Temperate- and high-latitude forests have been shown to contribute a carbon sink in the Northern Hemisphere, but fewer studies have addressed the carbon balance of the subtropical forests. In the present study, we integrated eddy covariance observations established in the 1990s and 2000s to show that East Asian monsoon subtropical forests between 20 degrees N and 40 degrees N represent an average net ecosystem productivity (NEP) of 362 +/- 39 g C m(-2) yr(-1) (mean +/- 1 SE). This average forest NEP value is higher than that of Asian tropical and temperate forests and is also higher than that of forests at the same latitudes in Europe-Africa and North America. East Asian monsoon subtropical forests have comparable NEP to that of subtropical forests of the southeastern United States and intensively managed Western European forests. The total NEP of East Asian monsoon subtropical forests was estimated to be 0.72 +/- 0.08 Pg C yr(-1), which accounts for 8% of the global forest NEP. This result indicates that the role of subtropical forests in the current global carbon cycle cannot be ignored and that the regional distributions of the Northern Hemisphere's terrestrial carbon sinks are needed to be reevaluated. The young stand ages and high nitrogen deposition, coupled with sufficient and synchronous water and heat availability, may be the primary reasons for the high NEP of this region, and further studies are needed to quantify the contribution of each underlying factor.

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High carbon dioxide uptake by subtropical forest ecosystems in the East Asian monsoon region

In this study, fine-resolution multimodel climate projections over China are developed based on 35 climate models and two emissions scenarios (RCP4.5 and RCP8.5) from phase five of the Coupled Model Intercomparison Project (CMIP5) by means of Bias Correction and Spatial Disaggregation. The yearly-averaged temperature is projected to increase by 0.8 to 1.6 °C (0.8 to 1.7 °C), 1.5 to 2.7 °C (2 to 3.7 °C), and 1.9 to 3.3 °C (3.4 to 6 °C) under RCP4.5 (RCP8.5) in three time slices (2010–2039, 2040–2069, and 2070–2099), respectively. The most warming occurs in winter and the least in summer, and the inland areas in the northwest will warm much faster than the southeast. Under the background of surface warming, the probability of extreme low temperatures in winter defined as the monthly temperature being lower than the 9th percentile of the climatological distribution will sharply reduce to 0.1–1.7% under RCP4.5 for the period 2010–2039 and even lower for the following decades. For precipitation change, a remarkable increase is found over most areas of China except the Southwest, ranging from approximately 2 to 20%. The projected precipitation changes are highly robust in northern China, but inconsistent in southern China. In spite of widespread precipitation increases, most areas of China quantified by the Palmer Drought Severity Index are projected to become drier as a consequence of increasing evaporation driven by temperature increases. Detailed examination shows that drought that is moderate or severe according to current climate standards will become the norm in the future. Not only will incidences of severe and extreme drought increase dramatically in the future, but extreme wet events will also become more probable. Furthermore, the increasing drought risk in Southwest China and the Qinghai-Tibetan Plateau is nearly twice that for other parts of China.

A CMIP5 multimodel projection of future temperature, precipitation, and climatological drought in China

Recent advances in the study of the characteristics, processes, and causes of spatio-temporal variabilities of the East Asian monsoon (EAM) system are reviewed in this paper. The understanding of the EAM system has improved in many aspects: the basic characteristics of horizontal and vertical structures, the annual cycle of the East Asian summer monsoon (EASM) system and the East Asian winter monsoon (EAWM) system, the characteristics of the spatio-temporal variabilities of the EASM system and the EAWM system, and especially the multiple modes of the EAM system and their spatio-temporal variabilities. Some new results have also been achieved in understanding the atmosphere-ocean interaction and atmosphere-land interaction processes that affect the variability of the EAM system. Based on recent studies, the EAM system can be seen as more than a circulation system, it can be viewed as an atmosphere-ocean-land coupled system, namely, the EAM climate system. In addition, further progress has been made in diagnosing the internal physical mechanisms of EAM climate system variability, especially regarding the characteristics and properties of the East Asia-Pacific (EAP) teleconnection over East Asia and the North Pacific, the “Silk Road” teleconnection along the westerly jet stream in the upper troposphere over the Asian continent, and the dynamical effects of quasi-stationary planetary wave activity on EAM system variability. At the end of the paper, some scientific problems regarding understanding the EAM system variability are proposed for further study.

