Review of ozone and temperature lidar validations performed within the framework of the Network for the Detection of Stratospheric Change

Abstract

The use of assimilation tools for satellite validation requires true estimates of the accuracy of the reference data. Since its inception, the Network for Detection of Stratospheric Change (NDSC) has provided systematic lidar measurements of ozone and temperature at several places around the world that are well adapted for satellite validations. Regular exercises have been organised to ensure the data quality at each individual site. These exercises can be separated into three categories: large scale intercomparisons using multiple instruments, including a mobile lidar; using satellite observations as a geographic transfer standards to compare measurements at different sites; and comparative investigations of the analysis software. NDSC is a research network, so each system has its own history, design, and analysis, and has participated differently in validation campaigns. There are still some technological differences that may explain different accuracies. However, the comparison campaigns performed over the last decade have always proved to be very helpful in improving the measurements. To date, more efforts have been devoted to characterising ozone measurements than to temperature observations. The synthesis of the published works shows that the network can potentially be considered as homogeneous within ¡2% between 20-35 km for ozone and ¡1 K between 35-60 km for temperature. Outside this altitude range, larger biases are reported and more efforts are required. In the lower stratosphere, Raman channels seem to improve comparisons but such capabilities were not systematically compared. At the top of the profiles, more investigations on analysis methodologies are still probably needed. SAGE II and GOMOS appear to be excellent tools for future ozone lidar validations but need to be better coordinated and take more advantage of assimilation tools. Also, temperature validations face major difficulties caused by atmospheric tides and therefore require intercomparisons with the mobile systems, at all sites.

Long-term trends observed in the middle atmosphere temperatures using ground based LIDARs and satellite borne measurements

“…In general, there exist 8-15 measurements in each month regardless of the season during the above mentioned periods. Detailed description of this LIDAR system is given in Keckhut et al (2004). Another LI-DAR has been operated in Sao Jose dos Campos, Brazil since 1972 and is mainly dedicated to the study of mesospheric sodium at the 589 nm resonant line in the 80-105 km altitude range (Batista et al, 2008).…”

Geophysical validation of temperature retrieved by the ESA processor from MIPAS/ENVISAT atmospheric limb-emission measurements

“…All lidar systems participating in the EQUAL project (except the one operating from Esrange) are part of the Network for the Detection of Atmospheric Composition Change (NDACC, www.ndacc.org). Their measurements are regularly monitored for their quality via measurement and algorithm intercomparison campaigns performed under the NDACC protocol (Keckhut et al, 2004). Lidar profiles are routinely archived in the ENVISAT validation database at NILU (www.nilu.no).…”

“…The temperature profile can be determined from the measurements using a seed value at the top of the profile, which is taken from statistical atmospheric models such as the MSIS90E model (Hedin, 1991). In an aerosol free atmosphere, temperatures are typically measured from 30 to around 60 km with an accuracy close to 1 K (Keckhut et al, 2004). Above this altitude the accuracy deteriorates rapidly.…”

Tropospheric ozone profiles by DIAL at Maïdo Observatory (Reunion Island): system description, instrumental performance and result comparison with ozone external data set

“…-the LI1200, a lidar dedicated to tropospheric water vapour (Hoareau et al, 2012;Dionisi et al, 2015;Vérèmes et al, 2017) and stratospheric-mesospheric temperature measurements (Morel et al, 2002;Keckhut et al, 2004Keckhut et al, , 2015Sivakumar et al, 2011a);…”