Scientific Theme: Advanced Modeling and Observing Systems

Theme report: Climate System Variability
the OMI total ozone column data product. Analysis of CR-AVE comparisons found no significant differences
between the MLS and CAFS integrated ozone columns at flight altitudes between 17 and 20 km (or above the 100mb
pressure level). The standard deviation for the matched data was 1.5%. At flight altitudes between 15 and 17 km
(or 146- and 100-mb atmospheric pressure, respectively) the average bias was less than 1% with less than 1%
standard deviation. The analysis of the matched data at altitudes below 15 km (or below 146-mb pressure level)
indicated less than 1% bias between the MLS and CAFS ozone columns. The analysis of the data over the entire
range of altitude between 13 and 19 km shows that the agreement between the two systems is within 3% (two
standard deviation level). The above results help to assure the quality of the tropospheric ozone column derived as a
difference between the OMI total ozone column and the MLS integrated stratospheric ozone column.
PSD04 Decadal Climate and Global Change Research
GOAL:
(i) Improve understanding of long-term climate variations through analysis of observations and hierarchies of GCM
experiments. (ii) Seek dynamical explanations of oceanic variability and changes through observational analyses
and GCM experiments. (iii) Provide attribution for long-term regional climate changes.
MILESTONE PSD04.1:
Diagnose impacts of ENSO-related and non-ENSO related tropical SST changes over the last 50
years.
ACCOMPLISHMENTS FOR PSD04.1:
CIRES researchers have applied a pattern-based filtering technique developed by Penland and Matrosova [J. Clim.,
2006] to partition the ENSO-related and ENSO-unrelated portions of tropical SST anomaly fields on a month-bymonth
basis throughout the 135-yr (1871-2005) historical climate record. They have also assessed the global
impacts of the ENSO-related and ENSO-unrelated tropical SST trends over the last 50 years using the
NCAR/CAM3 and the NCEP/GFS atmospheric general circulation models, with particular emphasis on the impacts
on precipitation trends over the Americas, western Africa, and Europe. Both GCMs indicate substantial precipitation
trend responses in these regions to the tropical SST trends that are generally in excellent mutual agreement and with
the observed precipitation trends.
Both the ENSO-related and the ENSO-unrelated portions of the tropical SST trends are found to be important in this
regard. Specifically, the ENSO-unrelated SST trends account for most of the precipitation trends in areas bordering
the Atlantic Ocean, whereas the ENSO-related SST trends account for most of the North American precipitation
trends. It is interesting that the observed moistening trend over the eastern U.S. has generally not been captured by
coupled climate model simulations of the 20th century. If its attribution to the ENSO-related SST trends suggested
by this study is correct, then the failure of the coupled models may be partly due to their general tendency to
misrepresent ENSO variability, and therefore likely also the ENSO-related tropical SST trends and their global
impacts.
MILESTONE PSD04.2:
Assess possibility of abrupt climate change over North America in the next several decades
triggered by continued warming of the Indian Ocean.
ACCOMPLISHMENTS FOR PSD04.2:
The tropical oceans have warmed significantly over the last half-century, especially in the already warm Indian and
western Pacific basins. An extensive set of atmospheric GCM integrations were performed with a prescribed
continuation of this warming trend. These runs suggest that the continued tropical ocean warming will gradually
modify the atmospheric jet streams to the point where the ability of the jet streams to channel atmospheric
disturbances along the upper tropospheric waveguide will undergo a relatively sudden shift sometime in the next
century. This will cause relatively rapid shifts in the climates of North America and Europe.
MILESTONE PSD04.3:
Assess impacts of coupled air-sea interactions, decadal ocean dynamics, land-surface
feedbacks, and land-use changes on decadal atmospheric variability.
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