A comparison of eddy-covariance and large aperture scintillometer measurements with respect to the energy balance closure problem

Abstract

Abstract.We analyzed the seasonal variations of energy balance components over three different surfaces: irrigated cropland (Yingke, YK), alpine meadow (A'rou, AR), and spruce forest (Guantan, GT). The energy balance components were measured using eddy covariance (EC) systems and a large aperture scintillometer (LAS) in the Heihe River Basin, China, in 2008 and 2009. We also determined the source areas of the EC and LAS measurements with a footprint model for each site and discussed the differences between the sensible heat fluxes measured with EC and LAS at AR. The results show that the main EC source areas were within a radius of 250 m at all of the sites. The main source area for the LAS (with a path length of 2390 m) stretched along a path line approximately 2000 m long and 700 m wide. The surface characteristics in the source areas changed with the season at each site, and there were characteristic seasonal variations in the energy balance components at all of the sites. The sensible heat flux was the main term of the energy budget during the dormant season. During the growing season, however, the latent heat flux dominated the energy budget, and an obvious "oasis effect" was observed at YK. The sensible heat fluxes measured by LAS at AR were larger than those measured by EC at the same site. This difference seems to be caused by the so-called energy imbalance phenomenon, the heterogeneity of the underlying surfaces, and the difference between the source areas of the LAS and EC measurements.

Analysing surface energy balance closure and partitioning over a semi-arid savanna FLUXNET site in Skukuza, Kruger National Park, South Africa

“…For instance, Wilson et al (2002) also recorded an annual mean EBR of 0.84, ranging between 0.34 and 1.69 in an extensive study investigating 22 FLUXNET sites across the globe; EBR in ChinaFLUX sites ranged between 0.58 and 1.00, with a mean of 0.83 (Yuling et al, 2005); according to Were et al (2007), EBR values of about 0.90 were found over shrub and herbaceous patches in a dry valley in southeast Spain, whereas Chen et al (2009) showed a mean of 0.98 EBR for their study in the semi-arid region of Mongolia, and an EBR value of 0.80 was found by Xin and Liu (2010) in a maize crop in semi-arid conditions, in China. Using data from the Tibetan Observation and Research Platform (TORP), Liu et al (2011) observed an EBR value of 0.85 in an alfalfa field in semi-arid China. for the different seasons ranged between 0.70 and 1.12, with a mean of 0.92 ± 0.19.…”

Monitoring of Evapotranspiration in a Semi-Arid Inland River Basin by Combining Microwave and Optical Remote Sensing Observations

“…The latter were collected from the Watershed Allied Telemetry Experimental Research (WATER) and provided by the Cold and Arid Regions Sciences Data Center at Lanzhou (available at http://westdc.westgis.ac.cn/ (accessed on 1 November 2014)) [63][64][65]. The ground measurements of latent heat flux with a time interval of 30-minute by the eddy covariance method at the towers were measured and processed.…”

Change in frozen soils and its effect on regional hydrology, upper Heihe basin, northeastern Qinghai–Tibetan Plateau

“…The borehole depths are 100 m for T1, 69 m for T2, 50 m for T3, 90 m for T4, and 20 m for T5 and T7. The HiWATER experiment Liu et al, 2011) provided the soil moisture data from 1 January to 31 December 2014 at the A'rou Sunny Slope station (100.52 • E, 38.09 • N).…”