasonal forecast performance for summer precipitation over the western North Pacific

2020 ◽  
Vol 15 (10) ◽  
pp. 104041 ◽  
Author(s):  
Yi-Peng Guo ◽  
Xiangbo Feng ◽  
Nicholas P Klingaman ◽  
Zhe-Min Tan
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Hadley Circulation ◽  
Summer Precipitation ◽  
Warm Pool ◽  
Seasonal Forecast ◽  
Forecast Performance ◽  
Pacific Warm Pool

Impacts of the Boreal Spring Indo-Pacific Warm Pool Hadley Circulation on Tropical Cyclone Activity over the Western North Pacific

2018 ◽  
Vol 31 (4) ◽  
pp. 1361-1375 ◽  
Author(s):  
Yi-Peng Guo ◽  
Zhe-Min Tan
Keyword(s):  
Tropical Cyclone ◽  
South China Sea ◽  
South China ◽  
North Pacific ◽  
Western North Pacific ◽  
Hadley Circulation ◽  
Warm Pool ◽  
Westerly Wind ◽  
Pacific Warm Pool ◽  
Sst Gradient

This study investigated the impacts of the interannual variability in the boreal spring regional Hadley circulation over the Indo-Pacific warm pool (IPWP) on the tropical cyclone (TC) activity over the western North Pacific (WNP). The principal modes of the interannual variability in the IPWP Hadley circulation were calculated using empirical orthogonal function (EOF) analysis. The leading mode (EOF-1) features cross-equatorial southerly wind anomalies over the Indian Ocean and Maritime Continent and has an evident impact on WNP TC activity during summer. In the summer following a positive phase of the EOF-1, a cyclonic circulation anomaly, with upward motion, positive relative vorticity anomalies, and weak sea level pressure, dominates the WNP, and this favors increased TC genesis. However, large positive vertical wind shear anomalies over the South China Sea and Philippine Sea inhibit the TC intensification. A positive wind–sea surface temperature (SST)–precipitation feedback was found to facilitate the ability of the signal of the EOF-1 to persist until the summer. The westerly wind anomalies converge around 10°N over the WNP, thus increasing precipitation, and this increased precipitation enhances the westerly wind anomalies via a Gill-type response. The strengthened westerly wind anomalies increase total wind speeds, which in turn cool the SST in the Bay of Bengal and the South China Sea, and warm the SST in the eastern WNP, increasing the zonal SST gradient. Consequently, this increased zonal SST gradient further enhances the westerly wind anomalies, strengthens the monsoon trough, and increases the WNP precipitation further. Therefore, the WNP precipitation anomalies are sustained into the summer.

Meridional SST gradient in the western North Pacific warm pool associated with typhoon generation

2008 ◽  
Vol 35 (12) ◽  
pp. n/a-n/a ◽  
Author(s):  
N. Sato ◽  
R. Shirooka ◽  
M. Yoshizaki ◽  
Y. N. Takayabu
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Warm Pool ◽  
Pacific Warm Pool ◽  
Sst Gradient ◽  
Meridional Sst Gradient

scholarly journals Decadal Change of the Western North Pacific Summer Monsoon Break around 2002/03

2017 ◽  
Vol 31 (1) ◽  
pp. 177-193 ◽  
Author(s):  
Ke Xu ◽  
Riyu Lu
Keyword(s):  
Summer Monsoon ◽  
North Pacific ◽  
Western North Pacific ◽  
Meridional Circulation ◽  
Warm Pool ◽  
Mariana Islands ◽  
Decadal Change ◽  
Pacific Warm Pool ◽  
Break Region ◽  
The Western Pacific

