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This paper focuses on the interdecadal variation in drought in Northeast China (NEC) in recent decades. Two dry and wet periods have occurred in the past 61 years (1950–2010). The mechanism underlying the interdecadal variation in drought in NEC is further analyzed; the results indicate that the direct cause is the interdecadal change of the Okhotsk High (OH). A strong (weak) OH is conducive (detrimental) to the convergence of cold air transported by northeast cold vortex and water vapor from the east of NEC, eventually leading to an increase (decrease) in precipitation. Furthermore, we seek to understand why OH displays such an interdecadal variation. The interdecadal increases and decreases in sea ice in the Barents Sea and the Kara Sea explain most of the interdecadal change of the OH. When more sea ice is present in this area, more energy is transferred eastward from the sea ice area to Northeast Asia, weakening the OH; in contrast, less sea ice strengthens the OH. Sensitivity simulations by Community Atmosphere Model, version 4 (CAM4) using sea ice forcing in the Barents Sea and the Kara Sea yield similar results to the observed data, further confirming our conclusion. The results of this paper provide a new understanding of the interdecadal variation in drought in NEC, and it may help to improve our ability to predict drought and provide early warning in the future. Key Points: The drought over Northeast China has significant interdecadal variability during the past decadesThe Okhotsk High acts as the direct factor causing interdecadal changes in NEC drought by affecting atmospheric circulationThe interdecadal increases and decreases in sea ice in the Barents Sea and the Kara Sea can modulate the Okhotsk High changes [ABSTRACT FROM AUTHOR]

Inactive ice wedges are still present today at Yituli'he in the middle Da Xing'anling (Greater Hinggan) Mountains in northeastern China, which is the southernmost known site (50°37′N) with ice wedges in the Northern Hemisphere. However, it is uncertain whether the ice-wedge isotope composition, characterized by low δ18O, δD and low deuterium excess values, is representative of the isotope signature of a broader region. In this paper, the ice-wedge isotope compositions were examined in the context of the stable isotopes of precipitation from the nearby Global Network of Isotopes in Precipitation ( GNIP) stations. In addition, the pollen spectra from the host sediments were analysed to provide additional information on local vegetation in order to better understand the climate conditions favouring ice-wedge formation. The pollen spectra suggest that the Yituli'he ice wedges developed during the colder and wetter period after 6000 cal. a BP. The isotopes in the Yituli'he ice wedges are consistent with the isotope background recorded in atmospheric precipitation collected at the nearby GNIP stations. When the snow-melt froze into ice veinlets, the isotope signals did not change substantially because of the strong, cold, continental anticyclones in winter as well as a strong temperature inversion that prevail in the Da Xing'anling Mountains. As the climate pattern did not change substantially, the neoglacial cold period is unlikely to have allowed for strong secondary fractionation of isotope records during ice-wedge formation. Thus, the annual isotope signature can be interpreted as a valid archive of climate data. [ABSTRACT FROM AUTHOR]

This paper investigates monthly and seasonal precipitation-temperature relationships (PTRs) over Northeast China using a method proposed in this study. The PTRs are influenced by clouds, latent and sensible heat conversion, precipitation type, etc. In summer, the influences of these factors on temperature decrease are different for various altitudes, latitudes, longitudes, and climate types. Stronger negative PTRs ranging from −0.049 to −0.075 °C/mm mostly occur in the semi-arid region, where the cold frontal-type precipitation dominates. In contrast, weaker negative PTRs ranging from −0.004 to −0.014 °C/mm mainly distribute in Liaoning Province, where rain is mainly orographic rain controlled by the warm and humid air of East Asian summer monsoon. In winter, surface temperature increases owing to the release of latent heat and sensible heat when precipitation occurs. The stronger positive PTRs ranging from 0.963 to 3.786 °C/mm mostly occur at high altitudes and latitudes due to more release of sensible heat. The enhanced atmospheric counter radiation by clouds is the major factor affecting increases of surface temperature in winter and decreases of surface temperature in summer when precipitation occurs. [ABSTRACT FROM AUTHOR]

