Asian Monsoon Area Research Articles

Ground-based cloud microphysical observations at Mount Lu in the East Asian monsoon region from 2015 to 2020

Ground-based cloud microphysical observations were continuously conducted at Mount (Mt.) Lu site from 2015 to 2020, which is located in the East Asian monsoon areas of eastern China. The statistical characteristics of cloud microphysics under different meteorological conditions were analyzed by using visibility, cloud droplet and raindrop size distribution data, and meteorological variables. The mean cloud droplet number concentration (Nc), liquid water content (LWC) and effective diameter (De) are 151 cm−3, 0.08 g m−3 and 11.4 μm, respectively. Nc and LWC observed at Mount Lu are lower than the observation results of cloud from other mountain stations all over the world. Broader cloud droplet spectra are correlated with higher temperatures and lower wind speeds. The clouds are classified into nonprecipitating, lightly-raining and raining clouds. Statistics show that lightly-raining and raining clouds account for 66% of all clouds. Nc and LWC of lightly-raining (drizzling) clouds are highest, while spectral width of raining clouds is largest. Spectral dispersion of raining clouds converges to the narrow range of 0.4–0.7. Notably, medium sized cloud droplets (11–40 μm) promote the formation of large cloud droplets (40–50 μm, pre-drizzle size) and drizzle drops which initiate the auto-conversion from condensation to collision-coalescence growth. This study relying on in-situ continuous cloud observation from mountain station are helpful to understand cloud microphysical structures in East Asian monsoon region, and fitting parameters also provide observational evidence for numerical models.

Wet canopy photosynthesis in a temperate Japanese cypress forest.

This study aimed to reveal the mechanism and significance of wet canopy photosynthesis during and after rainfall in temperate coniferous ecosystems by evaluating the influence of abaxial leaf interception on wet canopy photosynthesis. We used the eddy covariance method in conjunction with an enclosed-path gas analyser to conduct continuous ecosystem CO2 flux observations in a Japanese cypress forest within the temperate Asian monsoon area over 3years. The observation shows that wet-canopy CO2 uptake predominantly occurred during the post-rainfall canopy-wet period rather than the during-rainfall period. Then, the measured canopy-wet net ecosystem exchange was compared with the soil-vegetation-atmosphere transfer multilayer model simulations under different parameter settings of the abaxial (lower) leaf surface wet area ratio. The multilayer model predicted net ecosystem exchange most accurately when it assumed the wet area ratio of the abaxial surface was 50% both during and after rainfall. For the wet canopy both during and after rainfall, the model overestimated CO2 uptake when it assumed no abaxial interception in the simulation, but underestimated CO2 uptake when it assumed that the entire abaxial leaf surface was wet. These results suggest that the abaxial surface of the Japanese cypress leaf is only partly wet to maintain stomatal openness and a low level of photosynthesis. These results allow for an evaluation of the effect of rainfall on forest carbon circulation under a changing climate, facilitating an improvement of ecosystem carbon exchange models.

Comparison of the Causes of Erosion-Deposition between Yellow River, Yangtze River and Mekong River Subaqueous Deltas II: Comparative Analysis

The estuary delta is an area where human economic activities are active and natural ecological environment is fragile. With global change and the intensification of human activities, coastal and seabed erosion around the world is becoming more and more serious. In this paper, we used the Delft 3D numerical simulation to compare the hydrodynamic effects of sediment transport paths in the Yellow River delta (river-controlled type), Yangtze River delta (tidal type) and Mekong River delta (tidal wave type) in the East Asian monsoon area, and analyzed the causes of accumulation erosion landform distribution in three different types of subaqueous deltas. This study finds the Yellow River Delta has experienced varying degrees of erosion at the estuary, but its subaqueous delta is still dominated by deposition; the Yangtze River Delta has ensured the stability of its shoreline under the influence of artificial shoreline reinforcement, but the subaqueous delta (water depth: 0–15 m) is in a state of erosion all year round; and in the Mekong River Delta the erosion occurs in both its shoreline and subaqueous delta. Additionally, only by analyzing the erosion and deposition within the transport range of resuspended sediment, the changes in the properties of the entire subaqueous delta could be recognized. The research results can not only be helpful to analyze whether the change of river sediment will lead to the change of delta type under human influence, but also provide more powerful scientific support for the protection of delta ecological environment, geological environment safety and geological disaster prevention.

