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Abstract: The Yu-Xue-Fen-Cun (YXFC) is one of the government archives of the Qing Dynasty (1644–1911) in China. It records the beginning/ending dates, duration and rainfall infiltration depths into soil and snowfall accumulation for individual precipitation event. By comparing YXFC with instrumental data, a set of criteria used to identify the rainy season was established. This set of criteria was used to reconstruct the initial/final dates and length of rainy season during 1736–1900 and 1955–2000 at three sites (including Taiyuan, Datong and Yulin) based on both YXFC records and instrumental data. The results show that there is evident inter-decadal variation in rainy season length, with periodicity of 16–20a, 30–40a and 50–60a. The length of the rainy season gradually increases before the mid-19th century and decreases afterward, and the length of rainy season in 1736–1840 is statistically significantly longer than that in 1955–2000. These findings suggest that the intensity of the East Asian Summer Monsoon (EASM) became weaker from the mid-19th century, reaching the weakest condition in 1955–2000 during the context of the past 260 years. [Copyright &y& Elsevier]

Abstract: The purpose of the paper is to extract and make the best use of rainfall information contained in the Chinese historical archives of Qing Dynasty, and reconstruct the precipitation series during 1736–1911. The study followed the Yu-Fen-Cun (rainfall infiltration depth) observation method in Qing Dynasty, to conduct soil infiltration experiment under the natural rainfall conditions during 2004–2006. The related parameters, such as precipitation, intensity, initial soil moisture content and infiltration depth have been measured at 10 stations (east of 105°E, 30°–40°N) with representative climatic conditions and soil physical texture in the middle and lower reaches of the Yellow River and Yangtze-Huaihe River Valley. The statistical results indicate that precipitation is the primary influencing factor to infiltration depth and is positively correlated with the infiltration depth. Additionally, the effects of every factor on infiltration depth are significantly different between the middle and lower reaches of the Yellow River and Yangtze-Huaihe River Valley. Finally, the relationship equations of precipitation and infiltration depth are established for each site, most of which can pass over 60% of the variance explanations and provide quantitative models to reconstruct the precipitation series using Yu-Fen-Cun records in Qing Dynasty. [Copyright &y& Elsevier]

We reconstructed a 500-year long winter (November to February) temperature series with a yearly resolution in southern China. The series is based on six types of proxies extracted from historical documents, including the southern limits of frost disaster, freezing disaster and snow, along with snowfall days and the first/last frost disaster dates. In the reconstruction, linear regression models are established among each proxy and regional winter temperature. Variance matching, minimum selection, and envelope analysis methods are performed to eliminate non-homogeneous effects because of different proxy types, missing data, and the changing amount of records. Compared with the average temperatures during 1851–1950, the reconstruction shows that southern China experienced a cold period in the first 40 years of the sixteenth century with an average of −0.40 °C with frequent extremes. An upturning occurred during the 1540s to mid-1560s, followed by a stable phase until the 1620s. Then the temperature started to fall from the 1630s and reached its lowest in 1660, where it dropped to −2.01 °C. Moreover, the mean value was −0.49 °C between the years 1648–1697, which was the coldest 50 years over the last five centuries. The temperatures during the eighteenth century to the middle of the twentieth century was characterized by annual to decadal fluctuations, with two moderately warm intervals in the 1770s and 1840s–1850s, as well as three moderately cold intervals in 1790s, 1830s, and 1870s to the mid-1890s. Over the recent century, the warming rate since 1901 was 0.56 °C/100a, whereas the temperature reached 0.32 °C/10a after 1979. The hottest five years during the last five centuries all occurred after 1990. [ABSTRACT FROM AUTHOR]

The potential causes of megadroughts over North China (NC) in the preindustrial period were investigated using eight climate models evolved using CMIP5/PMIP3 and multiple proxy data. The full forcing experiments driven by both external forcing and internal variability show that megadroughts in NC were accompanied by extensive decadal drying over the Northern Hemisphere (NH), particularly in most of North America and Europe. The spatial pattern of hydroclimate matched well with the proxy-based illustration. However, such hydroclimate conditions over NH were difficult to reproduce in control experiments driven solely by internal variability. This finding suggests that external forcing may be a crucial factor leading to megadroughts in NC and simultaneous decadal drying over the NH. Moreover, external forcing may lead to climate cooling. Climate cooling weakened the pressure gradient from the West Pacific to East Asia and hence reduced the water vapor to land; meanwhile, local vertical downward movement occurred in the cooling climate background, which was unfavorable to air convection over NC. Both reduced water vapor and weakened air convection led to less precipitation. Meanwhile, there was a negative NAO, which intensified the eastward wave train at mid-latitudes. Consequently, the North American trough and European trough deepened, the northerlies in the post trough pattern intensified, and the water vapor from the high-latitude continent or polar areas was low, which was unfavorable to precipitation. This study implies that the megadrought in NC and simultaneous hydroclimatic spatial pattern over the NH may be underestimated in the CMIP5 climate prediction, which excludes external forcing. • Megadrought in North China co-occur with extensive dry anomaly over North Hemisphere. • The dry-anomaly hydroclimate pattern occurs in global cooling, declined water vapor. • Abnormal external forcing, e.g., volcanic eruption, is necessary for the dry-anomaly. • Effects of abnormal external forcing may be active through negative NAO pattern. [ABSTRACT FROM AUTHOR]