In this paper, we study the spatiotemporal characteristics of precipitable water, precipitation, evaporation, and water–vapor flux divergence in different seasons over northeast China and the water balance of that area. The data used in this paper is provided by the European Center for Medium-Range Weather Forecasts (ECMWF). The results show that the spatial distributions of precipitable water, precipitation, and evaporation feature that the values of elements above in the southeastern area are larger than those in the northwestern area; in summer, much precipitation and evaporation occur in the Changbai Mountain region as a strong moisture convergence region; in spring and autumn, moisture divergence dominates the northeast of China; in winter, the moisture divergence and convergence are weak in this area. From 1979 to 2010, the total precipitation of summer and autumn in northeast China decreased significantly; especially from 1999 to 2010, the summer precipitation always demonstrated negative anomaly. Additionally, other elements in different seasons changed in a truly imperceptible way. In spring, the evaporation exceeded the precipitation in northeast China; in summer, the precipitation was more prominent; in autumn and winter, precipitation played a more dominating role than the evaporation in the northern part of northeast China, while the evaporation exceeded the precipitation in the southern part.The Interim ECMWF Re-Analysis (ERA-Interim) data have properly described the water balance of different seasons in northeast China. Based on ERA-Interim data, the moisture sinks computed through moisture convergence and moisture local variation are quite consistent with those computed through precipitation and evaporation, which proves that ERA-Interim data can be used in the research of water balance in northeast China. On a seasonal scale, the moisture convergence has a greater influence than the local moisture variation on a moisture sink, and the latter is variable slightly, generally as a constant. Likewise, in different seasons, the total precipitation has a much greater influence than the evaporation on the moisture sink. [ABSTRACT FROM AUTHOR]

This study examines potential benefits of performance‐based multi‐model ensembles (MMEs) in projecting the impacts of climate change on extreme precipitation indices over East Asia (EA) using the data from 19 GCMs in the coupled model intercomparison project 5 (CMIP5). The Taylor skill score is adopted as the measure of the model skills in simulating the spatial and interannual variability of the selected extreme precipitation indices over four EA regions. The overall rank based on the total skill score (TSC) is used to construct two skill‐based MMEs, MME of high‐skill, MMH (MME of low‐skill, MML) that include the top (bottom) seven models, in addition to the simple ensemble of all 19 GCMs (ENS). Inter‐GCM consistency is measured using the signal‐to‐noise ratio (SNR). In the present‐day period, MMH yields higher skill scores than MML and ENS for almost all extreme precipitation indices as well as regions. Regional variations in biases, inter‐model consistency, and TSC are large. The inter‐model consistency is highest for Northern China and Manchuria and is lowest for Southern China. The most notable differences in the key properties of climate change signals from the three MMEs among the three ensembles are that the climate change signals from MMH and ENS exceed the 90% significance level in much larger areas than those from MML. However, the differences in the climate change signals between MMH and MML are generally below the 90% significance level. The SNR of the projected climate change signals shows that MMH yields more consistent climate change signals than ENS/MML. Both the SNR differences and the area in which statistical significance exceed the 90% level suggest that constructing climate change signals from a group of higher‐skill models may yield more reliable projections than constructing MMEs from the entire models or a group of lower‐skilled models. The domains used in the study (SOUTH: 110°–140°E, 20°–30°N, MIDDLE: 110°–140°E, 30°–40°N), NORTH: 110°–140°E, 40°–50°N, EA: 110°–140°E, 20°–50°N) [ABSTRACT FROM AUTHOR]

