Stable isotopic characteristics of precipitation in Lanzhou City and its surrounding areas, Northwest China

Identifying the source of atmospheric moisture over arid deserts using stable isotopes (2H and 18O) in precipitation

“…Secondary evaporation below the cloud is commonly great in low humidity conditions and then results in a negative correlation between atmospheric humidity and precipitation δ 18 O (Araguás‐Araguás et al, ; Clark & Fritz, ; Peng, Mayer, Harris, & Krouse, ). Chen et al () observed this trend in Lanzhou and its surrounding areas. However, we find that precipitation δ 18 O and atmospheric humidity are weakly correlated on both daily and monthly scales in the Alxa Desert Plateau (Figure c).…”

“…Our study site is located along the direction of the East Asian summer monsoon path, which is similar for Changsha, Lanzhou, and Shiyang River Basin. But other studies have found different sources of atmospheric moisture such as from the westerly cyclonic system for the Shiyang River Basin (located approximately 160 km southeastward from the AYQ; Ma et al, ) and westerly, easterly, and northerly currents depending on the season for Lanzhou (Chen et al, ). Because our study site is located northwestward further from these sites, it seems unlikely that the East Asian summer monsoon can reach the southeast edge of the Alxa Desert Plateau.…”

“…Moreover, the temporal variation of precipitation δ 18 O values does not agree well with that of atmospheric humidity (Figure and Figure S1). This suggests that atmospheric humidity is not an important factor controlling isotope values of precipitation in the Alxa Desert Plateau and also implies that the meteorological conditions in this plateau are different from those in Lanzhou (Chen et al, ). It is also found that the slope and intercept of the isotope relationship increase as atmospheric humidity increases (Figure c).…”

“…Similar findings were also obtained in other places of North China (Ma et al, ; Wang et al, ; Wu et al, ). Recently, Chen et al () found that daily δ 18 O was positively correlated with daily atmospheric temperature in Lanzhou and its surrounding areas. However, they pointed out that the temperature effect on an annual basis is not significant in the region, which is different from our result.…”

“…In this water‐limited environment, understanding the scarce water resources for the area is vital; however, several important questions still remain. They include (a) Is the isotopic characteristic of local precipitation similar to that of the surrounding areas such as Heihe River, Shiyang River, and Lanzhou (Chen et al, ; Guo, Feng, Wei, Li, & Liu, ; Ma et al, ; Wu et al, )? (b) What are the sources of local precipitation?…”