The potential causes of megapluvials over Yangtze–Huaihe River valley (YHRV) during the last millennium were investigated using the Community Earth System Model-Last Millennium Ensemble (CESM-LME) simulation data and multiple proxy data (i.e., reconstruction and paleoclimate assimilation data). Herein, we first depicted the spatial hydroclimatic pattern over the Northern Hemisphere when megapluvials occurred in the YHRV during the last millennium. The proxy and simulation data both showed that megapluvials in YHRV were accompanied by extensive decadal drought in western Asia and northwestern India, also located in mid to low latitudes. Then, by diagnosing the dynamic processes, we found that the baroclinic structure over western Asia and northwestern India caused anomalous geopotential heights, and hence triggered the negative phase of the Circumglobal Teleconnection (CGT). The eastwards wave train at mid-latitudes disturbed by the CGT mode, triggered lower-level northerlies and upper-level southerlies over the northern part of the YHRV and, as a consequence, led to anomalous strong convection near the YHRV. Together with abundant water vapour from the Pacific Northwest, there was a synergistic effect on megapluvial events over the YHRV. Finally, we analysed the linkage of surface temperature in western Asia and northwestern India and megapluvials in the YHRV. Land surface heating over western Asia and northwestern India may largely stimulate the formation of a negative CGT mode through local feedback of air–land interactions and, as a result, affect precipitation anomalies downstream, such as in the YHRV. It is therefore necessary to consider anomalous high surface temperatures in western Asia and northwestern India as important predictors for interdecadal severe floods in the YHRV. • Abnormal drought existed in northwestern India (NI) and western Asia (WA) when megapluvials were present in the YHRV. • The CGT mode was triggered by the high temperature of NI and WA through air–land interactions. • Abundant water vapour from the Pacific Northwest and strong convection over the YHRV led to megapluvials. [ABSTRACT FROM AUTHOR]

Abstract Proxy-based reconstructions of the Asian Summer Monsoon exhibit variability over multiple scales, from inter-annual to centennial. The relationship between East Asia Summer Monsoon (EASM) variability and the El Niño-Southern Oscillation (ENSO) over the last millennium remains unclear and a focus of current research. This study investigates this relationship using observations, reanalysis data, proxy-based reconstructions, and a control simulation using the Community Earth System Model (CESM). The results derived from both the observation/reanalysis/proxy-based reconstruction and the simulation show consistently that the relationship between EASM strength and Niño3.4 SST is divergent. The observation/reanalysis data illustrate strong negative correlations between Niño3.4 SST and EASM strength at an annual scale in the 1920s-1930s and 1980s-1990s, with weak correlations during other periods. The proxy-based reconstruction demonstrates strong negative correlations at inter-decadal scales from the 1360s to the 1530s, with either weak correlations or positive correlations during other periods. Moreover, the simulations reveal positive correlations in some periods and negative or weak correlations in other periods. The simulations demonstrate that the divergent relationship may be derived from multi-decadal variations in Pacific SST caused by internal variability in the climate system, likely due to the Inter-decadal Pacific Oscillation (IPO). The EASM variation is usually in (out of) phase with Niño3.4 SST during the positive (negative) phase of the IPO. In the positive phase of the IPO, there is a tripolar pattern expressed in a cyclone-anticyclone-cyclone arrangement at pressure level of 850 hPa from the tropics to mid-latitudes over the northwest Pacific. Warming of the Niño3.4 strengthens the tropical cyclone by weakening the trade winds and subsequently strengthening the subtropical anticyclone, leading to a strong Meiyu front, which suggests a strong EASM. However, in the negative phase of the IPO, a huge cyclone occupies the northwest Pacific. Warming of the Niño3.4 strengthens the cyclone by weakening the trade winds, which leads to a weak Meiyu front, which suggests a weak EASM. These results may be helpful in further understanding the mechanisms through which the ENSO and IPO impact the atmospheric circulations in the Asian Pacific, especially regarding the long-term variations in EASM at inter-annual to inter-decadal scales. [ABSTRACT FROM AUTHOR]

