North China Drought Research Articles

Analysis of the Variability Characteristics and Applicability of SPEI in Mainland China from 1985 to 2018

Drought is one of the most destructive natural disasters in China and can cause serious environmental and socio-economic impacts. Based on monthly precipitation and temperature data from 571 meteorological stations, the Standardized Precipitation Evapotranspiration Index (SPEI) was calculated on a 12-month scale (SPEI-12) from 1985 to 2018 in mainland China, and it was compared with the records of the Bulletin of Flood and Drought Disasters in China to verify its drought monitoring accuracy. Then, run theory was used to explore in depth the spatiotemporal distribution of drought characteristics and trends in various climatic sub-regions. The results showed that: (1) the comparison with the Bulletin of Flood and Drought Disasters in China indicated that the results of SPEI-12 monitoring drought had high accuracy and could identify drought events in mainland China. (2) About 70% of the regions in mainland China experienced droughts more than 50 times, and about 43% of the regions had drought durations of between 100 and 110 months. Nearly 11% of the regions had drought severities of more than 130, which were mainly located in the Northwest Desert (NWC), the southern part of Northeast China (NEC), and the western part of North China (NC). (3) In the past 34 years, the droughts in the Northwest Desert (NWC), the western part of Inner Mongolia (IM), and the Qinghai-Tibet Plateau (TP) showed an aridity trend, while the droughts in South China (SC) and eastern Central and South China (CSC) presented a mitigation tendency. (4) Specifically, the droughts in South China (SC) were more influenced by precipitation, while those in the Northwest Desert (NWC) and Northeast China (NEC) were influenced by temperature and potential evapotranspiration, and the evolution of drought in North China (NC) and the Qinghai-Tibet Plateau (TP) was mainly influenced by soil moisture. The study could provide scientific guidance and a reference for drought response and sustainable development in China.

Comprehensive Assessment and Variation Characteristics of the Drought Intensity in North China Based on EID

Abstract Under the new background of climate change, it is very important to identify the characteristics of drought in North China. Based on the daily meteorological drought comprehensive index from 494 national meteorological stations in North China during 1961–2019, the drought processes and their intensity are identified by applying the “extreme” intensity–duration (EID) theory. Then, the stage variation characteristics of the drought trend, the average drought intensity, and the drought frequency are analyzed. The results show that among the five drought intensity indices the process maximum intensity demonstrates the greatest correlation coefficient with the disaster rate of drought in North China. Therefore, the process maximum intensity of drought is selected as the annual drought intensity to analyze the drought characteristics in North China. According to the climate warming trends, the study period is divided into three stages, that is, 1951–84 (stage I), 1985–97 (stage II), and 1998–2019 (stage III). The comprehensive results show that the drought intensity in North China has significant stage characteristics. In stage I, the drought shows an increasing trend in most parts of North China, but its average intensity is relatively weaker, with a lower severe drought frequency. The drought also shows an increasing trend in most parts in stage II, with a more significant increase rate than that in stage I, and the average drought intensity is the strongest and the severe drought frequency is the highest. In stage III, the drought shows a decreasing trend in some areas, and the average intensity is the weakest, with a lower severe drought frequency. Significance Statement In this paper, we develop a drought intensity formula, the maximum intensity of drought, based on the “extreme” intensity–duration theory. The maximum intensity of drought was then calculated and selected as an annual drought intensity to analyze the drought characteristics in North China. We found that the annual drought intensity better captured the extremity and the patterns of drought process than that obtained with single indices and comprehensive indices. The results show a decreasing trend of drought in North China after 1998.

