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highlights of FY00 and immediate objectives
In this section, some research highlights are listed that may be of interest to those persons less concerned with the intricate details of GFDL research. Selected are items that may be of special significance or interest to this wider audience.
Most of the items in this section have been ordered according to the current NOAA Strategic Plan Elements, which are divided roughly according to time scale:
- Advance Short-Term Forecasts and Warnings
- Seasonal to Interannual Climate Forecasts
- Predict and Assess Decadal to Centennial Changes
Recognizing that much scientific progress has application to phenomena at a wide variety of time scales, a number of items have been placed into a category which cuts across the time scales represented by the previous elements:
- Basic Geophysical Processes
This avoids an awkward force-fit of certain topics into a particular time scale and highlights the fundamental role that these topics play as building blocks for progress in multiple research areas.
Note that the categories described above are organized differently than the GFDL research project areas presented in the main body of the report. This is but another reflection of the variety and interplay of activities within such a fertile research environment. As an aid in cross-referencing, the number in parentheses following each highlight refers to sections in the main body of the report.
ADVANCE SHORT-TERM FORECASTS AND WARNINGS
The need for short-term warning and forecast products covers a broad spectrum of environmental events which have lifetimes ranging from several minutes to several weeks. Some examples of these events are tornadoes, hurricanes, tsunamis, and coastal storms, as well as "spells" of unusual weather (warm, cold, wet, or dry). Benefits of these products can be measured in terms of lives saved, injuries averted, and expenses spared. NOAA's vision for improvement in this area involves operational modernization and restructuring, strengthening of observing and prediction systems, and improved applications and dissemination of products and services.
Efforts at GFDL are centered around the development of numerical models which may be used in the prediction of "short-term" atmospheric and oceanic phenomena. Simulations from these models are studied and compared with observed data to aid in the understanding of the processes which govern the behavior of the various phenomena.
With regard to tropical weather systems, efforts are aimed at understanding and forecasting the genesis, growth, and decay of tropical storms and hurricanes. In extratropical regions, interest includes the development of severe weather systems, the interaction of medium-scale atmospheric flow with that on larger scales, and the influence of the underlying topographic features. Experimental prediction of regional-scale weather parameters weeks in advance is being pursued; included in this context is the study of "ensemble forecasting." With regard to the marine environment, forecasts of coastal conditions on a day-to-day basis can be made by coupling of ocean and atmosphere models. Ocean models are also used to simulate and forecast coastal and estuarine environments, the response of coastal zones to transient atmospheric storms, and Gulf Stream meanders and rings.
ACCOMPLISHMENTS FY00
Model simulations of the Madden-Julian Oscillation (MJO) are revealing new details about the predictability of this phenomena. Analysis of the impact of the MJO on tropical storms in the model has also pointed to the potential for some skill in several week lead predictions of tropical storm activity (4.1.8).
The conversion of the GFDL modeling system to a distributed memory system was successfully completed. This ensures the efficiency of the forecast system for operational implementation at NCEP for the 2000 tropical season, as well as for future research applications at GFDL. The conversion effort was made particularly difficult because of the complex nature of the GFDL moving nested grid framework. The new design incorporates two-dimensional decomposition. Operational forecasts will now be made for 5 days instead of 3 days. Work was also completed in porting the coupled model to the new NCEP system, making the model available for the 2000 hurricane season in the Tropical Atlantic (6.1.3, 6.4).
Forecasting hurricane intensity remains a challenging goal. For the 1999 season, however, the GFDL system did exhibit skill for forecast periods of 48hr and beyond. When adjusted for initial bias, the GFDL model showed skill relative to climatology and persistence for the entire 72h forecast period with mean errors 11, 17, and 17 knots at 24, 48, and 72hrs, respectively. This is evidence that forecast system changes made in prior years, including the addition of initial asymmetries, resulted in improvements for the 1999 season. As in the 1998 season, the coupled model achieved significant improvements in the hurricane intensity forecasts compared to the operational atmosphere-only GFDL model. The mean absolute error of the sea-level pressure forecasts was reduced by about 31%. There are indications that improvements in resolution and physical parameterizations relating to the boundary layer and cumulus convection will lead to further improvements in intensity forecasts (6.3, 6.4).
