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• The calculation method of seasonal agricultural grey water footprint in monsoon region was established. • The reference condition was used as the natural background concentration of TP. • The GWF results were 1.60 and 1.38 times of the zero as the natural background concentration in the rainy season and dry season, respectively. • The agricultural GWF showed seasonal differences. Grey water footprint accounting is of great significance to water resources management. The two important parameters of grey water footprint accounting, the natural background concentration of pollutants and the pollutant export coefficient, have obvious seasonal differences in the monsoon region, while the possible seasonal differences of grey water footprint in the monsoon region had been less considered in the previous research of grey water footprint accounting. This paper calculated the seasonal agricultural grey water footprint of Zhangjiakou City in North China by taking the river reference condition of total phosphorus as its natural background concentration and considering the seasonal difference of river reference condition of total phosphorus and the pollutant export coefficient. The results showed that the agricultural grey water footprint calculated with the reference condition of total phosphorus as the natural background concentration were 1.60 and 1.38 times of that calculated with zero as the natural background concentration in the rainy season and dry season, respectively. Due to the seasonal difference in the proportion of pollutants entering the river and the reference condition of total phosphorus, the agricultural grey water footprint showed obvious seasonal differences. The agricultural grey water footprint in rainy season was 11.73 times higher than that in dry season. In the composition of agricultural grey water footprint in Zhangjiakou from 2003 to 2018, the grey water footprint of livestock and poultry accounted for a large proportion. Districts and counties with relatively large agricultural grey water footprint in Zhangjiakou were concentrated in the south and north of Zhangjiakou, mainly including Zhuolu, Huailai, Yuxian, Xuanhua and Zhangbei; The districts and counties with relatively small agricultural grey water footprint were mainly located in the urban area of Zhangjiakou, including Qiaodong District, Qiaoxi District and Xiahuayuan District. This paper could clarify the seasonal difference of agricultural grey water footprint accounting in monsoon region and promote the development of grey water footprint accounting methods. [ABSTRACT FROM AUTHOR]

Abstract The Eocene was an interval of climate evolution, when the extreme high temperatures of the earliest Cenozoic gave way to a global cooling trend. Fine-grained lacustrine sediments of Eocene age from northeastern China represent an excellent archive to study long-term environmental and climatic changes at high-resolution. The Huadian Basin is a Cenozoic, fault-bounded basin in Jilin Province, northeastern China. Though small in area, it contains numerous oil shale- and coal-bearing layers, which provide an abundant Middle to Late Eocene palynoflora. Eighty-five palynomorph genera and one hundred palynomorph species were identified in the Huadian Formation, allowing to distinguish 4 palynozones. The nearest living relatives of the recovered palynomorph taxa suggest the presence of subtropical evergreen and deciduous broad-leaved forests during deposition of the Huadian Formation. Using the coexistence approach (CA), we calculated seven paleoclimatic parameters, which indicate a subtropical warm and humid climate with a mean annual temperature above 13.6 °C and a mean annual precipitation of at least 887 mm. However, the climate became cooler and drier during the transition from the lower Oil Shale Member to the upper Carbonaceous Shale Member. Palaeoclimatic data from the various Middle and Late Eocene basins of northeastern China (i.e., the Huadian, Fushun, Yilan, Hunchun and Jishu basins) were compared with data from North American and European basins. Middle Eocene climate in the Northern Hemisphere was generally warm and humid, and the mean annual temperature and precipitation in northeastern China were similar to those in North America, though slightly lower than those of Europe. Similar trends in temperature and precipitation on different continents support the existence of a global Mid-Eocene cooling event. This paper is the first systematic study of Middle to Late Eocene seasonality in the Huadian Basin. Our results show an apparent differentiation in both temperature and precipitation between summer and winter, supporting the view that the East Asian Monsoon was established in northeastern China already during the Middle to Late Eocene. This Middle and Late Eocene monsoon was likely driven by the development of Pacific trade winds and an alternating, seasonal high- and low-pressure system over Siberia. The climatic changes observed in our dataset, especially the precipitation changes, appear to have played an important role in controlling oil shale formation in the Huadian Basin. A warmer and more humid climate, with abundant precipitation and high subsidence rates, formed a deeper Huadian depositional lake. High productivity and stable stratification provided the abundant organic matter and favorable preservation conditions necessary for oil shale accumulation. Highlights • The Middle-Late Eocene palynoflora were firstly systematically studied in Huadian Basin. • We quantitatively estimated the Middle-Late Eocene climate based on CA method. • A globally cooler phase was recognized in the Middle Eocene. • Climate seasonality in the Middle-Late Eocene supports the EAM was already prevalent in NE China. • Changes in climate, especially precipitation, play an important role in oil shale formation. [ABSTRACT FROM AUTHOR]

