In summer 2014, north China and large areas of northeastern Asia (NCNEA) suffered from the most severe drought of the past 60 years. This study indicates that the East Asian summer precipitation in 2014 exhibited a tripole anomaly, with severe negative anomalies in NCNEA, strong positive anomalies in south China, South Korea, and Japan, and intense negative anomalies in the western North Pacific. Along with the severe tripole precipitation anomalies, there were strong intensities of the Silk Road pattern, the Pacific–Japan pattern, and the Eurasian teleconnection pattern, which were responsible for the strong precipitation anomaly in 2014 through changes to the western Pacific subtropical high (WPSH) and the East Asian trough. Further analysis indicates that the sea surface temperature (SST) in the North Pacific was nearly the warmest in the past 60 years and, together with the strong SST warming in the warm pool region, thus caused the strong Pacific–Japan teleconnection pattern, southward positioning of the WPSH, and weakened East Asian summer monsoon. Additionally, the summertime sea ice cover in the Arctic Ocean was anomalous, resulting in high SST in the Laptev–Kara Sea and, hence, triggering a strong Eurasian teleconnection pattern and contributing to the severe drought of NCNEA. Furthermore, the intense warming over the European Continent and Caspian Sea favored the Silk Road pattern, also contributing to the southward positioning of the WPSH and the NCNEA drought. The NCNEA severe drought was therefore the joint result of Pacific SST anomalies, Arctic sea ice anomalies, and warming over the European Continent and Caspian Sea.

基于1960—2016年黄土高原49个气象台站日最高气温和月降水数据,论文利用百分位高温阈值和标准化降水指标对黄土高原干旱和热浪时空变化特征进行了分析,识别并探讨了干旱和热浪同时发生事件的演变规律。结果表明：① 黄土高原热浪频次整体呈增加趋势,日高温热浪增加趋势最大,增速达到0.29次/a,1995年之后增加趋势更为明显,显著增加区域集中在山西东北部、青海省东部和甘肃中南部;② 1960—2016年黄土高原旱涝指数呈下降趋势,即表现为由涝转旱,20世纪90年代初为旱涝变化的转折点,年旱涝指数下降趋势显著区占整个研究区的62%,其中黄土高原沟壑区南部、陕北南部、山西南部、甘肃东部干旱趋势较为明显;③ 干旱和热浪同时发生事件总体呈现增加趋势,增速为0.66次/10 a,其中1960—1979年呈下降趋势,降速为-0.26次/a,1980—2002年呈增加趋势,2003年之后变化趋势较为平稳;空间上,山西东部、陕北南部和甘肃东南部发生频次较高,并且显著增加区主要位于山西东北部、甘肃中东部和宁夏北部。

Based on daily maximum temperature and monthly precipitation data of 49 meteorological stations on the Loess Plateau during 1960-2016 and using the 90th percentile of the temperature as extreme temperature thresholds and standardized precipitation index (SPI), this study examined the spatiotemporal variation characteristics of heatwaves and droughts and the dynamics of concurrent droughts and heatwaves across the Loess Plateau. The results show that: 1) The occurrence frequency of heatwaves presented an increasing trend on the Loess Plateau during the recent 57 years with a liner tendency of 0.29 times/a, of which a significant increasing trend was detected after 1995. The significantly increasing areas were mainly distributed in the northeast of Shanxi Province, eastern Qinghai Province, and southern and central Gansu Province. 2) Standardized precipitation index (SPI) showed a downward trend in the recent 57 years, indicating a trend from water-logging to drought, and the early 1990s was a turning point. Particularly, areas with the declining trend of SPI12 accounted for 62% of the whole study area, and regions with significant drought were mainly distributed in the south of the gully areas of the Loess Plateau, the southern part of Northern Shaanxi, the south of Shanxi Province, and the east of Gansu Province. 3) The simultaneous occurrence frequency of droughts and heatwaves showed an overall increasing trend, with a growth rate of 0.66 times/10 a. From 1960 to 1979 it showed a declining trend of -0.26 times/a, then an increasing trend of 0.52 times/a from 1980 to 2002, while a steady increasing trend was detected after 2003. Spatially, the high incidence of droughts and heatwaves was observed in the eastern of Shanxi, the south of Northern Shaanxi, and the southwest of Gansu; areas with increasing trend were mainly concentrated in the northeast of Shanxi, central and eastern Gansu, and northern Ningxia.

