The influences of typhoon‐induced mixing in a shallow lake

Abstract

Vertical mixing affects the vertical transport of biochemical materials and modifies the characteristics of basin‐scale internal waves in subtropical, subalpine Yang Yuan Lake (YYL), in the north central region of Taiwan. Vertical mixing in YYL is generally caused by typhoons (strong winds and heavy rainfalls) during the spring, summer and early fall, or by cooling of the water column during late fall and winter. Vertical mixing caused by typhoons significantly affects internal thermal dynamics and biochemical processes, with basin‐scale internal waves enhanced before complete mixing occurs, and temporal variations of water temperature dramatically changing after typhoon events. This study quantitatively determines when the complete mixing (defined as homogenous temperature in a water column) occurs on the basis of the balance between kinetic energy and potential energy and also shows what meteorological conditions contribute to the vertical mixing. Data on water column thermal profiles and meteorological variables were collected by a wireless, instrumented buoy in the deepest location of YYL and from a nearby meteorological station, from spring 2004 to summer 2006. This study also investigated how a physical process (internal waves) is affected by the mixing associated with typhoons. Signal processing and a two‐layer model of the water column are used to understand the characteristics of basin‐scale internal waves.

Contribution of extreme meteorological forcing to vertical mixing in a small, shallow subtropical lake

“…For instance, wind forcing is a dominant factor for vertical mixing in a thermally stratified, shallow lake (Tuan et al, 2009). The relationship between wind speed and precipitation was positively strong for rainstorm events that caused vertical mixing in a small, shallow lake (Kimura et al, 2012a). If focusing only on the SLM, mixing events accompanying large air pressure gaps were likely dominated by wind-turbulence mixing in the lake surface where the effects of wind and heating/cooling reached (Fig.…”

Influence of Thermal Stratification on Seasonal Net Ecosystem Production and Dissolved Inorganic Carbon in a Shallow Subtropical Lake

“…10.1029/2020JG005907 2 of 17 water column is stratified from early April to October and is usually well-mixed in winter from December to February (Kimura et al, 2012;Tsai et al, 2008).…”

Influence of thermal stratification on seasonal net ecosystem production and dissolved inorganic carbon in a shallow subtropical lake

“…water column is stratified from early April to October and is usually well-mixed in winter from December to February (Kimura et al, 2012;Tsai et al, 2008).…”

“…Lake size has also been revealed to be one of the most critical factors controlling CO 2 emissions, with small lakes having more considerable contributions from convection to gas transfer velocities (Read et al, 2012;Vachon & del Giorgio, 2014). Heavy rainfall, wind shear, and convective mixing are essential meteorological forces that cause vertical mixing in small lakes; in shallow lakes, stratification can cause internal waves, which in turn can cause mass transport (Kimura et al, 2012(Kimura et al, , 2014(Kimura et al, , 2017. Therefore, to accurately estimate C fluxes from small lakes, it is necessary to clarify the mechanisms of vertical mixing and the collapse of stratification.…”