Meteorological Drought, Hydrological Drought, and NDVI in the Heihe River Basin, Northwest China: Evolution and Propagation

Figure 3

Boxplots showing MD duration and severity in the UHRB (a, c) and in the MHRB (b, d) based on SPI using thresholds of −1, −1.5, and −2 for different timescales at different periods (the dot and midline in the boxplots are the mean and median; the upper and lower boundaries of box are the interquartile range).

(a)

(b)

(c)

(d)