Vegetation succession, climate change and cold events during 9.2–8.0 cal kyr BP in eastern China: High-resolution pollen evidence from the Yangtze delta plain area

High resolution pollen records in the northern edge of subtropical China are crucial to understand the pattern of postglacial vegetation change and climate transition. Here we present vegetation succession and climate change during 9.2–8.0 cal kyr BP based on sub-decennial scale pollen data. Pollen spectra show that Quercus (evergreen) &Cyclobalanopsis were relatively stable during the whole period, while Quercus (deciduous) were gradually decreased. Pollen-based climate change shows gradual warming during this period, and noticeably, the rapid warming during 8610–8545 cal yr BP can be detected according to the sharp decrease of Quercus (deciduous). Our results show two cold and dry events at 8.5 ka and 8.2 ka. The 8.5 ka event is rarely reported in the East Asian Monsoon area, while the 8.2 ka event is frequently mentioned. In this study, the 8.2 ka event has two peaks, similar to the previous reports from the Yangtze delta area and Dongge Dong Cave. In the Yangtze delta area, the vegetation and climate change show a strong relationship with the high latitude area, indicating that they are not only related to solar activity, but also impacted by the high latitude climate events. However, the impacts of these events on the Asian monsoon area still need further studies to verify.

Prediksi Perubahan Iklim Ekstrem di Kota Palembang dan Kaitannya dengan Fenomena El Niño-Southern Oscillation (ENSO) Berbasis Machine Learning

The purpose of this study is to provide predictions of climate conditions and trend of temperature rise in the city of Palembang in the 21st century. The BMKG station data used, namely SK Palembang and SM SMB II from the 2000-2020 period were analyzed based on the agreement of the Expert Team for Climate Change Detection and Indices (ETCCDI). ). Analysis using google colab shows that rainfall in the city of Palembang has a fairly high variability and a decrease in the number of rainy days that occur in the city of Palembang with the trend of air temperature, namely TMAXmean and TMINmean, has increased significantly by 2.40C for 50 years. Based on the correlation analysis between rainfall and El Niño-Southern Oscillation (ENSO) with Google Colab, a negative relationship was found. The El Niño-Southern Oscillation (ENSO) index used is the Niño 3.4 index. The study concluded that although the geographical location of Palembang city is located in the Asian Monsoon area, the ENSO phenomenon does not significantly affect rainfall variability in Palembang city.

Comparison of the Causes of Erosion–Deposition between Yellow River, Yangtze River, and Mekong River Subaqueous Delta l: Model Building

An estuary delta is an area with active human economic activities and a fragile natural ecological environment. With the intensification of global changes and human activities, coastal and seabed erosion around the world is becoming more and more serious. This study compared the hydrodynamic effect and sediment diffusion path at the Yellow River subaqueous delta (river control type) and the Yangtze River subaqueous delta (tide-river type) in the East Asian monsoon area using a Delft 3D numerical simulation to analyse the causes of the distribution of accumulation and erosion landform in the different types of subaqueous deltas. This study found that the river deltas were dominated by the river when the accumulation landforms concentrated in the direction of the Coriolis forces, which was due to hydrodynamic erosion driven by wind, and the sediment diffusion range was mainly concentrated in shallow water areas (water depth < 6 m), resulting the Yellow River subaqueous delta presenting the pattern of “northern erosion and south accumulation”. The Yangtze River subaqueous delta was controlled by tidal effects, making the southern part of the estuary more susceptible to erosion. The research results can not only further deepen the understanding of the physical process and mechanism of erosion and deposition in the subaqueous delta but also provide stronger scientific support for the deltas’ ecological environment protection, geological environment safety, and disaster geology prevention.

A millennium ENSO-related droughts and floods occurrences documented by fossil phytoliths in core sediments of Poyang Lake, East China