Interannual Variability in August Drought in Northern China and the Corresponding Climate Shift

AbstractThis study examines August droughts in northern China (north of 35°N) at interannual and interdecadal timescales. During the period from 1968 to 1992, the precipitation in the western and eastern regions of northern China showed an out‐of‐phase pattern. During the period from 1994 to 2018, the climate in the Tarim Basin became wetter, but there was no significant connection with drought in North China. Further studies demonstrated that the Atlantic sea surface temperature (SST) and regional soil moisture anomalies were related to drought changes in northern China. Before the early 1990s, the east‐west standardized precipitation index dipole mode in northern China was physically linked with the wet soil in central Asia in the preceding June; moreover, the wet land surface could persist until August and cause anticyclonic and cyclonic systems over Mongolia and the subtropical northwestern Pacific, thus contributing to precipitation surplus in northwest China and a deficit in North China. After the early 1990s, however, wet conditions over the Tarim Basin were related to wet soil in the East European Plain in the preceding July: the wet soil could persist into August and generate anomalous circulation over the Tarim Basin, leading to abnormal humidity. Additionally, the SST conditions in the North (South) Atlantic are key sources of climate predictability for northern China drought at the interseasonal scale after (before) the early 1990s.

Role of the Tibetan Plateau in Northern Drought Induced by Changes in the Subtropical Westerly Jet

AbstractThe Tibetan Plateau (TP), the so-called water tower of Asia, plays an important role in the water cycle. However, few studies have linked the TP’s water vapor supply with the climate over North China. In this study, we found that changes in the subtropical westerly jet (SWJ) dynamically induce drought in North China, and the TP plays an important role in this relationship. During July–August for the period of 1981–2019, the SWJ center between 75° and 105°E obviously shifted northward at a rate of 0.04° per year. Correspondingly, the zonal winds in the southern subtropics were incredibly weakened, causing the outflow of water vapor from the TP to decrease dramatically. Combined with numerical simulations, we discovered that a reduction in water vapor transport from the TP can obviously decrease the precipitation over North China. Sensitivity experiments demonstrated that if the water vapor outflow from the eastern border of the TP decreases by 52.74%, the precipitation in North China will decrease by 12.69% due to a decrease in the local cloud fraction caused by a diminished water vapor content in the atmosphere. Therefore, although less water vapor transport occurs in the upper troposphere than in the lower troposphere, the impact of transport from the TP in the former on the downstream precipitation cannot be ignored.

Indicator-based spatiotemporal characteristics of apple drought in North China

Indicator-based spatiotemporal characteristics of apple drought in North China

Moisture and Energy Budget Perspectives on Summer Drought in North China

AbstractWe investigate the physical processes behind summer drought in North China by evaluating moisture and energy budget diagnostics and linking them to anomalous large-scale circulation patterns. Moisture budget analysis reveals that summer drought in North China was caused dynamically by reduced vertical moisture advection due to anomalous subsidence and reduced horizontal moisture advection due to anomalous northeasterly winds. Energy budget analysis shows that reduced latent heating was balanced dynamically by decreased dry static energy (DSE) divergence in the middle-to-upper troposphere. Linking these results to previous work, we suggest that summer drought in North China was predicated on co-occurrence of the positive phases of the Eurasian (EU) and Pacific–Japan (PJ) teleconnection patterns, potentially modulated by the circumglobal teleconnection (CGT). In the typical case, the negative phase of the CGT intensified the positive EU-related upper-level cyclone. Resulting upper-level cooling and positive surface feedback imposed a cold-core surface anticyclone that weakened with height. By contrast, when the positive phase of the CGT occurred in tandem with the positive EU and PJ patterns, the anticyclone had a warm core and intensified with height. The two cases were unified by strong subsidence but exhibited opposite meridional advection anomalies. In the cold-core cases, meridional moisture inflow was reduced but meridional DSE export was enhanced, further limiting precipitation while maintaining negative thermal anomalies. In the warm-core case, which only occurred once, enhanced meridional inflow of water vapor supplied moisture for sporadic precipitation while reduced meridional DSE export helped to maintain strong static stability.

