Abstract
Abstract. This work uses the synergy of collocated microwave radiometry and near-infrared imagery to study the marine boundary layer water vapor. The Advanced Microwave Scanning Radiometer (AMSR) provides the total column water vapor, while the Moderate Resolution Imaging Spectroradiometer (MODIS) near-infrared imagery provides the water vapor above the cloud layers. The difference between the two gives the vapor between the surface and the cloud top, which may be interpreted as the boundary layer water vapor under certain conditions. As a by-product of this algorithm, we also store cloud top information of the MODIS pixels used, a proxy for the inversion height, as well as the sea surface temperature and total column water vapor from the AMSR measurements. Hence, the AMSR–MODIS dataset provides several of the variables associated with the boundary layer thermodynamic structure. Comparisons against radiosondes and GPS radio occultation (GPSRO) data demonstrate the robustness of these boundary layer water vapor estimates. We explore the annual cycle of the number of observations as a proxy for stratus cloud amount, in well-known stratus regions; we then exploit the 16 years of AMSR–MODIS synergy to study for the first time the annual variations of the boundary layer water vapor in comparison to the sea surface temperature and the boundary layer cloud top height (equivalent to the inversion height) climatologies, and lastly we explore the climatological behavior of these variables on stratocumulus-to-cumulus transitions.
Highlights
The boundary layer may be defined as the lower part of the troposphere that is directly influenced by the presence of the Earth’s surface through turbulence
The aim of this study is to show results from a ∼ 16-year boundary layer column water vapor (BL-CWV) dataset derived from the synergy of microwave and near-infrared satellite imagery
As discussed by Ao et al (2012), we found that the sharpness parameter is largest over the eastern subtropical oceans where stratocumulus occur, with maximum average values of around 2.7 near the coast of Chile
Summary
The boundary layer may be defined as the lower part of the troposphere that is directly influenced by the presence of the Earth’s surface through turbulence. This layer mediates the exchanges of energy, momentum, water, carbon, and pollutants between the surface and the rest of the atmosphere and responds to surface forcing with a timescale of about an hour or less (Stull, 1988). Boundary layer processes are crucial for understanding cloud–climate feedback mechanisms (e.g., Teixeira et al, 2011). Despite their importance, boundary layer processes are still not well represented in weather and climate models. One major issue in the development of accurate boundary layer parameterizations is the lack of global measurements
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