Four-Dimensional Model Assimilation of Data A Strategy for the Earth System Sciences (1991) / Chapter Skim
Currently Skimming:
4 Needs for Future Model-Assimilated Data Sets
4 Needs for Future Model-Assimilated Data Sets
Pages 36-47
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 36... ...
. While the study of baroclinic instability and wave cyclones has been a central theme of dynamic meteorology for over 40 years, the generation, maintenance, and decay of these synoptic weather systems are still far from completely understood, and new field programs for their study are being organized.
|
From page 37... ...
. Important research issues concerning LF\I include barotropization, that is, the increasingly barotropic character of atmospheric motion as the characteristic period increases, the existence and explanation of multiple flow regimes for the same external conditions, and the emergence and life cycle of localized coherent eddy structures (Ghil and Childress, 1987~.
|
From page 38... ...
, that is, the net transfer of water substance from the earth's surface to the atmosphere. Global atmospheric forecast models, through the data assimilation process, should ultimately provide accurate estimates of temporally and areally averaged vertically integrated vapor flux divergence E - P over most areas of the world.
|
From page 39... ...
An additional motivation for using models for mesoscale data assimilation is that the resolution of conventional operational data has often been insufficient to define the detailed characteristics of mesoscale meteorological processes. Use of fine-and models, with appropriate mesoscale physics, is necessary in order to generate a data set for subsequent analysis.
|
From page 40... ...
3 to 10 Days Although objective analysis and numerical prediction originated from the demand for synoptic weather forecasts of ~ and 2 days, the scope of forecasts has gradually extended to the medium-range hme scale of 3 to 10 days. Simultaneously, analysis techniques have recognized the importance of using numerically predicted fields as a background field for analysis, and of requiring dynamical consistency among variables, resulting in the continuing development of data assimilation methodology.
|
From page 41... ...
(1987) recommend that the directional accuracy of surface winds from future scatterometers be substantially improved.
|
From page 42... ...
For forecasts in this category, reliable data assimilation of large-scale atmospheric circulation features is required to produce appropriate initial conditions. In addition, accurate observed sea surface temperatures must be specified at the initial times.
|
From page 43... ...
discontinuities in data assimilation procedures, it is recognized that data assimilation techniques have improved markedly, especially in the tropics, and that these model-assimilated data sets have proven extraordinarily valuable in examining the low-frequency variability of the global atmosphere. It has been suggested that modelassimilated data sets be periodically reanalyzed by NMC and other operaiional or research centers to include new or omitted observations as improved data assimilation techniques and more accurate assimilation models are developed.
|
From page 44... ...
No ocean data are used to initialize the model; therefore, errors in the observed winds can lead to errors in the initial specification of the ocean state. A more comprehensive routine effort at ENS O prediction using coupled GCMs would require the assunilation of ocean data and would produce ocean model-assimilated data sets as a by-product.
|
From page 45... ...
Making predictions on time scales of a few years to beyond a hundred years requires careful initialization of the ocean state. There is evidence that the ocean SST affects climate on decadal time scales (e.g., Palmer, 1986)
|
From page 46... ...
On time scales of thousands of years, the coupled climate state presumably loses all memory of the initial ocean state. In order to determine the influence of the initial ocean state, climate runs of coupled global models starting from slightly different initial conditions in the ocean must be done.
|
From page 47... ...
A recommended resolution for such selected regions is 10 x 10 x 50 km levels. A data set of barely satisfactory length for the study of low-frequency variability and atmosphere-ocean interactions, atmosphere-land interactions, and dynamics-chemistry-radiation interactions is 30 to 40 years.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.