Observed Diurnal Cycle Climatology of Planetary Boundary Layer Height

Abstract

An observational climatology of the planetary boundary layer height (PBLH) diurnal cycle, specific to surface characteristics, is derived from 58 286 fine-resolution soundings collected in 14 major field campaigns around the world. An objective algorithm determining PBLH from sounding profiles is first developed and then verified by available lidar and sodar retrievals. The algorithm is robust and produces realistic PBLH as validated by visual examination of several thousand additional soundings. The resulting PBLH from all existing data is then subject to various statistical analyses. It is demonstrated that PBLH occurrence frequencies under stable, neutral, and unstable regimes follow a narrow, intermediate, and wide Gamma distribution, respectively, over both land and oceans. Over ice all exhibit a narrow distribution. The climatological PBLH diurnal cycle is strong over land and oceans, with a distinct peak at 1500 and 1200 LT, whereas the cycle is weak over ice. Relative to midlatitude land, the PBLH variability over tropical oceans is larger during the morning and at night but much smaller in the afternoon. This study provides a unique observational database for critical model evaluation on the PBLH diurnal cycle and its temporal/spatial variability.

Simulation of nitrate, sulfate, and ammonium aerosols over the United States

“…To correct this issue, we have modified the model to define a minimum mechanical mixing depth, calculated based on the local friction velocity (Lin and McElroy, 2010;Koracin and Berkowicz, 1988;Heald et al, 2012); any GEOS-5 mixed layer depths below this value are set to the minimum mechanical mixing depth. This modification yields nighttime mixed layer depths that are more consistent with observations (Liu and Liang, 2010), and more realistic diurnal variations in predicted aerosol concentrations. Zhang et al (2012) suggest that nitrate concentrations may be over-predicted owing to an overestimate of nighttime nitric acid formation through heterogeneous N 2 O 5 hydrolysis, N 2 O 5 + H 2 O → 2HNO 3 , as N 2 O 5 concentrations build up due to the gas phase reaction of NO 2 with NO 3 .…”

“…The offline GEOS-5 meteorological fields used here display unrealistically low mixed layer depths at night, compared with observed mixed layer depths (Liu and Liang, 2010). This bias causes GEOS-5 driven GEOS-Chem simulations to predict an artificially large build up of aerosols at night and corresponding high biases in predicted daily and monthly average concentrations.…”

Probabilistic stability and ‘tall’ wind profiles: theory and method for use in wind resource assessment

“…eff is the long-term mean inverse ABL depth, which is somewhat biased by stable conditions so that h eff ∼300-500 m, consistent with the distributions P (h) given by [20] (c.f. also [15]).…”

Estimation of atmospheric mixing layer height from radiosonde data

“…The mixing layer begins to develop after sunrise due to the increased turbulent fluxes associated with surface-absorbed solar radiation and heating (Medeiros et al, 2005;Liu and Liang, 2010). The value of h reaches its maximum during the late afternoon over land (Liu and Liang, 2010;Bianco et al, 2011;Svensson et al, 2011). Comparing Fig.…”

“…A possible explanation for the deep h along the semiarid Rocky Mountains in the southwestern US is that the low soil moisture characteristic of the high elevations provides enough sensible heat flux to extend the h. However, because the region spans several time zones, the spatial variations observed at a fixed time may be affected by temporal variations. The mixing layer begins to develop after sunrise due to the increased turbulent fluxes associated with surface-absorbed solar radiation and heating (Medeiros et al, 2005;Liu and Liang, 2010). The value of h reaches its maximum during the late afternoon over land (Liu and Liang, 2010;Bianco et al, 2011;Svensson et al, 2011).…”