The Standardized Precipitation Evapotranspiration Index (SPEI) was computed based on the monthly precipitation and air temperature values at 609 locations over China during the period 1951–2010.Various characteristics of drought across China were examined including: long-term trends, percentage of area affected, intensity, duration, and drought frequency. The results revealed that severe and extreme droughts have become more serious since late 1990s for all of China (with dry area increasing by ∼3.72% per decade); and persistent multi-year severe droughts were more frequent in North China, Northeast China, and western Northwest China; significant drying trends occurred over North China, the southwest region of Northeast China, central and eastern regions of Northwest China, the central and southwestern parts of Southwest China and southwestern and northeastern parts of western Northwest mainly due to a decrease in precipitation coupled with a general increase in temperature. In addition, North China, the western Northwest China, and the Southwest China had their longest drought durations during the 1990s and 2000s. Droughts also affected western Northwest, eastern Northwest, North, and Northeast regions of China more frequently during the recent three decades. The results of this article could provide certain references and triggers for establishing a drought early warning system in China. © 2013 Royal Meteorological Society

Are droughts becoming more frequent or severe in China

Drought is one of the most complex and harmful natural disasters. A study on the temporal and spatial patterns and the evolution of drought can provide a scientific basis for predicting drought occurrences. Based on a multi-source dataset, we select a suitable control drought indicator for improving the vegetation health index (VHI), optimize its algorithm through Pearson correlation analysis, and compare the VHI performance before and after the improvement for various vegetation types. Results show that (1) the self-calibrated Palmer drought severity index is more suitable than the standardized precipitation evapotranspiration index for improving the VHI; (2) the contribution of the thermal condition index to the VHI in most parts of the world is higher than that of the vegetation condition index; (3) the enhanced VHI significantly improves the detection of vegetation drought; and (4) vegetation drought events occurring in high latitudes tend to worsen, and the response of different vegetation types to drought is significantly different. Our research presents a step forward in improving the effectiveness of the VHI in detecting vegetation drought and thus its application prospects. Furthermore, the response characteristics of various vegetation types to drought are identified, deepening our understanding of vegetation drought, which may help decision-makers and authorities to develop better mitigation and adaptation strategies to reduce losses caused by these events. 

Improving the drought monitoring capability of VHI at the global scale via ensemble indices for various vegetation types from 2001 to 2018

Global assessment of lagged and cumulative effects of drought on grassland gross primary production

Due to the complex coupling between phenology and climatic factors, the influence mechanism of climate, especially preseason temperature and preseason precipitation, on vegetation phenology is still unclear. In the present study, we explored the long-term trends of phenological parameters of different vegetation types in China north of 30°N from 1982 to 2014 and their comprehensive responses to preseason temperature and precipitation. Simultaneously, annual double-season phenological stages were considered. Results show that the satellite-based phenological data were corresponding with the ground-based phenological data. Our analyses confirmed that the preseason temperature has a strong controlling effect on vegetation phenology. The start date of the growing season (SOS) had a significant advanced trend for 13.5% of the study area, and the end date of the growing season (EOS) showed a significant delayed trend for 23.1% of the study area. The impact of preseason precipitation on EOS was overall stronger than that on SOS, and different vegetation types had different responses. Compared with other vegetation types, SOS and EOS of crops were greatly affected by human activities while the preseason precipitation had less impact. This study will help us to make a scientific decision to tackle global climate change and regulate ecological engineering.

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Long-Term Vegetation Phenology Changes and Responses to Preseason Temperature and Precipitation in Northern China

The complexity and randomness of drought events make its description difficult. Although previous studies have analyzed the characteristics of drought events in different regions, there are few studies to explore the influence of the selection of time intervals on the extraction of drought events. To make up for the deficiency of traditional drought event characteristic analysis, we compared and analyzed the drought event characteristics extracted at different time intervals (1, 5, 10, and all years). Additionally, a new drought event percentage area index was constructed based on the non-divided time method. The Mann–Kendall and Theil-Sen analysis methods were used to investigate its variation trend from 1960 to 2018. The results show that the shorter the time interval, the more significant the change in drought severity, but the more likely it is to separate a drought event, causing accuracy errors. Furthermore, the extraction of drought events with a short time interval tends to underestimate the time change of extreme drought and overestimate the time change of mild drought. Moreover, the non-divided method can more accurately extract the features of drought events. The drought event percentage index can effectively quantify the drought situation in different regions by introducing the spatial dimension’s description. The global drought event percentage index rose slightly from 1960 to 2018, with a slope of 0.026% per year. Finally, the drought event characteristic analysis methods adopted in this paper are flexible, effective, and simple, providing possible scientific references for other types of drought research.

Investigating the effect of improved drought events extraction method on spatiotemporal characteristics of drought

 The monthly standardized precipitation evapotranspiration index (SPEI) can
be used to monitor and assess drought characteristics with 1-month or
longer drought duration Based on data from 1961 to 2018 at 427
meteorological stations across mainland China, we developed a daily SPEI
dataset to overcome the shortcoming of the coarse temporal scale of monthly
SPEI Our dataset not only can be used to identify the start and end dates
of drought events, but also can be used to investigate the meteorological,
agricultural, hydrological, and socioeconomic droughts with a different timescales In the present study, the SPEI data with 3-month (about 90 d)
timescale were taken as a demonstration example to analyze spatial distribution
and temporal changes in drought conditions for mainland China The SPEI
data with a 3-month (about 90 d) timescale showed no obvious intensifying
trends in terms of severity, duration, and frequency of drought events from
1961 to 2018 Our drought dataset serves as a unique resource with daily
resolution to a variety of research communities including meteorology,
geography, and natural hazard studies The daily SPEI dataset developed is
free, open, and publicly available from this study The dataset
with daily SPEI is publicly available via the figshare portal (Wang et al,
2020c), with https://doiorg/106084/m9figshare12568280  Highlights A multi-scale daily SPEI dataset was developed across mainland China
from 1961 to 2018
The daily SPEI dataset can be used to identify the start and end days of the
drought event
The developed daily SPEI dataset in this study is free, open, and
publicly available

/pdf/a-multi-scale-daily-spei-dataset-for-drought-24yk06ow32.pdf

Jiang Cong

Papers

A multi-scale daily SPEI dataset for drought characterization at observation stations over mainland China from 1961 to 2018