Cross-validation of Advanced Microwave Sounding Unit and lidar for long-term upper-stratospheric temperature monitoring

A comparison between NOAA-16 Advanced Microwave Sounding Unit (AMSU) and lidar upper-stratospheric temperature measurements for the period from 2001 to 2007 for purposes of temperature monitoring is presented. Monthly means of lidar data from the Observatoire de Haute-Provence and AMSU data over Western Europe were found to have high correlation, particularly in winter months, when based on measurements for overlapping nights but lower correlation when different sets of days were used for the monthly mean calculation. This result implies that temperatures from lidar measurements are representative of an area relatively larger than its location, in a monthly mean timescale. However, the effect of temporal sampling arising from the fact that lidar measurements are only made in nights without visible cloud cover introduces discrepancies that propagate on the calculation of temperature tendencies. The estimated cooling rate based on lidar and AMSU data sets are in good agreement, although they are more negative than trends previously found based on the Stratospheric Sounding Unit data record from 1979 to 2005 for the middle-upper stratosphere. In addition, the effect of NOAA satellite drift was to produce a difference (between monthly means for day and night passes) of up to 3 K near the stratopause, which must be accounted for particularly when a longer time series will be available.