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Characteristics, processes, and causes of the spatio-temporal variabilities of the East Asian monsoon system

In this study, we investigate the different impacts of El Nino and El Nino Modoki on China rainfall in their decaying phases. During spring, in the decaying year of El Nino events, there are positive rainfall anomalies south of the Yangtze River, whereas no obvious rainfall signals are found in the same season for the decaying El Nino Modoki. In the subsequent summer season, the wet signal south of the Yangtze River associated with El Nino continues, while suppressed rainfall now appears in the northern Yangtze–Huaihe River region. In contrast, the rainfall is above normal in the region from the Huaihe River to the Yellow River, and below normal in southern China during the summer of the decaying El Nino Modoki events. The distinct China rainfall anomaly is mainly attributed to the difference between the evolution and location of the anomalous western North Pacific (WNP) anti-cyclone associated with El Nino and El Nino Modoki events. For the case of El Nino, the WNP anti-cyclone brings plentiful moisture to southern China; meanwhile it shifts the ridge of sub-tropical high westward in both spring and summer. These tend to induce positive rainfall anomalies in the southern Chinese region. In contrast, due to fast decaying of El Nino Modoki, the anomalous WNP anti-cyclone becomes weak so that there are no significant rainfall anomalies in China. In summer, however, the WNP anti-cyclone re-invigorates possibly associated with a subsequent developing La Nina and extends more northwestward towards the inland region, compared to its El Nino counterpart. The anomalous moisture transport and sub-tropical high activity associated with this WNP anti-cyclone result in different summer rainfall anomalies in China. Copyright © 2010 Royal Meteorological Society

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Different impacts of El Niño and El Niño Modoki on China rainfall in the decaying phases

The present study investigates the roles of El Nino–Southern Oscillation (ENSO) and the Pacific decadal oscillation (PDO) in the relationship between the East Asian winter monsoon (EAWM) and the following East Asian summer monsoon (EASM). The variability of the EAWM is divided into an ENSO-related part named EAWMEN and an ENSO-unrelated part named EAWMres. Corresponding to a weak EAWMEN, an anomalous low-level anticyclone forms over the western North Pacific (WNP) and persists from winter to the following summer. This anticyclone enhances southerlies over the coast of East Asia in summer. Hence, a weak EAWMEN tends to be followed by a strong EASM and vice versa. As such, a link is established between the EAWMEN and the EASM. The persistence of this WNP anticyclone may be mainly attributed to the sea surface temperature anomalies associated with the ENSO-related EAWM part in the tropical Indian Ocean and the extratropical North Pacific. In contrast, corresponding to a weak EAWMres, the anomalous WN...

Roles of ENSO and PDO in the Link of the East Asian Winter Monsoon to the following Summer Monsoon

The variabilities of the East Asian summer monsoon arc an important research issue in China, Japan, and Korea. in this paper, progresses of recent studies on the intrascasonal, interannual, and interdecadal variations of the East Asian monsoon, especially the East Asian summer monsoon, and their causes are reviewed. Particularly, studies on the effects of the ENSO cycle, the western Pacific warm pool, the Tibetan Plateau and land surface processes on the variations of the East Asian summer monsoon are systematically reviewed.

