Surface latent heat flux (LHF) is an important component in the heat exchange between the ocean and atmosphere over the tropical western North Pacific (WNP). The present study investigates the factors of seasonal mean LHF variations in boreal summer over the tropical WNP. Seasonal mean LHF is separated into two parts that are associated with low-frequency (> 90-day) and high-frequency (≤ 90-day) atmospheric variability, respectively. It is shown that low-frequency LHF variations are attributed to low-frequency surface wind and sea-air humidity difference, whereas high-frequency LHF variations are associated with both low-frequency surface wind speed and high-frequency wind intensity. A series of conceptual cases are constructed using different combinations of low- and high-frequency winds to inspect the respective effects of low-frequency wind and high-frequency wind amplitude to seasonal mean LHF variations. It is illustrated that high-frequency wind fluctuations contribute to seasonal high-frequency LHF only when their intensity exceeds the low-frequency wind speed under which there is seasonal accumulation of high-frequency LHF. When high-frequency wind intensity is smaller than the low-frequency wind speed, seasonal mean high-frequency LHF is negligible. Total seasonal mean LHF anomalies depend on relative contributions of low- and high-frequency atmospheric variations and have weak interannual variance over the tropical WNP due to cancellation of low- and high-frequency LHF anomalies.

地表潜热通量 (LHF) 是热带西北太平洋 (WNP) 海洋与大气之间热交换的重要组成部分。本研究调查了热带 WNP 北半球夏季 LHF 季节性平均变化的因素。季节性平均 LHF 分为两部分，分别与低频（> 90 天）和高频（≤ 90 天）大气变率相关。结果表明，低频 LHF 变化归因于低频表面风和海气湿度差异，而高频 LHF 变化与低频表面风速和高频风强度有关。使用低频和高频风的不同组合构建了一系列概念案例，以检查低频风和高频风幅对季节性平均 LHF 变化的各自影响。说明高频风波动只有在其强度超过低频风速时才会对季节性高频LHF有贡献，在此情况下高频LHF存在季节性积累。当高频风强小于低频风速时，季节性平均高频LHF可以忽略不计。总季节性平均 LHF 异常取决于低频和高频大气变化的相对贡献，并且由于低频和高频 LHF 异常的抵消，热带 WNP 的年际变化较弱。