基于134个气象站点1960-2016年逐日最高温和相对湿度数据,辅以趋势分析、空间分析和相关分析等方法,对秦岭—淮河地区热浪时空变化特征进行分析,探讨了赤道东太平洋海温异常与热浪变化的相关关系。结果表明：①近57年秦岭—淮河地区热浪呈现“非线性、非平稳和阶段性”的变化过程,年代变化可分为3个阶段：1960-1972年热浪呈现东西分异,分界线大致位于112°E,以东地区热浪异常偏多,以西地区则“高低交替”波动;1973-1993年热浪维持“低位波动”,并在20世纪80年代中期呈现快速增加;1994-2016年,关中平原、秦巴山区、巫山山区和四川盆地热浪维持“高位波动”,黄河下游、淮河平原和长江下游热浪则经历从“相对偏多”向“相对偏少”的转变;②在影响因素方面,最高温波动变化是秦岭—淮河地区热浪频次年代变化的主导因素,相对湿度变化的影响相对较弱;③近57年来关中平原热浪年代变化与赤道太平洋西部海温异常关系更为密切,长江流域与东部海温异常关系更为密切;对于黄河下游和秦巴山区的热浪变化与不同分区赤道太平洋海温异常关系均较弱。

In the context of global warming, the likelihood of concurrent heat waves is expected to increase in most parts of China, which will have social and environmental impacts. However, heat wave characteristics are likely to vary regionally. Based on maximum daily temperature and relative humidity data from 134 meteorological stations for the 1960-2016 period, the spatiotemporal variation in heat waves was investigated for the Qinling-Huaihe region. We also analyzed the relationship between El Ni?o-Southern Oscillation (ENSO) and heat waves. We found that the heat waves in the past 57 years in the study region can be characterized as non-smooth and non-linear. Three distinct phases of decadal change were identified. During the first phase (1960-1972), with 112°E as the dividing line, heat waves were highly variable with alternating highs and lows in the western part of the region, but occurred at high frequency in the eastern part. During the second phase (1973-1993), heat waves showed low-amplitude fluctuations across the entire region, and rapidly increased in the mid-1980s. The third phase (1994-2016) saw high-amplitude fluctuations in heat waves in the western part of the region, but heat waves decreased in the eastern part. Our results show that over the entire region, the extremes in heat have been more sensitive to daily maximum temperature than regional relative humidity changes. Thus, the cooling of daily maximum temperature along the Huai River led to a decreasing heat wave spatial extent. There was also a notable difference in the relationship between ENSO and heat waves in the Qinling-Huaihe region: a strong positive correlation in the north and a weak negative correlation in the south were observed. Particularly, heat waves on the Guanzhong Plain have been closely related to Ni?o 4, whereas the relationship has been weak along the lower reach of the Yangtze River. The Ni?o 1+2 and Ni?o 3 indices showed significant negative correlations with heat waves across the lower reach of the Yangtze River. In the lower reach of the Yellow River and Qinling-Daba Mountains, the variations in heat waves have been weakly correlated with equatorial Pacific sea surface temperature anomalies. In addition, there has been more close relationship between temperature anomalies of equatorial Western Pacific and decadal variation of heat waves on the Guanzhong Plain in recent decades, which has contributed to enhanced warming on the Guanzhong Plain and along the lower reach of the Yangtze River.

