Introduction to the OSSE/OSE Project

This project encompasses several well-established atmospheric OSSE/OSE efforts currently existing at Goddard. It is funded under the NASA MAP program with the research title: "Observing System Experiments (OSE and OSSE) to Evaluate and Enhance the Impact of Current and Future Satellite Observations."
The project is managed by Dr. Oreste Reale of the Goddard Laboratory for Atmospheres (GLA). Dr. Juan Carlos Jusem, also of the GLA, provides valuable expertise to the OSSE/OSE effort. The Software Integration and Visualization Office (SIVO) provides support to the GLA in the form of software development, experiment execution, data management, and assistance with certain scientific tasks. The GLA and SIVO OSSE/OSE team have formed or maintained collaborations with many research groups, both outside and within NASA, to help promote satellite research through the use of OSSE's and OSE's. These groups include GSFC researchers in the Global Modeling and Assimilation Office (GMAO) and Sounder Reserach Team (SRT); NOAA researchers at NCEP, ESRL and AOML; and the private research company Simpson Weather Associates.

OSSE Description

An Observing System Simulation Experiment, or OSSE, is a type of observing system experiment in which synthetic meteorological observations are used as a surrogate for real observations. The assimilation of these observations and subsequent free forecasts are conducted the same as with real observations. The synthetic obs are usually extracted from a long forecast from a high resolution, state-of-the art model, known as a "nature run", which acts as a proxy atmosphere specifically for the OSSE. The primary objective of an OSSE is to assess the potential impact on NWP of assimilating observations from proposed/future observing systems. In this way, the benefits of an observing system can be estimated before it is designed, built and launched into orbit. Trade-offs in instrument or orbital configurations and methods of assimilating a new type of observing system can be determined by an OSSE and ultimately result in both time and cost savings. Data impact experiments, in which synthetic observations from existing and proposed observing systems are added or removed from the experiment, can identify an optimal configuration for a future observing network and help recognize weaknesses in the processing or assimilation of the observations. The same data assimilation systems, models, and diagnostic tools used for performing OSE's are also used for OSSE's.

Why Perform OSSE's?

- The costs of designing, building, and maintaining new instruments are very high

- To quantify impacts of new instruments

- To test design trade-offs for a particular instrument

- To prepare data assimlations systems for optimal use of new observation types

OSSE Players

+ Player Diagram

Methodology

For OSSE's, the nature run is a proxy for the real atmosphere. It is from the nature run dataset that simulated observations are generated. As with real observations measured in the real atmosphere, simulated observations are assimilated both with and without certain observing systems included. Forecasts are then executed from these assimilations. The output from both the assimilations and forecasts are evaluated in a variety of ways. The results of the evaluation can be used to either calibrate the OSSE system to enhance realism, or to tune various components of the system to improve performance. This can feedback to the nature run, the method used to simulate observations, or the Data Assimilation System (DAS).

In the initial iterations through this cycle, comparisons are made between experiments using simulated and real observations, both using the same DAS and forecast model. Inconsistencies in results between the simulated world and real world may necessitate a calibration of one or more components of the OSSE system. Calibration may involve, for example, improving the errors that are applied to the simulated observations or enhancing certain nature run fields to achieve greater realism.

After the initial calibration is performed, the OSSE system is ready for actual experiments with new observing systems. At this point, another iterative process will commence in which simulated observations from new
instruments are introduced. Results of assimilations and forecasts with and without these new observations are evaluated. The nature run provides the truth data against which all of these simulated experiments are verified. Impacts that are neutral or negative, i.e. below the expectations of the new instrument, will require tuning of one or more OSSE components. The tuning may involve, for example, super-obbing or thinning of the simulated observations, refining the observation error estimates used in the DAS, or introducing an improvement to the DAS itself all of which would be designed to increase the usefulness of the observations and ultimately improve impact.

+ Methodology diagram

Diagrams of Key OSSE Components

+ OSSE Flow diagram

+ Example of spin-up for an OSSE Experiment

+ Example of Assimilation and Forecast Execution

+ Basic Schematic for Evaluating an OSSE

OSSE Collaborators

+ GMAO (Goddard Modeling and Assimilation Office)
Dr. Michele Rienecker, Head
Dr. Rienecker provides the OSSE/OSE group with access to the GEOS-5 DAS with which all experiments are conducted.

Dr. Lars Peter Riishojgaard, Acting Director of the JCSDA.
Dr. Riishojgaard is the GMAO's main point of contact for the OSSE/OSE group and provides valuable scientific advice for many of the group's activities.

+ NOAA/NCEP
Dr. Stephen Lord, Head
Dr. Michiko Masutani is the NCEP's main point of contact for the OSSE/OSE group and interacts with the group on many OSSE activities.

+ Simpson Weather Associates
Dr. David Emmitt, President
Dr. Emmitt provides a variety of simulated lidar data to the OSSE/OSE group for detailed evaluation using the GEOS-DAS.

+ NOAA/AOML (Atlantic Oceanographic Meteorological Laboratory)
Dr. Robert Atlas, Head
Dr. Atlas was the original PI for the OSSE/OSE efforts at NASA and continues to interact with the OSSE/OSE group.

+ NOAA/ESRL (Earth System Research Laboratory)
Dr. Alexander McDonald, Head
Dr. Tom Schlatter is the main point of contact. ESRL contributes to the development of the OSSE framework for the Joint OSSE effort.