دانلود رایگان مقاله انگلیسی ویژگی های فضایی و زمانی خشکسالی در آسیای میانه در طول سال های 1966-2015 - الزویر 2018

abstract

In drought-prone regions like Central Asia, drought monitoring studies are paramount to provide valuable information for drought risk mitigation. In this paper, the spatiotemporal drought characteristics in Central Asia are analyzed from 1966 to 2015 using the Climatic Research Unit (CRU) dataset. Drought events, as well as their frequency, duration, severity, intensity and preferred season, are studied by using the Run theory and the Standardized Precipitation Evapotranspiration Index (SPEI) at 3-month, 6-month, and 12-month timescales. The Principle Components Analysis (PCA) and the Varimax rotation method, the Sen's slope and the Modified Mann-Kendall method (MMK), as well as the wavelet analysis are adopted to identify the sub-regional drought patterns and to study the drought trend, periodicity and the possible links between drought variation and large-scale climate patterns, respectively. Results show that the drought characteristics in Central Asia vary considerably. The Hexi Corridor region and the southeastern part suffered from more short-term drought occurrences which mostly occurred in summer while the northeastern part experienced fewer droughts with longer duration and higher severity. Central Asia showed an overall wetting trend with a switch to drying trend since 2003. Regionally, the continuous wetting trend is found in north Kazakhstan while a consistent drying in the Aral Sea and Hexi Corridor region is observed in the last half-century. For 2003–2015, a significant drying pattern is detected in most Central Asia, except the northern Kazakhstan. A common significant 16–64-month periodical oscillation can be detected over the six sub-regions. The drought changes in Central Asia are highly associated with ENSO but less related to the Tibetan Plateau pressure. The North Atlantic Oscillation has an influence on drought change in most Central Asia but less for the Hexi Corridor and the drought variation in eastern Central Asia is affected by the strength of the Siberian High.

5. Conclusions

The understanding of the spatial and temporal variation of drought characteristics is vital for water resources management and drought mitigation. Based on long-term CRU dataset and multiscalar SPEI (i.e. SPEI3, SPEI6 and SPEI12), a series of drought characteristics including drought duration, frequency, severity, intensity, peak value and starting season are comprehensively investigated during 1966–2015 in this paper. The PCA and Varimax rotation technique are used for regionalization. The drought events and drought characteristics are analyzed based on the Run theory; the drought trend is detected by using the Sen's slope and the MMK method. Finally, the drought periodicity and the possible links between drought variation and large-scale climate patterns are investigated based on the wavelet analysis. The main results are summarized as follows.

(1) Based on the PCA and Varimax rotation method, Central Asia is divided into six sub-regions with different temporal drought variations which include the northwest (NW), the north Kazakhstan (NK), the southwest (SW), the northeast (NE), the southeast (SE) and the Hexi Corridor region (HX).

(2) Three periods are found with the most severe drought events during the last half-century which are the 1973–1979 for the sub-regions of NW, NK, SW and SE; 1983–1988 for the subregions of SE and HX and the 1997–2003 for NE, NK, SW, SE and HX.

(3) The patterns of drought characteristics vary considerably in Central Asia. Specifically, the HX and the eastern part of SE are characterized by higher drought duration with lower drought intensity and severity. While NE experienced relatively fewer drought events with longer duration and severity, drought events over HX, SE, and part of NK seem to frequently occur in summer.