Impact of climate change on evaporation

Besides runoff, evaporation is also a major component of water cycle. Its variation is closely related to the climate conditions, such as temperature, wind speed, etc.

Guo et al. (2005) investigated the trend of evaporation in Yellow river-Huaihe river basin and analyzed its possible reasons based on the observed pan evaporation data from 117 observatories during the period of 19562000. A significant decrease trend of -50 mm/10a in the evaporation was found in the area. The maximum rate of decrease was up to 80mm/10a over the plain area. The most evident decrease in pan evaporation was observed in the southeastern Haihe basin and the lower Yellow River in spring and Huaihe River basin in summer. The decrease of pan evaporation is likely due to the decreasing sunshine duration, the weakening solar radiation, and the decreasing wind speed. Whereas, the change in vapor pressure deficit (VPD) was not significant.

The author investigated the temporal and spatial distributions of pan evaporation in China by using the pan evaporation (diameter 20 cm) and corresponding meteorological data from 465 stations (Shen, 2005). The influence of energy balance and aerodynamic terms in Penman formula on the evaporation and its changes was analyzed at the same time. The main results are as follows: (1) the average pan evaporation in China was about 1629 mm and exhibited an obvious decreasing trend through all of the four seasons, especially in summer. The trend and amplitude of evaporation variation varied with season and region; (2) It is very likely that the decrease of evaporation resulted from the decrease of solar radiation, temperature diurnal range, wind speed and VPD; (3) Based on the coefficients of partial correlation of the temperature, wind speed, actual vapor pressure and sunshine duration, the rising temperature accounted for the increase of evaporation, while the decrease of wind speed, actual vapor pressure and sunshine duration caused the decrease of evaporation. The influence of the four factors on evaporation varied with the season and region; (4) Analysis of energy balance and aerodynamic terms in Penman formula demonstrated that the decrease of pan evaporation in the eastern region mainly resulted from the significant decrease of energy offered to the evaporation, while the pan evaporation's decrease in the western areas was mainly due to the reducing dynamics offered to the evaporation.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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