Search

The pan evaporation process is essential to understanding the climate change of pan evaporation. To study the physical process of pan evaporation and its interactions with the surrounding environment, an elaborate pan evaporation experiment was carried out by means of micrometeorological method in the arid region of northwest China, in which hourly pan evaporation was measured by E601B, Class A and D20 pans, the local actual evapotranspiration was measured using eddy correlation system. Our results show that the pan water surface and the surrounding land surface constitute a significant non-uniformity of heat and moisture, and the non-uniformity energy exchange between them has an important influence on pan evaporation rate. As the environmental humidity changes, daily actual evapotranspiration and pan evaporation rates have a contradictory tendency, with the relationship between these two evaporations presenting a clear asymmetrical complementary behavior. In addition, a simple pan non-uniformity intensity index ( I E ) is defined as the ratio of pan evaporation to the Penman potential evaporation ( LE ppman ) ( I E = LE pan / LE ppman ). This index reflects the non-uniformity intensity between pan water and the surrounding land. Meanwhile, the comparison of complementary relationship corresponding to three types of pans shows that the degree of complementary relationship asymmetry linearly rises as the intensity of non-uniformity between pan and surrounding environment increases. [ABSTRACT FROM AUTHOR]

• The impact of wind farms on the local climate is not simply warming and cooling. • Air temperature becomes colder and the land surface temperature becomes warmer at night. • The significant increase in evapotranspiration may be due to the impact of wind farms. • Wind farm has no or negligible effect on vegetation growth both spatially and temporally. To explore the possible local climatic and environmental impacts of an onshore wind farm in North China, meteorological observation and satellite remote sensing data around the wind farm were collected, and the soil chemical composition within and outside of the wind farm was determined. Our analysis revealed changes in the spatial patterns of wind, air temperature (T a), ground surface temperature (T s), land surface temperature (LST), evapotranspiration (ET), and the normalized difference vegetation index (NDVI) from before to after the construction of the wind farm. The two datasets of meteorological observations showed that wind speed decreased after the construction of the wind farm, with one dataset indicating a significant decrease. Since the construction of the farm, T a and T s have shown increasing trends, and ET has shown a significant increasing trend. The nighttime T a and LST showed opposite trends, with T a decreasing and LST increasing. The change in LST was the greatest at the wind farm and in its downwind zone, indicating that the operation of the wind farm affects the LST within and beyond the 10 km buffer zone. After the wind farm construction, the NDVI showed a significant positive trend. However, increases in the concentrations of Ti and Co were observed, suggesting that the construction and operation of wind farm may promote vegetation growth and cause soil pollution. The monitoring of wind farms needs to be strengthened to reveal the long-term impacts of wind farms on local climates and ecosystems. [Display omitted] [ABSTRACT FROM AUTHOR]