A study on precipitation trend and fluctuation mechanism in northwestern China over the past 60 years

Abstract

This paper focuses on the mechanism of the trend and oscillation in precipitation records in northwestern China over the past 60 years. The results from regression and orthogonal wavelet decomposition show a clearly ascending in annual precipitation since 2000, which is contributed mostly by significant increase in autumn and winter precipitations, while almost no trend can be identified in spring and summer time, which shows a weak descending in non-linear form. This may be in connection with different warming rates in seasons. There is a significant anti-correlation between the precipitation and the North Atlantic oscillation (NAO) on the inter-annual scale. About 80% of their variances concentrate on inter-annual and multi-decadal scales. The multi-decadal components of NAO index have a phase leading about 10 years to corresponding precipitation, about 4-5 years leg for AMO. Hence, NAO index can be used as an indicator for inter-decadal change of the precipitation. Other results from combination-difference analysis show that the NAO in extreme negative phase could lead to the precipitation increase in central Asia and northwestern China, owing to increase in eastward water-vapor transport from south Europe to Northwestern China, which causes an increase in column water vapor content in the above areas, and meanwhile the transient eddy activity becomes intensified in the areas or north with a further south route moving from Europe, Central Asia throughout northwestern China. On the contrary, a dry climate might appear in the areas when meet extreme positive phase of NAO. Thus, NAO's oscillation is one of the most important mechanisms for inter-annual change in precipitation of northwestern China.

Spatiotemporal Variation in Precipitation and Water Vapor Transport Over Central Asia in Winter and Summer Under Global Warming

“…The sources of water vapor in spring, autumn and winter in Central Asia include the Arctic Ocean, the Mediterranean Sea, the Black Sea and the Caspian Sea, whereas the water vapor in summer mainly comes from the Atlantic Ocean and continental Europe in the mid-and high latitudes (Shi and Sun, 2008;Guan et al, 2019). Dai et al (2011) analyzed the constant water vapor field in the troposphere from Xinjiang to the Atlantic Ocean and found that the main sources of water vapor in Xinjiang were from lakes and oceans to the west. With the current trend in global warming, more water vapor is sourced from high latitudes, such as the North Atlantic and Arctic oceans.…”

Response of Morphological Characters and Photosynthetic Characteristics of Haloxylon ammodendron to Water and Salt Stress

“…Since the end of 1980s, the climate in Xinjiang Uygur autonomous region has been warming and humidifying as a result of global climate change [8]. In the past 20 years since the beginning of the 21st century, there have been two trends in Xinjiang Uygur autonomous region's climate: one is that the total precipitation in Xinjiang Uygur autonomous region continues to increase; the other is that extreme precipitation events have fluctuated and increased [9], significantly affecting the vegetation in the desert areas [10]. Therefore, the study of morphological and photosynthetic characteristics of Haloxylon ammodendron under water and salt gradient will provide scientific basis for the response of Haloxylon ammodendron to global change.…”