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Marine heatwaves (MHWs) are extreme climatic events that can have a significant impact on marine ecosystems and their services across the world. We examine the spatiotemporal variation of summer MHWs in the north Indian Ocean (NIO) and find that the whole NIO Basin exhibits a pronounced spatial variability as well as a significant increasing trend in MHW frequency. We show that the NIO has two leading MHW modes linked to two distinct sea surface temperature (SST) patterns during summer. The first MHW mode is associated with basinwide warming, which is preconditioned by a decaying El Niño-Southern Oscillation (ENSO) and sustained throughout the summer by anomalous northeasterlies extending from the anticyclonic circulation of the western North Pacific subtropical high (WNPSH). The combined effect of thermocline warming due to downwelling oceanic planetary waves, decreased wind-induced evaporative cooling, and enhanced insolation cause basinwide summer MHWs. The second MHW mode exhibits a zonal dipole pattern, which has unfavorable cooling conditions in the previous seasons. The second MHW mode is associated with a phase change of ENSO and is greatly influenced by the formation of an interhemispheric pressure difference (IHPD) due to strengthening of the Australian high (AH) and weakening of the WNPSH. The IHPD induces cross-equatorial southerly winds across the eastern Indian Ocean. These winds favor the transformation of basinwide cooling conditions into zonal SST patterns via wind-evaporation-SST and thermocline-SST feedback, causing MHWs with a zonal dipole pattern. These MHW modes have a significant influence on the distribution and intensity of summer precipitation in the NIO. [ABSTRACT FROM AUTHOR]

Southerly wind in the lower troposphere is an essential feature of East Asian summer monsoon (EASM) circulation, which is reported to be enhanced under global warming scenarios and interglacial epochs. Based on an analysis of an ensemble of CMIP6 models, this study shows that the magnitude of intensification of the EASM circulation is much smaller under global warming scenarios than during interglacial epochs. Distinct changes in the western North Pacific subtropical high (WNPSH) are responsible for the different responses of the EASM circulation. The WNPSH is substantially enhanced during interglacial epochs, which acts to strengthen the southerly wind associated with the EASM on the western flank of the WNPSH. However, the change in the WNPSH is insignificant and cannot strengthen the EASM under global warming scenarios, and the weakly enhanced EASM circulation may be a direct response to intensified heating over the Tibetan Plateau. The land-ocean thermal contrast explains the different responses of the WNPSH. During interglacial epochs, the summertime surface warming over the subtropical North Pacific is much weaker than over Eurasia due to the large thermal inertia of the ocean to increased insolation, and the WNPSH is intensified as a response to the suppressed latent heating over the subtropical North Pacific. The fast response of the WNPSH to abrupt quadrupling of CO2 without sufficient ocean warming is an analog to the interglacial epochs, but it is offset by the effect of slow oceanic warming, resulting in an insignificant change of the WNPSH under global warming scenarios. [ABSTRACT FROM AUTHOR]

The Silk Road pattern (SRP) is a well-known teleconnection pattern along the upper-level westerly jet over the Eurasian continent during boreal summer. The SRP has experienced an interdecadal change around the late 1970s. The present study identified a new change of the SRP around the late 1990s, which is characterized by significant weakening and zonal phase shift of the major centers of the SRP during the recent decades. The recent reshaping of the SRP is attributed to an enhanced impact of precipitation anomalies over the northeastern Indian summer monsoon (ISM), which is associated with the leading mode change of the ISM precipitation anomalies around the late 1990s. The interdecadal weakening of the upper-level westerly jet over central and East Asia also favors the southward movement of the SRP during recent periods. The differences of the features, climate impact, and causes related to the recent SRP change from those related to the SRP change around the late 1970s are also contrasted in this study. [ABSTRACT FROM AUTHOR]

