he aerosol in the troposphere and the Planetary Boundary Layer (PBL) plays an important role in a number of atmospheric phenomena, air quality, cloud formation, radiation balance and chemical processes. The aerosol is also a convenient tracer in the observation of the PBL development. The backscatter lidar is already an established tool for continuous aerosol profiling, where a long-term experience is accumulated in both case studies and routine network observations.
The lidar is a single-wavelength, backscatter-depolarization instrument. The block diagrams of the optical and electronic parts are presented respectively in Figs.1 and 2. The specifications of the subsystems are given in Table 1.
The lidar is assembled in a box, as shown in Fig. 3. Outside of this box are the computer for operation control and, if necessary, an air-cooling unit.
The development of the lidar and its adaptation for measurements in the PBL and lower troposphere, emerges from a similar lidar development for airborne operation. From its airborne predecessor, the reported instrument inherited the compact and robust design, and the stable alignment. The lidar is compact and mounted in an environmental protection box (54cm * 58cm * 58 cm), what makes it convenient for transportation to remote campaign sites. The data acquisition and the house-keeping electronic systems are controlled by a microprocessor, and an embedded PC is used to control the lidar measurements and to temporarily store before transmitting the collected data to the server.
The alignment of the lidar is performed before placing it in the environmental housing. Thanks to its small size, its alignment may be performed when it is oriented in horizontal or slant directions towards convenient hard targets. The signals used to control the alignment in our practice are, once corrected for range, the returns from local hills at approximately 2 km, 4 km and 8 km, respectively, increasing in a sequence. During the procedure, apertures with different diameters are placed in front of the receiver. The alignment is controlled by maximizing the received signal from the same target and by its proportionality to the area of the apertures. The stability of the alignment after placing the lidar in its environment box is achieved by two means: first, by the specific design of the output mirror control mechanics; second, by temperature stabilization of the overall lidar structure inside the environmental housing.
Data and image products are sent to the server upon process completion via a ScriptFTP script. The image files and raw data files are automatically archived. Index files necessary for site navigation and display are appended to upon data arrival in server. Data and images are presented on this site, with the L2 image products accessed through the public links below.
Campbell, J.R., J.S. Reid, D.L. Westphal, J. Zhang, J.L. Tackett, B.N. Chew, E.J. Welton, A. Shimizu, N. Sugimoto, K. Aoki, and D.M. Winker, "2012: Characterizing the Vertical Profile of Aerosol Particle Extinction and Linear Depolarization over Southeast Asia and the Maritime Continent: The 2007-2009 View from CALIOP", Atmos. Res., doi:10.1016/j.atmosres.2012.05.007.
Campbell, J. R., Tackett, J. L., Reid, J. S., Zhang, J., Curtis, C. A., Hyer, E. J., Sessions, W. R., Westphal, D. L., Prospero, J. M., Welton, E. J., Omar, A. H., Vaughan, M. A., and Winker, D. M. , "2012: Evaluating nighttime CALIOP 0.532 Î¼m aerosol optical depth and extinction coefficient retrievals", Atmos. Meas. Tech., 5, 2143-2160, doi:10.5194/amt-5-2143-2012.
Campbell, J.R., E.J. Welton, N.A. Krotkov, K. Yang, S.A. Stewart, and M.D. Fromm. , "Likely Seeding of Cirrus Clouds by Stratospheric Kasatochi Volcanic Aerosol Particles Near a Mid-Latitude Tropopause Fold", Atmos. Environ., 46, 441-448, 2012.
Berkoff, T.A., M. Sorokin, T. Stone, T. Eck, R. Hoff, M. Canini, E.J. Welton, and B.N. Holben. , "Nocturnal aerosol optical depth measurements with a small-aperture automated photometer using the moon as a light source", J. Atmos. Oceanic Tech., 28, 1297-1306, 2011.