The impact of initial conditions on the quality of GFDL operational tropical cyclone forecasts was investigated in two studies. On average, the assimilation of GOES satellite winds into the GFDL regional domain led to improvements from 5-12% in track and 4-8% in intensity (6.2.2). On the other hand, the quality of GFDL forecasts was also improved by using two different global analyses: the UKMET analysis, and a test AVN analysis scheduled for operational implementation for the 2000 season. Both of these global analyses improved GFDL track forecasts by more than 20% (6.2.3). Further improvements in operational forecasts are anticipated with improved global and regional assimilation systems which optimally ingest data.
Prior studies have shown a modest increase (~5-10%) in the intensity of very strong hurricanes in a high CO2 climate, as compared to the strongest hurricanes in a control climate. However, studies to date have neglected the effect of hurricane/ocean coupling (i.e., the local SST cooling induced by the hurricane) on the intensity changes. To evaluate how a CO2-induced enhancement of hurricane intensity could be altered by the hurricane/ocean coupling, a series of idealized hurricane experiments was performed using the GFDL Hurricane Prediction System coupled to the Princeton Ocean Model (POM). The results indicate that a CO2-induced intensification still occurs even when the hurricane/ocean coupling effects are included; ocean coupling appears to have only a small impact on the magnitude of this intensification (6.3.1).
PLANS FY01
- Studies will continue on increasing the grid resolution of multiply-nested meshes in the GFDL hurricane model. A study of the optimal grid configuration of the nested model for distributed memory systems will be undertaken. More realistic representation of the eye and eyewall of intense hurricanes will be investigated, as well as the influence of the large-scale environmental flow.
- The initialization of the GFDL hurricane model will be improved with continued development of a four-dimensional approach in which both routine observations and supplemental storm data can be ingested into the initial condition.
- Developmental work to improve the hurricane model initialization, ocean interaction, model physics, and resolution will continue. This is critical for improved intensity prediction skill. A significant number of case studies will be needed to evaluate the impact of these efforts on track and intensity forecast skill.
SEASONAL TO INTERANNUAL CLIMATE FORECASTS
Seasonal to interannual climate fluctuations have far-reaching consequences for agriculture, fishing, water resources, transportation, energy consumption, and commerce, among others. Short-term climate anomalies which persist from a season to several years affect rainfall distributions, surface temperatures, and atmospheric and oceanic circulation patterns. Reliable climate forecasts may be used to reduce the disruption, economic losses, and human suffering that occur in connection with these anomalies. NOAA's vision for improvement in this area is based on better predictive capability, enhanced observations, greater understanding of climate fluctuations, and assessment of impacts.
The study of seasonal to interannual climate fluctuations at GFDL is based on both theoretical and observational studies. Available observations are analyzed to determine the physical processes governing the behavior of the oceans and atmosphere. Mathematical models are constructed to study, simulate, and predict the coupled ocean-atmosphere, land-surface, sea-ice system.
Simulations based on the numerical models maintained at GFDL, in conjunction with observations, are used to study climate variations on seasonal and longer time scales. Processes under study include large-scale wave disturbances and their role in the general circulation, the effects of boundary conditions such as sea surface temperature and soil moisture, influence of clouds, radiation, and atmospheric convection, and the "teleconnection" of atmospheric anomalies across the global atmosphere. Furthermore, experimental model forecasts are used to evaluate atmospheric predictability and to assess skill in forecasting atmospheric and oceanic climate anomalies, both in general and in connection with the El Niño-Southern Oscillation phenomenon. Also, a more accurate representation of the state of the global ocean is being studied through data assimilation for better initialization of seasonal-interannual forecasts.
ACCOMPLISHMENTS FY00
Model simulations of the response of the stratosphere to the observed (1979-1997) changes in ozone and in the well-mixed greenhouse gases (carbon dioxide, methane, nitrous oxide and halocarbons) produce a pattern of temperature change similar to that observed. The response is largely due to ozone change in the polar lower stratosphere and to greenhouse gas change in the upper stratosphere (3.5.5).
GCM simulations employing the observed aerosol enhancements in the stratosphere following the eruption of Mt. Pinatubo reveal that the radiative flux anomalies induced are in good agreement with those observed, with the small residual differences attributable to deficiencies in the simulation of cloud cover variability and aerosol optical property inputs (3.5.4).
