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In this paper, the intensity, area and duration of future droughts in China are analyzed using the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI). The SPI and SPEI are used to evaluate the simulation ability of drought characteristics with the regional climate model COSMO-CLM (CCLM). The projected intensity and duration of future drought events are analyzed for the period 2016-2050 under three different respective concentration pathways (RCPs). The simulated and projected drought events are analyzed by applying the intensity-area-duration method. The results show that CCLM has a robust capability to simulate the average drought characteristics, while some regional disparities are not well captured, mainly the simulation of more drought events of shorter duration in Northwest China. For the future period 2016-2050, more intense dryness conditions are projected for China. An increase in evapotranspiration is found all over China, while a reduction in precipitation is apparent in the southern river basins. The increase in evapotranspiration plays an important role in the changes of future droughts over the northern river basins and southern river basins. Under RCP2.6, drought events of longer duration and with higher frequency are projected for the southwest and southeast of China. Under RCP4.5 and RCP8.5, a continuing tendency to more dry conditions is projected along a dryness band stretching from the southwest to the northeast of China. More frequent drought events of longer duration are projected in the southwestern river basins. For all future droughts, larger extents are projected, especially for events with long-term duration. The projected long-term drought events will occur more often and more severe than during the baseline period, and their central locations will likely shift towards Southeast China. The results of this study can be used to initiate and strengthen drought adaptation measures at regional and local scale, especially in the south of China. [ABSTRACT FROM AUTHOR]

In this study, the intensity, area, and duration of droughts in China are analyzed using the Standardized Precipitation Index (SPI). The SPI was calculated on monthly data for 530 meteorological stations in China for the period 1960-2013. The time series were analyzed for ten major hydrological regions of China, respectively. The relationships between the intensity and the area of droughts for a specific duration were analyzed by the intensity-area-duration method. The results show that areas with a significant trend in dryness can be found in a band reaching from the southwest to the northeast of China, while areas with significant trends in wetness are especially detected in the northern river basins in recent decades. In addition, for recent years (2000-2013), most of the ten major hydrological regions show opposite trends in the SPI when compared to the whole study period (1960-2013) except for the central and southwestern parts of China. This dryness/wetness trends are related to the intensity and duration of drought events, which have been stronger and lasted longer in the detected dryness band except for some northern river basins. A regional shift of drought centers is found from the northwest to the southeast within Central China. Moreover, a decreasing trend in drought area is observed, which might be related to the regional changes in precipitation pattern associated with the atmosphere-ocean interaction. Changes in the SST of the Tropical Pacific and the Tropical Indian Ocean may have resulted in frequent severe drought events of small areal extent in the central and southwestern parts of China. For the study period, the most severe droughts that covered large areas mainly occurred in the north and west of China during the mid-to-late twentieth century. However, in the early twenty-first century, the most severe droughts were located in the southwest of China covering areas less than 0.7 million km. Conclusively, drought areas show a decreasing tendency, while more intense droughts of longer duration have been experienced, especially in the south of China, in the last decades. [ABSTRACT FROM AUTHOR]

Time series of the average annual Palmer drought severity index (PDSI) and standardized precipitation index (SPI) were calculated for 483 meteorological stations in China using monthly data from 1961 to 2005. The time series were analyzed for 10 large regions covering the territory of China and represented by seven river basins and three areas in the southeast, southwest, and northwest. Results show that the frequencies of both dry and wet years for the whole period are lower for southern basins than for the northern ones when estimated by PDSI but very similar for all basins when calculated by SPI. The frequencies of dry and wet years calculated for 5- and 15-yr subperiods by both indices show the upward dry trends for three northeastern basins, Songhuajiang, Liaohe, and Haihe; a downward dry trend for the northwest region; a downward wet trend for the Yellow River basin; and an upward wet trend for the northwest region. Trend detection using PDSI indicates statistically significant negative trends for many stations in the northeastern basins (Songhuajiang, Liaohe, Haihe, and Yellow) and in the middle part of the Yangtze, whereas statistically significant positive trends were found in the mountainous part of the northwest region and for some stations in the upper and lower Yangtze. A moderately high and statistically significant correlation between the percentage of runoff anomaly (PRA) and the annual average PDSI and SPI was found for six large rivers. The results confirm that PDSI and SPI indices can be used to describe the tendency of dryness and wetness severity and for comparison in climate impact assessment. [ABSTRACT FROM AUTHOR]

