Radiation observations (2021-2022) of alpine grasslands in Qilian Mountains

Quantifying the elevation dependency of radiation partitioning in high-altitude mountains is vital to projecting regional energy balance while remains largely uncertain. The surface radiation partitioning parameters among a meadow (3200 m), shrub (3400 m), and forb (3600 m) along a southern slope of the Qilian Mountains were conducted. The four-component radiation, including downward shortwave (Rs) and longwave (Ld) radiation, upward shortwave (Ru) and longwave (Lu) radiation have been continuously monitored by a net radiometer (CNR-4 for the meadow and forb, CNR-1 for the shrub, Kipp & Zonen, Netherlands) at 1.5 m above the ground. The net radiometers were mounted horizontally on relatively flat (slope < ~3oC) homogeneous grasslands. Air temperature and humidity were measured at 2.0 m above the ground by a thermohygrometer (HMP45C, Vaisala, Finland). Precipitation was collected with a tipping bucket rain gauge at a height of 0.5 m. 10 cm soil temperature and volumetric water content were integratedly measured by a coaxial impedance dielectric reflectometry (Hydra probe II, Stevens, USA) for the meadow and forb. They were measured by a temperature probe (107T, Campbell, USA) and a time dominance reflectometry (CS616, Campbell, USA) for the shrub, respectively. All measurements were recorded in a datalogger at 30-minute intervals. The observation had been conducted since August 2002 for the shrub, June 2014 for the meadow, and August 2018 for the forb. The three observations have been fenced with 10 m × 10 m since deployment. Because of power failure and logistical difficulties, large data gaps were especially common for the highest forb in the first two years. The half-hourly data were analyzed from 2021 and 2022 with high-quality measurements for the three sites. The radiation data gaps of the forb mainly happened during the nights of September and October 2022 and were not interpolated.