The transpiration of trees is an important factor in the surface energy balance and the hydrosphere-atmosphere-biosphere water vapor cycle. It is also the main cause of a tree’s ecological effects, such as cooling and humidification. A major challenge is to establish a model that can accurately predict the transpiration rate of urban trees at different time scales. To address this challenge, field measurements are used to obtain the instantaneous and hourly transpiration rates of four common subtropical trees (Bauhinia blakeana, Mangifera indica, Ficus microcarpa and Michelia alba), and their cooling effects are analyzed. The transpiration rate for the four trees ranges from 18 to 54 mg m⁻² s⁻¹, and the estimated energy loss due to transpiration ranges from 178 to 274 W/m², with an average of 229 W/m². On average, 33.2 % of incoming solar radiation is converted into latent heat. The Shuttleworth-Wallace model, including canopy resistance and soil resistance parameters, is adapted to urban tree characteristics in built-up environments. The resulting model is a theoretical model that provides a new methodology and reasonable results for predicting an urban tree’s transpiration rate under urban conditions. Its accuracy at different time scales is verified with field measurements. The predictability of water vapor cycle, thermal comfort and surface energy budgets in urban environments will be enhanced by incorporating the transpiration model into urban canopy model. Future applications and development of this model will help provide guidelines for sustainable urban planning and urban landscape management in terms of water vapor cycle and heat island mitigation.

树木的蒸腾作用是影响表面能平衡以及水圈-大气-生物圈水蒸气循环的重要因素。这也是造成树木生态效应（如降温和加湿）的主要原因。一个主要的挑战是建立一个模型，该模型可以准确地预测不同时间尺度上城市树木的蒸腾速率。为了应对这一挑战，现场测量用于获得四种常见的亚热带树（Bauhinia blakeana，Mangifera indica，Ficus microcarpa和Michelia alba）的瞬时和每小时蒸腾速率，并分析了它们的降温效果。四棵树的蒸腾速率为18至54 mg m ^-2  s ^-1，并且因蒸腾作用而产生的能量损失估计为178至274 W / m ²，平均为229 W / m ²。平均而言，入射的太阳辐射中有33.2％被转换为潜热。Shuttleworth-Wallace模型（包括冠层阻力和土壤阻力参数）适用于建筑物环境中的城市树木特征。结果模型是一种理论模型，为预测城市条件下城市树木的蒸腾速率提供了新的方法和合理的结果。通过现场测量验证了其在不同时间尺度上的准确性。通过将蒸腾模型纳入城市林冠模型，可以提高城市环境中水汽循环，热舒适性和表面能收支的可预测性。