Abstract
The land surface influences the atmospheric boundary layer (ABL) through its impacts on the partitioning of available energy into evaporation and warming. Previous research on understanding this complex link focused mainly on site-scale flux observations, gridded satellite observations, climate modeling, and machine-learning experiments. Observational evidence of land surface conditions, among which soil moisture, impacting ABL properties at intermediate landscape scales is lacking. Here, we use a combination of global weather balloon soundings, satellite-observed soil moisture, and a coupled land-atmosphere model to infer the soil moisture impact on the ABL. The inferred relationship between soil moisture and surface flux partitioning reflects distinctive energy- and water-limited regimes, even at the landscape scale. We find significantly different behavior between those two regimes, associating dry conditions with on average warmer (≈3 K), higher (≈400 m) and drier (≈1 kPa) afternoon ABLs than wet conditions. This evidence of land–atmosphere coupling from globally distributed atmospheric measurements highlights the need for an accurate representation of land–atmosphere coupling into climate models and their climate change projections.
Highlights
The diurnal evolution of the atmospheric boundary layer (ABL), the well-mixed layer between the land surface and free troposphere, plays a key role in weather conditions and air quality at the Earth’s surface
ABL dynamics are sensitive to heat and moisture inputs from the land surface, which are directly regulated by soil moisture availability and its impact on the partitioning of surface energy fluxes[15], and by incoming solar radiation, which dictates the amount of energy available for partitioning at the land surface
We find that the select days with convective warm conditions, excluding days on ESA CCI soil moisture (0.73; Supplementary Fig. 1), which validates which sublimation occurs, avoiding complexities related to frozen both the land surface schemes applied in CLASS4GL and confirms surface water and substantial variation in the seasonal cycle of that soil moisture leaves a signature in the vertical profiles, as surface flux partitioning during the cold season and focusing on measured by balloon soundings, by affecting the surface flux days which are driven by sensible heat and governed by partitioning
Summary
The diurnal evolution of the ABL, the well-mixed layer between the land surface and free troposphere, plays a key role in weather conditions and air quality at the Earth’s surface. Due to vertical convective mixing of air from the land surface to the top of the ABL, the vertical temperature and humidity profiles integrate surface heterogeneity and free tropospheric conditions over distances tens of times the ABL height We refer to this as the landscape scale throughout this study. We find that the select days with convective warm conditions (see “Preprocessing adjusted initial soil moisture from CLASS4GL correlates well with of weather balloon soundings” in Methods), excluding days on ESA CCI soil moisture (0.73; Supplementary Fig. 1), which validates which sublimation occurs, avoiding complexities related to frozen both the land surface schemes applied in CLASS4GL and confirms surface water and substantial variation in the seasonal cycle of that soil moisture leaves a signature in the vertical profiles, as surface flux partitioning during the cold season and focusing on measured by balloon soundings, by affecting the surface flux days which are driven by sensible heat and governed by partitioning. This product is the only global observational soil moisture with an adequate time period available and has been used successfully in similar applications before[38,44]
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