Droughts and floods caused by extreme hydroclimatic events in East Asian monsoon area often have serious effects on human society. The Poyang Lake region has always been one of the most severe floods and droughts in East China. In order to explore the relationship between monsoon climate change and occurrence of drought/flood, this study rebuilt a high-resolution (~10 yr) of temperature and aridity change history of the past 1000 years. Phytolith assemblages together with the climatic indices revealed 3 phases of paleoenvironmental changes over the last millennium: (1) Medieval Warm Period (MWP) during 900–1370 AD witnessed increased monsoon precipitation and frequent floods corresponding to strong El Niño–like state; (2) Little Ice Age (LIA) during 1370–1800 AD experienced severe droughts coupling with decreased monsoon precipitation and intensive La Niña–like state; (3) Current Warm Period (CWP) during 1800–2003 AD encountered highly frequent floods related to the increased monsoon precipitation modulated by strong El Niño–like state. Our results confirmed that there is a connection between solar irradiance, ENSO activity and monsoon precipitation in the subtropical East China. On interannual-decadal timescales, due to the modulation of ENSO on the location of the Western Pacific Subtropical High (WPSH) and Meiyu Belt, the occurrences of droughts and floods affected by ENSO-related monsoon precipitation has significantly affected not only the sedimentary environment, but also human activities, which is significant for the prediction of future prevention of droughts and floods in the East Asian monsoon region against the background of global warming.

Population genetics unveils large-scale migration dynamics and population turnover of Spodoptera exigua.

Migration is a widespread phenomenon among many insect species, including herbivorous crop pests. At present, scant information exists on the long-range migration of the polyphagous armyworm, Spodoptera exigua and its underlying climatic determinants (i.e. East Asian or South Asian monsoon circulation). In this study, we employed a population genetics approach to delineate S.exigua migration patterns across multiple Asian countries. Using mitochondrial cytochrome I (COI) and microsatellite markers, low-to-moderate levels of genetic diversity were detected among 101 S.exigua populations collected across China, Pakistan and Vietnam. Haplotype diversity and nucleotide diversity did not differ between years. Two spatially explicit genetic clusters were detected, an eastern and a western clade, with the former comprising populations in the East Asia monsoon area. No genetic differentiation was recorded among armyworm populations in the year-round breeding area, nor among those of the overwintering and nonoverwintering areas. Five of the most widespread mitochondrial haplotypes reflected the extensive gene flow across at a large spatial scale. Low-to-moderate levels of genetic diversity were observed, and evidence was found for genetic clustering in certain geographical areas. Accordingly, our unique insights into S.exigua population genetics and spatiotemporal migration dynamics help to guide applied ecological studies, ecological intensification schemes or (area-wide) pest management campaigns in China and abroad. © 2021 Society of Chemical Industry.

Canopy conductance and gas exchange of a Japanese cypress forest after rainfall‐induced wetness

AbstractIncreased stomatal conductance of the dry leaves right after wetness ended was reported before, while few studies paid attention to this phenomenon in canopy scale and its contribution to the forest carbon sink function. Therefore, we observed the continuous change of canopy wetness and ecosystem fluxes after wetness ended by using wetness sensors and eddy covariance method for a Japanese cypress forest (Chamaecyparis obtuse Sieb. Et Zucc.) in the Asian monsoon area. Larger gc (canopy conductance) were found in the relationships with both vapor pressure deficit and Rn (net radiation) during the first several hours after wetness ended. The results for λE (latent heat flux) were similar to that of gc in spring and summer. Net ecosystem exchange (NEE) in the relationships with Rn at different stages after wetness ended did not show clear difference except in spring. Nevertheless, annual summed‐up NEE showed that the average CO2 uptake at the first several hours after wetness ended was larger than the usual dry period. These results suggest that the improved stomatal opening at the first several hours after wetness ended plays a significant role in the canopy‐scale gas exchange processes.

Stalagmite evidence for East Asian winter monsoon variability and 18O-depleted surface water in the Japan Sea during the last glacial period

In the East Asian monsoon area, stalagmites generally record lower and higher oxygen isotope (δ18O) levels during warm humid interglacial and cold dry glacial periods, respectively. Here, we report unusually low stalagmite δ18O from the last glacial period (ca. 32.2–22.3 ka) in Fukugaguchi Cave, Niigata Prefecture, Japan, where a major moisture source is the East Asian winter monsoon (EAWM) that carries vapor from the warm surface of the Japan Sea. The δ18O profile of this stalagmite may imply millennial-scale changes, and high δ18O intervals that are related to Dansgaard–Oeschger (D–O) interstadials. More importantly, the stalagmite exhibits low overall δ18O values; the mean δ18O (− 8.87‰) is distinctly lower than the mid-Holocene mean of another stalagmite from the same cave (4.2–8.2 ka, − 7.64‰). An interpretation assuming a more intense EAWM and greater vapor transportation during the last glacial period, compared with the mid-Holocene, contradicts the limited inflow of the Tsushima Warm Current into the Japan Sea because of lowered sea level. Additionally, our model calculation using δ18O data from meteoric water indicated that the amount effect of winter meteoric water was insignificant (1.2‰/1000 mm). Low stalagmite δ18O for the last glacial period in Fukugaguchi Cave most likely resulted from 18O-depleted surface water, which developed in the isolated Japan Sea. The estimated amplitude of the δ18O decrease in surface water was ~ 3‰ at most, consistent with the abnormally low values for foraminifera (by ~ 2.5‰) in sediment during the last glacial period, shown by samples collected from the Japan Sea. This is the first terrestrial evidence of 18O depletion in Japan Sea surface water during the last glacial period.