Temporal and Spatial Distribution of Multi-scale Drought in North China

The North China is located in the East Asian monsoon region. The uneven spatial and temporal distribution of water resources leads to frequent drought disasters, and drought has increasingly become a limiting factor for regional development. In this paper, the intrinsic evolution characteristics of multi-scale spatial and temporal distribution of meteorological drought in the past 57 years in North China are analyzed by using standardized precipitation evapotranspiration index and ensemble empirical mode decomposition with multi-time scale features. The results show that the North China region was generally humid in the 1960s and 1970s. Drought in the 1980s and 1990s increased relatively. The interannual SPEI of North China changed in 1991, and entered a relatively dry period in the late 1990s and 2000s. From the SPEI index sequence, the scale characteristics of each scale were extracted. It was found that the SPEI sequence of the three-month time scale in North China mainly existed in the three scale ranges of monthly, interannual and intergenerational, At the same time, through the comparison of the temporal and spatial distribution characteristics of the summer drought in june and august 2002 in North China, it was found that the severe drought in august 2002 was caused by the temporal and spatial overlap of short-term scale and long-term drought events.

The 2017–2018 Winter Drought in North China and Its Causes

A meteorological drought was observed over North China in the 2017–2018 winter, which was accompanied by record-breaking consecutive non-precipitation days over many regions of central North China. Inspection on historical observations beginning in 1951 suggest that it was the fourth driest winter during the past 67 years. The possible cause of this drought was then analyzed. It has been suggested that the co-occurrence of the positive phase of the Eurasian (EU) teleconnection pattern and La Niña have played a crucial role. On one hand, both the positive phase of the EU pattern and La Niña could have enhanced the lower-tropospheric northerly winds over East Asia. The northward water vapor transport towards North China was thereby weakened, providing an unfavorable moisture environment for precipitation. On the other hand, the EU-like wave pattern in the mid-latitude was conducive to anomalous descending motion over mid-latitude East Asia, creating an unfavorable dynamical condition for precipitation. A combination of the above two effects lead to the occurrence of the North China drought in the 2017 winter.

Evaluating the performance of five twentieth-century reanalysis datasets in reproducing the severe drought in northern China during the 1920s-1930s

Drought is the major natural disaster that affects northern China and has regional distinctions in duration, strength, and spatial range. Using five sets of twentieth-century reanalysis data, we investigated a decadal-scale extreme drought recorded in historical documents and tree-ring chronologies during late 1920s to early 1930s. The results indicated that the characteristics of drought were different in North China and the middle reach of the Yellow River. Drought in North China showed an interannual variation coinciding strongly with El Nino. For the middle reach of the Yellow River, a persistently dry period lasting from 1922 to 1932 was found, while the driest years were 1928 and 1929.The dataset ERA-20C had better performance than other reanalysis datasets in both regions. The drought that happened in North China during these years may have been primarily determined by ENSO. The joint impact of PDO and AMO may have been responsible for the decadal dry anomaly in the middle reach of the Yellow River.

Alleviation of Drought Stress in Turfgrass by the Combined Application of Nano-compost and Microbes from Compost

Drought stress is a key environmental factor limiting the growth and productivity of plants. Turfgrasses are often affected by drought in north China due to water shortage. In the present study, the impact of nanosized compost either alone or in combination with drought tolerant isolates from compost on turfgrass response to drought was investigated. Municipal solid waste (MSW) compost was processed into nanosized particles and added in turfgrass soil. Microorganisms in the MSW compost were screened for drought stress tolerance using increasing concentrations of polyethylene glycol (PEG 6000). Festuca arundinacea Schreb. plants were inoculated with this mixture and exposed to drought stress by reducing the amount of water added at vegetative growth stage. The drought-tolerant isolates from compost were identified as Bacillus cereus, Lysinibacillus sp. and Rhodotorula glutinis. Our results revealed that nanocompost and microbial inoculation minimized the drought stress-imposed effects significantly increasing shoot biomass, root biomass, and chlorophyll content. Similarly, nanocompost-treated and inoculated seedlings showed higher levels of antioxidant enzymes and lower MDA content compared to nontreated control under drought stress. The combination of nano-sized compost and microbial inoculation were more efficient than nanocompost alone in terms of influencing growth and physiological status of the seedlings under drought stress. Our data suggest that nanocompost combined with drought-tolerant isolates may enhance drought tolerance in turfgrass by promoting plant growth and increasing the capacity to eliminate toxic reactive oxygen species (ROS).