Abstract Most estimates of Chinese regional Surface Air Temperatures since the late-19th century have identified two relatively warm periods – 1920s–40s and 1990s–present. However, there is considerable debate over how the two periods compare to each other. Some argue the current warm period is much warmer than the earlier warm period. Others argue the earlier warm period was comparable to the present. In this collaborative paper, including authors from both camps, the reasons for this ongoing debate are discussed. Several different estimates of Chinese temperature trends, both new and previously published, are considered. A study of the effects of urbanization bias on Chinese temperature trends was carried out using the new updated version of the Global Historical Climatology Network (GHCN) – version 4 (currently in beta production). It is shown that there are relatively few rural stations with long records, but urbanization bias artificially makes the early warm period seem colder and the recent warm period seem warmer. However, current homogenization approaches (which attempt to reduce non-climatic biases) also tend to have similar effects, making it unclear whether reducing or increasing the relative warmth of each period is most appropriate. A sample of 17 Chinese temperature proxy series (12 regional and 5 national) is compared and contrasted specifically for the period since the 19th century. Most proxy series imply a warm early-20th century period and a warm recent period, but the relative warmth of these two periods differs between proxies. Also, with some proxies, one or other of the warm periods is absent. [ABSTRACT FROM AUTHOR]

One of the main obstacles that hamper the application of zeolites is the high consumption of expensive structure-directing agent. Herein, we reported the mechanochemisty-mediated solventless synthesis of AlPO 4 -11 aluminophosphate molecular sieve with low dosage of diisopropylamine (DIPA) as the structure-directing agent. The influences of DIPA/Al 2 O 3 ratio, fluoride ions, seed crystals and high-energy mechanochemical pretreatment on the synthesis of AEL-type zeolite were investigated in detail. Both DIPA and fluoride ions are indispensable for the successful synthesis of AEL phase. The resultant AEL molecular sieves were characterized by XRD, SEM, TG-DTA, CHN elements analysis, and N 2 physisorption. The results indicate that the introduction of seed crystals cannot improve the phase purity and crystallinity of the resulting products. On the other hand, high-energy mechanochemical pretreatment not only can affect the morphology of AEL zeolite, but more importantly, can also reduce the consumption of structure-directing agent. [ABSTRACT FROM AUTHOR]

The hydroclimatic patterns in eastern China (EC) over the past millennium, both influenced by solar activity and Pacific decadal oscillation (PDO), are presented based on the climatic reconstructions and simulations. For strong solar activity, a consistent pattern exists where drought appears in the majority of EC initialized from the cold PDO phase, which is related to less moisture caused by the negative East Asia/Pacific-like (EAP-like) pattern and the enhanced western Pacific subtropical high (WPSH). When the initial condition with a neutral or warm PDO phase is set up, there is a tripole-like pattern from north to south, i.e., drought–flood–drought for the neutral PDO phase and flood–drought–flood for the warm PDO phase, which is related to the positive EAP-like pattern with various moisture transportation paths. For weak solar activity, there are dipole-like patterns where drought occurs in the northern part of the Yangtze River and flood appears in the southern part initialized from the cold or warm PDO phase, which is possibly related to the influence of the weakened WPSH. When the initial condition is the neutral PDO phase, there is a tripole-like pattern from north to south (flood–drought–flood) in EC affected by the weakened WPSH and the intensive India–Burma trough. Notably, the vertical velocity anomalies of airflow, representing the vertical moisture transportations, correspond well with the hydroclimatic patterns in EC whenever the various initialization strategies of PDO phases are employed. • Hydroclimatic patterns in eastern China (EC) are related to solar activity and PDO. • A consistent pattern in EC for strong solar period (SS) and cold PDO initial phase. • The tripole-like patterns for SS and the neutral or warm PDO initial phase. • A tripole-like pattern for weak solar period (WS) and neutral PDO initial phase. • The dipole-like patterns for WS and the cold or warm PDO initial phase. [ABSTRACT FROM AUTHOR]

