Environmental Engineering Reference
In-Depth Information
1. The global mean temperature tended to increase in the troposphere and decrease
in stratosphere in the two periods of 1958-1978 and 1979-2002. However, the
change rate and patterns of the temperature trends show significant differences
between the two periods. A heterogeneous temperature structure is observed
over the tropical and middle-high latitudes. Both stratospheric and tropospheric
temperature trends in the two periods are similar in the two reanalysis datasets
and were also confirmed in the MSU measurements for 1979-2002 although
there are different temperature trend rates between the two reanalyses and the
MSU measurements over the Antarctic zone and tropical eastern Pacific.
2. During the two periods, common features were observed showing the most
sensitive areas of DJF TAs to solar forcing emerge over the Arctic, the northern
high and middle latitudes, and the tropical-subtropical eastern Pacific. The
patterns of DJF TAs associated with the solar forcing in the lower stratosphere
and the middle troposphere were similar in each of the three datasets; the
exception areas are located over the tropical oceans and most of the middle-high
latitudes in the southern hemisphere. The TA response in DJF to solar forcing has
a substantial spatial heterogeneity. The stratospheric TAs have more uniform
values, while the tropospheric TAs have a wavelike pattern alternating between
positive and negative values over both northern and southern middle latitudes.
3. Except for the possible impacts from the reanalysis datasets with and without the
satellite data assimilation, the different temperature responses in the two periods
can be reasonably explained by the solar, ENSO, QBO, and stratospheric aerosol
forcing.
This analysis reaffirms the core forcing parameters for atmospheric temperature
trends as solar, ENSO, QBO, and stratospheric aerosols. The analyses show many
similar features and trends of approximately the same magnitude. However, there
are many discrepancies that need to be explained. On the positive side, two
independent reanalyses using different models, assimilation processes, and data
ingest quality control demonstrate similar trends, regional changes, and anomalies.
This is good news for both the weather and climate communities that are trying to
converge on similar trends and improve the reliability of climate forcing estimates.
However, there are some clear discrepancies between the pre- and post satellite era
analyses. Coincidently, the inclusion of satellite data into the operational models
started in late 1978 and aligns with a potential climate shift identified in the
literature. This leaves open the question as to whether the reversal in the polar
regions may have been due to the addition of satellite data or possibly an actual
change in the climate near 1977-1978.
An updated set of global multi-satellite microwave measurements which
includes the use of satellite intercalibration techniques as a method for obtaining
improved temperature accuracy was used for comparison. This analysis shows that
the satellite microwave measurements during the 1979-2002 period are very
consistent with the reanalyses. It is acknowledged the satellite data is not a truly
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