Aerosol forcing of extreme summer drought over North China

The frequency of extreme summer drought has been increasing in North China during the past sixty years, which has caused serious water shortages. It remains unclear whether anthropogenic forcing has contributed to the increasing extreme droughts. Using the National Centers for Environmental Prediction and the National Center for Atmospheric Research (NCEP/NCAR) re-analysis data and Coupled Model Intercomparison Project Phase 5 (CMIP5) model simulations with various combinations of historical forcings, the authors investigated the driving mechanism behind the observed changes. Metrological drought is usually measured by precipitation anomalies, which show lower fidelity in current climate models compared to large-scale circulation patterns. Based on NCEP/NCAR re-analysis, a linear relationship is firstly established between the weakest regional average 850 hPa southerly winds and extreme summer drought. This meridional winds index (MWI) is then used as a proxy for attribution of extreme North China drought using CMIP5 outputs. Examination of the CMIP5 simulations reveals that the probability of the extreme summer droughts with the first percentile of MWI for 1850–2004 under anthropogenic forcing has increased by 100%, on average, relative to a pre-industrial control run. The more frequent occurrence of extremely weak MWIs or drought over North China is ascribed from weakened climate and East Asian summer monsoon (EASM) circulation due to the direct cooling effect from increased aerosol.

Does a Strong El Ni\xf1o Imply a Higher Predictability of Extreme Drought?

The devastating North China drought in the summer of 2015 was roughly captured by a dynamical seasonal climate forecast model with a good prediction of the 2015/16 big El Niño. This raises a question of whether strong El Niños imply higher predictability of extreme droughts. Here we show that a strong El Niño does not necessarily result in an extreme drought, but it depends on whether the El Niño evolves synergistically with Eurasian spring snow cover reduction to trigger a positive summer Eurasian teleconnection (EU) pattern that favors anomalous northerly and air sinking over North China. The dynamical forecast model that only well represents the El Niño underpredicts the drought severity, while a dynamical-statistical forecasting approach that combines both the low- and high-latitudes precursors is more skillful at long lead. In a warming future, the vanishing cryosphere should be better understood to improve predictability of extreme droughts.

