Evaluation of the Temperature Trend and Climate Forcing in the Pre- and Post Periods of Satellite Data Assimilation - Satellite-based Applications on Climate Change - page 50

conclusions. This analysis possibly suffers from the same issues. As the science
becomes more complicated, it is difficult to understand the effects from a variety of
data sources combined with models which may have many physical interactions
contributing to a single outcome. Part of the purpose of this study is to resolve the
similarities and differences between two recognized reanalyses that use different
models and a direct satellite measurement to help resolve what is real and possibly
what is not in terms of climate forcing impacts.
In the present work, the multiple linear regression analysis results for the lower
stratospheric and the middle tropospheric temperature changes associated with the
solar variability, ENSO, QBO, and stratospheric aerosols are reported for the two
reanalyses datasets (NCEP/NCAR and ERA-40) for the two periods of 1979-2002
and 1958-1978. The satellite Microwave Sounding Unit (MSU) measurements are
only reported in the period of 1979-2002 when it was used in the operational
forecasting. The data and analysis techniques are described in the following section.
The linear trend of the temperature and their differences in the two periods are
offered in Sect. 4.3 . Section 4.4 presents the multiple regression analyses for the
temperature and the impacts of the selected set of climate forcings. Section 4.5
gives the final summary.

4.2 Data and Methodology

To understand the temperature trends and the climate forcings, the data used in this
study include two reanalyses, one satellite retrieval dataset and climate forcing
indices including solar F10.7-cm radio flux, ENSO, QBO, and stratospheric aerosol
optical depth (AOD) data. A data period was chosen consistent with available data
from both the NCEP/NCAR and ERA-40 reanalyses (1958-2002). All datasets
except for the satellite-retrieved data spanned the two periods 1958-1978 and
1979-2002.

4.2.1 NCEP/NCAR Reanalysis

The monthly NCEP/NCAR reanalysis (Kalnay et al. 1996 ) with a 2.5 2.5 grid

resolution is used for the two periods of 1979-2002 and 1958-1978. It should be
noted that the reanalysis period of 1958-1978 has no satellite data. The Television
Infrared Observation Satellite (TIROS) Operational Vertical Sounder (TOVS) data,
the Microwave Sounding Unit (MSU), the High-Resolution Infrared Radiation
Sounder (HIRS), and the Stratospheric Sounding Unit (SSU) information were
not available before the end of 1978. The Special Sensor Microwave/Imager
(SSM/I) data was assimilated in this system from 1993. The reanalysis has 17
pressure levels that range from 10 hPa to the surface (1,000 hPa).