With the intensification of global warming, different regions face constantly changing hydroclimatic conditions, which brings significant uncertainty in the assessment of drought-wetness under the backdrop of global warming and the study of drought. events. The core zone of the “westerlies-dominated climatic regime” mainly includes five Central Asian countries and China’s Xinjiang, which is located in the heart of the Eurasian continent and is dominated by the westerly circulation.
Its climatic and hydrological changes are distinct from monsoon regions and have received widespread attention in recent years. As an important indicator to measure the change in the dry-wet trend and the change in drought events, the use of drought indices also varies in different regions. Therefore, the selection of the most appropriate index to reflect changes in aridity and characteristics of drought events in that region becomes the basis for interpreting and revealing the facts and mechanisms of hydroclimatic change.
To address the above challenges, the research group of Professor Wei Huang of Lanzhou University evaluated the ability of three indices: the Standardized Precipitation Evapotranspiration Index (SPEI), the Standardized Moisture Anomaly Index (SZI), and the self-calibrating Palmer Drought Severity Index (scPDSI). ) to describe the dry-wet characteristics and drought events in the core zone of the “westerlies-dominated climatic regime” from several dimensions such as climate, hydrology, and vegetation.
The research findings reveal important insights into the dry-wet trend and drought events in the study area. Over the past 60 years, Kazakhstan has experienced uniform drying, while the four southern Central Asian countries have witnessed drier conditions in the western part and wetter conditions in the eastern part.
This is consistent with the observed slight increase in precipitation in Kazakhstan and in four southern Central Asian countries, accompanied by a significant increase in potential evapotranspiration, which ultimately led to drier conditions. In Xinjiang, the hydroclimatic variables, SZI and scPDSI show a trend towards more humidity, especially in summer. However, the SPEI showed an opposite pattern of change.
The researchers noted that the SPEI, which is more sensitive to potential changes in evapotranspiration, worsens the severity of regional drought in arid and semi-arid regions due to rising temperatures. Consequently, it cannot be used to study drought in the core zone of the “westerlies-dominated climatic regime.”
The team also assessed the ability of the index to identify different levels of drought events in the study area. SZI uses a standardization approach based on a nonlinear three-parameter probability cumulative distribution function to improve the representation of drought conditions. However, actual climate change often deviates from the normal distribution, resulting in an underestimation of extreme and severe drought events in the SZI.
On the other hand, scPDSI mainly focuses on evaluating the severity of regional drought to provide a better reflection of the overall drought situation in the area. As a result, it can effectively increase drought events in most parts of Xinjiang in the corresponding period. In summary, scPDSI is more suitable for monitoring and identifying drought characteristics, including extreme drought events, in the core zone of the “westerlies-dominated climatic regime.”
These research findings provide a valuable theoretical foundation for the use and development of drought indices, as well as for monitoring, identifying, and predicting drought events in dry areas. They will contribute greatly to the estimation and understanding of climate and environmental risks in the future, as the effects of human activities continue to increase in dry regions.
Huiwen Guo et al, Evaluation of the application of multiple drought indices in the core zone of the “westerlies-dominated climatic regime”, Science China Earth Sciences (2023). DOI: 10.1007/s11430-022-1097-0
Provided by Science China Press
Citation: Evaluation of the use of multiple drought indices in the core zone of the ‘westerlies-dominated climatic regime’ (2023, July 19) retrieved 19 July 2023 from https://phys.org/news/2023-07- applicability-multiple-drought-indices-core.html
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