From NASA’s Scientific Visualization Studio: The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission is a joint Earth-science project launched in 2018 by NASA and the German Research Centre for Geosciences to continue the work of the earlier GRACE mission. It consists of two satellites flying about 137 mi (220 km) apart in the same orbit around Earth, constantly measuring tiny changes in the distance between them. These variations occur because changes in Earth’s gravity, caused by shifting masses such as melting ice sheets, groundwater depletion, and ocean circulation, slightly alter the satellites’ speeds and separation. By precisely tracking these changes, GRACE FO allows scientists to map how water moves across the planet, improving our understanding of climate change, sea-level rise, and global water resources.
This visualization uses data from GRACE FO to create an index based on percentile dryness, categorizing the degree of wetness or dryness within three domains: groundwater storage, root zone soil moisture, and surface moisture. It updates weekly, and extends back over a period of a year from the current week.
This visualization is created by the NASA Scientific Visualization Studio
One in the eye for the BBC…
story tip
Hi all Since you are all interested in science and obtaining the best and most accurate measurements possible maybe you (those in the US) could call your local representative and voice your displeasure at the gutting of science and products which is currently happening – specifically NCAR/NCEP R1 reanalysis product which will be no longer available – which means that PIOMAS sea-ice volume estimates will no longer be produced for the foreseeable future. Maybe an article on WUWT may raise the profile of the cuts which are currently happening. See: https://psc.apl.uw.edu/research/projects/arctic-sea-ice-volume-anomaly/
Note the cuts not only impact current measurements but mean that replacement of satellites currently in orbit may not happen before the old satellites fail meaning disruption of continuous measurements.
Sorry, after $40T in debt and the politicians find more personal benefit from spending all the money on open borders, fraud and the MIC, the tax payers are tapped out for any other Gimme Money programs. Keeping Somalians in G Wagons and Mansions is more important than even paying for national security.
Hmm. I was aware of the GRACE project, but had no idea it could distinguish between subsurface and surface drought conditions. These animations are very neat – I’ve long been annoyed at the Thursday drought maps at https://www.drought.gov/data-maps-tools/us-drought-monitor or better, https://droughtmonitor.unl.edu/ . There’s a big difference between my grass turning brown and my well running dry. Where I live now, in a small river valley, means there’s no chance of the latter. OTOH, there is a NH Historical Marker across the street about that All New England Flood of 1936, but let me stick to the topic.
How does GRACE do this? I understand the gravity measurements, at least as far as their use in petroleum prospecting, and other static gravity maps. So that extends to deep ground water and ice cover readily. As for more of what’s going on, here’s a brief summary from https://nasagrace.unl.edu/About.aspx :
The spatial (>150,000 km2) and temporal (monthly with a significant time lag) resolutions of the GRACE and GRACE-FO fields limit their direct applicability for drought assessment. In order to increase the resolution, eliminate the time lag, and isolate groundwater and other components from total terrestrial water storage, scientists at NASA/GSFC integrate the GRACE and GRACE-FO data with other ground- and space-based meteorological observations (precipitation, solar radiation, etc.) within the Catchment Land Surface Model, using Ensemble Kalman smoother type data assimilation (Zaitchik et al., 2008, Kumar et al., 2016). The resulting fields of soil moisture and groundwater storage variations are then used to generate drought indicators based on the cumulative distribution function of wetness conditions during 1948-2014 simulated by the Catchment model.
Local gravimeters are good for localized ground water assessments. This somewhat the opposite problem with the GRACE data.
One problem is that the things listed are not the only means by which gravity can change.
Among the others are various forms of earth movement. Earth movements, not just earthquakes, but slower movements as the tectonic plates slide against each other.
Magma moving in the mantle, even regions of high and low air pressure.
I remain unimpressed by GRACE.
It measures minute differences in the gravity field – and thereafter the entire process is endless modeling play-games.
Gravity field is the sum effect of the distribution of mass operating in one-over-r-squared space. I cannot see any unique solution to the question of whether a perceived change in mass distribution happened here, there, or in multitudes of tiny bits hither and yon.
I am open to enlightenment
Work through these animations day by day and see big swings in indicated drought. I don’t know about the data they are using but going from extremely wet to extremely dry in the same spot over a couple day period doesn’t pass the sniff test. FYI I was just looking at my state where I know the weather, topography and where the major cities are located.
Very cool. It will help out in my farm management later this year.
Space science given light speed limitations – a solution looking for a problem.
Two satellites traveling overhead mapping the surface. The resolution of the pair MUST be aligned to the direction of travel, so you would expect that ANY single data point should not be a square pixel but should actually be a strip that runs at 90 degrees to the orbit.
That would be physics dictating the outcome.
Even if the orbit was inclined at 45 degrees to the equator, (allowing the eventual mapping in two orientations, each 90 degrees apart), how do you account for the time delay between the two shots?
It has already been pointed out in the comments that the data goes from dry to wet in the space of days, so surely the time between the orthogonal shots must be less than the time interval where a change occurs.
I doubt that the resolution offered by this pair of satellites offers square pixels. Prove me wrong.
An example of an inclined orbit. Not exactly a short time between orbits when considering the pixel sizes offered as data.