Linking Holocene East Asian monsoon variability to solar forcing and ENSO activity: Multi-proxy evidence from a peatland in Northeastern China

High-resolution proxy-based paleoenvironmental records derived from peatlands provide important insights into climate changes over centennial to millennial timescales. In this study, we present a composite climatic index (CCI) for the Hani peatland from northeastern China, based on an innovative combination of pollen-spore, phytolith, and grain size data. We use the CCI to reconstruct variations of the East Asian summer monsoon (EASM) intensity during the Holocene. This is accomplished with complete ensemble empirical mode decomposition (CEEMD), REDFIT, and cross-wavelet coherency analysis to reveal the periodicities (frequencies) of the multi-proxy derived CCI sequences and to assess potential external forcing of the EASM. The results showed that periodicities of ca. 300–350, 475, 600, 1075, and 1875 years were present in the Hani CCI sequence. Those periodicities are consistent with previously published periodicities in East Asia, indicating they are a product of external climate controls over an extensive region, rather than random variations caused by peatland-specific factors. Cross-wavelet coherency analysis between the decomposed CCI components and past solar activity reconstructions suggests that variations of solar irradiation are most likely responsible for the cyclic characteristics at 500-year frequency. We propose a conceptual model to interpret how the sun regulates the monsoon climate via coupling with oceanic and atmospheric circulations. It seems that slight solar irradiation changes can be amplified by coupling with ENSO events, which result in a significant impact on the regional climate in the East Asian monsoon area.

Evaluation of Yield and Energy of Greenhouse Tomato Production in Each Asian Monsoon Area Using Cultivation Simulator Considering Growth Condition

In recent years, the Asian monsoon region has a large business opportunity for the global food market for Japan. In this study, the authors evaluated the crop growth conditions and energy of greenhouse tomato production in several Asian monsoon areas. In these evaluations, a cultivation simulator considering growth conditions was used. In the calculation of the energy required to maintain the cultivation environment of the greenhouse, the photosynthesis rate of the plants and the transpiration rate were also calculated by simulation. As a result, the difficulty of greenhouse tomato production under high temperature and humidity conditions in Asia and the differences in crop growth conditions among these regions could be clarified by this analysis. In the future, it was suggested that it would be necessary to reduce the temperature of the greenhouse while maintaining the amount of photosynthesis.

Spatiotemporal Evolution of Evapotranspiration in China after 1998

Changes in water circulation and uneven distributions of water resources caused by global warming are prominent problems facing the world at present. It is important to understand the influencing factors, and evapotranspiration (ET) is a key parameter for measuring the water cycle. However, understanding of spatiotemporal changes in actual evapotranspiration and its mechanism is still limited by a lack of long-term and large-scale in situ datasets. Here, the evolution of evapotranspiration in typical East Asian monsoon areas in China from 1989 to 2005 was analyzed with global land ET synthesis products. Evapotranspiration in China showed evident interdecadal variations around 1998; it decreased before 1998 and subsequently increased, which is inversely related to global ET changes. We further divided China into water-control and energy-control regions to discuss the factors influencing ET changes in each region. The interdecadal variations in increasing ET after 1998 in China were dominated by increasing potential evaporation in the energy-control region. An analysis using the empirical orthogonal function (EOF) method found that this occurred because ET is mainly manifested as decadal changes controlled by climate warming in the energy-control region and as interannual variations in the water-control region. The different feedbacks of ET on climate change in the two regions were also reflected in the difference in energy partition. The change in the Bowen rate (BR) did not increase climatic differences between energy- and water-control zones, but increases in the BR in arid summers significantly affected local weather and climate.

