Long-term trends in marine boundary layer properties over the Atlantic Ocean
Date
2019Abstract
The marine boundary layer (MBL) is a key component of Earth’s climate system, and its main characteristics (height, entrainment efficiency, energy and mass fluxes, cloud formation processes, etc.) are closely linked to the properties of the inversion layer, which generally determines its height. Furthermore, cloud response to a warmer climate, one of the main sources of uncertainty in future climate projections, is highly dependent on changes in the MBL and in the inversion-layer properties. Long-term trends of the time series of MBLparametersat32stationsin theAtlanticOceanhavebeenanalyzedusingconvenientlyhomogenized radiosonde profilesfrom 1981to2010.Ingeneral,decreasingtrends are foundinthe strength andthicknessof the inversion layer and in the difference between the precipitable water vapor (PWV)in the free troposphere andtheMBL.Incontrast,positivetrendsarefoundintheheightofthebottomoftheinversionlayer,thelapse rates of virtual and equivalent potential temperatures, the PWV within the boundary layer, and the sea surface temperature (SST). The weakening trend of the inversion layer and the increasing desiccation of the free troposphere relative to the MBL could have important consequences for both the evolution of low cloud cover in a greenhouse-warming climate and the fragile local ecosystems, such as ‘‘cloud forests.’’