Water vapor emissions in urban areas are important processes in urban hydrology and urban climate. We evaluated the spatial and temporal characteristics of water vapor fluxes, based on measurements at an urban center for six years, suburban landscape for five years, and urban park for one year in Sakai, Osaka, Japan. The magnitudes of the water vapor emissions were approximately half for the urban center and one-fourth for the suburb compared with evapotranspiration in a planted forest near the city. Anthropogenic water vapor emissions were estimated to be high in the urban center, resulting in higher water vapor emissions in the urban center than in the suburb. The water vapor emissions at the three landscapes were controlled by net radiation and surface wetness, where surface conductance decreased with days after a rain event. Evapotranspiration of the urban park was comparable to that of the planted forest due to the dry urban atmosphere, known as the oasis effect. The green fraction explained the spatial variation in the annual water vapor emissions. Based on the linear perturbation analysis, the changes in water vapor emissions by urbanization could be determined by a balance between increased anthropogenic water vapor emissions and decreased surface conductance.

城市地区的水蒸气排放是城市水文学和城市气候中的重要过程。我们根据在日本大阪市坂田市的城市中心六年，郊区景观五年和城市公园一年的测量结果，评估了水蒸气通量的时空特征。与城市附近人工林的蒸散量相比，城市中心的水蒸气排放量约为一半，而郊区则为四分之一。据估计，城市中心的人为水蒸气排放量很高，导致城市中心的水蒸气排放量高于郊区。这三个景观的水蒸气排放量受净辐射和表面湿度的控制，其中降雨后几天，表面电导率下降。由于干燥的城市大气，绿洲效应使城市公园的蒸腾量与人工林的蒸腾量相当。绿色部分解释了每年水蒸气排放量的空间变化。基于线性扰动分析，可以通过人为增加的水蒸气排放量与减少的表面电导之间的平衡来确定城市化过程中水蒸气排放量的变化。