CAQIMS - Components, Illinois State Water Survey

Climate and Atmospheric Science

Climate, Air Quality and Impact Modeling System (CAQIMS)

A Basis for Achieving Economic, Societal and Environmental Goals in Illinois

Xin-Zhong Liang
Department of Atmospheric Sciences and Illinois State Water Survey, Institute of Natural Resource Sustainability, University of Illinois
Planetary Boundary Layer

1. Liu, S. and X.-Z. Liang, 2010: Observed Diurnal Cycle Climatology of Planetary Boundary Layer Height. J. Climate.

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 are then subject to various statistical analyses. It is demonstrated that PBLH occurrence frequencies under stable, neutral and unstable regimes follow respectively a narrow, intermediate and wide Gamma distribution 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 respectively 15 and 12 LST, whereas the cycle is weak over ice. Relative to mid-latitude 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 data base for critical model evaluation on the PBLH diurnal cycle and its temporal/spatial variability.

frequency distributions
Figure. The frequency distributions for occurrences of the stable (SBL, white), neutral (NRL, hatched), and unstable (CBL, shaded) regimes at 3-hr intervals (LST) across the diurnal cycle. The total number of data records at each LST is also plotted (star) using the scale on the right.

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