The modulation of westerlies‐monsoon interaction on climate over the monsoon boundary zone in East Asia

AbstractMonsoon boundary zone (MBZ) is a transitional zone between the arid Central Asia (ACA) and humid Asia monsoon area, located in North China‐Mongolia. During boreal summer, both the mid‐latitude westerlies and East Asian Summer monsoon (EASM) play essential roles in the precipitation variations in the MBZ, via causing anomalous cold air mass from the west and warm/humid air from the south to the MBZ. In this study, we defined a summer westerly index (SWI) over the key westerly domain (35°‐42.5°N, 80°‐100°E) and an EASM index (EASMI) over the key EASM domain (25°‐35°N, 107.5°‐125°E) to investigate westerlies‐monsoon interaction and their effect on MBZ climate. The results show that westerlies and EASM have a synergistic effect on the precipitation in the MBZ and this synergistic effect could be amplified by the westerlies‐monsoon interaction. The westerlies and EASM interaction could induce a local cyclonic anomaly in the MBZ, this cyclonic anomaly further intensifies the westerlies and monsoon flow through a dynamical amplification, favours the precipitation in the MBZ. The MBZ precipitation also contributes to maintain the cyclonic anomaly via the latent heating release. The interannual variability of westerlies is largely modulated by the mid‐latitude Silk Road pattern (SRP) and the meridional displacement of the Asian westerly jet (AWJ), and the EASM variability is mainly modulated by El Niño‐Southern Oscillation (ENSO), the combined effects from these mid‐latitude circulation systems and tropical SST contribute to the climate variability in MBZ.

Seasonal divergence between soil water availability and atmospheric moisture recorded in intra-annual tree-ring δ18O extremes

Intra-annual variability of tree-ring oxygen stable isotopes (δ18O) can record seasonal climate variability and a tree’s ecophysiological response to it. Variability of sub-annual tree-ring δ18O maxima and minima, which usually occur in different parts of the growing season, may exhibit different climatic signals and can help in understanding past seasonal moisture conditions, especially in Asian monsoon areas. We developed minimum and maximum tree-ring δ18O series based on sub-annual tree-ring δ18O measurements of Pinus massoniana at a humid site in southeastern China. We found that interannual variability in minimum tree-ring δ18O is primarily controlled by the July–September soil water supply and source water δ18O, whereas the maximum latewood tree-ring δ18O is primarily controlled by the relative humidity (RH) in October. The maximum of variability of earlywood tree-ring δ18O records the RH of October of the previous year. We used minimum and maximum tree-ring δ18O to develop two reconstructions (1900–2014) of seasonal moisture availability. The summer soil water supply (July–September self-calibrated Palmer drought severity index) and the RH in fall show contrasting trends, which may be related to late-growing seasonal warming leading to a high vapor capacity and high atmospheric moisture. Our findings are valuable for research that aims to explore seasonal moisture changes under anthropogenic climate change and the ecological implications of such contrasting trends.

Transport of the 2017 Canadian wildfire plume to the tropics via the Asian monsoon circulation

Abstract. We show that a fire plume injected into the lower stratosphere at high northern latitudes during the Canadian wildfire event in August 2017 partly reached the tropics. The transport to the tropics was mediated by the anticyclonic flow of the Asian monsoon circulation. The fire plume reached the Asian monsoon area in late August/early September, when the Asian monsoon anticyclone (AMA) was still in place. While there is no evidence of mixing into the center of the AMA, we show that a substantial part of the fire plume is entrained into the anticyclonic flow at the AMA edge and is transported from the extratropics to the tropics, and possibly the Southern Hemisphere particularly following the north–south flow on the eastern side of the AMA. In the tropics the fire plume is lifted by ∼5 km in 7 months. Inside the AMA we find evidence of the Asian tropopause aerosol layer (ATAL) in August, doubling background aerosol conditions with a calculated top of the atmosphere shortwave radiative forcing of −0.05 W m−2. The regional climate impact of the fire signal in the wider Asian monsoon area in September exceeds the impact of the ATAL by a factor of 2–4 and compares to that of a plume coming from an advected moderate volcanic eruption. The stratospheric, trans-continental transport of this plume to the tropics and the related regional climate impact point to the importance of long-range dynamical interconnections of pollution sources.