Analysis of the GFDL GCTM tropospheric column ozone, generated without the biomass burning NOx source, has shown that a reduced South Atlantic Ocean September maximum can still be produced. This suggests that the ozone phenomenon existed prior to the advent of agricultural burning by humans (2.3.3).
Episodic trans-Pacific pollution events greatly exceed background levels, with Asian contributions to episodic O3 events over the western US currently in the 3 - 10 ppbv range and growing to 40 ppbv, a factor of 4 increase (2.3.4).
Coupled models suitable for seasonal-interannual prediction are being developed using the new Flexible Modeling System. Efforts to coordinate coupled model development between all global modeling groups at GFDL are underway (4.1).
Tests with FMS atmospheric models suggests that increases of vertical and horizontal resolution may have significant impact on the quality of seasonal-interannual simulations and predictions (4.1.4).
The impact of low clouds on seasonal-interannual predictions is even larger than previously believed. Low clouds over both land and ocean regions have significant impacts on the general circulation and the seasonal cycle in the tropics. Efforts to develop improved low cloud parameterizations are continuing (4.1.5).
Expanded ensembles of one year coupled model predictions have provided further evidence that in certain years, the evolution of the sea surface temperatures in the tropical Pacific is not predictable for lead times of more than a few months (4.1.10).
Simulations of dipole sea surface temperature variability in the tropical Indian ocean have revealed new aspects of this phenomena, in particular, the sensitivity to the preconditioned state of subsurface thermal structure on the onset of this "coupled dipole mode". Potential impacts on seasonal prediction are being evaluated (4.1.11).
An ensemble adjustment filtering technique for data assimilation has been developed. The method is better than current state-of-the-art methods in low order models. As an example of the power of the assimilation method, assimilations of synthetic observations of only surface pressure in a global primitive equation model were able to reproduce many details of the circulation in the free atmosphere (4.2.1).
Initial versions of an adjoint for the MOM ocean model have been developed as a first step towards implementing four-dimensional variational data assimilation in MOM (4.2.2).
The relative contribution of land use, carbon dioxide fertilization, and nitrogen fertilization in U.S. forests has been quantified. Results show that land use is the primary factor governing the rate of carbon sequestration in U.S. forests (5.4.1).
A new terrestrial biosphere model, the Ecosystem Demography model, has been set up to examine the impact of human land-use on the terrestial carbon cycle of North America (5.4.1).
The time evolution of carbon isotopes in the atmosphere has been used to infer sources and sinks of terrestrial carbon. Results for 1993-95 indicate the presence of a terrestrial carbon sink in the mid latitudes of the northern hemisphere and a tropical carbon source (5.4.2).
Progress has been made in applying adjustments to a global network of 87 radiosonde stations so as to render their temperature time series more temporally homogeneous. These adjusted data are valuable in the study of global temperature trends (6.1.1).
Multiple satellite records of tropical-mean water vapor have been compared with a model simulation to assess our ability to monitor and predict low-frequency changes in total precipitable water, which is an important quantity for the detection of climate change. The comparison demonstrated excellent agreement between the observed variations in tropical water vapor and those predicted by the model integration (6.2.1).
A coupled model has been developed utilizing a one-dimensional ocean mixed-layer model with variable depth and a GFDL atmospheric GCM. A large suite of experiments has been completed with this model under various SST forcing scenarios. These integrations have shed new insights on the impact of ENSO on the variability of the extratropical atmosphere-ocean system and the Asian-Australian monsoons (6.3).
A decade-long effort to involve the university community in the analysis and design of GFDL model experiments has concluded. This collaboration has expanded our knowledge of the effects of anomalies in surface boundary conditions on interannual and interdecadal variability of the atmosphere, and of the dynamical and statistical nature of different types of atmospheric fluctuations (6.5).
