Spatial variability of the surface energy balance of Lake Kasumigaura and implications for flux measurements

Abstract

Spatial variability of lake surface energy balance and its causes are not understood well. 90-m resolution energy balance maps of Lake Kasumigaura (172 km 2) in Japan obtained by interpolating stations' data and bulk equations allowed investigation of these issues. Due to lake-scale variation in meteorological variables and small-scale fluctuations of surface temperature Ts, surface heat fluxes were found differed horizontally at two distinctive scales while radiative fluxes were more uniform. The key variable Ts to surface fluxes was only homogenous for directions with a longer fetch or under calm wind conditions. Using these findings, the suitability of flux station locations, one at the center of the lake and another within a cove, were considered. Although both locations satisfied the fetch requirements, Ts was not always found to be homogeneous in the cove, making this location less suitable for flux measurements, an issue that has been overlooked in scientific communities.

Wind as a Main Driver of Spatial Variability of Surface Energy Balance Over a Shallow 102‐km2 Scale Lake: Lake Kasumigaura, Japan

“…Sugita et al (2014) and Sugita (2020) also indicated the spatial variability of surface fluxes in Lake Kasumigaura by a similar approach as Lofgren and Zhu (2000) but with a finer space resolution (90 m). In the case of Sugita et al (2014), evaporation was studied over 5 years, but other EB components were not studied.…”

“…Naturally, there are no obvious reasons that this should be true. As a scale of the footprint of measured fluxes is usually of the order of 10 2 to 10 3 m on water surfaces (e.g., Mammarella et al, 2015; Sugita, 2020; Zhao & Liu, 2018), spatial variability cannot be captured by single‐point measurements if the lake scale is >10 2 to 10 3 m.…”

“…In the case of Sugita et al (2014), evaporation was studied over 5 years, but other EB components were not studied. All EB components were studied in Sugita (2020) but only for three cases on clear days in winter. It is possible that cloudy conditions suppressed spatial variability on the lake's surface.…”

Thermal regime, energy budget and lake evaporation at Paiku Co, a deep alpine lake in the central Himalayas

“…The components of energy budget are not uniform at large lake and the meteorological station near the lake centre is usually expected to produce more accurate estimation of heat flux (Sugita, 2019). To check the representativeness of hydrometeorology at the shoreline of Paiku Co, we first compare air temperature and relative humidity between shoreline and lake centre.…”

“…For example, due to different heat properties between lake water and the land, lake water plays a cooling role in summer and warming role in winter (Scott and Huff, 1996). As such, investigations of lake water and energy budgets, which provide basic information regarding the loss and gain of water and energy, are important in ascertaining the role of lakes in local to regional scale communities (Sugita et al, 2019).…”