the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Jul 2025
China's Three Major Cereal Crops Exposure to Compound Drought and Extreme Rainfall Events
Abstract. Under the backdrop of global climate change, the increasing intensity and frequency of anomaly climate events have led to a rise in compound extreme events. China's large population exacerbates the pressure of agricultural production, and compound drought and extreme rainfall events (CDER) can cause considerable damage to soil structure, thereby disrupting normal agricultural activities. Previous studies have revealed the impacts of the individual event, but the spatiotemporal characteristics of CDER and their effects on agricultural production remain obscure. This study focuses on compound disaster events in China's nine major agricultural regions, where drought and extreme rainfall events occur within 5 days. The results show that compound disasters are mainly concentrated in the northwest, southwest, and northern regions. The impact area of compound disasters is largest in summer, and the frequency and intensity of drought-rainfall events are higher than those of rainfall-drought events. Further analysis at the crop growth stage scale reveals the exposure of the three major cereal crops (rice, wheat, and maize) during their growth stage. The study reveals that maize generally has the highest and most variable disaster risk, rice has the lowest risk with minimal fluctuations, and wheat has moderate risk with large variations. The risk evolution in each agricultural region follows a universal pattern of "first rising and then declining", with the peak occurring around 2010. This study elucidates the spatiotemporal distribution patterns of this novel compound disaster and provides constructive insights for disaster prevention and mitigation through more refined risk assessments.
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RC1: 'Comment on egusphere-2025-2732', Anonymous Referee #1, 18 Jul 2025
The manuscript provides a timely and valuable contribution by assessing the exposure of China's three major cereal crops to Compound Drought and Extreme Rainfall Events (CDER) from a crop growth-stage perspective. By integrating high-resolution spatial data with phenological information, the authors reveal the spatiotemporal patterns and crop-specific risks of CDER across nine key agricultural regions. The use of a dual-index method—combining standardized soil moisture and percentile-based rainfall thresholds—represents a methodological advancement, and the focus on dynamic exposure trends fills a critical gap in current agricultural disaster risk research. The findings have important implications for climate-resilient agricultural planning and disaster mitigation.Here are my questions and suggestions:
- Keyword Correction: I noticed that the manuscript refers to “crop maturity exposure” as a keyword, whereas the study itself clearly focuses on the growth stage of crops when assessing exposure. This appears to be a terminology error and should be corrected for consistency and accuracy.3. Writing Format Details: A few stylistic and formatting issues should be addressed: On line 57, there is an unnecessary dash (“-”) that should be removed. After the first appearance of “Compound Drought and Extreme Rainfall Events” and its acronym CDER, the full term should not be repeatedly spelled out. CDER should be used throughout the manuscript for conciseness and clarity.5. Justification of Growth Stage Lengths (Page 8, Line 181): The manuscript states that “we select 130 days for maize, 100 days for rice, 300 days for winter wheat, and 100 days for spring wheat.” This assignment of growth stage lengths lacks explanation. The authors should provide a rationale or cite appropriate agronomic references to justify these durations, as they play a critical role in exposure calculation.
- 4. Figure 4 Legend Clarification: The figure title for Figure 4 should clearly indicate what the yellow and blue colors represent, as this is currently unclear to the reader.
- 2. Figure Formatting: In Figures 3 and 7, the subplots are labeled using uppercase letters (A, B, C, D). To maintain consistency and follow standard formatting conventions, I recommend converting these to lowercase letters with parentheses, i.e., (a), (b), (c), (d), etc., to avoid unnecessary confusion.
Citation: https://doi.org/10.5194/egusphere-2025-2732-RC1 -
AC1: 'Reply on RC1', Hanming Cao, 22 Jul 2025
Response to Comment 1:
(1) We have corrected the issues related to keyword details.
(2) We have fixed the spelling error at line 57 as you pointed out.
(3) We have standardized the abbreviation format for “Compound Drought and Extreme Rainfall Events.”
(4) We provide the following explanation regarding the selection of the crop growth periods:The distribution of different varieties of the three major cereal crops across China is relatively extensive. Therefore, it is not feasible to represent the growth period of each crop type by selecting a single representative variety; instead, multiple data sources need to be collected and weighed comprehensively.
For rice, the average growth period of the late rice in double-cropping systems used in this study is approximately 88 days (Liu et al., 2018), and around 117 days (Li et al., 2011). Ultimately, this study adopts a growth period of 100 days for rice.
For maize, the major varieties cultivated in China and their respective growth periods investigated in this study are as follows: Xianyu 335 (Zea mays L. cv. Xianyu335), approximately 130 days; Demeiya 1 (Zea mays L. cv. Demeiya1), approximately 110 days; Denghai 605 (Zea mays L. cv. Denghai605), ranging from 100 to 130 days; Longping 206 (Zea mays L. cv. Longping206), approximately 101 days; Jindan 1771 (Zea mays L. cv. Jindan1771), approximately 125 days; Gaonong 1206 (Zea mays L. cv. Gaonong1206), approximately 129 days; Shanyu 580 (Zea mays L. cv. Shanyu580), approximately 130 days; Tianyu 219 (Zea mays L. cv. Tianyu219), approximately 129 days. Taking these into account, this study uses 130 days as the growth period for maize.