• Paddy rice expansion resulted in a net cooling through the growing season. • Asymmetric pattern of LST change was found in the day and night. • Considerable seasonal variability in the cooling effects. • Nonradiative cooling exceeded radiative warming in paddy rice expansion. The pending extensive rice expansion in northeastern Asia, especially in northeast China, affects regional climate by altering both biogeochemical and biophysical processes. While the biogeochemical effects (e.g., CO 2 , CH 4) of rice expansion have attracted plenty of attention, its biophysical effects have not been well documented, especially its influences on diurnal and seasonal land surface temperature (LST). In this study, we used a pair-wise comparison approach to examine biophysical effects of paddy rice expansion at different temporal scales (diurnal and seasonal) in northeast China, based on satellite-derived biophysical proxies and a high-resolution crop map in 2017. We found that the daily mean LST of rice paddies was 0.5 °C lower than that of corn and soybean fields during the growing season (from May to September), as a result of daytime cooling (-1.8 and -2.0 °C) and nighttime warming (0.8 and 1.1 °C), which subsequently led to a narrower diurnal LST range (-2.6 and -3.0 °C) than in upland crops (i.e. corn and soybean). The cooling effects were stronger in the early period of the growing season (May and June) than in the late season (July to September). Using a temperature response model, we found that the nonradiative processes (i.e., evapotranspiration and sensible heat) dominated the LST response in paddy rice, while the radiative process (i.e., albedo) played a secondary role. The daytime cooling and nighttime warming implies that we need to consider the unsymmetrical diurnal LST dynamics when evaluating the short-term effects of paddy rice expansion. Stronger cooling effects in the early growing season has to be accounted for when modeling its biophysical impacts at seasonal scale. This study explained the local climate effects of rice expansion through the biophysical mechanism with both radiative and nonradiative controls on the surface energy balance, which can contribute to improved modeling of biophysical effects of land use change. [ABSTRACT FROM AUTHOR]

It still remains uncertainty whether China's future investment is conducive to carbon reduction of Belt and Road (B&R) region or not. Here, the possible impact of China's investment was revealed by comparing the CO 2 emissions of B&R region in different Chinese investment scenarios. The results showed that CO 2 emissions of B&R region will cumulatively increase by 1973 Gt in 2018–2100 in the "No-Chinese Investment Scenario (NIS)". Regionally, the India (IND), Middle East Central Asia (MECAsia), and Southeast Asia and its surrounding (SEAsia) has the largest increment. Comparing with the NIS, the CO 2 emissions of B&R region will cumulatively decrease by 44.16 Gt and 79.48 Gt, respectively, in the "Business-as-usual Chinese Investment Scenario (BIS)" and "Strengthening Chinese Investment Scenario (SIS)". Regionally, the cumulative CO 2 emissions of all subregions will decrease in BIS and SIS, of which SEAsia and MECAsia have the largest decrement. Technique and structural effects of China's investment have positive impact on cumulative CO 2 emission reduction of B&R region, especially in the structural effect. The scale effect has the negative contribution, but it cannot neutralize the positive impact induced from technique and structural effects. As a result, China's future investment is conductive to reducing CO 2 emission of B&R region and holding the temperature increase below 2 °C. [ABSTRACT FROM AUTHOR]

Large-scale palaeoclimate reconstructions can be very sensitive to the proxy records they are based on, and hence to the criteria used to select proxy records. Data selection rarely follows objective criteria that are applicable to all types of proxies, including both low- and high-resolution records. Thus, there is a need for a uniform and transparent approach to assess the suitability of input proxy data for a reconstruction. Here, we develop classification criteria that are applicable to multiple proxy types and evaluate different selection strategies using a network of 62 millennium-long terrestrial hydroclimate proxy records from Monsoon Asia. Our results reveal that robust evidence for a coherent climate signal and high dating accuracy are important criteria for benchmarking the suitability of each proxy record. We determine these criteria by reviewing the literature for each record (rather than screening against instrumental data). We show that the proposed selection approach can yield a network with a stronger common signal. By evaluating the uncertainty and centennial variability of composite reconstructions, from differently selected subsets of the proxy network, it appears beneficial to use suitable proxies stemming from different archives, as well as having a dense network of proxy sites. We suggest that future large-scale palaeoclimate reconstructions might be improved by evaluating proxy networks according to the universal categories presented here and, if indicated, removing less suitable records. This will strengthen the climate signal in the final reconstruction, allowing more precise inferences about past climate variability and more robust comparisons with climate model simulations. • Suitability of proxy records should be estimated based on literature review. • Semi-quantitative criteria: evidence for climate signal and dating accuracy. • Proposed selection approach can yield a network with a stronger common signal. • Multi-proxy approach is beneficial to preserve various frequency domains. [ABSTRACT FROM AUTHOR]

From a cursory reading of Li & Yang's comments [[6], henceforth LY2019] on our recent review article, [13] [henceforth S2018], some readers might think that LY2019 is somehow disputing our analysis and conclusions. In their Section 1.2, LY2019 claim that there are "only about 200 stations totally in China" in both version 3 and version 4 of the Global Historical Climatology Network (GHCN) dataset. At the end of the section, we will show that whichever school-of-thought you favour, LY2019 were still wrong in their Section 1.3 to dismiss the significance of the comparison between observed trends and the CMIP5 multi-model ensemble average hindcast. In other words, the average Chinese temperature trends hindcasted by the CMIP5 models is determined almost entirely by the choice of forcing datasets used by the modelling groups. [Extracted from the article]