Abstract A significant decadal change is detected in the break of the western North Pacific summer monsoon (WNPSM) around 2002/03. For the period 1979–2002, the monsoon break occurs in early August, accompanied by noticeable convection suppression over the ocean to the east of the Mariana Islands (10°–20°N, 140°–160°E). However, for the period 2003–11, the monsoon break there is delayed until mid-August. This decadal change is attributable to the differences in the evolution of the WNPSM. Over this break region, convection becomes weaker after its peak in late July for the former period, and the monsoon break appears in early August. In contrast, for the latter period, convection continues strengthening in late July and reaches its peak in early August, and the monsoon break is delayed until mid-August. The differences in the evolution of sea surface temperature (SST) in the western Pacific warm pool region are responsible for the decadal change in the evolution of the WNPSM. In contrast to the former period, for the latter period the southern extent of the warm pool is remarkably warmed, and tends to be higher than the northern extent in mid- and late July, which enhances atmospheric convection nearby but inhibits the development of convection over the northern extent through a local meridional circulation. As the SST in the northern extent continues warming and becomes higher than that in the southern extent, the convection over the northern extent reaches its maximum intensification in early August. The presented results highlight that the spatial pattern of SST changes can modulate the subseasonal evolution of the WNPSM.

scholarly journals Impact of the Indo-Pacific Warm Pool on the Hadley, Walker, and Monsoon Circulations

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1030
Author(s):  
Hye-Ryeom Kim ◽  
Kyung-Ja Ha ◽  
Suyeon Moon ◽  
Hyoeun Oh ◽  
Sahil Sharma
Keyword(s):  
Dominant Role ◽  
Hadley Circulation ◽  
Walker Circulation ◽  
Warming Trend ◽  
Warm Pool ◽  
Vital Role ◽  
Natural Variability ◽  
Natural Mode ◽  
Monsoon Circulation ◽  
Pacific Warm Pool

The Indo-Pacific warm pool (IPWP) is enclosed by a 28 °C isotherm and plays a vital role in controlling atmospheric circulations. However, the effects of changes in regional warm pool sea surface temperatures (SSTs) remain unexplored. We divided the IPWP into the Indian and Pacific sectors and distinguished their responses to natural variability and global warming. Furthermore, we examined the impacts of the interannual variability (IAV) in warm pool SST on the tropical Hadley, Walker, and monsoon circulations. The Hadley circulation was affected by warm pool SST warming, i.e., warmer SSTs over the warm pool strengthened the upward branch of Hadley circulation, whereas the downward branch was respectively weakened and strengthened in the Northern and Southern Hemispheres. Walker circulation was strengthened (weakened) in the warming (natural) mode. Consequently, the Walker circulation is weakened since the natural variability of warm pool SST plays a more dominant role rather than the warming trend of SSTs over the warm pool. Furthermore, our analysis displays that warm pool warming has little impact on the monsoon circulation. Our findings highlight the different roles of the IAV of warm pool regions in each tropical circulation as part of the warming trend and natural variability.

Regime Change of the Boreal Summer Hadley Circulation and Its Connection with the Tropical SST

2011 ◽  
Vol 24 (15) ◽  
pp. 3867-3877 ◽  
Author(s):  
Ran Feng ◽  
Jianping Li ◽  
Jincheng Wang
Keyword(s):  
High Frequency ◽  
Regime Change ◽  
Hadley Circulation ◽  
Warm Pool ◽  
Boreal Summer ◽  
Tropical Atlantic ◽  
Asymmetric Mode ◽  
Pacific Warm Pool ◽  
Highly Correlated ◽  
Relationship Of

Abstract The year-to-year variability of the boreal summer [June–August (JJA)] Hadley circulation (HC) is dominated by an asymmetric mode centered in the Northern Hemisphere (AMN) and a quasi-symmetric mode centered at 5°N (QSM). The regime change of the JJA HC is revealed by the phase reversal of the time series of the AMN, showing significant weakening of the northern part of the JJA HC and a reversed seesaw relationship of the zonal-mean updraft over 10°–20°N and around the equator. This transition is accompanied by the southward retreat of the HC core and is well correlated with the weakening of tropical summer monsoons. The strong warming trends of the sea surface temperature over the tropical Atlantic and Indo–west Pacific warm pool play an important role in the regime change of the JJA HC. The high-frequency interannual variability of the JJA HC, however, is mainly featured by the QSM and is highly correlated with the Niño-3.4 index, implying that ENSO’s influence is mainly on the high-frequency interannual time scale.

