Changes of Extreme Agro-Climatic Droughts and Their Impacts on Grain Yields in Rain-Fed Agricultural Regions in China over the Past 50 Years

Min Liu,Ying Guo,Jing Hao,Yanfang Wang

doi:10.3390/atmos13010004

Abstract

Climate change and climate extremes and their impacts on agriculture, water resources, and ecosystems have become important issues globally. Agricultural sustainability and food security are facing unprecedented challenges due to the increasing occurrence of extreme climatic events, including, notably, extreme droughts in recent years in China. In this study, a threshold determination model of extreme agro-climatic droughts (EADs) was built based on the cumulative probability distribution functions (CDF) of an agricultural drought index—the consecutive days without available precipitation (CDWAP). The CDWAP was established by combining meteorological data with the characteristics of cropping patterns and the water requirement in different growing periods of crops. The CDF of CDWAP was obtained based on the relationship of CDWAP and its occurrence frequency. Based on the model, the spatial pattern of the thresholds of EADs and the threshold exceedance time series of EADs in 500 meteorological stations were obtained, and then changes in the frequencies and intensities of EADs in China and their impacts on grain yields in rain-fed regions during the past 50 years were analyzed. The results follow: (1) The threshold value of EADs in China gradually increased from southeast to northwest. The stations of the highest value were located in the Northwest China, with the CDWAP more than 60 days, while the lowest value was in the middle reaches of the Yangzi River, with the CDWAP less than 16 days. (2) The frequencies and intensities of the EADs increased mostly in the east areas of the Hu Huanyong line, which was also the main agricultural production region in China. The North China (NC) and Southwest China (SW) regions showed the highest increasing rates of the EADs; their frequencies and intensities were 11.3% and 2.2%, respectively, for the NC region, and 9.3% and 2.7%, respectively, for the SW region. (3) Case studies in the NC, SW, and SE regions indicated that there was a negative correlation between grain yields and EAD frequency and intensity; i.e., the low grain yields often occurred in the year with relatively higher frequency or/and stronger intensity of EADs. The correlation coefficients of grain yield and EAD were generally greater than that of merely extreme climatic droughts; therefore, the study of EAD is necessary when researching the impacts of extreme drought events on grain yield.

Highlights

According to the Fifth Assessment Report of the Intergovernmental Panel on ClimateChange (IPCC), climate extremes are occurring worldwide at a rapidly increasing rate in an enlarged scope during the 21st century [1]
Sepxatoiafl–CTeDmWporAalPP,atwterhniloef EEADD tVharrieastihonold was determined by consecutive dry days fromOnthceethpeetrhsrpesehcotlidvweaosfdecfilinmeda,ttohleotghrye.shTohldeeExcDeedthanrceeshtimoledsearliessowaads oesptitmedatetdhteo corresp oavsbattlahuieneiEnoAdfDetxhi.neFd9oic5retsthh. eFpoiner rttehcneesnfirtteyiqlouefeonEfcAytDhofe, EwcAueDmch, wuosleeattotihovekeathpnenrtouimablaembs oialfxittihmyeuidrmiasntcnroiunbasuleocticuoctuinvrerfeudnnrcyection of days without available precipitation (MCDWAP) as the index instead of the average intensity of threshold exceedance due to the average consecutive days without available precipitation (CDWAP) may weaken the meaning of the ”extremes”
The relative change rates of the extreme agro-climatic droughts (EADs) frequencies and intensities in the four regions of Northeast region (NE), North China (NC), SC, and WC were positive in the research period (Table 3), and the increasing change rates of frequency were obviously greater than that of intensity

Summary

Introduction

According to the Fifth Assessment Report of the Intergovernmental Panel on ClimateChange (IPCC), climate extremes are occurring worldwide at a rapidly increasing rate in an enlarged scope during the 21st century [1]. The climate models predict that the global water cycle will strengthen under the accelerating global warming, with more frequently occurring and intensified climate extreme events in many areas globally, both in extreme precipitation and extreme drought [2]. This has attracted the worldwide attention of the scientific community, governments, and the public. The occurrence of droughts accounted for about one-third of the total five types of climate disasters (droughts, floods, typhoons, freezing, and dry–hot winds) in China during 1949–2005, with droughts ranked first among various climate disasters [5]. Zhang et al (2014) concluded that drought was the most frequent disaster during 1991–2009, with the highest proportion, 79%, among all the agro-meteorological disasters [6]

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Methods

Results

Conclusion