b'Environmental geophysicsEnvironmental geophysicsthis is the amazing partthe distancedata from other sources that allowed between them was known to better thanthem to decide what caused the 10 microns. So, this pair of satellites actedchange in gravity. These additional data as a big gravimeter, with the changingsources included long-term rainfall distance between the satellites (after arecords, Landsat imagery, reports on few corrections) being directly relatedwater use, etc.to gravity variation under the track ofThirty-four trends were identified the satellites. By repeating the data setsworldwide, (Figure 1 is from the every 30 days, the system measured thepaper). Changes were divided into change in gravity of all in its path overfive categories: Probable and possible and over again for 14 years. The pixel sizetrends caused by climate change (8 of 34 from system ranges from about 300 x 300responses), probable and possible trends km at the poles to about 450 by 450 kmcaused by direct human impact (think at the equator, so yes the scale is prettygroundwater use, dam building, etc. - 14 Mike Hatchcoarse.of 34 responses), and probable trends Associate Editor for I am aware that I am using the past tensecaused by natural variation (12 of 34).Environmental geophysicsfor the Grace data setsGrace 2 (theI could study Figure 1 for hours, looking michael.hatch@adelaide.edu.au second in the pair) burned up on re- for trends; the analysis that they entry to the Earths atmosphere in 2017.provide is very interesting and worth The good news is that the all new andspending time with. The numbering of improved Grace FO pair were launched in Grace mapping of2018so there will be more data like thiseach trend is related to approximate to look at for the foreseeable future. importance of that trend. The largest terrestrial water changes observed (Regions 1 to 5) are Rodell and his team processed the dataall related to changes in ice content at storage from the system, looking for gravityhigh latitudes. In the groundwater world changes that could be attributed(just to pick one example), I found it Welcome readers to this issues(mostly) to change in Terrestrialvery interesting that this work identified column on geophysics applied to theWater Storage (TWS)at any givenone area, Region 11, west of Urumqi in environment. This column is dedicatedlocation. TWS is the content sum of theChina, where the change to the TWS to the recent Australasian Explorationgroundwater, soil moisture, surfacehas not been previously documented, Geoscience Conference (AEGC), heldwater, snow and ice at a given location.and was attributed in this paper largely from September 2 to 5 in Perth. They then categorised the observedto intense local irrigation not until now Actually, in this column Im going tochange patterns over the surface of theappreciated for the sheer magnitude of review one of the most interestingEarth, in conjunction with additionalits effect.papers that I have seen in yearswhich I found in the process of doing research for one of my talks at the AEGC. The paper is from Nature in 2018 by Dr Matthew Rodell from the Hydrological Sciences Lab at the NASA Goddard Space Flight Centre and six others (Rodell et al. 2018). In this article, Rodell and his co-authors interpret 14 years of Grace Satellite data, from launch in 2002 to nearly the end of the mission in 2016, and attribute the observed changes in gravity to changes in water budget around the worldmore below.For those of you who dont know (and I didnt until I researched the project as part of my talk and yes, it is true some of this information is sourced from Wikipedia) the Grace Satellites are a pair of satellites that were in very close to N-S polar orbit, at approximately 500 kmFigure 1.Annotated map of TWS trends taken from Rodell et al. 2018. Trends in TWS (in cms per year) altitude. At this altitude and attitude theobtained on the basis of GRACE observations from April 2002 to March 2016. The cause of the trend in each pair of satellites collected a completeoutlined study region is briefly explained and colour-coded by category. The trend map was smoothed with set of global data every 30 days. The paira 150-km-radius Gaussian filter for the purpose of visualization: however, all calculations were performed at were separated by about 220 kmandthe native 3o resolution of the data product.OCTOBER 2019 PREVIEW 38'