Stratospheric Changes Observed With Lidar

.Recently it has been recognised that one must take into account the stratospheric behaviour in many aspects of the studies of climate changes. In addition to the direct contribution of the stratosphere on climate, the observation of the stratosphere may be used as a "fingerprint" of various climate forcing. Key parameters for stratospheric monitoring concern primarily ozone, temperature and wind. To provide the earliest and the best confidence of trend detection and quantification, it requires long series of frequent observations averaged on a weekly or monthly basis. In opposite to in-situ measurements carried on balloons or rockets, remote sensing techniques from ground appear well adapted for long-term monitoring in using a single instrument for decades, self-calibrated, with no physical interactions between the sensor and the medium. Lidar are highly valuable as it requires vertical profiles to better undersdand processes and to separate the different climate forcing. However, many instrumental changes need to be made for any instrument operating on a routine basis over decades. the main limited factor is the inhomogeneities in the data series. Instrumental and algorithm improvements may cause temporal inhomogeneity in reducing the amplitude of some bias. Also sites or protocol measurement changes may introduce spurious changes. The main limited factor is the inhomogeneities in the data series. Instrumental and algorithm improvements may cause temporal inhomogeneity in reducing the amplitude of some bias. Also sites or protocol measurement changes may introduce spurious changes. A international network of high-quality remote-sounding research stations for observing and understanding the anthropogenic changes of the stratosphere was decided in 1886 and first observations started in 1991: the Network for the Detection of Stratospheric Changes (NDSC). The goals of this network are to make the earliest possible identification of changes in the stratospheric ozone layer and related parameters, to study the variability of the stratosphere, to provide an independent calibration of satellite sensors and to provide data required by multi-dimensional chemical and dynamical models. First trend estimates for ozone and temperature are already possible at the Observatoire de Haute Provence (OHP)