干旱和臭氧浓度升高对元宝枫早生和晚生叶片色素和脱落酸含量的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 干旱和臭氧浓度升高对元宝枫早生和晚生叶片色素和脱落酸含量的影响 DOI: 10.5846/stxb201505060933 作者: 作者单位: 中国科学院生态环境研究中心,中国科学院华南植物园,中国科学院生态环境研究中心,中国农业科学院农业资源与农业区划研究所,中国科学院生态环境研究中心 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31170424，41571053，71533005） The effects of elevated ozone and chronic drought on leaf pigments and abscisic acid contents in early and late-flush leaves of Shantung maple (Acer truncatum Bunge) Author: Affiliation: Research Center for Eco-Environmental Sciences，Chinese Academy of Sciences,South China Botanical Garden, Chinese Academy of Sciences,Central South University,Institute of Agriculture Resources and Regional Planning, Chinese Academy of Agriculture Sciences,Research Center for Eco-Environmental Sciences，Chinese Academy of Sciences 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:臭氧和干旱是威胁我国北方城市植物生长的两大重要因素。于2012年利用开顶式气室，通过设置4个处理（AW-大气环境和水分充足；AW+60-大气增加60 nL/L臭氧+水分充足；AD-大气+干旱处理；AD+60-大气增加60 nL/L臭氧+干旱处理），开展了大气臭氧浓度升高（以下简称“臭氧”）和干旱对元宝枫秋季变色期主要色素含量及脱落酸（ABA）含量的影响研究。结果表明：（1）早生叶在臭氧处理后，总叶绿素和类胡萝卜素分别下降了21%和29.6%、花青苷和类黄酮相对含量显著升高了34.1%和7.3%、脱落酸含量增加了19.8%。干旱处理后，早生叶总叶绿素显著下降了18.7%、花青苷和类黄酮相对含量分别显著升高了37%和7.4%、脱落酸含量显著升高了13%。叶片的上述生理变化将会导致叶片提前变红、叶片早衰和提前脱落。（2）晚生叶在干旱处理后总叶绿素含量减少了18.8%，脱落酸含量增加了33.4%，臭氧以及与干旱共同处理未对晚生叶产生显著影响。（3）臭氧和干旱共同处理后，早生叶总叶绿素含量、花青苷和叶片脱落酸含量存在显著交互作用，交互作用缓解了叶片总叶绿素的下降和花青苷的上升，但未缓解叶片脱落酸含量的增加。综上，早生叶和晚生叶对臭氧和干旱处理的响应不同，早生叶对臭氧处理响应大于晚生叶，而晚生叶对干旱更敏感。臭氧和干旱处理均加速了叶片衰老，二者共同处理后叶片脱落风险增加。 Abstract:The changing color of leaves in autumn is not only necessary for the growth of foliage trees but is also important for urban landscape interests. Red color in maple leaves relates to the synthesis of anthocyanin and the degraded pigments. Ozone (O3) is an important phytotoxic pollutant, which may affect the basic physiological functions of plants due to its highly reactive oxidative characteristics. The increased consumption of fossil fuels in China has led to increased emission of O3 precursors and visible plant injury induced by high O3 concentration frequently occurs around Beijing. In addition, trees are often subjected to periodic drought in North China with the frequency and the severity of drought events projected in the background of climate change. Drought in summer usually coincides with episodes of high O3 concentrations, which, together, may affect plant growth including color expression and leaf senescence of foliage tree species in fall. Although numerous publications have reported the effects of elevated O3 concentration or drought stress on trees, little is known about the possible interactions between anthocyanin and flavonoid in Asian maple species. To investigate the effects of chronic drought stress and elevated O3 concentrations on leaf pigments and abscission of Shantung maple (Acer truncatum Bunge), we set up 12 open-top chambers with four treatments (AW: non-filtered ambient air and well watered; AW+60: non-filtered ambient air plus 60 nL/L O3 and well watered; AD: non-filtered ambient air and drought; AD+60: non-filtered ambient air plus 60 nL/L O3 and drought) in a suburb of Beijing, China. Total chlorophyll (total Chl), carotenoid (Car), anthocyanin, flavonoid, and abscisic acid (ABA) contents in early and late-flush leaves were measured in October of the first year. Leaves that unfolded from July 1 to 7 were marked as early-flush leaves and the AOT40 (The cumulative O3 exposure, which was described as the accumulated hourly mean O3 concentrations over 40 ppb during O3 fumigation period) was 28.2 μL L-1 h when harvested. Late-flush leaves unfolded from September 1 to 7 and the AOT40 was 14.2 μL L-1 h when harvested. The results showed: (1) For early-flush leaves, elevated O3 significantly decreased the total Chl and Car contents by 21% and 29.6%, respectively, increased anthocyanin and flavonoid relative contents by 34.1% and 7.3%, respectively, and increased ABA contents by 19.8%. Drought stress decreased the total Chl by 18.7%, increased the relative contents of anthocyanin and flavonoid by 37% and 7.4%, respectively, and increased ABA contents by 13%. These physiology changes would collectively lead to leaf reddening, senescence, and abscission in advance of autumn. (2) Late-flush leaves only responded to drought treatments as indicated by a significant decrease of 18.8% in total Chl and an increase of 33.4% in ABA contents. (3) Significant interactions were found in total Chl, anthocyanin, and ABA contents of early-flush leaves, as indicated by the fact that the decrease in total Chl and increase in anthocyanin were mitigated, but the increase in ABA contents was aggravated. In conclusion, early and late-flush leaves responded differently to elevated O3 and drought stress. Early-flush leaves responded more to ozone treatment, while late-flush leaves were more sensitive to drought stress. Both treatments lead to leaf early senescence and their interactive treatments may increase the risk of early abscission. This study may provide a better understanding of autumnal leaf growth and the phenology response to elevated O3 and drought stress in the coming future. 参考文献 相似文献 引证文献

Seasonality in anthropogenic aerosol effects on East Asian climate simulated with CAM5

