Close Correlation Between Vertically Integrated Tropospheric Water Vapor and the Downward, Broadband Thermal‐Infrared Irradiance at the Ground: Observations in the Central Arctic During MOSAiC

Abstract The impact of the vertical distribution of tropospheric water vapor on the cloud‐free downward, broadband thermal‐infrared irradiance was quantified using observations in the Central Arctic, north of 85°N, collected during the Arctic winter. The water vapor profiles were measured with a temporal resolution of using a Raman lidar. The observations revealed maximum values of integrated water vapor (IWV) contents of . Seven measurement cases of several‐hour durations of slowly changing air masses were examined. Furthermore, 53 rather short‐term (10 min) measurement cases were studied. The temporal evolution of the slowly changing air masses revealed a linear relationship between and IWV with slopes between 7.17 and and a coefficient of determination larger than 0.95 for most of the selected cases. The slopes and the ordinate intercepts showed a dependence on the water vapor‐weighted mean temperature (representative temperature of the water vapor distribution). The temperature determined with the Stefan‐Boltzmann law from correlated with the representative temperature with a coefficient of determination of 0.92. The analysis of 53 independent short‐term observations of different air masses confirmed the linear relationship between and IWV at wintertime cloud‐free conditions in the Arctic (coefficient of determination of 0.75, slope of , and ordinate intercept of ).