Global warming has caused unevenly distributed changes in precipitation and evapotranspiration, which has and will certainly impact on the wet-dry variations. Based on daily meteorological data collected at 91 weather stations in Northeast China (NEC), the spatiotemporal characteristics of dry and wet climatic variables (precipitation, crop reference evapotranspiration (ET0), and humid index (HI)) are analyzed, and the probable reasons causing the changes in these variables are discussed during the period of 1961-2014. Precipitation showed non-significant trend over the period of 1961-2014, while ET0 showed a significant decreasing trend, which led to climate wetting in NEC. The period of 2001-2012 exhibited smaller semiarid area and larger humid area compared to the period of 1961-1980, indicating NEC has experienced wetting process at decadal scale. ET0 was most sensitive to relative humidity, and wind speed was the second most sensitive variable. Sunshine hours and temperature were found to be less influential to ET0 in the study area. The changes in wind speed in the recent 54 years have caused the greatest influence on ET0, followed by temperature. For each month, wind speed was the most significant variable causing ET0 reduction in all months except July. Temperature, as a dominant factor, made a positive contribution to ET0 in February and March, as well as sunshine hours in June and July, and relative humidity in August and September. In summary, NEC has experienced noticeable climate wetting due to the significantly decreasing ET0, and the decrease in wind speed was the biggest contributor for the ET0 reduction. Although agricultural drought crisis is expected to be partly alleviated, regional water resources management and planning in Northeast China should consider the potential water shortage and water conflict in the future because of spatiotemporal dry-wet variations in NEC. [ABSTRACT FROM AUTHOR]

This study develops a new variance-based uncertainty assessment framework to investigate the individual and combined impacts of various uncertainty sources on future extreme floods. The Long Ashton Research Station Weather Generator (LARS-WG) approach is used to downscale multiple general circulation models (GCMs), and the dynamically dimensioned search approximation of uncertainty approach is used to quantify hydrological model uncertainty. Extreme floods in a region in northeastern China are studied for two future periods: near term (2046-65) and far term (2080-99). Six GCMs and three emission scenarios (A1B, A2, and Bl) are used. Results obtained from this case study show that the 500-yr flood magnitude could increase by 4.5% in 2046-65 and by 6.4% in 2080-99 in terms of median values; in worst-case scenarios, it could increase by 63.0% and 111.8% in 2046-65 and 2080-99, respectively. It is found that the combined effect of GCMs, emission scenarios, and hydrological models has a larger influence on the discharge uncertainties than the individual impacts from emission scenarios and hydrological models. Further, results show GCMs are the dominant contributor to extreme flood uncertainty in both 2046-65 and 2080-99 periods. This study demonstrates that the developed framework can be used to effectively investigate changes in the occurrence of extreme floods in the future and to quantify individual and combined contributions of various uncertainty sources to extreme flood uncertainty, which can guide future efforts to reduce uncertainty. [ABSTRACT FROM AUTHOR]

Human activities are known to increase interference with runoff. Conversely, human activities related to utilizing and managing water resources are primarily determined by annual runoff processes dominated by precipitation distribution. With this view, the soil and water assessment tool was used to quantify human-induced annual runoff changes at different periods and under different patterns of precipitation in seven catchments in Northeast China. The conclusions are as follows. First, although human activities have distinct regional characteristics, an increase in reduced runoff is found for the catchments under investigation; human-induced runoff changes are more significant in the catchment where water resources are limited. Second, the interannual runoff distribution is significantly disturbed in the catchment with large reservoirs. Third, human-induced runoff changes are similar under all patterns of precipitation in the catchment where annual precipitation is less than 500 mm and intense human activities play a dominant role in runoff. Fourth, in general catchments, runoff changes more significantly during relatively drier years or years with uneven precipitation distribution. Finally, human-induced runoff change is related to both annual precipitation characteristics and operations of the reservoirs for catchments in which reservoirs played a significant role. [ABSTRACT FROM AUTHOR]

