Inter-comparison of Vertical Profiling Instruments for Boundary Layer Measurements in an Urban Setting

A collection of surface based remote sensing instruments have been deployed In the NYC metro area for the purpose of characterizing the lower atmosphere and investigating air flow and atmospheric dispersion. With the addition of a network of rooftop surface stations and by ingesting data from various other available observational networks as well as assimilated data from modeling systems, we are able to compare the vertical profiling instruments to one another, identifying the strengths and weaknesses of the various assets that comprise the network of urban environmental observations. We compare the return signals from radar wind profilers (RWP), sodars and lidars. These comparisons allow us to calibrate the performance of similar instruments and they point out the issues that must be addressed when using non similar instruments for making similar observations. As an example, the wind rose plots from two roof top mounted sodars are shown in Fig. 1. Fig. 1a shows the wind rose from the Sodar on top of a building (about 100 m above sea level and 200 m above the sodar) at Steven's Institute of Technology in Hoboken, NJ and Fig 1(b) is the wind rose from the Sodar on top of a midtown Manhatten high rise (about 240 m above sea level and 20 m above the sodar). This particular day gave very similar observations whereas on other days there is a significant difference between the two sodar returns. These observations are also being compared to the return signals from two Radar wind Profilers in the area and various observations from surface stations as well as mesoscale simulations. In addition to the mean wind fields observations, these instruments are also capable of providing information on atmospheric stability and boundary layer heights. We are comparing observations from the surface networks and Doppler profilers to aerosol concentration vertical profiles and by using automated algorithms we determine mixing layer heights. This correspondence between mixing layer heights determined from aerosol lidar backscatter and convective mixing layer heights as measured by the radar wind profilers is usually very good during daytime where convective heating is dominant. However, the aerosol layer approach is still being investigated. Comparisons between Lidar returns and Ceilometer returns are illustrated. We have used both an edge detection filter approach and a wavelelt approach for determining the mixing layer heights. We find that the edge detection filters used for processing lidar is not well suited for the low SNR of the ceilometer and the wavelet approach is more robust there. Besides providing an important service to the New York City Metropolitan Area by supplying useful and timely air transport information, the network may act as a test bed for advanced studies of the dispersion of air particles under complex conditions with applications such as air pollution monitoring and support for emergency management. Acknowledgement This work was partially supported by the NOAA Interdisciplinary Scientific Environmental Technology (ISET) Cooperative SCIENCE Center under grant # NA06OAR4810187