The age of the oldest aeolian sand in the Otindag sandland

The Otindag sandland, located at the boundary of the East Asian monsoon area, is sensitive to climate change and is therefore an ideal place to investigate past environmental evolution. Due to frequent volcanic eruptions that have occurred since the Cenozoic, numerous interbeds of multi-stage basalt and sand exist in the stratigraphic sequence, which allowed older sand to be preserved due to the protective effect of the overlying rock. Previous studies of climate change in the sandland mainly focused on the time interval since the last glacial period, and information is lacking regarding climate change over longer timescales and younger volcanic activity. The key reason for this is that suitable geological carriers are rare, which prevents the expansion of the desired sediment chronological scale. In order to establish the chronological framework, samples of the sandy paleosoil, aeolian sand, lacustrine sand and volcanic baked layer were collected and dated by the optically stimulated luminescence (OSL) method. The conventional SAR, TT-OSL and pIRIR(200,290) procedures were used to obtain equivalent doses of quartz and feldspar. To ensure the accuracy of the dating data, the age of the feldspar dating of the oldest aeolian sand sample (TBB) was compared with the quartz result, and the quartz and feldspar ages were found to be consistent with each other within the error range. Considering the error of the age measured by TT-OSL (384.2±68.0 ka) exceeded 10%, the age measured by the pIRIR(200,290) method (321.2±11.5 ka) was adopted to represent the deposition age of the aeolian sand sample. In addition, the age of the oldest sand deposition in the three sections of the Otindag sandland may reach 300 ka, mainly due to the different thermal history and provenance from other areas such as Loess Plateau, resulting in the different saturation dose and dose rate lever of quartz or feldspar. The sedimentary age framework established by OSL dating enabled the reconstruction of the evolution process of the Otindag Sandland. The climate was cold and dry during the periods corresponding to 321.2, 160.3−151.6 and 4.4 ka, and the aeolian sand material quickly accumulated during these times, as dunes were activated and the sandland expanded. During the periods corresponding to 5.0 ka and 2.4−1.3 ka, sandy soil developed efficiently, implying the dunes were fixed. The oldest lacustrian sand age is 320.4±16.0 ka for quartz dated by the SAR method. Hence, aeolian sand and lacustrine sand developed in the same period, which indicates that there was a landscape where dunes and lakes coexisted around 320.4 ka, such as at present. The Optical Stimulated Luminescence dating results of the volcanic baking layer and the underlying coarse sand layer confirm that volcanic activity occurred around 321.2 and 155.0 ka. Combined with results of previous research, this study indicates that the northeast and northwestward basement faults of the northern margin of the North China Craton and the Central Asian orogenic belt are characterized by extensional tectonic properties in the background setting of plate subduction, and relative uplift and settlement occur in the sandland formation zone.

Global Monsoon Changes under the Paris Agreement Temperature Goals in CESM1(CAM5)

Based on experiments with the Community Earth System Model, version 1 (Community Atmosphere Model, version 5) [CESM1(CAM5)], and an observational dataset, we found that CESM1-CAM5 is able to reproduce global monsoon (GM) features, including the patterns of monsoon precipitation and monsoon domains, the magnitude of GM precipitation (GMP, the local summer precipitation), GM area (GMA), and GM percentage (the ratio of the local summer precipitation to annual precipitation). Under the Paris Agreement temperature goals, the GM in CESM1-CAM5 displays the following changes: (1) The GMA is ambiguous under the 1.5°C temperature goal and increases under the 2.0°C temperature goal. The increase mainly results from a change in the monsoon percentage. (2) The GM, land monsoon and ocean monsoon precipitation all significantly increase under both the 1.5°C and 2.0°C goals. The increases are mainly due to the enhancement of humidity and evaporation. (3) The percentages of GM, land monsoon and ocean monsoon feature little change under the temperature goals. (4) The lengths of the GM, land monsoon and ocean monsoon are significantly prolonged under the temperature goals. The increase in precipitation during the monsoon withdrawal month mainly accounts for the prolonged monsoons. Regarding the differences between the 1.5°C and 2.0°C temperature goals, it is certain that the GMP displays significant discrepancies. In addition, a large-scale enhancement of ascending motion occurs over the southeastern Tibetan Plateau and South China under a warming climate, whereas other monsoon areas experience an overall decline in ascending motion. This leads to an extraordinary wetting over Asian monsoon areas.

