Impact of Fractional Vegetation Coverage Increase on Air Temperature Change in Liaoning Province

Fractional vegetation coverage (FVC) is one of the most important land surface parameters. Changes in FVC directly impact the redistribution of land surface energy as well as regional and even global climate change. Studying the effects of increased FVC on regional climate is crucial for future projections of regional climate change, which are necessary for adapting and mitigating global warming. In this paper, long-term weather research and forecasting (WRF) model simulation experiment with default FVC in WRF and actual FVC calculated using the Normalized Difference Vegetation Index of the moderate-resolution image spectroradiometer from 2001 to 2018 were simulated in Liaoning province. The analysis yielded the following results. (1) The increase in vegetation coverage decreased the annual average temperature in Liaoning province by 0.48°C, demonstrating the largest drop of 0.71°C in summer, 0.35°C and 0.66°C in spring and autumn, respectively, and the smallest drop of 0.2°C in winter. The increase in FVC had a significant cooling effect on the daily maximum and minimum air temperatures, among which the responses of the daily minimum temperature to the increase in vegetation coverage were greater than that of the maximum temperature, and the increase in FVC exhibited a good spatial consistency with the temperature cooling. (2) The significant increase in annual and seasonal FVC from 2001 to 2018 had a cooling trend on the annual and seasonal averages and maximum and minimum temperatures, particularly on the minimum temperature. (3) The increase in evapotranspiration causes an increase in the latent heat flux and a decrease in the sensible heat flux, which are primarily responsible for the decrease in air temperature caused by the increased FVC. The decrease in minimum temperature occurs mainly due to the decrease in the surface temperature driven by increased vegetation coverage, leading to a decrease in the upward long-wave radiation at night. In general, the larger the increase in FVC, the more pronounced will be the cooling effect, and the increase in FVC can reduce the rate of climate change in Liaoning Province.