In recent decades, under the global warming, drought disasters have had a significant impact on society and economy in China, and the intensity and disastrousness of droughts have significant regional characteristics. It is very important to understand the spatial and temporal characteristics of drought disasters and their associated economic losses for future drought loss estimation, regional drought disaster risk management, and drought resource allocation. Therefore, based on meteorological drought composite indexes from 1961 to 2022 and drought disaster loss data from 2001 to 2022 in China (except Hong Kong, Macau and Taiwan), the spatial and temporal changes of drought disasters and their periodic characteristics were deeply analyzed, and the correlation between drought disasters and economic losses in different provinces was explored. The results show that the drought intensity has interannual and interdecadal trends, the annual average drought intensity exists a two-year oscillation characteristic, and in the monsoon period, the drought intensity shows two significant change cycles of 9 years and 19 years. The drought intensity shows a distribution characteristic of strong in the south and weak in the north, the three strong drought centers in the south are located in the southwest, the middle of Huanghuai and the southeastern of South China. After 2000, the overall crop drought-affected area, the area with no harvest, the affected population and the overall direct economic losses in China show a decreasing trend, but in the northeast and southwest regions the direct economic losses are more prominent. The correlation between drought disasters and direct economic losses in different provinces is different. On the whole, southern regions are more affected by drought, especially in the central part of the Yangtze River Basin, where drought intensity is closely related to economic losses. In addition, the direct economic losses caused by drought in different regions are not only affected by drought intensity and frequency, but also related to crop planting area, drought resistance ability, population and environment.
Under climate warming, drought is still the most serious agro-meteorological disaster affecting maize production in Jilin Province. Accurately assessing drought risk and grasping the quantitative relationship between drought risk and yield could provide scientific reference for ensuring the safety of maize production. Based on the daily meteorological data, maize developmental stages and maize yield data from 1961 to 2020 in Jilin Province, the drought risk index of maize was constructed, its spatial distribution characteristics were analyzed. Moreover, the response relationship between relative meteorological yield and drought risk index was discussed. The result show that drought risk index of maize at each developmental stage decreased successively from northwest to southeast in Jilin Province. During maize growing season, drought risk was the highest at the stage from sowing to seedling, while it was the lowest at the stage from milking to maturing. Drought risk index had negative correlation with relative meteorological yield of maize. Furthermore, absolute value of correlation coefficient was the largest at the stage from tasseling to milking. The maximum comprehensive drought risk index was generally above 2.5 in the west, which might cause nearly 70% loss of maize yield. Besides, maximum comprehensive drought risk index in the middle was about 2.0, and disaster loss rate could reach 50%. In the western and central parts of Jilin Province, relationship between drought risk index from tasseling to milking and relative meteorological yield was a parabola going downwards, as well as the relationship between comprehensive drought risk index and relative meteorological yield. If comprehensive drought risk index was between 0.0 and 2.0, relative meteorological yield might be positive or negative. If comprehensive drought risk index was between 2.0 and 4.0, relative meteorological yield showed a downward trend, and disaster loss rate increased obviously.
Under the severe situation of global warming, regional high temperature and drought events are becoming more frequent, posing a major threat to ecological environment, food security, economic development and life and health. From April to June 2024, high-temperature and drought events occurred again in North China, Northwest China, and Southwest China, causing significant losses in agricultural production. This study utilized various data to preliminarily analyze the characteristics and causes of the high-temperature and drought processes in above three regions. The results show that the drought in southwest China mainly occurred in April, while the drought in North China and Northwest China began to emerge in April, with the intensity gradually increasing and the range expanding from May to June. With the intensification of drought, the abnormal range of regional maximum temperature expanded significantly. The number of hot days in Northwest China reached a new record, and the highest temperature anomaly reached its peak in May, which was one month ahead of the most severe drought period (June) in this region. The high temperatures in southwest China and North China were close to historical extremes. Further analysis indicates that the drought in North China is mainly influenced by the circulation in the Pacific region, while high temperatures are mainly affected by the circulation in the low-latitude Pacific and the Western Pacific Warm Pool. The drought in Northwest China is mainly influenced by the Western Pacific Subtropical High and the Arctic Vortex in the Northern Hemisphere, and the main influence on high temperatures comes from the North Atlantic. The factors affecting high temperatures and drought in the Southwest China are more complex, but mainly concentrated in the Northern Hemisphere Subtropical High and the low-latitude Pacific and Indian Oceans. From the perspective of circulation and water vapor, the main causes of the drought in North China and Northwest China are the development and maintenance of the continental high pressure, while the drought process in Southwest China is affected by the northward shift of the Western Pacific Subtropical High, which allows the dry and hot air currents from the Indian subcontinent to control this area, leading to water vapor divergence and ultimately causing high-temperature drought.
In order to study the variation trend of climatic characteristics of consecutive dry days (CDDS) in arid and semi-arid regions of China the variation characteristics of CDDS and their differences in the period of 1961-1990 and 1991-2020 in the study area were analyzed by using the daily precipitation data from 74 meteorological stations in arid and semi-arid regions of China from 1961 to 2022. The CDDS equal to 16 days and above were focused on, and the CDDS of 16 to 25 days, 26 to 40 days, 41 to 60 days and above 60 days were defined as partial drought, moderate drought, severe drought and extreme drought, respectively. The results show that there are significant differences in the occurrence times and days of CDDS for 16 days and above in arid and semi-arid climates in China. Especially, the occurrence times and days of CDDS corresponding to severe drought and extreme drought in arid regions are about twice times and six times of those in semi-arid regions, respectively. Compared with the period of 1961-1990, during 1991-2020, the frequency of meteorological drought with different grades in the western part of the study area decreased significantly, while it increased in the central and eastern parts of the study area. In the western part of the study area, the number of drought days with different grades also decreased obviously, the number of partial and moderate drought days decreased, and the number of severe and extreme drought days increased. The significance test of difference show that there was no mutation in the frequency and days of drought with different grades at most meteorological stations in the arid and semi-arid regions.
Analyzing the evolution of dry and wet in Guangdong Province is of great significance for strengthening water resource utilization and maintaining ecological environment stability. Based on evapotranspiration product of MODIS (Moderate Resolution Imaging Spectroradiometer) and meteorological observation stations data, choosing CWSI (Crop Water Stress Index) as the index of drought, Mann-Kendall (M-K) trend analysis and contribution methods were adopted to spatial-temporal distribution characteristics of CWSI as well as dominant meteorological factors. The results were indicated as follows: the annual CWSI indicated a downward trend through M-K trend test (-2.8×10-3 per year), season in year with the most significant downward trend was in winter (-7.0×10-3 per year), followed by autumn and spring, and the weakest was in summer. The annual CWSI was characterized by high (dry) in the southeast and low (wet) in the northwest. The CWSI in northern Guangdong, Pearl River Delta, and some areas in western Guangdong were at a lower degree of variation, while in Zhaoqing and the eastern coastal areas of Guangdong were relatively high. The CWSI in western Guangdong were all located at a lower degree of variation during the four seasons. The change of relative humidity was the overall dominant factor in the trend change of CWSI in Guangdong region, with spatial relative humidity being the dominant factor at 44.19% stations in Guangdong, followed by wind speed (22.09%), temperature (18.61%), and sunshine duration (15.11%).