利用1981-2013年长江中下游地区90个气象观测站的逐日气温和降水资料、NCEP/NCAR逐日再分析资料及ERSSTv4海温资料，对2013年夏季发生于长江中下游地区的异常高温干旱事件基本特征及其可能影响机制进行了讨论。结果表明：（1）降水量较同期偏少49.43%，7月中、下旬出现旱情并逐步发展，8月上、中旬旱情最为严重，整体呈现中到重旱，局部地区达到特旱，气温偏高5℃以上；（2）受负EAP/PJ（东亚太平洋型/东亚日本型）遥相关型影响，西太平洋副热带高压（下称西太副高）面积偏大、西伸脊点异常偏西、强度偏强，长期控制长江流域，是诱发此次高温干旱的直接成因；东亚夏季风偏强、副热带西风急流偏北，致使长江流域暖湿空气偏强而冷空气不足，加之下沉气流影响，不利于形成降水。（3）8月第1候至第2候，受负"Silk Road"（丝绸之路）遥相关型影响，源自北大西洋的Rossby波沿急流波导区向东频散至东亚-太平洋地区，加强了负EAP/PJ遥相关型中高纬度两个高度异常中心，对其形态的维持与发展起着重要作用，将西太副高的异常发展推向鼎盛时期；（4）西太平洋暖池区海温异常偏高是负EAP/PJ遥相关型长期维持的重要原因；而7月北大西洋海温异常偏高与西风急流异常偏北密切相关，是影响东亚季风系统各成员配置的又一可能成因。

Based on the daily temperature and precipitation data of 90 stations from 1981 to 2013 in the middle and lower reaches of Yangtze River (MLRYR) in China, the NCEP/NCAR daily reanalysis data and monthly NOAA Extended Reconstructed Sea Surface Temperature v4 (ERSSTv4) data, the general characteristics and effect mechanism of the continuous hot-dry weather occurred in MLRYR during the summer of 2013 had been investigated. The results were shown as follows:(1) The rainfall was less 49.43% than the historical average. A drought was started in the middle and last dekad of July and then developed gradually, the most severe drought was happened in the first and middle dekad of August while the whole MLRYR was caught in moderate to severe drought, some local areas of MLRYR were reached special drought with the daily mean temperature on the high side 5℃. (2) Affected by the negative phase of EAP (East Asia Pacific)/PJ (Pacific Japan) teleconnection, WPSH (western Pacific subtropical high) was larger, stronger and the position was westward than normal, controlled MLRYR for a long time, which was one of the most direct reasons for why the heat wave and drought happened. Because of the strong EASM (East Asian summer monsoon) and northward EASWJ (East Asian subtropical westerly jet), the warm-moist and cold-dry air did not match in MLRYR, combined with the descending motion effects, which was not conducive to the formation of precipitation. (3) By the influence of "Silk Road"teleconnection from August 1st to 2nd pentad, Rossby waves originated from the North Atlantic along the westerly jet stream waveguide dispersed to East Asia-Pacific region, enhanced two height anomaly centers at middle and high latitude of the negative phase of EAP/PJ teleconnection, which played an important role in the maintenance and development of its morphology, and prompted the abnormal development of the WPSH to the peak period. (4) The high SST anomaly in the warm pool of the Western Pacific is the main reason for the long-term maintenance of negative EAP/PJ teleconnection. While the anomalous high SST in the North Atlantic Ocean in July is closely related to the westerly jet anomaly, which is an another possible cause for the configuration of the East Asian monsoon system.

By deriving the discrete equation of the parameterized equation for the New Medium-Range Forecast (NMRF) boundary layer scheme in the GRAPES model, the adjusted discrete equation for temperature is obviously different from the original equation under the background of hydrostatic equilibrium and adiabatic hypothesis. In the present research, three discrete equations for temperature in the NMRF boundary layer scheme are applied, namely the original (hereafter NMRF), the adjustment (hereafter NMRF-gocp), and the one in the YSU boundary-layer scheme (hereafter NMRF-TZ). The results show that the deviations of height, temperature, U and V wind in the boundary layer in the NMRF-gocp and NMRF-TZ experiments are smaller than those in the NMRF experiment and the deviations in the NMRF-gocp experiment are the smallest. The deviations of humidity are complex for the different forecasting lead time in the three experiments. Moreover, there are obvious diurnal variations of deviations from these variables, where the diurnal variations of deviations from height and temperature are similar and those from U and V wind are also similar. However, the diurnal variation of humidity is relatively complicated. The root means square errors of 2m temperature (T2m) and 10m speed (V10m) from the three experiments show that the error of NMRF-gocp is the smallest and that of NMRF is the biggest. There is also a diurnal variation of T2m and V10m, where T2m has double peaks and V10m has only one peak. Comparison of the discrete equations between NMRF and NMRF-gocp experiments shows that the deviation of temperature is likely to be caused by the calculation of vertical eddy diffusive coefficients of heating, which also leads to the deviations of other elements.