A radar initiated interlock system which protects overflying aircraft from the laser radiation from the remote sensing systems located at Table Mountain Facility of the Jet Propulsion Laboratory is described in detail.
The long‐term evolution of upper stratospheric ozone has been recorded by lidars and microwave radiometers within the ground‐based Network for the Detection of Stratospheric Change (NDSC), and by the space‐borne Solar Backscatter Ultra‐Violet instruments (SBUV), Stratospheric Aerosol and Gas Experiment (SAGE), and Halogen Occultation Experiment (HALOE). Climatological mean differences between these instruments are typically smaller than 5% between 25 and 50 km. Ozone anomaly time series from all instruments, averaged from 35 to 45 km altitude, track each other very well and typically agree within 3 to 5%. SBUV seems to have a slight positive drift against the other instruments. The corresponding 1979 to 1999 period from a transient simulation by the fully coupled MAECHAM4‐CHEM chemistry climate model reproduces many features of the observed anomalies. However, in the upper stratosphere the model shows too low ozone values and too negative ozone trends, probably due to an underestimation of methane and a consequent overestimation of ClO . The combination of all observational data sets provides a very consistent picture, with a long‐term stability of 2% or better. Upper stratospheric ozone shows three main features: (1) a decline by 10 to 15% since 1980, due to chemical destruction by chlorine; (2) two to three year fluctuations by 5 to 10%, due to the Quasi‐Biennial Oscillation (QBO); (3) an 11‐year oscillation by about 5%, due to the 11‐year solar cycle. The 1979 to 1997 ozone trends are larger at the southern mid‐latitude station Lauder (45°S), reaching −8%/decade, compared to only about −6%/decade at Table Mountain (35°N), Haute Provence/Bordeaux (≈45°N), and Hohenpeissenberg/Bern(≈47°N). At Lauder, Hawaii (20°N), Table Mountain, and Haute Provence, ozone residuals after subtraction of QBO‐ and solar cycle effects have levelled off in recent years, or are even increasing. Assuming a turning point in January 1997, the change of trend is largest at southern mid‐latitude Lauder, +11%/decade, compared to +7%/decade at northern mid‐latitudes. This points to a beginning recovery of upper stratospheric ozone. However, chlorine levels are still very high and ozone will remain vulnerable. At this point the most northerly mid‐latitude station, Hohenpeissenberg/Bern differs from the other stations, and shows much less clear evidence for a beginning recovery, with a change of trend in 1997 by only +3%/decade. In fact, record low upper stratospheric ozone values were observed at Hohenpeissenberg/Bern, and to a lesser degree at Table Mountain and Haute Provence, in the winters 2003/2004 and 2004/2005.
Satellite sensors provide global measurements of ozone concentration that can be used to study the effects of the implementation of the Montreal Protocol. However, a key issue in deriving long-term ozone trends from successive satellite instruments is inter-comparability. Ground-based measurements offer continuous time series, but only at a few locations. The combination of ground-based measurements with satellite data is therefore an effective means to evaluate satellite instrument inter-comparability. In this study, we present validation results of ozone profiles from three atmospheric sensors onboard ENVISAT by comparison with lidar measurements. Results for the SCIAMACHY ozone profiles (version 3.01) show reasonable agreement with ground-based measurements (0 to −20%). The MIPAS full-resolution (version 4.61) dataset has good agreement with lidar (0 to 10%), whereas a small positive bias (up to 20%) was found for the MIPAS reduced-resolution prototype data. GOMOS dark-limb data (version 5.00) agree very well (0 ± 5%) with the correlative data, but underestimate ozone concentration at the polar regions.
Results of an investigation of mesospheric temperature inversion layers using long-term lidar measurements at mid- and low-latitudes are reported. In this paper, new results from different lidar observations of the invasion layers will be presented.