Mesoscale (Zeta-model) simulations of realistic storm tracks have revealed different patterns of eddy structure and evolution corresponding to strong and weak zonal variations of the time-mean flow. Depending on the length of the storm track, the eddies tend to appear either in mobile wave packets or in quasi-stationary "couplets". The two patterns are most commonly observed in the Southern and Northern Hemispheres, respectively. It has been speculated that the interannual variability of the shape of the storm tracks in the Northern Hemisphere is controlled by variability in the low-level subtropical humidity. To investigate this possibility, the mesoscale simulations are now being conducted with explicit moisture and clouds, which have recently been added to the Zeta model (8.1).
PLANS FY01
- Analyses of the large number of integrations performed with various versions of the SKYHI model will continue, including integrations performed with different spatial resolutions, QBO modes, and tracer distributions. It will also include analyzing the sensitivity of the changes in stratospheric climate to different forcings (volcanic aerosols, "QBO", ozone, well-mixed gases, water vapor, sea-surface temperatures). The changes will be compared against the "natural" internal variability of the model using the 50-year "unforced" integrations.
- Coupled models for experimental prediction using FMS will be developed and tuned in order to produce a state-of-the-art seasonal ensemble prediction system. The new model will be used to produce ensemble predictions and long simulations of the coupled climate system.
- The Hybrid statistical atmosphere coupled model will be used to evaluate the capabilities of newly developed FMS atmospheric models and will also be used to help diagnose the response of the ocean to the Madden-Julian Oscillation and Westerly Wind Bursts.
- The ensemble adjustment filter will be tested in higher resolution primitive equation models and in prediction models with fully parameterized physics. Initial application of the filter to MOM will be explored.
- A four-dimensional variational assimilation of the TAO data in the Pacific will be performed using the new MOM4 and its adjoint.
- The new Ecosystem Demography model will be used to study the importance of terrestrial biospheric feedbacks for global climate.
- A new suite of integrations under different SST forcing scenarios will be used to investigate the nature of extratropical air-sea feedbacks associated with ENSO, the atmospheric responses to SST forcing in the Indian Ocean and western tropical Pacific, and the role of tropical Atlantic SST anomalies in atmospheric variability in the North Atlantic sector.
- The process of drafting a set of review and research papers on various foci of the GFDL/Universities collaborative project for model diagnosis will be completed. The manuscripts will be edited for publication in a special issue of a scientific journal.
- The sensitivity of cyclone evolution to position within the storm track will continue to be evaluated. In particular, the mechanisms responsible for the poleward progression of low-level cyclonic eddies will be further analyzed.
- Continuing idealized storm track simulations with the spherical-coordinate models should clarify the most important processes in the development, maintenance, and decay of the storm tracks. Sensitivity studies will be undertaken to clarify the features most important to cyclone evolution within them. The model is also being adapted to the GFDL Flexible Modeling System.
PREDICT AND ASSESS DECADAL TO CENTENNIAL CHANGES
Events such as the Sahel drought, the dust bowls in the Midwest, the Little Ice Age, stratospheric ozone depletion, and global warming may define eras in history. Events such as these have lifetimes of decades to centuries and their causes can be either natural or anthropogenic. An ability to predict such changes and to assess the causes is essential in long-range policy making. Adapting to these changes and reducing the effects of human activities will require enhanced predictive capability. NOAA's vision for improvement in this area is based on a commitment to research in climate and air quality, as well as to insure long-term climate and chemical records.
The related research efforts at GFDL require judicious combinations of theoretical models and specialized observations. The modeling efforts draw on principles from the atmospheric, oceanic, chemical, and biological sciences. One area of focus is long-term climate variability and secular change associated with the atmosphere and oceans. This area encompasses a number of topics, including the effects of changes in the concentration of atmospheric gases such as carbon dioxide, the simulation of past climates, and the variability of the oceanic thermohaline circulation. Another area of focus is the formation, transport, and chemistry of atmospheric trace constituents. This area addresses problems such as: the transport of quasi-conservative trace gases; the biogeochemistry of climatically significant long-lived trace gases; the transport, sources, and sinks of aerosols; the chemistry of ozone and its regulative trace species; the effects of clouds and aerosols on chemically important trace gases; and the impact of anthropogenic chlorofluorocarbons on stratospheric ozone amounts. Yet another area of focus relates to the modeling of the marine environment. It includes the dispersion of geochemical tracers in the world oceans, the oceanic carbon cycle and trace metal geochemistry, and ecosystem structures.