ABSTRACT Daily precipitation data from 34 weather stations in Northeast China from 1960 to 2008 are used to examine trends in the occurrence of dry days and prolonged dry episodes. Trends in the mean length and frequency of prolonged dry episodes, as well as the number of dry days within prolonged dry episodes ( DDPDE), are computed regionally and for individual stations at the threshold levels of 1 and 2 mm day−1. Regionally, the number of dry days is increasing in the summer half-year and decreasing in the winter half-year. DDPDE is significantly increasing in the summer half-year; the increased frequency of dry spells has the greatest effect. The mean length of prolonged dry episodes in the winter half-year has decreased significantly. Our results indicate that neither the frequency nor the mean length of prolonged dry episodes, alone, can adequately describe the short-term dry conditions of an area. Multiple characteristics of dry spells, including frequency, length, and the number of DDPDE should be considered. DDPDE is a function of both the frequency and length of dry episodes, but may be more influenced by one or the other characteristics of dry spells, depending on the season or region. [ABSTRACT FROM AUTHOR]

In this work, authors examine the variabilities of precipitation and surface air temperature (T2m) in Northeast China during 1948-2012, and their global connection, as well as the predictability. It is noted that both the precipitation and T2m variations in Northeast China are dominated by interannual and higher frequency variations. However, on interdecadal time scales, T2m is shifted significantly from below normal to above normal around 1987/1988. Statistically, the seasonal mean precipitation and T2m are largely driven by local internal atmospheric variability rather than remote forcing. For the precipitation variation, circulation anomalies in the low latitudes play a more important role in spring and summer than in autumn and winter. For T2m variations, the associated sea surface pressure (SLP) and 850-hPa wind (uv850) anomalies are similar for all seasons in high latitudes with significantly negative correlations for SLP and westerly wind anomaly for uv850, suggesting that a strong zonal circulation in the high latitudes favors warming in Northeast China. The predictability of precipitation and T2m in Northeast China is assessed by using the Atmospheric Model Inter-comparison Project type experiments which are forced by observed sea surface temperature (SST) and time-evolving greenhouse gas (GHG) concentrations. Results suggest that T2m has slightly higher predictability than precipitation in Northeast China. To some extent, the model simulates the interdecadal shift of T2m around 1987/1988, implying a possible connection between SST (and/or GHG forcing) and surface air temperature variation in Northeast China on interdecadal time scales. Nevertheless, the precipitation and T2m variations are mainly determined by the unpredictable components which are caused by the atmospheric internal dynamic processes, suggesting low predictability for the climate variation in Northeast China. [ABSTRACT FROM AUTHOR]

The analysis of two historical time series of temperature and precipitation in Northeast China, spanning, respectively, 1870–2004 and 1841–2004, performed by continuous wavelet transform and other classical and advanced spectral methods, is presented here. Both variables show a particular trend and oscillations of about 85, 60, 35 and 20 years that are highly significant, with a phase opposition at the centennial scale and at the 20-year scale. The analysis of the four temperature series relative to single seasons shows that the 20-year cycle is typical of the summer monsoon season, while the 35-year cycle is most evident in winter. The cycles of ~60 years and longer are present in all seasons. The centennial variation of temperature and precipitation describes well the 1970–1980 transition between a period of relatively strong East Asian Summer Monsoon (EASM), corresponding to high precipitation and relatively cool temperatures in Northeast China, and a conditions of weak EASM (low precipitation and warm temperatures). The connection of the detected local variations with large-scale climatic variability is deduced from the comparison with different climatic records (Northern Hemisphere temperature, Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation indexes). [ABSTRACT FROM AUTHOR]

This study was based on the daily meteorological data of 101 meteorological stations from 1971 to 2000 and the 0.25°×0.25° grid data from 1951 to 2100 simulated by RegCM3 under the future A1B climatic scenario published by National Climate Center, in combination with the demand of climatic condition for maize growth in Northeast China. The trajectory of agricultural climatic resources and the effects of climate change on variety distribution and climatic potential productivity of spring maize in Northeast China under future climate change were analyzed. The main agro-climatic resource factors include: the initial date daily average temperature stably passing 10°C (⩾10°C), the first frost date, the days of growing period, the ⩾10°C accumulated temperature, and the total radiation and precipitation in the growing period. The results showed that: (1) in the coming 100 years, the first date of ⩾10°C would be significantly advanced, and the first frost date would be delayed. The days of growing period would be extended, the ⩾10°C accumulated temperature and the total radiation would be significantly increased. However, no significant change was found in precipitation. (2) Due to the climate change, the early-maturing varieties will be gradually replaced by late-maturing varieties in Northeast China, and the planting boundaries of several maize varieties would be extended northward and eastward. (3) There would be a significant change in the climatic potential productivity of maize in Northeast China with the high-value gradually moving towards northeast. (4) It was an effective way to increase the climatic potential productivity of maize by appropriate adjustment of sowing date. [ABSTRACT FROM AUTHOR]

