2:00 PM - 2:15 PM
[ACG54-02] Vertical Structure of the Low-level Clouds over the Western North Pacific in Summer: Analysis Based on Aircraft Observations in Summer 2013 and 2022
Keywords:Cloud Physics, Boundary Layer, Aircraft Observation
Low-level clouds such as stratocumulus affect the global radiation budget and cause uncertainties in climate prediction. Our current basic picture of the vertical structures of stratocumulus clouds derive mostly from observations conducted over the subtropical eastern Pacific. However, direct in-situ observations of low-level clouds in the mid-latitudes including the western North Pacific, where low-level cloud cover is high in summer, remain limited.
This study aims to reveal the characteristics and formation processes of summer low-level clouds over the western North Pacific based on in-situ aircraft observations conducted in 2013 and 2022. We compared these results with those obtained in previous experiments conducted over the subtropical eastern Pacific, highlighting key differences in vertical structure of clouds.
We used data obtained from aircraft measurements conducted off the east coast of Hokkaido (western North Pacific) from late July to early August 2022. During these flights, we obtained 95 vertical profiles of clouds by ascending or descending the research aircraft.
In our analysis, we focused on adiabaticity of clouds (how much the observed liquid water content vertical distributions differ from adiabatic clouds), vertical coupling in the boundary layers (characterized by the difference in liquid water potential temperature between upper and lower layers), and inversion strength at cloud tops. To investigate the variability in cloud vertical structures, trajectory of the air parcels that formed the clouds was examined. To confirm whether the cloud vertical structure obtained from the summer 2022 observations is common in the western North Pacific, we analyzed aircraft data collected in July 2013 over the same domain.
Compared to subtropical low-level clouds, the clouds observed in the western North Pacific (midlatitude clouds) had a weaker temperature inversion at cloud tops and higher specific humidity above the cloud tops. The median cloud-top height was lower than that of the subtropical region, while some clouds reached 2000 m in height. These higher cloud-top clouds tended to have a non-adiabatic structure and decoupled boundary layers. Trajectory analysis suggested that the origin of the air parcels composing the clouds differed with altitude. In the presentation, we will discuss the characteristics and causes of these various vertical structures of the low-level clouds in the western North Pacific by also comparing with the aircraft data obtained in the same region in the summer of 2013.
This study aims to reveal the characteristics and formation processes of summer low-level clouds over the western North Pacific based on in-situ aircraft observations conducted in 2013 and 2022. We compared these results with those obtained in previous experiments conducted over the subtropical eastern Pacific, highlighting key differences in vertical structure of clouds.
We used data obtained from aircraft measurements conducted off the east coast of Hokkaido (western North Pacific) from late July to early August 2022. During these flights, we obtained 95 vertical profiles of clouds by ascending or descending the research aircraft.
In our analysis, we focused on adiabaticity of clouds (how much the observed liquid water content vertical distributions differ from adiabatic clouds), vertical coupling in the boundary layers (characterized by the difference in liquid water potential temperature between upper and lower layers), and inversion strength at cloud tops. To investigate the variability in cloud vertical structures, trajectory of the air parcels that formed the clouds was examined. To confirm whether the cloud vertical structure obtained from the summer 2022 observations is common in the western North Pacific, we analyzed aircraft data collected in July 2013 over the same domain.
Compared to subtropical low-level clouds, the clouds observed in the western North Pacific (midlatitude clouds) had a weaker temperature inversion at cloud tops and higher specific humidity above the cloud tops. The median cloud-top height was lower than that of the subtropical region, while some clouds reached 2000 m in height. These higher cloud-top clouds tended to have a non-adiabatic structure and decoupled boundary layers. Trajectory analysis suggested that the origin of the air parcels composing the clouds differed with altitude. In the presentation, we will discuss the characteristics and causes of these various vertical structures of the low-level clouds in the western North Pacific by also comparing with the aircraft data obtained in the same region in the summer of 2013.