Comparative Study On The Structural Characteristics And Mechanism Of The Atmospheric Boundary Layer Under Different Sea And Land Location Condition

The boundary layer height(PBLH)is an important parameter in understanding nearsurface land-atmosphere processes and improving mesoscale atmospheric models.This paper presents a statistical analysis of the spatial and temporal characteristics of boundary layer heights in Europe,North America,and China during 1990-2021,using radiosonde observations and reanalysis data.The study stations are classified into inland,coastal,and bay regions based on their location.Multiple linear regression and decoupling analysis were used to examine the dominant influence of boundary layer height and its spatial and temporal variability.The main findings are as follows:(1)The spatial and temporal variation characteristics of boundary layer height under different sea-land location conditions were statistically analyzed.There are spatial differences in the daily and seasonal cycles of boundary layer height,with the daily amplitude being the smallest in the coastal region and the largest in the inland region.The daily amplitude of PBLH in the bay region is generally between coastal and inland regions.PBLH in China reaches its maximum at 2:00 pm,with the western region having a larger daily amplitude than the eastern region.(2)The dominant factors of PBLH in the low boundary layer state are clarified.The wind field is the dominant factor affecting the nighttime PBLH.The nighttime inland and bay area PBLH is mainly influenced by wind speed,and the coastal area PBLH is influenced by both wind direction and wind speed.Coastal areas exhibit significantly higher PBLH under onshore flow conditions than under offshore flow conditions.this difference is most pronounced in winter and spring,and the effect of wind direction change on PBLH decreases with increasing latitude.The effect of nighttime wind speed on PBLH has a north-south difference in Europe and an east-west difference in North America.Besides,wind speed has a strong positive effect on daytime PBLH in winter.(3)The sensitivity of PBLH to the effects of near-surface temperature and specific humidity and the spatial and temporal variation were explored when daytime surface thermal factors were more influential.Temperature is the dominant controlling factor of daytime PBLH in inland areas.Daytime PBLH is dominated by specific humidity in high elevation and humid areas,and temperature in arid and semi-arid areas.The dominant factor of daytime PBLH in coastal areas varies with ocean currents.Coastal PBLH under the influence of warm currents is more sensitive to changes in temperature,and coastal PBLH under the influence of cold currents is more sensitive to changes in specific humidity.There are obvious seasonal variations and spatial heterogeneity in the dominant factors of PBLH in the bay.Temperature dominates PBLH in most areas in summer and autumn,with an expanded control over wet in spring and winter.Overall,our findings highlight the spatial and temporal variability in PBLH and its controlling factors across different regions,which can aid in improving the accuracy of mesoscale atmospheric models.