Half Of Precipitation Research Articles

Long‐distance atmospheric moisture dominates water budget in permafrost regions of the Central Qinghai‐Tibet plateau

AbstractPrecipitation plays an important role in permafrost hydrology; it can alter the hydrothermal condition of the active layer and even influence the permafrost aggradation or degradation. Moisture recycling from evaporation and transpiration can greatly contribute to local precipitation in some regions. This study selected four monitoring sites and used an isotope mixing model to investigate local moisture recycling in permafrost regions of the central Qinghai‐Tibet Plateau (QTP). The results showed that the local water vapour flux in the summer and autumn were dominantly influenced by westerlies and the Indian monsoon. Moistures for precipitation in Wudaoliang (WDL) and Fenghuoshan (FHS) mainly came from the western QTP, eastern Tianshan Mountains, western Qilian Mountains, and the surrounding regions. In comparsion, more than half of precipitation at Tanggula (TGL) was mostly sourced from the Indian monsoon. Local moisture recycling ratios at the four sites ranged from 14% ± 3.8% to 31.6% ± 4.8%, and depended on the soil moisture and relative humidity. In particular, the higher soil moisture and relative humidity promoted local moisture recycling, but frozen ground might be a potential influencing factor as well. The moisture recycling ratios of the study area were consistent with the results from both the Qinghai Lake Basin and the Nam Co Basin, but differed from those of the northwestern QTP. This difference may indirectly confirm the great spatial variability in precipitation on the QTP. Moreover, the rising air temperature and ground temperature, increasing precipitation, higher soil moisture, higher vegetation cover, and expanding lakes in the study area may be conductive to enhancing future local moisture recycling by altering ground surface conditions and facilitating the land surface evaporation and plant transpiration.

Characteristics of Green and Blue Water Flow of Hydrological Landscapes of Upper Heihe in Northwest China

Blue water and green water are of great importance for food production and maintenance of ecosystem. Blue/green water flow on landscape scale and its seasonal variation remains unclear. This study attempt to analyze characteristics of green and blue water flow on landscape scale.In this study, FLEX-Topo model was adopted. And upstream of Heihe River Basin (UHB) was selected as the study area, which was divided through topographic information into four landscapes, such as riparian area, grass hillslope, forest hillslope and bare soil/rock. Based on the analysis of the simulation during the period of 1979-2015, characteristics of green and blue water flow of the four landscapes was presented. The results showed that (1) FLEX-Topo proved to be an efficient approach for catchment hydrological process simulation as well as for green and blue water study; (2) Annual green water flow(GWF) of riparian area was 325.19 mm/a while its blue water flow(BWF) was 151.92 mm/a. GWF and BWF of grass hillslope was 270.50 mm/a and 199.91 mm/a, respectively; GWF of forest hillslope was 424.75 mm/a which is much greater than its BWF (42.11mm/a);as for bare soil/rock, GWF (227.96 mm/a) was a litter smaller than BWF (295.32 mm/a). From the results, its can be concluded that:(1)on annual scale, majority of precipitation and water reserve in riparian area, grass hillslope, forest hillslope became green water flow, especially in forest hillslope. More than half of precipitation in bare soil/rock turn to blue water flow; (3) seasonal variation of both green water flow and green water flow of the four hydrological landscapes synchronized with precipitation.