Characteristics Of Temperature And Precipitation Trend In The Yellow River Delta During The Past 50 Years And Analysis Based R/S

While ecological environment in The Yellow River Delta area is extremely fragile under the interaction of sea and land, the changing in underlying surface driven by intense human activity make this situation more serious. The reclamation process in nature wetland and landscape pattern affects the wetland function directly, which has a deep influence on the heat balance and steam emission characteristics of wetland surface, and result in the diversification of temperature and precipitation in this region. Based on daily temperature and precipitation interpolation data from Daily Dataset of Chinese Terrestrial Climate Data, the general trend and seasonal characteristics of the average annual temperature and annual precipitation changes during 1961-2010 in costal wetland region of the Yellow River Delta were analyzed with linear trend analysis, slip anomaly analysis and Mann-Kendall test, and rescaled range analysis(R/S) combined with non-periodic cycle analysis is used to calculate the Hurst index and non-cycle length of meteorological series. The results showed:(1) The average annual temperature in YRD Delta increased 1.85°C and its linear trend rate reached 0.37°C/10 a, especially mainly occurred in winter, reached 0.68°C /10 a. The annual average temperature changed abruptly in 1993 and a significant warming period was coming.(2) The annual minimum temperature increased 5.50°C in 50 years and changed abruptly in 1985, showed obvious pulling effect in the annual average temperature’s warming. But its seasonal variation is not obvious, and presented warming trend in whole year. The break point and seasonal variation of the annual maximum temperature is both not significant.(3) The accumulated reduction of precipitation reached 121.42 mm which mainly occurred in summer, accounted for 19.9% of average annual precipitation. The days of heavy rainfall and maximum continues drought decreased significantly, while the frequency and intensity of extreme precipitation kept a stable level.(4) The R/S analysis on meteorological series illustrate the Hurst phenomenon is both existed in annual average temperature, the annual maximum temperature, the annual minimum temperature and the annual precipitation series, but showed different non-cycle length. The annual precipitation and the annual minimum temperature series can hold for 10 years while the annual average temperature series can only hold for 8 years. The annual maximum temperature series showed severely oscillations for 6 years non-cycle length.(5) The warming and drought trend with characteristics of temperature rising in winter and drought in summer was obvious in costal wetland region of the Yellow River Delta. The underlying surface changes resulting from human activities was an important driving factor. Under the background of severely soil salinization and summer growing season, The loss of rainfall in summer has become one of the predominant factors for the regional ecological environment safety.