Four-Dimensional Model Assimilation of Data A Strategy for the Earth System Sciences (1991) / Chapter Skim
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3 Current and Future Applications of Model Assimilation Systems
3 Current and Future Applications of Model Assimilation Systems
Pages 21-35
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From page 21... ...
GLOBAL ATMOSPHERIC CIRCULATION As discussed in the previous chapter, current operational and research data assimilation systems at He larger global circulation assimilation centers fall into two main families, intermittent insertion and continuous insertion systems. Intermittent insertion is used in the meteorological centers of Canada; France; Japan; Australia; in He United States at the National Oceanic and Atmospheric Administration's (NOAA)
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From page 22... ...
For example, operational global models now show levels of skill for tropical cyclone track forecasts that are comparable with the best specialized models for Back forecasts. Important new developments in data assimilation methods are likely to be implemented at operational centers over the next 5 years.
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MESOSCALE1 ATMOSPHERIC CIRCULATIONS Limited-area operational models in the United States, Europe, and Japan that utilize data assimilation systems routinely produce background states for weather prediction. With some exceptions, these background states are determined by intermittent updating of the meteorological fields (Hoke et al., 1989; Golding, 1989)
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From page 24... ...
On the other hand, the use of limited-area operational models to produce data sets has the advantage that Special modeling efforts are not required, with the result that a much larger number of meteorological cases can be made available for research study. In many studies of mesoscale physical processes, model-based data sets have been generated without the assimilation of any synoptic-scale data during the forecast cycle (except for lateral boundary conditions)
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, open region using boundary data as continuous input. In a certain perspective this prediction converts data along the boundary into model-assimilated data sets throughout the region by means of a dynamically consistent interpolation in both space and time using the equations of motion.
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have used an experimental ocean circulation model to assimilate XBT observations taken in the tropical Pacific and have produced monthly fields of currents and thermal structure. The assimilation of data has successfully corrected model-induced diffusive drifts in the vertical thermal structure and has created model-assimilated data fields downstream of where actual data were introduced.
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From page 27... ...
The dynamics of such a model would adjust the surface fluxes internally, and, in principle, an optimal state of the coupled atmosphere-ocean system should emerge. As a final note, not a single oceanographic field program as yet has taken the value-added approach of presenting the wide diversity of field observations in the form of model-assimilated data set output of a numerical ocean model, even though such an output is the best means of ensuring that the venous and diverse observations are as dynamically consistent with each other as possible.
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From page 28... ...
The focus of surface hydrology on individual drainage basins, together win the treatment of precipitation as a measured or specified input to the system, has muted any requirement for global data sets. Thus, no system of international data exchange comparable to that for the atmosphere has been developed for traditional surface hydrological data (e.g., high-resolution
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. Consequently, a great deal of surface hydrological data exist for many regions that are not generally made available to the operational meteorological centers or the scientific community for inclusion in modelassimilated data sets.
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imagery together to infer precipitation from cloud height and brightness, scatteringmode passive microwave techniques to infer precipitation intensity from the scattering of ice particles, absorption-mode passive microwave techniques to infer precipitation intensity from the brightness temperature of a rain column of known depth, and active microwave techniques to infer precipitation intensity and condensation profiles from scattering and attenuation from raindrops. The ability to use observations from the established network of geostationary satellites to obtain space- and time-averaged precipitation estimates over the global tropics has led to the establishment of the Global Precipitation Climatology Program (GPCP)
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This 1986 experiment was conducted in southwestern France over a 100-km2 area. Surface and airborne heat flux measurements were combined with meteorological and hydrological observations to validate a mesoscale modeling effort.
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These data have been used to verify the consistency of the presently accepted chemical scheme for the middle atmosphere and to derive the distribution of fast-reacting radicals produced from chemical transformations of the measured trace gases Studies of specific chemical events in the troposphere over limited geographical domains, usually in connection with observational campaigns? are performed by coupling a rather detailed chemical kinetic code with a transport model.
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The full system is scheduled to operate for a 15-year period, presumably long enough to obtain a useful time series of earth observations for monitoring global change. From the point of view of producing global atmospheric data sets for climate research, a global satellite observational capability is essential.
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The availability of global data accelerated the development of techniques of global data assimilation. The resulting model-assimilated data sets provided good quality descriptions of the mass and wind fields and formed the basis for a wide range of research studies.
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CURRENT AND FUTURE APPrJCATIONS 35 sets provide a coherent synthesis and interpretation of all available information on the surface fluxes of momentum, heat, and moisture that drive ocean circulation models and ocean wave models.
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