ACCOMPLISHMENTS FY00
Simulated changes in Southern Hemisphere circulation in response to global warming have been found to project strongly on the so-called Southern Annular Mode (or Antarctic Oscillation). These changes appear to be indirect adjustments of the jet and storm tracks to changes in the large-scale radiative and thermal environment. Similar circulation changes, albeit larger in magnitude, have been observed during the last 30 years (2.2.4).
Coupled climate model integrations were conducted using two of the IPCC's key scenarios of greenhouse gas and sulfate emissions. These integrations represent part of GFDL's contribution to the IPCC Third Assessment Report. Under these scenarios, the model simulates a global warming of between 2.4°C and 3.5°C during the next 100 years (2.2.7).
Motivated by the observed trend in the Arctic/North Atlantic Oscillation (AO/NAO), the oceanic response of an anthropogenically forced coupled climate model to changes in the AO/NAO was examined. A sustained upward trend in the AO/NAO is found to delay the greenhouse gas-induced weakening of the thermohaline circulation by several decades (2.3.1).
A comparison was made between multidecadal North Atlantic climate variability simulated by a coupled model and analyses of both instrumental and proxy records. The combined instrumental/proxy data show a pattern of sea surface temperature variability that is similar to that simulated by the model. The 70-year time scale of the observed variability compares favorably with the model results, which indicate a time scale of 40-80 years (2.3.2).
In collaboration with the Hadley Centre for Climate Prediction, the first multicentury simulation of the ice age climate was conducted using a coupled atmosphere-ocean general circulation model. Interactions between the atmosphere and ocean were found to have an substantial impact on regional climate changes, particularly in the North Atlantic and eastern tropical Pacific (2.5.2).
In a coupled atmosphere-ocean model forced by a quadrupling of CO2, runoff increased in approximately 70 percent of the world's largest river basins. River basins located in middle and high latitudes of the Northern Hemisphere typically experienced increased runoff. Decreases in runoff occurred in a smaller number of locations, including some places in the southern United States (2.6.1).
Multi-decadal control integrations of the GFDL SKYHI model have produced results with significant quasi-decadal variability. The variations in concentration of nitrous oxide indicate apparent trends in the middle stratosphere of the order of 1% per year occur over timescales of a decade or more. Since the model has no interannual variations in chemistry or any interannual changes in external forcing, all these apparent trends in stratospheric composition must result from spontaneous internally-generated changes in transport. This suggests a significant role for natural variability in explanations of observed trends in stratospheric composition (3.4.3).
An assessment of the effect of Drake Passage on the earth's climate has been carried out using an idealized coupled model. The model shows that most major features of the Atlantic thermohaline circulation and the ocean's heat transport system can be explained by the existence of Drake Passage and the Antarctic Circumpolar Current, including the observed surface air temperature difference between 50°S and 50°N (5.1.3).
PLANS FY01
- A set of climate model ensemble integrations, including natural (solar, volcanic) and anthropogenic (greenhouse gases, sulfate aerosols) forcings will be completed. These ensemble integrations will be analyzed to determine the relative contributions of natural and anthropogenic forcings to global and regional temperature trends.
- The development and testing of key coupled climate model components will continue. Construction of the atmospheric component of the current-generation coupled climate model will be completed, and the model will be ported to GFDL's new high-performance computing system.
- New simulations of the effects of freshwater discharge into the North Atlantic Ocean will be completed. The results will be compared to previous runs with a lower resolution model, with a focus on identifying possible tropical climate teleconnections similar to those suggested by paleoclimate data.
- A major study is underway to determine the role of mesoscale eddies in balancing the northward Ekman transport in the latitude band of the ACC. A series of models with progressively finer resolution will illustrate how the ACC change in response to variable winds when eddies are explicitly resolved.
BASIC GEOPHYSICAL PROCESSES
A number of the research topics at GFDL cut across the various time scales characteristic of each of the foregoing sections. Progress on these topics impacts many other research areas which depend critically on the successful representation of numerous lower-level processes which are common to problems at all scales. Topics which fall into this category include hydrological processes, radiative transfer (including the effects of aerosols and clouds), cloud prediction/specification, "teleconnection" of atmospheric anomalies across the global atmosphere, satellite data interpretation, transport processes, gravity wave effects and parameterization, model resolution effects, and many other model enhancement efforts. As these processes become better understood and more accurately represented, benefits will accrue to a multitude of other research efforts.