Holocene climate dynamics derived from pollen record of Jiulongchi wetland in Fanjing Mountain, southwest China

An alpine wetland core was obtained to a depth of 4.0 m from the Fanjing Mountain in southwest China. Sections of the core were dated with 14C data obtained with high resolution mass spectrometry (AMS), and Holocene climate changes were inferred by categorizing predominant tree and fern vegetation identified from pollen and spore counts at various core depths. The temperature increased during 11.9–8.0 cal ka BP, and the warmest period was during 8.0–4.6 cal ka BP. Then, it gradually became cooler during the late Holocene. Our temperature estimates were in good agreement with the previous studies of the Holocene temperature in the Asian monsoon areas. There were two relatively wet periods of 10.7–8.0 cal ka BP and 4.6–2.6 cal ka BP. There was an asynchronous precipitation trend in the south, north and southwest China, which was probably due to the different monsoon impacts. In East Asian summer monsoon (EASM) area, the monsoon precipitation gradually transgressed northward during the early to middle Holocene and regressed southward during the late Holocene. Our results will be useful to improve the understanding of the coherent spatio-temporal patterns of climate evolution in EASM region in China.

黔西高原MIS3-MIS2期炭屑记录与火灾模式研究

PDF HTML阅读 XML下载 导出引用 引用提醒 黔西高原MIS3-MIS2期炭屑记录与火灾模式研究 DOI: 10.5846/stxb201801250200 作者: 作者单位: 六盘水师范学院 旅游与历史文化学院,西南大学 地理科学学院,中国地质科学院岩溶地质研究所;中国地质科学院岩溶地质研究所,中国地质科学院岩溶地质研究所;中国地质科学院岩溶地质研究所,六盘水师范学院 旅游与历史文化学院,六盘水师范学院 旅游与历史文化学院,六盘水师范学院 旅游与历史文化学院,六盘水师范学院 旅游与历史文化学院 作者简介: 通讯作者: 中图分类号: 基金项目: 贵州省教育厅自然科学基金（黔教合KY字[2014]284号）；贵州省科技厅联合基金项目（黔科合LH字[2014]7458号）；贵州省教育厅创新群体重大研究项目（黔教合KY字[2016]056号）；六盘水师范学院2011协同创新项目（LPSSYXTZX201402）；六盘水师范学院科技创新团队项目（LPSSYKJTD201701） Fire history can be obtained from the charcoal record on the southwest plateau of Guizhou Author: Affiliation: College of Geographic Science, Southwest University,,,,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:火灾与气候、植被存在复杂的关系，搞清东亚季风区的火灾模式及其发生机制，对预测未来气候变化及火灾防治具有重要意义。通过对黔西高原MIS3-MIS2期间的古湖相沉积物进行炭屑分析并结合AMS14C测年数据研究发现：MIS3晚期以来研究区的火灾主要发生于36.3-35 cal ka BP、26.2-17.6 cal ka BP期间，中粒炭屑和大炭屑分别在35、26.2、23.6 cal ka BP记录到3次地方火。研究区炭屑记录对冷干事件响应敏感，炭屑峰值区对应Heinrich事件（H事件）、末次冰盛期（LGM）等干旱事件，低值区对应DO事件，呈现千年旋回的特征。比对东亚地区的炭屑记录发现，在大范围的东亚季风区MIS2期比MIS3末期在火的强度和频率上都要高，与欧洲模式显著不同。火的发生机制可能受气候因素的控制，同时受植被类型的影响。 Abstract:Fire has a nonlinear relationship with climate and vegetation. Therefore, identifying the mode and mechanisms of fire in the East Asian monsoon area is very important when attempting to predict future climate change and improve fire management. A 110 cm continuous core from the southwest plateau of Guizhou was sampled at 1 cm intervals for charcoal analysis. The chronology of the core extended from MIS3 to MIS2. The results show that since the late MIS3, fire mainly happened in the 36.3-35 cal ka BP and 26.2-17.6 cal ka BP periods. Three local fires happened in the 35 cal ka BP, 26.2 cal ka BP, and 23.6 cal ka BP periods, and these were identified from the large and medium size charcoal particles. Comparison of the charcoal record with stalagmite and ice core records indicated that the peak in the charcoal record corresponds to cold-dry events, such as Heinrich and Last Glacial Maximun (LGM), and the low value area corresponds to DO events. These results have Millennium oscillation characteristics. A comparison with other charcoal records for the East Asian monsoon area showed that the intensity and frequency of fire in MIS2 was much stronger than in the late MIS3, which differs from the European pattern. The fire mechanism may be controlled by climatic factors and could be influenced by vegetation type. 参考文献 相似文献 引证文献