Radiation Controls the Interannual Variability of Evaporation of a Subtropical Lake

Abstract

Does lake evaporation increase or decrease under the scenario of climate warming? This paper aims to answer this question by investigating the controlling mechanism of interannual variations in lake evaporation at a subtropical lake. The research methodology is based on continuous eddy covariance measurement over >7 years and a diagnostic analysis using the surface energy balance principle. The results indicate that lake evaporation was enhanced mainly by increasing energy inputs including solar radiation and incoming longwave radiation and was weakened by surface feedback through outgoing longwave radiation. The incoming longwave radiation was positively correlated with cloud cover. Bowen ratio and surface albedo had slight effect on the change of lake evaporation. The annual lake evaporation can be predicted by the Priestly-Taylor model using a larger coefficient of 1.39 than the original value of 1.26, suggesting that advection or entrainment in the atmospheric boundary layer may play a role in lake evaporation. Special Section:Water-energy-carbon fluxes over terrestrial water surfaces Key Points:• Incoming shortwave and incoming longwave radiation controls the interannual change of lake evaporation • Annual Bowen ratio and incoming and outgoing longwave radiation are predictable functions of temperature change • The Brutsaert formula with a constant relative humidity predicts well the interannual variability in the incoming longwave radiationSupporting Information:• Supporting Information S1 • Table S1

Estimation of Water Surface Energy Partitioning With a Conceptual Atmospheric Boundary Layer Model

“…The determination of α is quantitatively related to the Bo (Assouline et al, 2016;Eichinger et al, 1996). The value of α is widely accepted as ranging from 1 to 1.4 with a mean value of 1.26 (Brutsaert, 2005;Lhomme, 1997b;Xiao et al, 2020;L. Zhang et al, 2017).…”

Intra-Seasonal and Intra-Annual Variation of the Latent Heat Flux Transfer Coefficient for a Freshwater Lake

“…A surprisingly weak relationship has been found between Rn and LE using the EC and in-situ hydrometeorological observations; however, it was reported by many studies that the radiative heat flux plays a dominant role in evaporation on a monthly scale [14,45]. The weak correlation can be attributed to the hysteresis behavior between incoming radiation and LE [47].…”

“…In this study, it was set to the widely accepted α = 1.26. Its value over water surfaces may vary between 1.1 and 1.4 [14,34,38], especially in a diurnal scale [11,[39][40][41]; however, it was confirmed by many theoretical studies and observations that 1.26 is feasible in most of the cases [13,42]. The PT equation is written as:…”

“…There are estimation methods that combine the EB with different approaches that are commonly employed. The Penman-Monteith and Priestley-Taylor methods belong to these, and their applicability was proved by many studies [13,14], but they can only be used at daily or longer time scales. In these methods, the heat storage term of the EB is crucial otherwise a strong seasonal bias may occur.…”

A dataset of microclimate and radiation and energy fluxes from the Lake Taihu eddy flux network

“…Accurate observation of the lake microclimate and lake-air interactions will help to better manage this water resource and to better predict how it may be affected by environmental changes. Towards that end, an increasing number of studies have employed the eddy covariance (EC) methodology to monitor physical state (temperature, wind, humidity) and process variables (momentum flux and radiation and energy fluxes) in the lake environment (Vesala et al, 2006;Blanken et al, 2011;Nordbo et al, 2011;Wang et al, 2014;Li et al, 2015;Yusup and Liu, 2016;Du et al, 2018;Hamdani et al, 2018;Xiao et al, 2018;Wang et al, 2019). Unlike EC studies in land ecosystems, however, data from these lake studies are rarely published as data pa-pers or are rarely archived in public data depositories accessible by the broader scientific community.…”