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

Abstract

Abstract 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.