Estimating climatological planetary boundary layer heights from radiosonde observations: Comparison of methods and uncertainty analysis

Abstract

[1] Planetary boundary layer (PBL) processes control energy, water, and pollutant exchanges between the surface and free atmosphere. However, there is no observationbased global PBL climatology for evaluation of climate, weather, and air quality models or for characterizing PBL variability on large space and time scales. As groundwork for such a climatology, we compute PBL height by seven methods, using temperature, potential temperature, virtual potential temperature, relative humidity, specific humidity, and refractivity profiles from a 10 year, 505-station radiosonde data set. Six methods are directly compared; they generally yield PBL height estimates that differ by several hundred meters. Relative humidity and potential temperature gradient methods consistently give higher PBL heights, whereas the parcel (or mixing height) method yields significantly lower heights that show larger and more consistent diurnal and seasonal variations (with lower nighttime and wintertime PBLs). Seasonal and diurnal patterns are sometimes associated with local climatological phenomena, such as nighttime radiation inversions, the trade inversion, and tropical convection and associated cloudiness. Surface-based temperature inversions are a distinct type of PBL that is more common at night and in the morning than during midday and afternoon, in polar regions than in the tropics, and in winter than other seasons. PBL height estimates are sensitive to the vertical resolution of radiosonde data; standard sounding data yield higher PBL heights than high-resolution data. Several sources of both parametric and structural uncertainty in climatological PBL height values are estimated statistically; each can introduce uncertainties of a few 100 m.

Lidar-based remote sensing of atmospheric boundary layer height over land and ocean

“…Below the capping inversion, usually the ABL is assumed to be well mixed. These different methods tried to identify ABL top characteristics to determine BLH with different variables such as temperature or humidity gradient, but often give different BLHs (Seidel et al, 2010). The diurnal boundary layer aerosol structures over different surfaces were further investigated.…”

“…However, in operational forecast models, regional models, or global climate models, the ABL is still poorly simulated due to complex processes at small temporal and spatial scales (Lenderink and Holtslag, 2000;Hannay et al, 2009;Wyant et al, 2010). The modeled ABL is also not fully evaluated due to the lack of a reliable global BLH climatology database (Seidel et al, 2010). Therefore, a better understanding of the ABL structure and physical processes is required to improve model simulations.…”

“…Usually, the BLH is indirectly diagnosed from an analysis of thermodynamic variables, turbulence-related parameters or measuring concentrations of tracers, by using different definitions of the BLH with respect to the various characteristics of the ABL, as reviewed by Seidel et al (2010). However, different definitions often give different BLH results, and no standard BLH definition exists (Seidel et al, 2010). Seidel et al (2010) recommended either the parcel method or the Richardson number (RI) method to be the most reliable method.…”

“…The ABL is generally described as the lowest layer of atmosphere that is directly influenced by the Earth's surface, and responds to changes in the surface within a short amount of time (Stull, 1988). Usually, the BLH is indirectly diagnosed from an analysis of thermodynamic variables, turbulence-related parameters or measuring concentrations of tracers, by using different definitions of the BLH with respect to the various characteristics of the ABL, as reviewed by Seidel et al (2010). However, different definitions often give different BLH results, and no standard BLH definition exists (Seidel et al, 2010).…”

“…However, different definitions often give different BLH results, and no standard BLH definition exists (Seidel et al, 2010). Seidel et al (2010) recommended either the parcel method or the Richardson number (RI) method to be the most reliable method. The RI method is applied to radiosonde data in this study, as detailed in Sect.…”