Final Report - From Measurements to Models: Cross-Comparison of Measured and Simulated Behavioral States of the Atmosphere Page: 2 of 3
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MSTC establishes an exhaustive set of recurring climate regimes that form a "skeleton"
through the "observations" (model output) throughout the occupied portion of the climate phase
space formed by the characteristics being considered. MSTC facilitates direct comparison of
ensemble members and ensemble and temporal averages since the derived climate regimes
provide a basis for comparison. Moreover, by mapping all land cells to discrete climate states,
the dynamic behavior of any part of the system can be studied by its time-varying sequence of
climate state occupancy. MSTC is a powerful tool for model developers and environmental
decision makers who wish to understand long, complex time series predictions of models. Strong
predicted interannual trends were revealed in this analysis, including an increase in global
desertification; a decrease in the cold, dry high-latitude conditions typical of North American and
Asian winters; and significant warming in Antarctica and western Greenland.
Publication resulting from this work:
Hoffman, F.M., W.W. Hargrove Jr., D.J. Erickson III, and R.J. Oglesby (2005): Using clustered
climate regimes to analyze and compare predictions from fully coupled general circulation
models. Earth Interactions, 9, 1-27.
3.) Current climate cloud regimes in ARM data and GCM simulations
We applied the k-means clustering technique to 5 years of ARM ARSCL data at the
ARM Manus and Nauru Tropical West Pacific sites, to the same 5 years of International Satellite
Cloud Climatology Project (ISCCP) data for the entire tropics, and to 5 years of simulations
using the GISS Model E GCM (Chen and Del Genio, 2007). The ISCCP cluster analysis
produces 6 independent cloud regimes corresponding approximately to known tropical "weather
states" such as deep convection, anvil clouds, midlevel cumulus congestus, isolated cirrus, trade
cumulus and marine stratocumulus. These states also exist at Manus and Nauru, making them
representative of the overall tropical behavior, with the exception that the stratocumulus regime,
which is typical of the eastern oceans, is very infrequent in both places.
We used ARSCL to diagnose the distribution of highest cloud top heights at both sites for
each cluster. This diagnostic varies relatively little from one cloud regime to another, because
high thin cirrus are ubiquitous in the tropics. It is only when the full ARSCL distribution of
clouds is analyzed that significant differences among the ISCCP cloud regimes become evident.
Comparison to the ISCCP cloud top height distribution indicates that ISCCP systematically
underestimates the highest cloud top and overestimates midlevel top clouds because it sometimes
sees through high thin cirrus, cannot distinguish multilayer clouds, and sometimes uses
erroneous input temperature and humidity profiles. We tested the ability of the ISCCP cloud
regimes and the ARSCL vertical cloud profiles to capture systematic variations associated with
the Madden-Julian Oscillation. Using 8 MJO events in ISCCP and 4 events that also affected
Manus and are visible in ARSCL data, we plotted the composite cloud regimes and structure as a
function of phase relative to the MJO peak. We find that there is a systematic transition in cloud
heights and cover from one phase to another that supports the idea of the "discharge-recharge"
mechanism of convection height regulation by tropospheric moisture as an important process for
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Del Genio, Anthony D; Hoffman, Forrest M & Hargrove, Jr, William W. Final Report - From Measurements to Models: Cross-Comparison of Measured and Simulated Behavioral States of the Atmosphere, report, October 22, 2007; United States. (digital.library.unt.edu/ark:/67531/metadc885711/m1/2/: accessed May 24, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.