Spatio-temporal characteristics of compound high temperature and drought events during critical rice growth periods in Sichuan Province based on the Copula function

doi:10.11755/j.issn.1006-7639-2026-02-0175

Abstract

Abstract:

Under global warming, compound events of heat and drought pose a far greater threat to agricultural production than individual extremes. Based on daily precipitation and maximum temperature data from 92 meteorological stations in Sichuan Province druing 1981-2022, this study employed the Standardized Precipitation Evapotranspiration Index (SPEI) and the Standardized Temperature Index (STI) to characterize drought intensity and high temperature intensity， respectively. A joint probability distribution model of heat and drought intensities was constructed using the Copula function, and the spatiotemporal characteristics of compound heat-drought events during the critical rice growth periods (booting-heading and heading-maturity) were analyzed systematically. The results indicated that: 1) The Generalized Extreme Value (GEV) distribution was identified as the optimal marginal distribution for both drought intensity and heat intensity at most stations across the two growth stages, with better goodness-of-fit observed at the booting-heading stage than the heading-maturity stage. 2) The Gumbel Copula was selected as the optimal joint distribution model for the majority of stations, revealing a tendency for heat and drought events to occur in tandem. 3) In the seven rice-planting subregions, compound events characterized by mild heat and mild drought exhibit the highest occurrence probability, with joint return periods ranging from 9 to 20 years during the booting-heading stage. Spatially, the central Sichuan Basin, southern Sichuan Basin, and basin peripheral areas are high-frequency regions. The booting-heading stage was the critical growth period with a higher occurrence probability of compound stress. 4) Compared with the period 1981-2000, both the frequency and intensity of compound heat-drought events increased across all seven rice-planting subregions during 2001-2022, and the increases in heat frequency and intensity were more pronounced than drought. In summary, over the past two decades, the risk of compound heat-drought events during the rice growth period in Sichuan Province has intensified, with heat-related risk rising at a particularly rapid rate.

Key words: Sichuan, critical growth period of rice, high temperature, drought, compound event, Copula function

摘要：

在全球气候变暖背景下，高温与干旱复合事件对农业生产的危害远超过单一灾害。基于四川省92个气象站1981—2022年逐日降水量和最高气温数据，结合标准化降水蒸散指数和标准化温度指数，利用Copula函数构建高温与干旱强度的联合概率分布模型，系统分析水稻关键生育期（孕穗—抽穗期、抽穗—成熟期）高温干旱复合事件的时空特征。结果表明：1）在大部分站点中，广义极值分布（Generalized Extreme Value，GEV）是水稻两个生育期内干旱强度和高温强度的最优边际分布，且孕穗—抽穗期的拟合度优于抽穗—成熟期；2）Gumbel Copula被选为大部分站点最优的联合分布模型，揭示高温与干旱事件存在协同发生倾向；3）在7个水稻种植区中，轻度高温叠加轻度干旱的复合事件发生概率最高，联合重现期为9~20 a（孕穗—抽穗期）。空间上，盆中、盆南、盆周等区域为高频区，孕穗—抽穗期是复合胁迫发生概率更高的关键生育期；4）与1981—2000年相比，2001—2022年7个水稻种植区高温干旱复合事件频率及强度均呈增加趋势，且高温频率与强度的增幅均高于干旱。近20 a来，四川省水稻生育期内高温干旱复合事件风险正在加剧，高温风险正在快速累积。

关键词: 四川, 水稻关键生育期, 高温, 干旱, 复合事件, Copula函数

CLC Number:

P466
S16

PU Changlin, CHEN Dongdong, ZHANG Yufang, WANG Xiaodong, ZOU Yujia. Spatio-temporal characteristics of compound high temperature and drought events during critical rice growth periods in Sichuan Province based on the Copula function[J]. Journal of Arid Meteorology, 2026, 44(2): 175-188.

蒲长林, 陈东东, 张玉芳, 王晓东, 邹雨伽. 基于Copula函数的四川水稻关键生育期高温干旱复合事件时空特征分析[J]. 干旱气象, 2026, 44(2): 175-188.

Figures/Tables 13

Fig.1 Spatial distribution of rice planting regions （the color shaded） and 92 meteorological stations （dots） in the study area

Tab.1 The time division of key rice growth stages in different regions of Sichuan Province

区域	孕穗—抽穗	抽穗—成熟
川西南宽谷	7月21日—8月10日	8月11日—9月10日
川西南山地	7月21日—8月10日	8月11日—9月10日
盆南	7月1—10日	7月11日—8月10日
盆西	7月21日—8月10日	8月11日—9月10日
盆中	7月21—31日	8月1日—9月10日
盆东	7月21日—8月10日	8月11—31日
盆周	7月21日—8月20日	8月21日—9月30日

Tab.2 Classification criteria for high temperature and drought intensity levels

干旱或高温强度	SPEI	STI
轻度	-1.0<SPEI≤-0.5	0.5≤STI<1.0
中度	-1.5<SPEI≤-1.0	1.0≤STI<1.5
重度	SPEI≤-1.5	STI≥1.5

Fig.2 Statistics of annual average intensity grades of high temperature (a, b) and drought (c, d) during the booting-heading (a, c) and heading-maturity (b, d) stages in different rice planting regions of Sichuan Province from 1981 to 2022

Fig.3 Spatial distribution of cumulative occurrence frequency of compound high temperature and drought events during the booting-heading (a) and heading-maturity (b) stages in rice planting regions of Sichuan Province from 1981 to 2022 (Unit: times)

Fig.4 Cumulative occurrence frequency of high temperature (a) and drought (b) in different rice planting regions, growth stages and periods in Sichuan Province from 1981 to 2022

Fig.5 Fitted curves of the optimal marginal distributions of SPEI (a) and STI (b) during the booting-heading stage of rice at Xuyong Station from 1981 to 2022

Fig.6 Spatial distribution of optimal marginal distribution functions of SPEI (a, c) and STI (b, d) during the booting-heading (a, b) and heading-maturity (c, d) stages in rice planting regions of Sichuan Province from 1981 to 2022

Fig.7 Spatial distribution of optimal Copula functions of high temperature and drought intensity during the booting-heading (a) and heading-maturity (b) stages in rice planting regions of Sichuan Province from 1981 to 2022

Fig.8 Joint cumulative probability (a, c) and corresponding return period (b, d) of SPEI and STI during the booting-heading (a, b) and heading-maturity (c, d) stages of rice at Xuyong Station from 1981 to 2022 (Black dots represent compound high-temperature and drought events)

Fig.9 The cumulative distribution functions and their 90th percentiles (Q90) of high temperature and drought intensity in different rice planting regions of Sichuan Province during different growth stages and periods

Fig.10 Spatial distribution of the combined recurrence periods of high temperature and drought with different grades during the booting-heading stages in rice planting regions of Sichuan Province （Unit： a）

Fig.11 Spatial distribution of the combined recurrence periods of high temperature and drought with different grades during the heading-maturity stages in rice planting regions of Sichuan Province （Unit： a）

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