Daily global solar radiation is an important input required in most crop models. In the present study, a sunshine-based model, the Ångström-Prescott model, is employed to estimate daily global solar radiation on a horizontal surface during the growing season in Northeast China. Data from six control groups are used. The controls include the entire sequence, precipitation days, and non-precipitation days both during the growing season and year-round. Estimations are validated by comparing the calculated values with the corresponding measured values. The results indicate that estimating daily global solar radiation during the growing season using data only from the growing season is better than using year-round data. Classifying days with respect to precipitation and non-precipitation is also unnecessary. The performance on estimating daily global solar radiation during the growing season using the entire data in growing season performs best. A sunshine-based equation is obtained using our method to estimate growing season daily radiation for all meteorological stations in Northeast China. The approved approach is expected to be beneficial to crop models and other agricultural purposes. [ABSTRACT FROM AUTHOR]

Trends of the tropical cyclones (TCs) influence on China and its four subregions, namely the South China (SC), East China (EC), Northeast China (NEC), and China's inland area (CI), are detected by applying quantile regression to the CMA-STI tropical cyclone best track and related severe wind and precipitation observation datasets. The results indicate that in the past 50 years, the number of TCs affecting China and its four subregions has remained steady, except that the frequency in extremely active years has decreased not only in China as a whole, but also in NEC. In addition, TC activity is found to have weakened over the northwest South China Sea, Guangdong, and Shandong Peninsula. However, the most important changes in seasonality are found in the first quartiles of the number of days of TCs affecting CI. While the extreme values of sustained winds all have decreasing trends, the extreme values of wind gusts are completely different not only among different orders of extreme values, but also among different subregions. However, the trends of extreme TC rainfall, namely the maximum storm precipitation and the maximum 1-h precipitation, are not significant. [ABSTRACT FROM AUTHOR]

Considering the differences between the Northeast China Cold Vortex (CV) and the Mid-Summer (MS) rainy period and their corresponding atmospheric circulations are comprehensively analyzed, and the objective identification methods of defining the annual beginning and ending dates of Northeast China CV and MS rainy periods are developed respectively. The annual beginning date of the CV (MS) rainy period is as follows. In a period from April to August, if daily regional mean precipitation ryi is larger than yearly regional mean precipitation R (or 2R) on a certain day, the station precipitation rs is larger than the station yearly mean precipitation 〈r〉 (or 2〈r〉) in at least 50% of stations in Northeast China, and this condition is satisfied in the following 2 (7) days, then this date is defined as the beginning date of the CV (MS) rainy period. While the definition of the ending date of the MS rainy period shows the opposite process to its beginning date. With this objective identification method, the multi-year average (1981–2010) beginning date of the CV rainy period is May 3, the beginning date of the MS rainy period is June 27, the ending day of the CV rainy period is defined as the day before the beginning date of the MS rainy period, and the ending date of the MS rainy period is August 29. Meanwhile, corresponding anomaly analysis at a 500-hPa geopotential height, 850-hPa wind, Omega and relative humidity fields all show that the definitions of the average beginning and ending dates of the CV and MS rainy periods have a certain circulation meaning. Furthermore, the daily evolution of the CV index, meridional and zonal wind index, etc. all show that these objectively defined beginning and ending dates of the CV and MS rainy periods have climate significance. [ABSTRACT FROM AUTHOR]