## 4 Validation of Water Body Temperature Field Calculation Model and Analysis of Test Results
### Analysis of Influencing Factors on the Cold Skin Characteristics of Water Bodies  
In Section 4.2, attention was drawn to the cold skin layer on the water surface based on experimental observations, and the underlying formation mechanism of this phenomenon was theoretically identified. The existence of the cold skin was further corroborated through direct measurements of the vertical profile and surface temperature distribution of the water body. To investigate how variations in environmental parameters influence the properties of the cold skin, the cold skin calculation model for water bodies was employed to analyze the effects of changes in parameters such as wind speed, the specific humidity difference between the near-surface and upper-air layers, and the temperature difference between the near-surface and upper-air layers on various heat fluxes and cold skin characteristics. Figures 12 and 13 depict the variations in heat fluxes at the gas-liquid interface and the properties of the cold skin under varying upper-air wind speeds. In the wind speed range of 0-10 m/s, as the wind speed increases, both the evaporation rate at the water surface and the convective heat exchange between the lower air layer and the surface water body intensify. As a result, the sensible heat flux and latent heat flux exhibit a linear increase with wind speed. Additionally, as wind speed rises, the MOS velocity scale parameter, which governs the thickness of the cold skin, also increases. Since the cold skin thickness  
Figure 11: Temperature distribution in the skin layer. Figure 10: Temperature distribution in vertical profile of water body. is inversely proportional to the velocity scale parameter, the thickness of the cold skin gradually diminishes with increasing wind speed, leading to a reduction in the absorption of shortwave solar radiation within the thin layer. Under the combined influence of these heat fluxes, the net heat flux at the interface increases. The temperature difference of the cold skin is proportional to the product of the net heat flux and the cold skin thickness. In the wind speed range of 0-10 m/s, there exists a critical point at approximately 2.5 m/s, where the temperature difference of the cold skin reaches its maximum value. Figures 14 and 15 depict the variations in heat fluxes at the gas-liquid interface and the properties of the cold skin under different near-surface to upper-air specific humidity differences. As shown in Figure 14, the near-surface to upper-air specific humidity difference primarily affects the latent heat flux, while its influence on other heat flux components is relatively limited. A larger specific humidity difference signifies a more intense water vapor exchange process between the near-surface air and the upper-air layers. During the upward diffusion of water vapor, the surface water body undergoes continuous evaporation, establishing a sustained water vapor circulation process. This process effectively removes heat from the surface water, contributing to a pronounced cooling effect. The thickness of the cold skin decreases as the specific humidity difference increases, primarily due to the density difference in the medium induced by the specific humidity difference. However, compared to the growth rate of the net heat flux, the rate of decrease in cold skin thickness with increasing specific humidity difference is relatively modest. As a result, under conditions where the net heat flux experiences a significant increase, the temperature difference of the cold skin becomes more sensitive to variations in heat flux, demonstrating a trend of increasing with the specific humidity difference. Figure 12: Effect of wind speed on each heat flux. Figure 13: Effect of wind speed on cold skin properties. Figures 16 and 17 illustrate the variations in heat fluxes at the gas-liquid interface and the properties of the cold skin under different near-surface to upper-air temperature differences.