The abrupt weakening of the East Asian summer monsoon (EASM) during Younger Dryas (YD) has been attributed to freshwater discharge into the North Atlantic ocean and resultant Northern Hemisphere cooling. Recent studies have found that sea ice variability in the Nordic Sea during the YD exerted a great influence upon the northern high-latitude climate. However, the influence of sea ice upon EASM evolution during YD event remains unclear. In this paper, we report two precisely-dated speleothem oxygen isotope records from the EASM-dominated region of central China. Our records archive abrupt changes in EASM variability during the YD event. Initially, there was a significant strengthening of the EASM during the mid-YD following the gradually increased Atlantic meridional overturning circulation (AMOC). Later this trend reversed at ∼12.15 ka due to northern high-latitude sea ice fluctuations and a consequent reduction of AMOC. At the YD termination, abrupt intensification of the EASM was synchronous with the rapid decline of sea-ice and recovery of the AMOC indicating that sea ice variability was a significant influence on high latitude climate and EASM variation during the YD. • A new speleothem δ18O record show significant EASM strengthening during mid-YD. • Mid-YD oscillation in EASM linked with NH sea ice variability. • Abrupt EASM intensification at YD termination synchronous with the rapid decline of sea ice. • Drier interval following the YD termination in central China. [ABSTRACT FROM AUTHOR]

During the 1990s, pronounced changes occurred in major climatological fields worldwide. In the Northern Hemisphere, regarding the major shifts in the dry and wet patterns, the mid-1990s decadal change occurred more rapidly in winter than in summer. What accompanied by this decadal change were the strengthened lower-tropospheric anticyclones over the subtropical Pacific Ocean and a northward shift of the midlatitude westerly jet stream across the Afro–Asia–Pacific region. Increased trade winds resulted in considerable sea surface cooling over the central and eastern Pacific regions. These circulation changes induced the poleward expansion of two boreal winter systems: convection over the Maritime Continent and dry conditions in North Africa and West Asia. Moreover, the weakening of the Arctic upper-tropospheric circulation further modulated the seasonal shift of the midlatitude jet stream. In boreal summer, the more gradual decadal change was associated with the westward shift of Asian monsoon and northward penetration of African monsoon. What used to be a substantial vertical coupling of the westerly flows above these two monsoons was weakened during the 1990s. Judging from the effects of these circulation changes, it appears that the different rate of change in the jet streams may have exerted a dynamic effect on the pace of the decadal change in different seasons. [ABSTRACT FROM AUTHOR]

A local and flexible definition of the monsoon season based on hydrological evidence is important for the understanding and management of Himalayan water resources. Here, we present an objective statistical method to retrieve seasonal hydrometeorological transitions. Applied to daily rainfall data (1951–2015), this method shows an average longitudinal delay of ~15 days, with later monsoon onset and earlier withdrawal in the western Himalaya, consistent with the continental progression of wet air masses. This delay leads to seasons of different length along the Himalaya and biased precipitation amounts when using uniform calendric monsoon boundaries. In the Central Himalaya annual precipitation has increased, due primarily to an increase of premonsoon precipitation. These findings highlight issues associated with a static definition of monsoon boundaries and call for a deeper understanding of nonmonsoonal precipitation over the Himalayan water tower. Plain Language Summary: Precipitation in the Himalayas determines water availability for the Indian foreland with large socioeconomic implications. Despite its importance, spatial and temporal patterns of precipitation are poorly understood. Here, we estimate the long‐term average and trends of seasonal precipitation at the scale of individual catchments draining the Himalayas. We apply a statistical method to detect the timing of hydrometeorological seasons from local precipitation measurements, focusing on monsoon onset and withdrawal. We identify longitudinal and latitudinal delays, resulting in seasons of different length along and across the Himalayas. These spatial patterns and the annual variability of the monsoon boundaries mean that oft‐used, fixed calendric dates, for example, 1 June to 30 September, may be inadequate for retrieving monsoon rainfall totals. Moreover, we find that, despite its prominent contribution to annual rainfall totals, the Indian summer monsoon cannot explain the increase of the annual precipitation over the Central Himalayas. Instead, this appears to be mostly driven by changes in premonsoon and winter rainfall. So far, little attention has been paid to premonsoon precipitation, but governed by evaporative processes and surface water availability, it may be enhanced by irrigation and changed land use in the Gangetic foreland. Key Points: We propose a new statistical definition of monsoon onset and withdrawal applicable a posteriori to daily precipitation time seriesMonsoon bounds show longitudinal delays and strong year‐to‐year variations, crossing commonly used seasonal calendric boundariesThe long‐term increase of annual precipitation in Nepal seems to be driven primarily by higher premonsoon rainfall [ABSTRACT FROM AUTHOR]

