Understanding the Atmospheric Boundary Layer in Complex Terrain with Radiosonde, Sodar, RASS, and Tower Data

摘要

A better understanding of the atmospheric boundary layer (ABL) is important to improved sensor siting, air pollution forecasting, deciphering air quality trends, dispersion model development, public health protection, and overall innovation in the field of air pollution control. Understanding of the ABL is especially challenging in complex terrain. A variety of equipment is used in the lowest portion of the ABL to sense the movement of air and its changing temperature with height. This paper examines the simultaneous temperature and wind measurements made by twice daily U.S. National Weather Service (NWS) radiosonde releases and a sound detection and ranging / radio acoustic sounding system (sodar/RASS) unit. Included are observations from a 10 m meteorological tower used to supplement the sodar/RASS measurements. The area examined is the complex terrain of Allegheny County, Pennsylvania. Analysis is based on radiosonde data collected from the Pittsburgh NWS field office (PIT) in western Allegheny County and sodar/RASS/10-m tower data collected from an industrial site located in Clairton, PA in southern Allegheny County. Meteorological measurements taken during the spring of 2019 along with other times of interest are evaluated. The PIT radiosonde data are 12Z (7 am EST) and 00Z (7 pm EST) readings, while the Clairton sodar/RASS/10-ni tower values are measurements made at 11:00Z - 11:15Z (6 am - 6:15 am EST) and 23:00Z - 23:15Z (6 pm - 6:15 pm EST) - the intervals that span the typical release times of the radiosondes. Results reveal differences in topography and suburban (PIT) versus more-urban (Clairton) settings along with differences in the measurement techniques. The impact of synoptic conditions and the urban heat island effect are proposed. Recommendations are given for siting of equipment and interpretation of results with respect to understanding the ABL in complex terrain.