Regarding spring wheat, the book Chinese Wheat Cultivation (Jin, 1961) indicates that the growth period of spring wheat generally exceeds 100 days, with the shortest around 80 days and the longest reaching approximately 190 days. The growth period of winter wheat typically exceeds 240 days, and can reach over 350 days in regions such as Linzhi, Tibet. Therefore, this study adopts a growth period of 100 days for spring wheat and 300 days for winter wheat.
Reference
Liu, Y., Chen, Q., Ge, Q., and Dai, J.: Spatiotemporal differentiation of changes in wheat phenology in China under climate change from 1981 to 2010, Sci. Sin.-Terrae, 61, 888–898, https://doi.org/10.1360/N072017-00100, 2018. (in Chinese)
Jin, S.: Chinese Wheat Cultivation, China Agriculture Press, 1961. (in Chinese)
Response to Comment 2:
We have added the relevant explanation.Response to Comment 3:
We have revised the figure accordingly to address this graphical detail.Citation: https://doi.org/10.5194/egusphere-2025-2732-AC1
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RC2: 'Comment on egusphere-2025-2732', Anonymous Referee #2, 22 Jul 2025
This study investigated the spatial-temporal variations of compound drought and extreme rainfall events in China, and quantified the exposure of three major cereal crops to these compound events. The assessment provides a significant contribution to the understanding of compound event risk given its dynamic and crop growth-stage perspective. Moreover, this study uses soil moisture data to monitor compound events from an agricultural perspective, which represents a methodological novelty. While, it can be further improved:
1. Section 2.3.1, it is not clear how the standardized soil moisture index (SSMI) was defined in this study. Also, how are the extreme rainfall events standardized?
2. Lines 249-254, the statements are not consistent with Fig.5 &6. For example: “CDERdr showed no significant trend in C7 and C8”, while it has significant decreasing trend in Fig.5.
3. Fig.7, the label for the subplot in the caption are not consistent with the figure (“A1, A2, A3, B1, B2, B3” V.S. “A, B, C, D, E, F”).
4. Lines 380-382 and Lines 393-395, the reference for these studies should be provided.
5. The inconsistent variations of planting area and crop exposure in Fig. 8, 9, &10 needs more discussions and explanations.
Citation: https://doi.org/10.5194/egusphere-2025-2732-RC2 -
AC2: 'Reply on RC2', Hanming Cao, 22 Jul 2025
Response to Comment 1:
For drought events, this study first applies a moving average with a window size of 7 to smooth the data. Subsequently, soil moisture data for the same period in historical records are standardized, and values below -σ were identified as drought events. The absolute value of these standardized anomalies is defined as drought intensity. For extreme rainfall, all extreme rainfall events within the same region are standardized and uniformly shifted to be greater than zero. The resulting values are used to represent extreme rainfall intensity.
Response to Comment 2:
Due to our oversight, some figures and tables in the manuscript were mistakenly uploaded using an earlier version in which drought events were defined differently, resulting in inconsistencies in the conclusions. This issue has been corrected in the revised manuscript, and a comprehensive check has been conducted.
Response to Comment 3:
We have revised the details of the figures as requested.
Response to Comment 4:
We have added the relevant references.
Response to Comment 5:
Simultaneously, It is noteworthy that the exposure of C3, C6, and C9 rose in lockstep with the expansion of maize-cultivated area. By contrast, although the cultivated areas of C1, C2, C4, C5, C7, and C8 increased steadily from 2000 to 2019, their exposure did not exhibit a sustained upward trajectory; rather, it generally peaked around 2009 and subsequently declined, revealing marked differences in trend. These patterns indicate that maize exposure is governed chiefly by intrinsic factors—such as the frequency of hazardous events—while the influence of cultivated area, though present, is comparatively modest.
Meanwhile, it is noteworthy that the exposure of C7, C8, and C9 changes in lockstep with the rice‑planted area. In particular, although the rice‑planted area in C4 has increased, its exposure has shown a consistently declining trend, revealing distinct differences among the trajectories. These findings indicate that rice exposure is strongly influenced by intrinsic factors such as event frequency, yet the planted area also exerts a substantial effect. This may be attributable to the relatively stable frequency and intensity of events in rice‑growing regions, which accentuates the impact of changes in planted area.
At the same time, the relationship between wheat exposure and its planted area proves to be relatively complex. Specifically, the exposure of C3, C8, and C9 increases in tandem with expansions in planted area, whereas in C2, C4, C5, C6, and C7 the planted area remains essentially stable while exposure fluctuates markedly, showing no comparable trend. Particularly noteworthy is C1, where the planted area varies substantially, yet exposure has consistently remained at an extremely low level. These findings suggest that wheat exposure is governed primarily by intrinsic factors—such as the frequency of hazardous events—while planted area, though influential to some extent, plays a comparatively minor role.
