Why is the daily variation of ocean surface water temperature greater in sunny days than cloudy days, windless days than windy days, low latitudes than high latitudes, and summer than winter?

The surface layer of seawater is a water mass in direct contact with the atmosphere, and the diurnal variation of surface temperature is in a sense the diurnal variation of atmospheric temperature (or solar radiation). ① Cloudy and sunny days: On cloudy days, the clouds are thick, which enhances the atmospheric inverse radiation. At this time, the clouds play the role of "insulation layer" at night. So the temperature difference between day and night on cloudy days is smaller than that on sunny days. Because almost all the heat of seawater comes from the thermal radiation of the atmosphere, the daily variation of the temperature of the corresponding surface seawater will become smaller. ② Low-latitude and high-latitude areas: Low-latitude areas are exposed to direct sunlight for a long time during the day, while high-latitude areas are not exposed to direct sunlight. Neither of them basks in the sun after nightfall, so the low latitudes are greatly influenced by the sun, and the daily variation of seawater temperature is also great. ③ Xia Dong: The daytime in summer receives more solar radiation than the daytime in winter. Take summer in the northern hemisphere as an example. At this time, the direct point of the sun falls in the northern hemisphere, and the southern hemisphere is in winter. Therefore, the northern hemisphere receives more solar radiation than the southern hemisphere. There is no solar radiation at night, summer or winter. Therefore, the daily variation of seawater temperature in summer should be large. ④ Windy and windless: As a dynamic factor, wind will cause turbulence, and turbulent mixing will transfer the heat of surface water to the lower layer, so its amplitude is small when there is wind.