ACCOMPLISHMENTS FY00
All GFDL models planned for use on GFDL's next supercomputing platform have been implemented for scalable systems. The implementation was based on a memory management scheme providing domain decomposition on rectilinear grids spanning shared or distributed address (1.1).
The exchange grid software which is used to do conservative interpolation between model grids in FMS was rewritten to increase performance on scalable architectures (1.1.3).
A management structure for software development was established at GFDL. An oversight and planning committee was established to provide scientific direction for FMS priorities while a model infrastructure team was created to manage and imlement software (1.3.1).
The Flexible Modeling System software and its documentation have been placed under the CVS version control system. This allows users to access both current and previous configurations of FMS code and allows for orderly code updaes (1.3.2).
A quarterly release schedule for FMS was implemented and the first officially supported release was made in conjunction with a lab-wide meeting to introduce users to FMS (1.3.3).
The Land Dynamics (LaD) model was developed as an extension of an earlier scheme with successful application in climate modeling. The performance of this model was evaluated by forcing it with observed hydrologic data and comparing simulated and observed runoff characteristics. The LaD model matches observations better than its predecessor (2.4.2).
Analysis of high-time-resolution Baseline Surface Radiation Network observations, coupled with results from radiative transfer computations, has led to the identification of aerosol signatures in the solar flux reaching the surface (3.1.3).
Radiative-convective model simulations of lapse rate changes due to aerosol-induced solar absorption in clouds reveal a strong dependence on the vertical distribution of clouds and the amount of absorbing aerosols incorporated in them (3.5.3).
Simulations with the GFDL SKYHI model have been used to examine interannual variability of long-lived greenhouse gases in the troposphere. The effects of the stratospheric quasi-biennial oscillation on stratospheric-tropospheric exchange was shown to significantly influence the tropospheric concentrations of nitrous oxide and methane (3.4.7).
Uncertainty in the intensity and frequency of precipitation in a GCM is a major contributor to the uncertainty of the simulated atmospheric aerosol burden. While monthly mean precipitation is represented reasonably well, the episodic nature of precipitation events is not. This affects the removal of the aerosol from the atmosphere, its residence time and thereby the radiative forcing (2.3.5).
The prognostic cloud parameterization of the Flexible Modeling System has been further refined and its performance thoroughly diagnosed. The parameterization is qualitatively able to reproduce the observed cloudiness distribution with some biases (e.g., too small liquid cloud drop radii and too optically thick clouds). However, the parameterization qualitatively reproduces the observed temperature dependence of low cloud optical thickness (3.2.4).
Deep convection in the intertropical convergence zone is the major mechanism acting to remove sulfate, carbonaceous aerosol, and mineral dust originating on the Indian subcontinent as it moves toward the Equator, according to studies performed with the GFDL limited-area non-hydrostatic model. The rates at which these aerosols are removed in the model match well aerosol observations on the NOAA ship Ron Brown during the Indian Ocean Experiment, INDOEX. These aerosols modify the clouds into which they are ingested, increasing the concentration of cloud drops and ice crystals and decreasing their size (3.2.2).
Ice generated by deep convection and its associated mesoscale circulations contributes substantially to both shortwave and longwave radiative forcing. This ice generation has been parameterized by using a sub-grid distribution of vertical velocities to model cloud microphysical processes at the physically realistic scales in general circulation models. The sub-grid spatial characteristics of parameterized convective systems have been analyzed and are consistent with satellite observations of convective shields (3.2.1).
A statistical atmospheric model that can be used for efficient evaluation of the impacts of the atmosphere in coupled model simulations has been developed. The statistical atmosphere has given new insight into the deficiencies and strengths of a variety of atmospheric observational products and general circulation models (4.1.3).
A new version of MOM (MOM 4) has been created that runs faster and uses memory more efficiently on computer systems with more than 50 processors (5.2.1).
GFDL's isopycnal coordinate ocean model (HIM 1.0) was officially released. The calling interface for HIM is compatible with that of MOM 4 and HIM development is managed with modern version control software (5.2.2).