Citation: https://doi.org/10.5194/egusphere-2025-2732-AC2
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AC2: 'Reply on RC2', Hanming Cao, 22 Jul 2025
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RC3: 'Comment on egusphere-2025-2732', Anonymous Referee #3, 28 Jul 2025
This is an interesting paper addressing a subject of significant agricultural importance. A basic criticism is that it is short of meteorological insight into the compound drought extreme rainfall events that can be highly damaging to agriculture. To assist readers in their meteorological comprehension of this compound risk, it would be instructive if the authors could provide some salient historical examples of drought/extreme rainfall, and the specific impact on rice, wheat and maize. In particular, the geographical extent of crop impact should be detailed. What are the largest areas affected by a compound event? It would then be informative if some comment could be made on the increasing likelihood of such key events in the future changing climate.
Citation: https://doi.org/10.5194/egusphere-2025-2732-RC3 -
AC3: 'Reply on RC3', Hanming Cao, 29 Jul 2025
1.The largest areas affected by a compound event
In 2011, China's middle-lower Yangtze River basin experienced an abrupt hydrological shift from prolonged drought to extreme flooding. After suffering the most severe drought in sixty years during winter and spring, the region was struck by four successive heavy rainfall events in June, resulting in catastrophic flooding. The most severe impacts occurred in Jiangxi Province, where approximately three million people were affected and agricultural losses reached 90,400 hectares (Deng and Chen, 2013). The most widely cultivated rice variety in the region is considered highly sensitive to extreme precipitation events. Over the past two decades, extreme rainfall has reduced China's rice production by one-twelfth (Fu et al., 2023).
2.some salient historical examples of CDERAmong the three crops, the exposure risk of maize and wheat covers a broader national extent, being widely distributed across all regions. Region C4 exhibits exposure risk that is markedly higher than in any other region, followed by C5 and C8, where the risk is chiefly concentrated on the North China Plain. A notable distinction between the two cereals is that maize exposure risk is comparatively elevated in C8, whereas wheat exposure risk in the same region remains relatively low. Owing to its geographically restricted cultivation zone, rice shows exposure risk only in C4, C7, C8, and C9; among these, region C7 registers the highest risk, and the areas of heightened risk are mainly situated in the middle reaches of the Yangtze River and the Pearl River Basin.
3.Some comment on the increasing likelihood of such key events in the future changing climate.
Under the context of global climate change, the likelihood of increased CDER events in the future is extremely high. This assessment is primarily based on the following scientific understanding: global warming enhances atmospheric water-holding capacity, making extreme rainfall events more frequent, while rising temperatures intensify soil moisture evaporation, making droughts more severe, forming a polarization trend of "wet gets wetter, dry gets drier"; the spatiotemporal heterogeneity of precipitation in China's monsoon climate zone is further exacerbated, and the instability of summer monsoons increases the possibility of alternating extreme events. Recent studies indicate that compound extreme events will significantly increase globally, with the occurrence rate of related events potentially increasing by 20-40% by mid-century (Steensen et al., 2025). In response to this trend, the following recommendations are proposed: improve CDER monitoring and early warning systems based on soil moisture, with priority coverage of high-risk areas such as northwest, southwest, and northern China; accelerate the breeding of crop varieties resistant to both drought and waterlogging dual stresses and promote precision agriculture technologies; innovate agricultural insurance and regional risk-sharing mechanisms; integrate compound extreme events into national climate adaptation strategies and formulate forward-looking policies to ensure long-term food security.
References
Deng Y. and Chen X.: Effects of Drought floods Abrupt Alternation on Growing Development of Rice and Consideration for Related Issues, Biol. Disaster Sci., 36, 217–222, 2013.
Fu, J., Jian, Y., Wang, X., Li, L., Ciais, P., Zscheischler, J., Wang, Y., Tang, Y., Müller, C., Webber, H., Yang, B., Wu, Y., Wang, Q., Cui, X., Huang, W., Liu, Y., Zhao, P., Piao, S., and Zhou, F.: Extreme rainfall reduces one-twelfth of China’s rice yield over the last two decades, Nat. Food, 4, 416–426, https://doi.org/10.1038/s43016-023-00753-6, 2023.
Steensen, B. M., Myhre, G., Hodnebrog, Ø., and Fischer, E.: Future increase in European compound events where droughts end in heavy precipitation, Npj Clim. Atmospheric Sci., 8, 267, https://doi.org/10.1038/s41612-025-01139-0, 2025.
Citation: https://doi.org/10.5194/egusphere-2025-2732-AC3
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AC3: 'Reply on RC3', Hanming Cao, 29 Jul 2025
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