scholarly journals Remote Connection of the Northeast Asian Summer Rainfall Variation Revealed by a Newly Defined Monsoon Index

2005 ◽  
Vol 18 (21) ◽  
pp. 4381-4393 ◽  
Author(s):  
Eun-Jeong Lee ◽  
Jong-Ghap Jhun ◽  
Chung-Kyu Park
Keyword(s):  
North Pacific ◽  
Western North Pacific ◽  
Asian Summer Monsoon ◽  
Northeast Asia ◽  
Summer Precipitation ◽  
Summer Rainfall ◽  
Rainfall Variation ◽  
Monsoon Index ◽  
Asian Summer ◽  
Northeast Asian

Abstract A new northeast Asian summer monsoon index is introduced to investigate the characteristics of the northeast Asian summer rainfall variation, including Korea, Japan, and northeast China, and its possible connection to the tropical and midlatitude circulations. The summer precipitation over northeast Asia is separated into two components associated with tropical forcing and midlatitude dynamics using this monsoon index. The connection between the northeast Asian summer rainfall and ENSO is clearly identified by separating the Tropics-related component from the northeast Asian summer rainfall. That is, the Tropics-related precipitation over northeast Asia tends to be enhanced after the mature phase of El Niño. On the other hand, it is revealed that the extratropics-related component of summer precipitation is connected to the Eurasian wave pattern with no significant lag correlation. The intensity of the western North Pacific anticyclone modulated by ENSO is a key factor in the variation of the northeast Asian summer precipitation. It is found that the warm SST over the tropical eastern Pacific plays an important role in establishing the western North Pacific anticyclone during the preceding winter of strong northeast Asian summer monsoon years, whereas convective activities over the Bay of Bengal are contributed to the modulation of the anticyclonic circulation in the summer. The warming over the Indian Ocean in the summer of strong monsoon years induces the development of the anticyclone over the western North Pacific and the suppressed convection over the western Pacific tends to enhance the northeast Asian summer rainfall through the Pacific–Japan or East Asia–Pacific teleconnections.

scholarly journals Western North Pacific Tropical Cyclones in the Met Office Global Seasonal Forecast System: Performance and ENSO Teleconnections

2020 ◽  
Vol 33 (24) ◽  
pp. 10489-10504
Author(s):  
Xiangbo Feng ◽  
Nicholas P. Klingaman ◽  
Kevin I. Hodges ◽  
Yi-Peng Guo
Keyword(s):  
Environmental Conditions ◽  
North Pacific ◽  
Western North Pacific ◽  
Propagation Speed ◽  
Seasonal Forecast ◽  
Forecast System ◽  
Ensemble Forecasts ◽  
Steering Flow ◽  
Enso Teleconnections ◽  
The Tropical Pacific

AbstractThe performance of the Met Office Global Seasonal Forecast System (GloSea5-GC2) for tropical cyclone (TC) frequency for the western North Pacific (WNP) in July–October is evaluated, using 23 years of ensemble forecasts (1993–2015). Compared to observations, GloSea5 overpredicts the climatological TC frequency in the eastern WNP and underpredicts it in the western and northern WNP. These biases are associated with an El Niño–type bias in TC-related environmental conditions (e.g., low-level convergence and steering flow), which encourages too many TCs to form throughout the tropical Pacific and slows TC propagation speed. For interannual TC frequency variability, GloSea5 overestimates the observed negative TC–ENSO teleconnection in the western and northern WNP, associated with an eastward shift in the ENSO teleconnection to environmental conditions. Consequently, GloSea5 fails to predict interannual TC variability in the northeast WNP (south of Japan); performance is higher in the southwest WNP (e.g., the South China Sea) where the sign of the TC–ENSO teleconnection is correct. This study suggests the need to reduce biases in environmental conditions and associated ENSO teleconnections in GloSea5 to improve the TC prediction performance in the NWP.

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