This study investigates the seasonality in anthropogenic aerosol optical depth (AOD) distributions and their effects on clouds and precipitation in East Asia with the Community Atmospheric Model version 5. The differences between the model experiments with and without anthropogenic emissions exhibit a northward shift of the maximal AOD change in East Asia from March to July and then a southward withdrawal from September to November, which are induced by East Asian monsoon circulation. Associated with the shift, the direct and semi-direct effects of the anthropogenic aerosols are the most pronounced in spring and summer, with a maximum center in North China during summer and a secondary center in South China during spring. The cloud liquid water path and shortwave cloud forcing changes, however, are the weakest in North China during summer. The indirect effect is the strongest in South China during spring, which is related to the large amount of middle-low level clouds in cold seasons in East China. A positive feedback between aerosol induced surface cooling and low-level cloud increase is identified in East China, which acts to enforce the aerosol indirect effect in spring. Accordingly, the climate response to the anthropogenic aerosols is also characterized by a northward shift of reduced precipitation from spring to summer, leading to a spring drought in South China and a summer drought in North China. The spring drought is attributed to both direct and indirect effects of the anthropogenic aerosols, while the summer drought is primarily determined by the aerosols' direct effect.

Frequency analysis and its spatiotemporal characteristics of precipitation extreme events in China during 1951–2010

This study investigates frequency analysis and its spatiotemporal characteristics of precipitation extremes based on annual maximum of daily precipitation (AMP) data of 753 observation stations in China during the period 1951–2010. Several statistical methods including L-moments, Mann-Kendall test (MK test), Student’s t test (t test) and analysis of variance (F-test) are used to study different statistical properties related to frequency and spatiotemporal characteristics of precipitation extremes. The results indicate that the AMP series of most sites have no linear trends at 90 % confidence level, but there is a distinctive decrease trend in Beijing-Tianjin-Tangshan region. The analysis of abrupt changes shows that there are no significant changes in most sites, and no distinctive regional patterns within the mutation sites either. An important innovation different from the previous studies is the shift in the mean and the variance which are also studied in this paper in order to further analyze the changes of strong and weak precipitation extreme events. The shift analysis shows that we should pay more attention to the drought in North China and to the flood control and drought in South China, especially to those regions that have no clear trend and have a significant shift in the variance. More important, this study conducts the comprehensive analysis of a complete set of quantile estimates and its spatiotemporal characteristic in China. Spatial distribution of quantile estimation based on the AMP series demonstrated that the values gradually increased from the Northwest to the Southeast with the increment of duration and return period, while the increasing rate of estimation is smooth in the arid and semiarid region and is rapid in humid region. Frequency estimates of 50-year return period are in agreement with the maximum observations of AMP series in the most stations, which can provide more quantitative and scientific basis for decision making.

Drought over East Asia: A Review

AbstractEast Asia is greatly impacted by drought. North and southwest China are the regions with the highest drought frequency and maximum duration. At the interannual time scale, drought in the eastern part of East Asia is mainly dominated by two teleconnection patterns (i.e., the Pacific–Japan and Silk Road teleconnections). The former is forced by SST anomalies in the western North Pacific and the tropical Indian Ocean during El Niño decaying year summers. The precipitation anomaly features a meridional tripolar or sandwich pattern. The latter is forced by Indian monsoon heating and is a propagation of stationary Rossby waves along the Asian jet in the upper troposphere. It can significantly influence the precipitation over north China. Regarding the long-term trend, there exists an increasing drought trend over central parts of northern China and a decreasing tendency over northwestern China from the 1950s to the present. The increased drought in north China results from a weakened tendency of summer monsoons, which is mainly driven by the phase transition of the Pacific decadal oscillation. East Asian summer precipitation is poorly simulated and predicted by current state-of-the-art climate models. Encouragingly, the predictability of atmospheric circulation is high because of the forcing of ENSO and the associated teleconnection patterns. Under the SRES A1B scenario and doubled CO2 simulations, most climate models project an increasing drought frequency and intensity over southeastern Asia. Nevertheless, uncertainties exist in the projections as a result of the selection of climate models and the choice of drought index.

