• Access: Data access will be directly from the NDACC database to the AVDC.
• Protocol: NDACC Protocol applies for Aura investigators.
• Timeliness: Different stations will participate with varying degrees of promptness. Many sites have agreed to provide data within weeks to one month; some sites will respond faster, in near-real-time to days. Implementation of a new standardized HDF5 file format (see below) will also occur with varying degrees of promptness. Past experience suggests that a fair amount a coaxing may be necessary to get many of the lidar investigators to implement the new format.

(July – December 2004, with focus on September-November)

• The JPL Table Mountain Facility and Mauna Loa Observatory lidars can, and will, provide essentially real-time data for AURA validation (ozone, temperature and aerosols). The TMF WV system should be fully operational in the September/October time frame, though it may not yet be independently validated. Tom McGee’s mobile lidar facility (upgrading to include Raman WV) will be able to provide early data. Historically, Ny Alesund and Hoehenpeissenberg have been good at responding quickly whereas the French controlled stations have been slower. Southern hemisphere sites most likely to make data available promptly are Lauder, NZ and La Reunion Stations. Updated tabulation of this information is in progress.

There are limitations with Raman WV lidar measurements not normally associated with ozone, temperature and aerosol lidar measurements:

• Maximum altitude: the maximum altitude that ground-based lidar can measure WV is limited by the inherently weak Raman backscattered signal. The probable highest lidar WV measurements will be made to 16 – 18 km by the TMF & MLO lidar, at elevations 2.3km and 3.5km respectively, which have the advantage of decreased/eliminated signal attenuation from the boundary layer. In general however, WV lidar systems will be challenged to reach the tropopause.
• Calibration: Raman WV lidar calibration constants must be determine using either an independent WV concentration at a reference altitude (usually made with a Vaisala sonde) or by using a calibration lamp or some other source with a known spectral intensity. As the calibration-constants fluctuate temporally, calibration must be done regularly, ideally but not always prior to each measurement. Calibration methods are currently very variable within the lidar community.

• Daulerio, P., C. Cornacchio, M. Iarlori, G. Rocci, F. Congeduti, G. Pappalardo, V. Rizi, L. Mona, F. Fierli, Intercomparison of water vapor retrieval between three Raman lidar stations, ILRC22, 12-16 July 2004.
• Sabatino, D., P. Di Girolamo, D. N. Whiteman, B. B. Demoz, E. V. Browell, S. Ismail, R. Ferrare, S. A. Kooi, A. Behrendt, V. Wulfmeyer, Water vapor measurements during the international H2O project: Intercomparisons between scanning Raman lidar and lase, ILRC22, 12-16 July 2004.
Immler F., O. Schrems, Lidar measurements of cirrus clouds in the northern and southern hemisphere during INCA (55°N, 53°S): A comparative study, Geophys. Res. Lett., 29(16 ), 10.209/2002GL015077, 2002.
• Neuber, R., Beyerle, G., Gathen, P. von der, Wahl, P., Dahl, A., Gross, M., McGee, Th., Klein, U., Steinbrecht, W. (2001). An intercomparison campaign of ozone and temperature measurements in the Arctic (NAOMI-98, Ny-Ålesund/Spitsbergen), Mem. Natl Inst. Polar Res., Spec. Issue, 54, 65-70, 2001.