Detection of planetary boundary-layer height with ARM ceilometers

Description

The height of the planetary boundary layer (PBL) is an important parameter for characterizing many atmospheric processes, including the dispersion of air pollutants and the formation of clouds. PBL depth is usually inferred from radiosonde measurements. However, at the ARM Climate Research Facility sites, balloon soundings occur only a few times per day and sometimes coincide with times that the PBL is rapidly developing. To improve the modeling of low-level clouds, an accurate measure of PBL height with higher temporal resolution is desired.

As part of the American Recovery and Reinvestment Act, an integrated Boundary Layer Cloud System was deployed in 2010 at each of the ARM Facility sites that comprises a suite of instruments including a laser ceilometer. The new Vaisala ceilometers have the capability of continuous monitoring of the aerosol structure within the PBL. Vaisala has developed an algorithm that uses an enhanced gradient method for robust, all-weather retrieval of PBL depth. A brief test of new software that applies the algorithm was conducted at the Southern Great Plains site in June 2011. An evaluation of the measurement of PBL height from the ceilometer, compared to that from the balloon-borne sounding system, will be presented.