Evaluation of the applicability of multiple drought indices in the core zone of “westerlies-dominated climatic regime”

Drought indices are frequently used to measure the intensity,start and end of droughts.However,the performances of these indices depend on regions and the type of droughts.Therefore,it is necessary to evaluate whether these indices are applicable for a given region.This study evaluated the ability of the self-calibrating Palmer Drought Severity Index(sc PDSI),the Standardized Precipitation Evapotranspiration Index(SPEI),and the Standardized Moisture Anomaly Index(SZI) to describe the dry-wet conditions and drought events in the core zone of the “westerlies-dominated climatic regime”.The results showed that the 12-month SZI(SZI12) and SPEI(SPEI12) have good correlations with precipitation and PET respectively,while the sc PDSI can capture the changes in precipitation and soil moisture.In Xinjiang region of China,the SZI12 and sc PDSI showed that this region gradually became wetter during 1961–2014,which was consistent with increased precipitation,decreased PET,and improved vegetation.However,the SPEI12 showed significant drying due to the strong influence of the PET,suggesting that this index exaggerated the drought conditions in this region.Precipitation in Kazakhstan and the southern Central Asian regions has increased slightly over the past 50 years,but the PET has greatly increased,altogether,all three indices suggested a drying trend in Central Asia.The evaluation of the ability of these drought indices to identify typical drought events in Xinjiang region of China suggested that the sc PDSI can better detect the typical drought events compared with the SZI12.In conclusion,the sc PDSI is the most suitable index for characterizing the long-term trend of hydroclimate conditions and drought events in the core zone of the “westerlies-dominated climatic regime”.This study provides a theoretical basis for the rational utilization and improvement of the drought index,which is critical for monitoring,attributing,and predicting of drought events in arid areas.

A 1556 year-long early summer moisture reconstruction for the Hexi Corridor, Northwestern China

We report a 1556 year-long tree-ring width chronology for the Hexi Corridor, in the arid Northwestern China,established by applying the signal-free regional curve standardization method to 416 juniper ring-width series. We found that drought in early summer(May–June) is the primary controlling factor for tree growth in this area. We then developed an early summer moisture(i.e., scPDSI) reconstruction from 455 CE to present. Our reconstruction captures multi-centennial scale moisture variations, showing two long-term dry periods during 800–950 CE and 1000–1200 CE, and two long-term wet periods during 1200–1450 CE and 1510–1620 CE. We found strong similarities between hydroclimatic changes in the Hexi Corridor and Qaidam Basin from interannual to centennial timescales; however, at multi-centennial(>300 years) timescales, hydroclimatic variations in the two regions showed significant regional differences. The Hexi Corridor witnessed a generally dry Medieval Climate Anomaly(MCA, here 800–1200 CE) and the drying 20 th century, whereas the Qaidam Basin experienced highprecipitation periods during the MCA and 20 th century. The different correlation pattern with Northern Hemisphere temperature suggest that the Qaidam Basin will receive more precipitation under global warming, whereas the Hexi Corridor will become dryer in the future.

Hydroclimatological data and analyses from a headwaters region of Mongolia as boundary objects in interdisciplinary climate change research

Collaborative work on increasingly complex hydroclimatic investigations often crosses disciplinary boundaries. Elements of scientific inquiry, such as data or the results of analyses can become objectified, or capable of being adopted and/or adapted by users from multiple disciplinary realms. These objects often provide a bridge for collaborative endeavors, or are used as tools by individuals pursuing multi-disciplinary work. Boundary object terminology was first formalized and applied by social scientists. However, few examples of the application of this useful framework are found in the hydrologic literature. The construct is applied here to identify and discuss how common researcb products and processes are used both internally and externally through providing examples from a project examining the historical and paleo proxy-based hydroclimatology of a headwaters region of Mongolia. The boundary object concept is valuable to consider when conducting and critiquing basic research, collaborating across multiple disciplinary teams as when studying climate change issues, as an individual researcher working in a cross boundary sense using methods from differing disciplines to answer questions, and/or when one group adapts the work of another to their own research problems or interpretive needs, as occurred with selected products of this project.