An in situ‐based analysis of the relationship between land surface “skin” and screen‐level air temperatures

This paper presents an analysis of the relationship between land surface temperatures (LST) and screen‐level air temperatures ( T 2m ) using in situ observations from 19 Atmospheric Radiation Measurement (ARM) deployments located in a range of geographical regimes. The diurnal cycle is resolved using 1 min observations: a particular focus of the study is on the relationship between daily extremes of LST (LST max , LST min ) and T 2m ( T max , T min ). Temperature differences are analyzed with respect to cloud, wind speed, and snow cover. Under cloud‐free, low wind speed conditions, daytime LST is often several degrees Celsius (°C) higher than T 2m at low‐to‐middle latitudes and at high latitudes during the summer months. In contrast, LST and T 2m are often close (e.g., within 2°C) under cloudy and/or moderate‐to‐high wind speed conditions or when solar insolation is low or absent. LST min and T min are generally well correlated ( r  > 0.8, often r  > 0.9), while seasonal correlations between LST max and T max are weaker ( r  > 0.6, often r  > 0.8). At high latitudes, LST and T 2m are well coupled in spring/autumn/winter; the relationship between LST and T 2m tends to weaken with decreasing latitude. The timing of daily extremes is also investigated and it is found that LST min and T min typically occur close to sunrise, with T min occurring slightly after LST min . LST max occurs close to solar noon, with T max typically occurring 1–3 hours later. This study will inform temperature data users on differences between LST and T 2m and aid development of methods to estimate T 2m using satellite LSTs.