Continuous temperature monitoring for two adjacent tropical crater lakes in Mexico at 4200 m amsl shows that the lakes have rhythmic episodes of heating and cooling with a duration of ~ 30 days during the warmest months. The episodes were caused by rise and decline of solar irradiance reaching the lake surface. One lake, El Sol, showed over each heating and cooling episode a stable mixed layer (~ 20 days) and a deeper layer with a weak thermal gradient. Temperatures below the mixed layer warmed progressively by eddy diffusion after the mixed layer formed. Stratification was followed by full mixing of the water column. Within the same crater, an adjacent second lake, La Luna, showed the same cycles of heating and cooling; it stratified daily but not over multiple days. The difference between the lakes (discontinuous polymictic, continuous polymictic) is explained by the lower transparency of El Sol, which led to greater heat uptake near the surface than the more transparent La Luna. Lower transparency of El Sol was caused by modest anthropogenic effects on total suspended solids and nutrient loading, i.e., small deviations from the natural condition of El Sol caused it to differ qualitatively from La Luna. Events observed in these lakes would not have been evident from weekly temperature records.

中文翻译：

---

两个热带高山湖泊加热和冷却控制热分层的节律性发作

对墨西哥 4200 米 amsl 的两个相邻热带火山口湖的连续温度监测表明，在最温暖的月份，这些湖泊有节奏的加热和冷却，持续时间约为 30 天。这些事件是由到达湖面的太阳辐照度的上升和下降引起的。一个名为 El Sol 的湖泊在每次加热和冷却过程中都显示出一个稳定的混合层（约 20 天）和一个具有较弱热梯度的更深层。混合层以下的温度在混合层形成后通过涡流扩散逐渐升温。分层之后是水柱的完全混合。在同一个火山口内，相邻的第二个湖 La Luna 显示出相同的加热和冷却循环；它每天分层，但不会超过多天。湖泊之间的差异（不连续的polymictic，连续多晶）是由 El Sol 较低的透明度解释的，这导致表面附近比更透明的 La Luna 吸收更多的热量。El Sol 透明度较低的原因是人为对总悬浮固体和营养负荷的影响不大，即与 El Sol 自然条件的微小偏差导致它与 La Luna 在性质上有所不同。从每周的温度记录来看，在这些湖泊中观察到的事件不会很明显。