Economic effects of drought on agriculture in North China

In the past three decades, global agriculture losses have continuously grown due to increasingly severe droughts. Compared with direct economic effects, there are great difficulties in evaluating the indirect economic effects of drought, which has severely lagged behind the urgent infor- mation needs for decision making. This study tries to solve the perplexity in the evaluation of the effects of drought on the price fluctuation of agricultural products by building a partial equilibrium model that describes the balancing process of supply and demand quantitatively. Using this model, a scenario analysis is applied to evaluate the price fluctuation of agricultural products caused by drought in North China. The results indicate that there is no major impact of drought on the market prices of eight major agricultural products. Even with the occurrence of a severe drought in North China, market prices of agricultural products will rise no more than 3.59 percent, which is less than the normal market price fluctua- tions of China's agricultural products. This study provides a tool for evaluating indirect economic effects of drought. The results of our case study could support decision making for China's food market regulation.

Modeled Influence of East Asian Black Carbon on Inter-Decadal Shifts in East China Summer Rainfall

AbstractTwo inter-decadal shifts in East China summer rainfall during the last three decades of the 20th century have been identified. One shift occurred in the late 1970s and featured more rainfall in the Yangtze River valley and prolonged drought in North China. The other shift occurred in the early 1990s and featured increased rainfall in South China. The role of black carbon (BC) aerosol in the first shift event is controversial, and it has not been documented for the second event. In this study, the authors used Geophysical Fluid Dynamics Laboratory’s (GFDL’s) atmospheric general circulation model known as Atmosphere and Land Model (AM2.1), which has been shown to capture East Asian climate variability well, to investigate these issues by conducting sensitive experiments with or without historical BC in East Asia. The results suggest that the model reproduces the first shift well, including intensified rainfall in the Yangtze River and weakened monsoonal circulation. However, the model captures only ...

Statistical properties of moisture transport in East Asia and their impacts on wetness/dryness variations in North China

Dryness and wetness variations in east China were analyzed using the standardized precipitation index (SPI) based on monthly precipitation data for 1961–2005. A drying trend over North China was observed, which can be attributed to decreasing precipitation since the late 1970s. Moreover, NCAR/NCEP reanalysis dataset was used to investigate causes behind the drying trend in North China. The moisture flux on the regional boundaries of East China was calculated and a higher wavelet power spectrum for low-latitude boundaries (based on 20 and 25°N) occurred with significant periods in a 1-year band during 1961–2005; however, since 1977, a significant 1-year period can no longer be detected on the northern boundary of South China (based on 35°N). The summer moisture flux during 1961–1977, when compared to the same during 1978–2005, has increased in East China. Good matches are found between moisture alterations and precipitation changes, and are also confirmed by the periods of moisture transport along different latitudes. The significant 1-year periods of moisture transport along the mid-latitude boundary (based on 35°N) have disappeared since 1977, which could be the causes behind the drought in North China. The disappearance of the significant 1-year band of moisture transport along the mid-latitude boundary (based on 35°N) in the late 1970s could be a result of the significantly decreased moisture transport in North China in summer. When southerly winds are weakened in East Asia, the southwesterly winds can only reach the south of the lower Yangtze River, which is the major cause behind the frequent summer droughts in North China in the recent years.

1876–1878 severe drought in North China: Facts, impacts and climatic background

Based on the reconstructed precipitation series in North China from historical documents, the 1876–1878 drought was identified as the most severe and extreme one in North China over the past 300 years. Meanwhile, the spatial patterns of seasonal and annual precipitation during 1876–1877 were analyzed and the social and economic impacts related with this drought event were evaluated according to the descriptions in the historical documents. The results indicated that this long-lasting drought started by the spring of 1876 and did not stop until the spring of 1878. Within the three years, the harvest failures brought the rice price increased to 5–10 times than that in the normal year, and the total population in the five provinces over North China decreased by more than 20 million due to a large number of dead people and migrations. In addition, related investigations suggested that the 1876–1878 drought was prevalent worldwide, which has possible link with abnormal high SST in the equatorial central and eastern Pacific, strong El Nino episode and positive AAO anomalies.