Proxy records of the East Asia summer monsoon (EASM) and temperature reveal an in‐phase relationship of the two since the Last Glacial Maximum (LGM), which is consistent with their expected physical relationship; but the response amplitude of EASM to temperature variation seemed larger over the Holocene than over the last deglaciation. Using a state‐of‐the‐art transient climate simulation, we confirm this proxy‐inferred phenomenon, and estimate the "sensitivity of EASM circulation to summer temperature over adjacent region" (defined as SMT here) is about five times over the Holocene of that over the last deglaciation. This varying SMT attributed to the diverse SMT under the solo forcing of orbital insolation and CO2 (eight times of the former vs. the latter), and their varying confounding effect along time. The results presented here should improve our understanding of the past change of EASM, and help project its variation magnitude under ongoing CO2‐forced global warming. Plain Language Summary: The East Asia summer monsoon (EASM) dominates the eco‐environment of a region where nearly 1.6 billion people live. Its past change pushed the evolution of ancient Chinese culture, and its future change under global warming will force 1/5 of the world population to adapt. Paleoclimate records reveal a robust phenomenon of stronger EASM under a warmer world and vice versa, but the sensitivity of EASM to temperature seemed varying since the last ice age. Climate simulation confirms this phenomenon and illustrates the dominance of forcing (changes in orbital parameter and CO2 concentration) in terms of response magnitude of EASM. Compared to the response of EASM to the orbital forcing in past, the response to ever‐growing CO2 forcing is relatively small. Key Points: Sensitivity of East Asia summer monsoon circulation to temperature was larger over Holocene than that over the last deglaciationDiverse sensitivity under orbital and CO2 forcing and their varying confounding effect determined this varying sensitivitySeasonal synchrony of temperature variation over ocean is a key to determine diverse sensitivity under each forcing [ABSTRACT FROM AUTHOR]

Rates of nest predation have frequently been shown to differ between fragmented and unfragmented habitats, but have rarely been compared among natural habitats in the same geographic region. In this study, artificial nests of two types (open cup and domed) were placed in four habitats (mangroves, monsoon rainforests, eucalypt woodlands and paperbark swamps) over 12 months in three localities near Darwin in the Australian monsoon tropics to determine the effects of habitat, season and nest type on the rate of nest predation. A quail egg and a similarly coloured plasticine egg were placed in each nest. Habitat had a strong effect on nest predation rates, with nests in mangroves experiencing predation rates more than four times higher than those in eucalypt woodlands and paperbark swamps. Despite the strong rainfall seasonality of the region, there was no consistent seasonal variation in nest predation rates. Nest type also had little influence on predation rates, except in paperbark swamps where open cup nests suffered a higher predation rate than domed nests. The study indicates that generalised nest predation rates for tropical regions, even for small areas (e.g. <17 km radius), might overlook substantial variation between habitats. Such variation confounds purported differences in nest predation rates between tropical and temperate regions. [ABSTRACT FROM AUTHOR]

Abstract Monsoon rainforests occur as scattered patches within a landscape dominated by eucalypt savannas across the wet–dry tropics of northern Australia. This study formed part of a larger project that investigated the interactions between frugivores and monsoon rainforest patches in the Top End of the Northern Territory. Phenological patterns in a set of 12 wet monsoon forests (WMF) and four dry monsoon forests (DMF) were examined by monitoring individuals of more than 100 species over 30 months. Phenological patterns of both WMF and DMF were closely related to the strongly seasonal climate. Leaf flush occurred before the onset of the wet season in WMF, and coincided with the onset of the wet in DMF. Major flowering peaks coincided with leaf flush in both forest types. Fruiting was concentrated in the wet season in both forest types, but fruiting peaks of WMF and DMF were separated by 3–4 months. Variations in fruiting patterns among forest types, patches, seasons and groupings of plant species (based on life form and ecological positioning) provide a mosaic of food resources for frugivores. This has important implications for the conservation and maintenance of the frugivore–rainforest system in northern Australia. [ABSTRACT FROM AUTHOR]