Wednesday, 17 January 2007
Satellite to ground-based lidar comparisons using MPLNET data products
Exhibit Hall C (Henry B. Gonzalez Convention Center)
MPLNET is a network of ground-based lidar systems that provide long-term observations of aerosol and cloud properties at approximately 10 different locations around the globe. Each site in the network uses an elastic-scattering lidar co-located with a sunphotometer to provide data products of aerosol optical and physical properties. Expansion of the network is based on partnering with research groups interested in joining MPLNET. Results have contributed to a variety of studies including aerosol transport processes and cloud studies. One of the key motivations for MPLNET is to contribute towards the calibration and validation of satellite-base lidars such as GLAS/ICESAT and CALIPSO. MPLNET will be able to provide comparisons to several of the key aerosol and cloud CALIPSO data products, including: layer height and thickness, optical depth, backscatter and extinction profiles, and the lidar ratio. However, comparisons between ground and satellite data must be undertaken carefully due to the spatiotemporal sampling differences between measurements. This is particularly true for cloud backscatter properties which often highly variable over short temporal and spatial scales. To improve comparisons, MPLNET "spatial constant" profiles can be generated by adjusting the temporal average in each altitude-bin to maintain a constant advection path length (CAPL) throughout the profile. Under conditions where advection is the dominant source of atmospheric motion, CAPL data would be expected to improve correlations with CALPISO results and other satellite data. The potential benefit of using this approach is illustrated using a simple statistical model to examine signal correlation behavior for different spatial scales and measurement orientations in a random signal scene. Initial measurements comparing satellite results to MPLNET CAPL data are also presented. New MPLNET web-based tools are anticipated to allow users to more easily display and retrieve MPLNET satellite coincident data, and to permit the selection of averaging intervals and the generation of CAPL profiles around satellite coincident times. A review of current and future MPLNET plans for satellite inter-comparisons will also be discussed.