Recent developments have emphasized the global impacts of climate change and have renewed commitments in renewable energy and energy meteorology. Wind energy depends largely on prevailing meteorological conditions on both local and large scales, thus, wind power optimization should aid its assessment and development. This study uses ERA-Interim daily data from 1979 to 2014 to investigate the impact of the East Asian Monsoon on wind power in Asia. Wind power increase in the Bay of Bengal region as wind vectors strengthened from winter (DJF, December-January-February) to summer (JJA, June-July-August), while the predominant direction shifted to southwesterly. The influence of the South China Sea on South East Asia resulted in increased wind power that peaked in winter. Probability distribution functions for four sub-regions revealed higher probabilities of relatively lower wind speeds in JJA, except for the South East region, where most probable wind speeds were reached in winter. The capacity factor also varied by region and by season. Power generation was lowest in JJA for all the regions except the South West. The South East region also had the highest power generated over the domain. This variation of wind power impacts the amount of energy that must be supplied by non-wind sources, termed Demand NetWind (DNW). Knowledge of DNW fluctuations thus becomes an important consideration for optimization of power plants, grid networking and reliability, and energy markets. [ABSTRACT FROM AUTHOR]

A high-resolution numerical model based on the Regional Ocean Modeling System (ROMS) was used to simulate the Yellow Sea Cold Water Mass (YSCWM) and revealed an extreme warm event of the YSCWM in the summer of 2007. This event was also captured by in situ observations. In August 2007, the average temperature of the YSCWM was above 1 °C higher than its climatological mean. The unusually-high temperature anomaly of the YSCWM could trace back to the winter 2006–07. Heat budget of the Yellow Sea deep water (YSDW) below 50 m depth, indicated that vertical mixing, rather than advection, in the winter 2006–07 played a crucial role in the generation of the warm event. With the seasonal thermocline disappearing in the winter 2006–07, a weak vertical mixing effect due to weak wind speeds and high heat content in the Yellow Sea upper water (YSUW) above the YSDW, together with strong advection effect, caused the YSDW to become quite warmer than its climatological mean. After that, the seasonal thermocline above the YSDW formed again and the warm YSDW persisted until the summer of 2007, resulting in the extreme warm event of the YSCWM. • An extreme warm event of the Yellow Sea Cold Water Mass (YSCWM) happened in the summer of 2007. • Vertical mixing, rather than advection, in the winter of 2006 played a crucial role in the generation of the warm event. • Weak vertical mixing effect, together with strong advection effect, made the YSCWM quite warmer than its climate state. [ABSTRACT FROM AUTHOR]

The summer moisture circulation anomaly over East Asia and the western North Pacific (WNP) couples well with the El Niño-Southern Oscillation (ENSO) in a quasi-4-yr period. The moisture circulation is dominated by two well-separated modes. The first mode exhibits an anticyclonic (cyclonic) moisture circulation over tropical-subtropical East Asia-WNP with an easterly (westerly) transport over the tropical WNPIndian Ocean; the second mode displays an alternating pattern with an anticyclonic (cyclonic) moisture circulation over the subtropical WNP layered between two cyclonic (anticyclonic) circulations. Both modes couple well with the ENSO signal during its quasi-4-yr cycle. Within the cycle, in the summer of a developing warm episode, the positive phase of the second mode plays a key role, while in the transitional summer between a decaying warm episode and a developing cool episode, the positive phase of the first mode tends to take effect. In the summer of a developing cool episode, the negative phase of the second mode plays an important role, while the negative phase of the first mode tends to take effect in the transitional summer between a decaying cool episode and a developing warm episode. The anticyclone (cyclone) over the Philippine Sea region serves as a bridge in the quasi-four-year coupling. Its establishment and eastward extension modify moisture circulation over East Asia-WNP. Conversely, the easterly (westerly) wind to the south of the anticyclone (cyclone) is beneficial for the formation and eastward propagation of the Kelvin wave and, hence, to the development of the quasi-4-yr periodic ENSO episode. [ABSTRACT FROM AUTHOR]

The article explores the spatiotemporal features of the Indian Ocean Dipole (IOD) on the sea surface and the subsurface ocean. It was found that the previous positive IOD is associated with the normal South China Sea summer monsoon. Also, a stronger 100-hPa South Asian High is induced by a positive IOD in the summer after an IOD year. Summer rainfall in China is said to exhibit various patterns corresponding to different phases of the IOD, as influenced by the 850-hPa Asian monsoon circulations, as well as the position of the 500-hPa subtropical high ridge.