Abstract
Almost half of the Earth’s land is covered by large river basins. Temporal variations of hydrological masses induce time-varying gravitational potential and temporal mass loading that deforms the Earth’s surface. These phenomena cause temporal variations of geoid/quasigeoid and ellipsoidal heights that result in temporal variations of orthometric/normal heights ΔH/ΔH*. The aim of this research is to assess ΔH/ΔH* induced by hydrological masses over large river basins using the Gravity Recovery and Climate Experiment (GRACE) satellite mission data. The results obtained reveal that for the river basin of a strong hydrological signal, ΔH/ΔH* reach 8 cm. These ΔH/ΔH* would be needed to reliably determine accurate orthometric/normal heights. The ΔH/ΔH* do not exceed ±1 cm in the case of the river basin of the weak hydrological signal. The relation between hydrological mass changes and ΔH/ΔH* was investigated. Correlations between ΔH/ΔH* and temporal variations of equivalent water thickness were observed in 87% of river basins subareas out of which 45% exhibit strong correlations. The ΔH/ΔH* determined over two river basins that characterize with the strongest and weakest temporal variations were analysed using the Principal Component Analysis method. The results obtained reveal that ΔH/ΔH* in subareas of the same river basin can significantly differ (e.g., ±2 cm in the Amazon basin) from each other, and are strongly associated with different spatio-temporal patterns of the entire river basin.
Highlights
The orthometric/normal heights, defined as a distance between the geoid/quasigeoid surface and a point on the Earth’s surface measured along the real/normal plumb line, are substantially needed for scientific research, e.g., for studying crustal deformation, as well as for a wide range of engineering applications such as construction and infrastructure projects
On the basis of Gravity Recovery and Climate Experiment (GRACE) satellite mission data, temporal variations of geoid/quasigeoid heights (Figure 3) and vertical deformations of the Earth’s surface (Figure 4) were estimated over large river basins specified in Figure 2 using Equations (4) and (5), respectively
This illustrates the relation between temporal variations of hydrological masses, temporal variations of geoid/quasigeoid heights and the crustal deformations in the vertical component
Summary
The orthometric/normal heights, defined as a distance between the geoid/quasigeoid surface and a point on the Earth’s surface measured along the real/normal plumb line, are substantially needed for scientific research, e.g., for studying crustal deformation, as well as for a wide range of engineering applications such as construction and infrastructure projects (i.e., roads, bridges, railways, dams, etc.). These heights are traditionally obtained using levelling measurements, and nowadays, more often by the combination of a high accuracy precise gravimetric geoid/quasigeoid height with an ellipsoidal height. Footrenextiaaml polne,twhehegnehoyidd/rqoluoagsicigalemoiadssseusrifnaccreeassaeloson tihnecrEeaartshe’ss,swurhfaicche (lFeiagdusret1oaa),stcheending the gegoriadv/iqtautiaosnigalepooidtesnutiraflaocne.thTehgiseoiisdd/quueastoigethoiedfsaucrtftahceast aalcscooirndcirneagsetos, twhheiNchelweatdosnt’os aloscwenodfinggrathveitation the reglaetoioidn/qbueatswigeeeonidthsuerfmacaes.sTahnisdisthdeuegtroatvhietaftaicotnthaal tpaoctceonrdtiianlgistoththeedNireewctolyn’ps rlowpoorftgiornavailta(ctifo.n[6th] e(Ch. 1, p. 1)).reOlantitohneboettwheerenhathnedm, tahsseainndcrtehaesgeroavf itthateiohnyadl prooltoengtiicaallismthaessdeisreoctnlythperoEpaorrtthio’nsaslu(crff.a[c6e] (iCnhd.u1c,eps. mass load t1h)a).t Orensuthltesointhderohwannwd,atrhde einlacsretiacsedeoffotrhme hatyidorno.loTghiceaol pmpaossseitseosncethnearEioarwthi’lslsoucrcfuacrewinhdeuncehsymdraoslsogical masselosaddecthreaat srees(uFlitgsuirne 1dbow). nTwhaerdrefeolarset,ictedmepfoormraaltivoanr.iaTthioenospopfohsiytedrsocleongaricioalwmilal soseccsuirndwihcaente that tempohinrydadlircvoaaltoergitaihctaaiolt nmtesamosspfeoosrratdlheovcrmaeraieastteriioc(nF/snigoourfrmeoar1tlbhh)o.emTigehtherrtices/fnmooreirg,mhtaetlminhpceorirgeahaltssvea/mdrieiagcthiroetnaisnsecorfbeayhsyetdw/drooelcofragecaictsoaelrsbm:yavstawsreiosations of geofaidct/oqrus:avsiagrieaotiiodnsheoifghgetsoidan/qduavseigretiociadl hdeeigfohrtsmaantdionvesrtoicfatlhdeeEfoarrmthat’isonsus rofaf cteh.e MEaortrhe’osvseurr,fanceeg. ative coefficMieonrtesovoefrc,onrergealatitvioencobeefftiwcieeenntstoefmcpororrealal tvioanriabteitownesenoftehmydpororalol gviacraialtmioansssoefs haynddrotelomgipcoalraml avsasreisations of orthanodmteetmripc/onraolrmvaarilahtieoingshotsf oarteheoxmpeetrcitce/dno. rTmhails hiseibgehctsauarsee eaxnpienctcerde.aTsehiisnishybedcraoulsoegaicnalinmcraesasesinwould resulthiyndarodloegcirceaalsmeaisnseosrwthooumldertersicu/lnt oinrma dael chreaigsehtins (oer.tgh.o,m[7e–tr1i0c/]n).ormal heights (e.g., [7,8,9,10])
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