An evaluation of uncertainties in monitoring middle atmosphere temperatures with the ground-based lidar network in support of space observations

Abstract

International audienceThe capability of the longest lidar data sets to monitor long-term temperature changes have been evaluated through comparisons with the successive Stratospheric Sounder Units (SSU) onboard NOAA satellites. Cross-consistency investigations between SSU and the lidar network can be considered as a first attempt to demonstrate how the synergistic use of space and ground-based instruments could provide reliable monitoring of the temperature of the middle atmosphere. The breakdown of the temperature cooling trend, and the following flattening observed in the satellite temperature series, are qualitatively confirmed by the lidars. However, there are still large differences that can either be due to SSU continuity (orbit drifts or weighting function modifications) or lidar operation changes (time of measurements, accuracy, sampling, etc.). SSU vertical weighting functions have been taken into account for comparisons. Some discontinuity events cannot be explained by the SSU weighting function drifts due to CO2. For the upper channels of SSU (peaking around 50 km) the results are probably sensitive to the mesospheric part of the lidar profiles that can explain some discontinuities. Tropical lidar stations show clear inter-annual differences with the SSU channels covering the lowest altitude range that need further investigations to understand if the origin is instrumental or geophysical. An attempt to derive non-linear trends with combinations of linear, hockey stick, and quadratic functions has been made. While the quadratic term is not highly significant, this approach allows the derivation of a better quantification of the linear trend terms

Temperature trends in the midlatitude summer mesosphere

“…[37] In B&L11 we have performed a detailed comparison with lidar measurements at the Observatory of HauteProvence in southern France (44 ı N) [Keckhut et al, 2011] and found very good agreement. Comparison with temperature trends derived from lidar measurements in the upper mesosphere/lower thermosphere at Fort Collins (41 ı N) published by She et al [2009] turns out to be more complicated since annually mean trends on geometrical altitudes for the period 1990-2007 are derived which makes it difficult to disentangle the geometrical/pressure altitude effect on trends in a height range where the background temperature gradient varies substantially with time and altitude.…”

“…Major progress has been achieved by analyzing long-term data records from groundbased, in situ, and satellite-borne measurements [see, for example, She et al, 2009;Keckhut et al, 2011;Kubicki et al, 2006;Keating et al, 2000]. Since the pioneering work of Roble and Dickinson [1989], extensive modeling has helped to identify the main reasons responsible for these trends, namely the increase of greenhouse gasses (GHG) [e.g., Akmaev et al, 2006;Schmidt et al, 2006;Garcia et al, 2007].…”

Evaluation of wind and temperature profiles from ECMWF analysis on two hemispheres using volcanic infrasound

“…Within the framework of the Atmospheric dynamics Research and InfraStructure in Europe (ARISE, http://arise-project.eu) project, a recent study has focused on comparisons between measurements from ground-based facilities and ECMWF analysis models over the time span ranging from July 2012 to May 2013. Measurements from colocated Rayleigh scatter lidar (temperature in the 30-70 km range [Keckhut et al, 2011]), mesospheric airglow (temperature around the mesopause region [Schmidt et al, 2013]), and Doppler radiometer (horizontal winds between 40 and 70 km [Rüfenacht et al, 2012]) facilities have been compared to the ECMWF analysis (up to 78 km altitude). It has been found that significant biases in temperatures and horizontal winds exist, primarily at higher altitudes and at shorter timescales.…”

Temperature Climatology with Rayleigh Lidar Above Observatory of Haute-Provence: Dynamical Feedback

“…Some differences with other lidar series have been reported [2] as well as differences between summer and winter estimates ( Figure 1). …”

“…While the continuity suffers from tidal effect due to the orbit changes from the successive satellites and their time drifting [2], the continuity is now insured by AMSU. Comparisons between lidar and AMSU reveal very good agreements when data obtained on the same days are considered and partial sampling appear critical [3].…”