Abstract
In this study, we use the long-term satellite data to investigate seasonal and interannual variation of low-cloud fraction (LCF) and the associated controlling factors over the eastern and western North Pacific. On the seasonal time scale, the enhanced LCF over the eastern North Pacific in summer is actively coupled with strong estimated inversion strength (EIS) and 700-hPa relative humidity, and the LCF over the western North Pacific in winter is large and mainly caused by increased sensible heat flux and tropospheric low-level cold advection. On the interannual time scale, the increased LCF over the eastern North Pacific in summer is associated with increased EIS and decreased sea surface temperatures, in which the El Niño plays an important role; the enhanced LCF over the western North Pacific in spring and winter has a positive correlation with enhanced sensible heat flux (SHF) and tropospheric low-level cold advection, which can be partly explained by the subpolar frontal zone (SPFZ) intensity.
Highlights
Low-level clouds play an important role in the global radiation balance, which includes longwave radiation emission, as well as absorption and reflection of solar shortwave radiation [1]
The estimated inversion strength (EIS) in winter exhibits a zonal minimum distribution over the mid-latitude western North Pacific (Figure 1d), where a Figure 1a,b displays the distributions of climatological low-cloud fraction (LCF) over the North Pacific in summer maximum LCF dominates
Compared to the summertime situation, the EIS in winter exhibits a zonal minimum distribution over the mid-latitude western North Pacific (Figure 1d), where a maximum LCF dominates. This is in contrast to the well-known liner relationship between EIS and LCF [13]
Summary
Low-level clouds play an important role in the global radiation balance, which includes longwave radiation emission, as well as absorption and reflection of solar shortwave radiation [1]. Zhao found that where thin water clouds and pollution are coincident, there is an increase in cloud longwave emissivity resulting from elevated haze levels. This results in an estimated surface warming under cloudy skies [2]. During episodes of high surface haze aerosol concentrations and cloudy skies, both the net warming and net cooling are amplified. The low cloud has an important influence on global climate change [3]. A small change in fractional coverage of low-level clouds can exert significant influences on weather and climate [4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