The Progresses of Recent Studies on the Variabilities of the East Asian Monsoon and Their Causes

[1] Using station rainfall observations and the ERA-40 reanalysis, this study investigates respective impacts of the East Asian winter monsoon (EAWM) and El Nino-Southern Oscillation (ENSO) on winter (November–March) rainfall in China by removing the interdependence between the EAWM and ENSO using a linear regression. It is found that circulation and temperature anomalies over the tropics and midlatitude North Pacific are mainly induced by ENSO, and those over the midlatitude Asia are closely linked to the EAWM. The warm ENSO induced lower-level southwesterly winds deflect from the southeast coast of China, and thus, the influence of ENSO on winter rainfall is mainly in southern China. The lower-level southerly winds associated with a weak EAWM penetrate northward over eastern China, and thus, the EAWM influences winter rainfall in eastern China.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2009JD012502

Respective impacts of the East Asian winter monsoon and ENSO on winter rainfall in China

The present study investigates the influence of South China Sea (SCS) SST and ENSO on winter (January–February–March; JFM) rainfall over South China and its dynamic processes by using station observations for the period 1951–2003, Met Office Hadley Center SST data for the period 1900–2008, and ERA-40 reanalysis data for the period 1958–2002 It is found that JFM rainfall over South China has a significant correlation with Nino-3 and SCS SST Analyses show that in El Nino or positive SCS SST anomaly years, southwesterly anomalies at 700 hPa dominate over the South China Sea, which in turn transports more moisture into South China and favors increased rainfall A partial regression analysis indicates that the independent ENSO influence on winter rainfall occurs mainly over South China, whereas SCS SST has a larger independent influence on winter rainfall in northern part of South China The temperature over South China shows an obvious decrease at 300 hPa and an increase near the surface, with the former induced by Nino-3 and the latter SCS SST anomalies This enhances the convective instability and weakens the potential vorticity (PV), which explains the strengthening of ascending motion and the increase of JFM rainfall over South China

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Influence of South China Sea SST and the ENSO on Winter Rainfall over South China

The present study investigates the impact of the East Asian winter monsoon (EAWM) on winter (January, February, and March, or JFM in short) rainfall over southeastern China (including South China and central eastern China) and its dynamical process by using station observations for the period 1951–2003 and the ERA-40 reanalysis for the period 1958–2002. It is found that there is a significant correlation between interannual variations of the EAWM and JFM rainfall over southeastern China. Analyses show that in weak EAWM years southwesterly anomalies at 700 hPa dominate over South China Sea, which transports more moisture into southeastern China, favouring rainfall increase. At the same time, the East Asian westerly jet weakens and displaces southward, contributing to the increase in ascending motion over southeastern China. The air temperature over southeastern China shows an obvious decrease at 300 hPa and increase near the surface. This enhances the convective instability and weakens the potential vorticity (PV), which explains the strengthening of ascending motion and the increase in JFM rainfall over southeastern China. In addition, the EAWM has impacts independent of El Nino Southern Oscillation (ENSO) on JFM rainfall over southeastern China. Moreover, the rainfall anomalies over central eastern China are more closely related to the EAWM than that in South China. Copyright © 2010 Royal Meteorological Society

Impact of East Asian winter monsoon on rainfall over southeastern China and its dynamical process

The present study investigates interdecadal variability of summer rainfall in Northwest China using station observations for the period 1951–2000 and the ERA-40 reanalysis for the period 1958–2000. It is found that Northwest China summer rainfall experienced an obvious interdecadal increase around 1978. Analyses show that summer circulation, temperature and potential vorticity anomalies over Asia vary vastly before and after 1978. During the period 1978–2000, cyclonic and anti-cyclonic circulation anomalies dominate over Northwest and North China, respectively. These are associated with the anomalous ascending motion over Northwest China, and their anomalous descending motion over North China. The temperature over Northwest China shows an obvious decrease at 300 hPa, but increase near the surface after 1978. This enhances convective instability, which contributes to the strengthening of ascent and the increase of summer rainfall in Northwest China during 1978–2000. Copyright © 2009 Royal Meteorological Society

Lian-Tong Zhou

Papers

The Progresses of Recent Studies on the Variabilities of the East Asian Monsoon and Their Causes

Respective impacts of the East Asian winter monsoon and ENSO on winter rainfall in China

Influence of South China Sea SST and the ENSO on Winter Rainfall over South China

Impact of East Asian winter monsoon on rainfall over southeastern China and its dynamical process

Interdecadal variability of summer rainfall in Northwest China and its possible causes