GRAV-D in relation to the NOAA Annual Guidance Memorandum (AGM)

Click here first, to read the NOAA Annual Guidance Memorandum

Comment from Dr. Dan Roman:

The GRAV-D program will fit nicely into the core competencies and strategic priorities identified in the AGM.

First, establishing a time-varying vertical datum would be extremely useful for determining actual sea level changes - a definite aspect of climate change. As water tables deplete or change around, any secular trends we identify and model through GRAV-D will impact the variations seen by GRACE and/or GRACE Follow-on.

Second, the gravimetric geoid will extend (and be extensively tested) into the littoral environment. The interest there is in understanding the transition from offshore to onshore for such things as storm surge. That also means we'll have defined the spatial environment in the maritime regions that is consistent with the terrestrial.

The GRAV-D connection with fisheries is a bit weaker, but arguably relevant for understanding where fish schools and where their food sources are located (see above discussion of maritime spatial reference). Additionally, a natural consequence to GRAV-D should be an improved Mean Dynamic Ocean Topography model. MDOT models provide good estimates of ocean currents' direction and flow rate, which would be useful in understanding the flow and distribution of nutrients that feed the base of the food chain (which ultimately feeds the fish) as well as understanding where an oil slick might go and when it might disperse.

Arctic science connections to GRAV-D are clear. The program is already working on establishing models for Alaska and ensuring that they tie into what the Canadians have, as well as what the Danes have for Greenland. That region already covers half of the Arctic.

Lastly, airborne profiles collected as a part of GRAV-D will ultimately be tied into the GRACE and eventually GOCE satellite gravity field models. However, the airborne data will first be tested against these models to validate both the models and the data. Several very long flights (thousands of km) will likely be needed to tie separate GRAV-D collection regions (averaging around 400 km by 500 km) together. Such flights would also be invaluable to analysis of the satellite gravity models, since the length of the profiles will provide a long continuous gravity observation useful for analyzing the largest gravity signals of the Earth. Such signals are sensed by the satellite garvity missions and perturb the orbits of all satellites.

Therefore, the case can be made that the GRAV-D program provides support to all priorities defined by NOAA for this year.

Regards, Dan Roman