Spatial distribution and temporal variation of reference evapotranspiration during 1961–2006 in the Yellow River Basin, China

Figures & data

Fig. 1 Location of the YRB and the meteorological stations used in this study (▴). The two straight lines show the division of the basin into upper, middle and lower regions.

Fig. 2 Mean monthly variations of the key meteorological variables for: the upper, middle and lower regions (see Fig. 1) and whole YRB in the period 1961–2006: (a) air temperature; (b) relative humidity; (c) wind speed; and (d) sunshine hours.

Fig. 3 Spatial distributions of mean seasonal and annual ET_ref during 1961–2006 in the YRB, China.

Fig. 4 The abrupt change tested by the Mann-Kendall method for annual ET_ref series of Yangcheng station for 1961–2006. Here, as the line C₁ is over the confidence line (P = 0.05), the cross-over point of C₁ and C₂ is the start point of abrupt change in this series.

Fig. 5 The upward trends (▴), downward trends (▪), and no trends (○) in annual ET_ref in the YRB, China in the 1961–2006 period, detected by the Mann-Kendall method.

Fig. 6 The time and frequency of the abrupt changes in ET_ref detected by the M-K method in the YRB in the 1961–2006 period, with the years when abrupt changes occurred (where two abrupt changes were detected at one station, the years are in brackets).

Fig. 7 Trends (mm year^-2) for the annual ET_ref from 1961 to 2006 in the YRB, China. Circles placed around the dots denote significant trend (0.05 level).

Fig. 8 The relative change in ET_ref due to changes in air temperature, wind speed, relative humidity and sunshine hours, respectively.