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 48

Chapter 4
Evaluation of the Temperature Trend and
Climate Forcing in the Pre- and Post Periods
of Satellite Data Assimilation
Alfred M. Powell Jr. and Jianjun Xu
Abstract Based on multiple linear regression analysis, three temperature datasets
from two reanalyses and one set of satellite observations have been used to evaluate
the different responses in the winter [December-February (DJF)] period in the pre-
and post periods of satellite data assimilation as they relate to a selected set of
climate forcings: solar, the stratospheric quasi-biennial oscillation (QBO), El Ni˜o
Southern Oscillation (ENSO), and stratospheric aerosol optical depth (AOD). The
two periods are defined as 1958-1978 when no satellite data was available to be
assimilated and the 1979-2002 period when satellite data was assimilated in the
operational forecast models. The multiple regression analysis shows that the solar
response of the DJF temperatures in the three datasets shows large-scale similarities
although there are differences over the southern middle-high latitudes and some
tropical areas. The stratospheric response showed the strongest DJF temperature
anomalies related to solar variability occurring over the Arctic, but its sign is
negative in 1979-2002 and positive in 1958-1978. The temperature features may
be partially explained by the impacts of the solar cycle, El Ni ˜ o Southern Oscilla-
tion, stratospheric quasi-biennial oscillation, stratospheric aerosols, and other
factors. In contrast, the tropospheric response, with a dynamic wavelike structure,
occurs over the middle latitudes. The tropospheric differences between the two
periods are not clearly resolved and raise questions about the efficacy of the
observations and our ability to use the observations effectively.