Based on the daily observational precipitation data at 147 stations in the Yangtze River Basin during 1960–2005 and projected daily data of 79 grid cells from the ECHAM5/ MPI-OM model in the 20th and 21st century, time series of precipitation extremes which contain AM (Annual Maximum) and MI (Munger Index) are constructed. The distribution feature of precipitation extremes is analyzed based on the two index series. Three principal results were obtained, as stated in the sequel. (i) In the past half century, the intensity of extreme heavy precipitation and drought events was higher in the mid-lower Yangtze than in the upper Yangtze reaches. Although the ECHAM5 model still can’t capture the precipitation extremes over the Yangtze River Basin satisfactorily, spatial pattern of the observed and the simulated precipitation extremes are much similar to each other. (ii) For quantifying the characteristics of extremely high and extremely low precipitation over the Yangtze River Basin, four probability distributions are used, namely: General Extreme Value (GEV), General Pareto (GPA), General Logistic (GLO), and Wakeby (WAK). It was found that WAK can adequately describe the probability distribution of precipitation extremes calculated from both observational and projected data. (iii) Return period of precipitation extremes show spatially different changes under three greenhouse gas emission scenarios. The 50-year heavy precipitation and drought events from simulated data during 1951–2000 will become more frequent, with return period below 25 years, for the most mid-lower Yangtze region in 2001–2050. The changing character of return periods of precipitation extremes should be taken into account for the hydrological design and future water resources management. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated future changes of dryness/wetness in ten large river basins: the Songhuajiang River basin, the Liaohe River basin, the Haihe River basin, the Yellow River basin, the Huaihe River basin, the Yangtze River basin, the Pearl River basin, the Southeast River basins, the Southwest River basins and the Northwest Inland River basins across China during the first 50 years of the 21st century. The study was carried out according to the Standardized Precipitation Index (SPI), which is calculated by monthly precipitation data of ECHAM5/MPI-OM. Three anthropogenic greenhouse gas emission scenarios, SRES-A2, SRES-A1B and SRES-B1 have been considered. The frequency of dry/wet periods in these river basins was calculated and the trend detected by the Mann–Kendall non-parametric test. The results reveal that there is a trend towards drier conditions from northeast to southwest China in scenario A2 and a similar spatial distribution pattern in scenario A1B and B1. Areas with a high frequency of drought are detected under all three scenarios. In the next half century, the Haihe River basin, northeast China, is expected to show a significant trend towards drier conditions, which pass the 95% confidence level in scenario A2. In the Yellow River basin, the Huaihe River basin, the Yangtze River basin and the Pearl River basin, an obvious trend towards wetter conditions has been detected in scenario A1B. The Songhuajiang River basin, the Haihe River basin, the Yellow River basin and the Huaihe River basin show a trend towards wetter conditions, which passed the 90% confidence level in scenario B1. The future dryness/wetness frequency situation is complex in the ten large river basins. [ABSTRACT FROM AUTHOR]

Droughts reflect the extent of water deficit on the land surface, and can be quantified by various indices. In current study, potential evapotranspiration (PET), which is one of factors that have great influence on the drought condition, is estimated by a set of models. The set consists of four temperature-decisive models (Hamon, Hargreaves-Samani, Oudin, Thornthwaite), two radiation-decisive models (Energy-Only and Priestley-Taylor) and two synthesis models (Penman and Penman-Monteith). Subsequently, Standardized Precipitation Evapotranspiration Index (SPEI) is applied to assess the spatial and temporal distributions of droughts for the arid, the semi-arid and semi-humid, as well as the humid climatic zones in China for 1961–2017. The results show that: (1) Taking China as a whole, annual PET estimated by Penman-Monteith (P-M) formula is about 1000 mm, which is in the middle of the range of results from eight algorithms. Annual PET values estimated by radiation-decisive methods are relatively close to those obtained by P-M, while temperature-decisive methods yield lower values and the largest disparity among the different PET models can be up to 2.5 fold. (2) Comparing to drought records, both P-M and Thornthwaite are suitable for assessing drought condition on the national scale, but the drought assessed by the Thornthwaite method is worse than that by the P-M method in 1990–2017 when warming is faster than before in the arid region. (3) Increase first and then decrease of values of the SPEI index are detected in China for 1961–2017 by all PET estimations. Averaged over entire China, the wetting trend has changed to drying in the early 1990s by P-M-based SPEI. More meteorological stations are found to experience droughts after the early 1990s, particularly in the western humid region and the central semi-arid and semi-humid region. In contrast, a wetness tendency is found in the arid region. (4) Patterns of the drought frequency and duration by all PET algorithms maintain relatively good correspondence in the semi-arid and semi-humid region as well as the humid region. But in the arid region, drought frequency obtained by P-M is lower than for radiation-decisive and temperature-decisive models, while drought duration is longer. • Eight algorithms clustered into three groups are used to estimate potential evapotranspiration (PET) for China in 1961–2017. • A wetness trend is detected by synthesis and radiation-decisive models based SPEI, while getting drier by temperature-decisive models in the arid region. • A case study in China shows that choice of potential evapotranspiration formulas influences largely on drought assessment. [ABSTRACT FROM AUTHOR]