Long-Term Observations of the Dynamics of the Continental Planetary Boundary Layer

Abstract

Time series of mixed layer depth, z i , and stable boundary layer height from March through October of 1998 are derived from a 915-MHz boundary layer profiling radar and CO 2 mixing ratio measured from a 447-m tower in northern Wisconsin. Mixed layer depths from the profiler are in good agreement with radiosonde measurements. Maximum z i occurs in May, coincident with the maximum daytime surface sensible heat flux. Incoming radiation is higher in June and July, but a greater proportion is converted to latent heat by photosynthesizing vegetation. An empirical relationship between z i and the square root of the cumulative surface virtual potential temperature flux is obtained (r 2 ϭ 0.98) allowing estimates of z i from measurements of virtual potential temperature flux under certain conditions. In fair-weather conditions the residual mixed layer top was observed by the profiler on several nights each month. The synoptic mean vertical velocity (subsidence rate) is estimated from the temporal evolution of the residual mixed layer height during the night. The influence of subsidence on the evolution of the mixed, stable, and residual layers is discussed. The CO 2 jump across the inversion at night is also estimated from the tower measurements.

Role of the residual layer and large-scale subsidence on the development and evolution of the convective boundary layer

“…The numerical experiments that do not consider subsidence overestimate the observed z 1 by less than 200 m. Long-term observations of the boundary layer show the importance of considering subsidence to obtain realistic approximations (Yi et al, 2001;Pietersen et al, 2014).…”

“…We obtain the value of subsidence to be included in DALES and MLM numerical experiments, following Yi et al (2001), by analyzing the observed vertical profile of the potential temperature at 01:30 and 07:30 UTC on 1 July 2011 (see Fig. 2).…”

“…Sorbjan (1996), Sullivan et al (1998) and Conzemius and Fedorovich (2006) studied the role of the entrainment processes; Moeng and Sullivan (1994), Fedorovich et al (2001), Fedorovich et al (2001), Pino et al (2003), Pino et al (2006a) and Pino and Vilà-Guerau de Arellano (2008) the contribution of shear in the generation and maintenance of CBL. Moreover, Yi et al (2001), de Arellano et al (2004), Casso-Torralba et al (2008) and Vilà-Guerau de Arellano et al (2009) studied the influence of CBL evolution on the carbon dioxide (CO 2 ) or isoprene budget.…”

A Method for Deriving the Boundary Layer Mixing Height from MODIS Atmospheric Profile Data

“…The results from clear days in winter and summer are mapped in Figure 10 for two example days. The mixing layer height is primarily driven by variation in the vertical flux of energy and momentum caused by the balance between the heating of the earth's surface by incoming solar radiation and radiative cooling of the surface [27][28][29]. Accordingly, as Figure 10 shows, the MH is lower in the winter and relatively higher in the summer, demonstrating that net radiation is the main factor driving the development of the PBL.…”

Evaluation of NWP results for wintertime nocturnal boundary‐layer temperatures over Europe and Finland

“…The main processes responsible for the formation of SBL are (1) cooling of the surface due to a negative radiation budget (Sun et al, 2003), (2) warm-air advection over a cold surface (Vihma et al, 2003), and (3) subsidence (Yi et al, 2001). A variety of subgrid-scale processes may occur in a SBL, e.g.…”