Comparison between temperature trends deduced from the Microwave Sounding Unit (MSU) and from radiosonde measurements reveals that there still remains a spurious downward drift in the MSU temperature record due to degradations in the satellite orbit, despite previous attempts to correct for this drift (6.2.2).
A long-term partnership between GFDL and PMEL has been established to facilitate the design of a user-friendly, web-based software package for visualizing and evaluating the output of FMS experiments. It is envisioned that this effort will produce a powerful and convenient tool for accessing and visualizing data sets from research centers throughout the world, and for assessing the performance of various FMS experiments to be conducted at GFDL (6.4).
Some aspects of the climate depend on the drag exerted by mountain ranges. A dynamically based parameterization of the total mountain drag has been developed and is being tested with twin experiments using the mesoscale model at coarse and high resolution. The new parameterization eliminates a certain tuning parameter and provides a much better geographical distribution of the source. The comparison between the parameterization and the resolved drag is further improved by applying a proposed nonlinear correction (8.2).
PLANS FY01
- The primary focus of FMS development will be to optimize FMS models for use on GFDL's new supercomputing system. It is anticipated that a number of simple modifications will lead to significant performance enhancements during the first six months that the new system is available.
- Design work on a single column model testing facility will be completed and the single column model will become part of official FMS releases.
- A number of enhancements to the FMS diagnostic manager will be made to support more elaborate run-time diagnostics. Among the new features will be diagnostics for limited spatial domains, better spatial averaging facilities, and the ability to output diagnostics for particular times of day.
- Quarterly releases of FMS will continue. Several major new features are planned for inclusion including a comprehensive biosphere model, a standardized coupled model as well as the new radiation code of the atmospheric processes group.
- Development and experimentation with prototypes of the atmospheric component of the next-generation coupled models will be undertaken.
- Tests of the solar and longwave radiative transfer parameterizations in the atmospheric GCM being developed in the FMS framework will continue, in particular accounting for random-maximum overlap configurations of the vertical profile of clouds.
- Examination of the impact of new radiative transfer parameterizations will cover an atmospheric model version containing the new radiation, convection and prognostic cloud parameterizations. A new gravity wave drag scheme will be incorporated into the atmospheric model. In addition to convectively-excited waves, attention will also be given to a new treatment of orographically-induced waves. The atmospheric model containing the new suite of physics will be subjected to extensive tests, both in the AMIP-style runs and "unforced" integrations.
- Analyses of solar and longwave fluxes and heating rates as obtained from the array of radiative transfer models will continue. In particular, the network of surface solar observing sites will be used to examine the climatological features of the inferred aerosol radiative effects. Radiative forcing due to atmospheric trace gases and aerosols (e.g., black carbon, dust) will be further analyzed. The influences due to microphysical effects of aerosols upon their radiative properties will be examined using a hierarchy of models.
- Further diagnosis of cloud parameterizations will continue. In particular, effort will be placed on diagnosing the reasons behind the qualitatively correct temperature dependence of low cloud optical depths obtained in the model simulation.
- MOM-4 will become a part of FMS and will be integrated into all global coupled models at GFDL.
- MOM 4 will be coupled to sea ice and atmospheric models using the FMS exchange grid.
- A project will be launched with external collaborators to develop operational radiosonde products for use in near real-time diagnosis of temperature variability in the free atmosphere.
- Further intercomparisons will be performed between the radiosonde and satellite observations of upper tropospheric water vapor on a station-by-station and satellite-by-satellite basis, so as to assess their utility for climate monitoring. Particular effort will focus on identifying and quantifying discontinuities associated with radiosonde instrumentation or satellite calibration changes.
- A fully operational version of a web-based data analysis and visualization package will be adapted for laboratory-wide use within GFDL. New output from various FMS experiments will be assembled and linked to this new diagnostic tool. The multitude of data resources available through the Distributed Oceanographic Data Systems (DODS) network will be exploited to facilitate intercomparisons between model-simulated and observational data sets.
- A correction for vertical wind shear in the drag parameterization is being formulated and will be tested in the same way as the rest of the scheme, i.e., with comparable high- and low-resolution experiments. The sensitivity of the drag to the treatment of the turbulent planetary boundary layer will also be examined.
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