Engineering topics

Ancellet, G.

Publications and source records attributed to Ancellet, G..

5 records

NASA NTRS2004

The NDSC ozone and temperature lidar alogorithm intercomparison ubutuatuve (A2I): project overview

In September 2003, the Lidar Working Group (LWG) of the Network for Detection of Stratospheric Change (NDSC) initiated an extensive project to compare the ozone and temperature algorithms used within NDSC. This initiative, referred to later as Algorithm Intercomparison Initiative (A2I), uses simulated lidar signals to test and compare various parts of the ozone and temperature lidar algorithms. In addition to the fact that it meets the requirement of the NDSC protocols, this exercise allows the detailed assessment, by all the participants, of some of the sources and magnitudes of various uncertainties associated with the algorithms, and/or with the theoretical assumptions made in these algorithms. The outcome of the A21 is to try to find common grounds in the way ozone and temperature can be retrieved in order to reduce and possibly eradicate discrepancies due to algorithm issues alone. Specific issues such as homogenizing the choice of Rayleigh extinction cross-sections, ozone absorption cross-sections, a priori information, and the definition of the vertical resolutions are among the primary targets of the A21 outcome.

lidar↗

NASA NTRS1994

Ozone transport during a cut-off low event studied in the frame of the TOASTE program

A study of ozone transfer to the troposphere has been performed during two phases of the evolution of a cut-off low using both ozone vertical profiles and objective analysis of the ECMWF to compute potential vorticity distributions and air mass trajectories. Ozone profiles were measured by a ground based lidar system at the Observatoire de Haute Provence (OHP, 43 deg 55 N, 5 deg 42 E). A stratospheric ozone transport into the troposphere has been observed during a tropopause fold which occurred at the beginning of the cut-off low formation and during the erosion phase of the cut-off low. From the estimate of the maximum ozone content transferred to the troposphere, both mechanisms have the same order of magnitude of influence on the ozone flux to the troposphere. On a time scale of a few days, the correlation is very good between the potential vorticity and the ozone time evolution in the vicinity of the upper level frontal system.

Ancellet, G.↗

NASA NTRS1992

The NDSC Primary Site at the Observatoire De Haute-provence: Ozone and Aerosols Observations (1986-1992)

The primary site of the newly implemented Network for Detection of Stratospheric Changes (NDSC) includes three main sites in the alpine regions of southern Europe. At one of these observatories, a coherent set of experimental systems has been established to monitor on a long-term basis ozone, aerosols, minor constituents, and temperature vertical distributions in the troposphere and stratosphere. Such techniques include several lidar systems, balloon-borne sondes and ultraviolet visible spectrometry. Lidar measurements of stratospheric aerosols are performed on a routine basis, since 1980. These include the vertical distribution of the extinction and backscattering coefficients from the tropopause. Recently, measurements performed following the eruption of Mount Pinatubo, have allowed researchers to follow the time evolution of the aerosol cloud in middle latitude regions.

Megie, G.↗

NASA NTRS1992

First Results from TROLIX 1991: an Intercomparison of Tropospheric Ozone Lidars

Within the framework of the European environmental research programme EUROTRAC, lidar systems for routine measurements of vertical ozone profiles throughout the planetary boundary layer and the free troposphere are currently under development. Several of these systems are now operational and an intercomparison experiment was undertaken in the period from June 10 to June 28, 1991 in Bilthoven, the Netherlands. The main scientific objectives defined for the campaign are: (1) compare the lidar measurements to in situ measurements of the ozone concentration; (2) determine how many and which wavelengths are needed for a sufficiently accurate ozone retrieval in the lower troposphere under realistic conditions; (3) assess the accuracy that can be achieved under realistic conditions; and (4) compare the performance of the participating systems.

Apituley, A.↗

NASA NTRS1992

A Multi-wavelength Ozone Lidar for the EASOE Experiment

The study of the ozone layer during winter and springtime in high latitude regions is a major issue in atmospheric research. For a better understanding of these problems, an important experimental campaign called EASOE (European Arctic Stratospheric Ozone Experiment) was organized by the European Community during the winter 1991-1992. Its main objective was to establish a budget of the ozone destruction processes on the whole northern hemisphere. This implied the simultaneous operation of different types of instruments located in both high and mid-latitude regions in order to study the destruction processes as well as the evolution of the ozone layer during the period of the campaign. A description will be given here of a mobile ozone lidar instrument specially designed for operation during the EASOE campaign. This system, which performs ozone measurements in the 5 to 40 km altitude range was located in Sodankyla, Finland as part of the ELSA experiment which also includes operation of another multi-wavelength lidar designed for polar stratospheric cloud measurements.

Godin, S.↗