Monotonic trend and abrupt changes for major climate variables in the headwater catchment of the Yellow River basin

Abstract

Abstract:On the basis of the mean air temperature, precipitation, sunshine duration and pan evaporation at 23 meteorological stations in the headwater catchment of the Yellow River basin from 1960 to 2001, the long-term monotonic trend and abrupt changes for major climate variables have been investigated. The plausible monotonic trend of annual climatic time series are detected using a non-parametric method. The abrupt changes have been investigated in terms of a 5 year moving averaged annual series, using the moving t-test (MTT) method, Yamamoto method and Mann-Kendall method. The results showed that the annual air temperature has increased by 0Ð80°C in the headwater catchment of the Yellow River basin during the past 42 years. One obvious cold period and one warm period were detected. The warmest centre was located in the northern part of the basin. The long-term trend for annual precipitation was not significant during the same period, but a dry tendency was detected. According to the Kendall slope values, the declining centre for annual precipitation was located in the eastern part and the centre of the study area. The long-term monotonic trend for annual sunshine duration and pan evaporation were negative. The average Kendall slopes are 29Ð96 h/10 yr and 39Ð63 mm/10 yr, respectively. The tests for abrupt changes using MTT and Yamamoto methods show similar results. Abrupt changes occurred in the mid 1980s for temperature, in the late 1980s for precipitation and in the early 1980s for sunshine duration and pan evaporation. It can be seen that the abrupt changes really happened in the 1980s for the climate variables. Different results are shown using the Mann-Kendall method. Both the abrupt changes of temperature and precipitation took place in the early 1990s, and that of pan evaporation occurred in the 1960s. The only abrupt change in sunshine duration happened during the similar period (in the 1980s) with the results detected by the MTT and Yamamoto methods. The abrupt changes which occurred in the 1990s and 1960s are not detectable using the MTT and Yamamoto methods because of the data limitation. However, the results tested by the MTT and Yamamoto methods exhibited great consistency. Some of the reasons may be due to the similar principles for these two methods. Different methods testing the abrupt climatic changes have their own merits and limitations and should be compared based on their own assumption and applicable conditions when they are used.

Spatial and Temporal Variations of Precipitation Extremes and Seasonality over China from 1961~2013

“…In China, Wang et al [17] found an abrupt decrease in the flood-season precipitation around the year of 1979 based on weather stations in the Haihe River Basin. Zhao et al [18] confirmed an abrupt decrease in precipitation during the late 1970s and middle 1980s was also observed in the upper Yellow River Basin.…”

Understanding changes and trends in projected hydroclimatic indices in selected Norwegian and Polish catchments

“…Some authors have also attempted to detect the trend and abrupt changes in time series separately (e.g. Zhao et al 2008), but this approach is not statistically satisfactory because the conclusions obtained from different tests may not be compatible (Shao et al 2010). Though a single trend test is considered appropriate for trend testing and detection with specified start and end times, it does not show whether any changes are due to gradual or abrupt occurrences .…”

Trends in temperature and rainfall extremes in the Yellow River source region, China

“…But summer precipitation (from June to September) showed a tendency to decline. Zhao et al (2007) reported that over the past 40 years the annual mean temperature has significantly increased by 0.8…”