SOIL MOISTURE: Daily, Anomaly and Forecasted values

Transcription

1 PRODUCT FACT SHEET: ACRONYME EUROPE Versin 1 (Sept. 2011) SOIL MOISTURE: Daily, Anmaly and Frecasted values Type Tempral scale Spatial scale Ge. cverage Sil misture Daily 5 km Eurpe Daily Sil Misture (pf) Sil Misture Anmaly (nrmalized) Frecasted Sil Misture trend n 7 days (pf day -1 ) Anmaly Frecasted n 7 days (nrmalized) DESERT Actin LMNH Unit - 1 -

2 Sil misture is ne f the imprtant variables in hydrlgic, climatlgic, bilgic, and eclgical prcesses because it plays a crucial rle in the interactins between the atmsphere and land surface. In fact, sil misture cntent affects surface evapratin, runff, albed, emissivity, and prtining f sensible and latent heat fluxes. Mrever, it represents a vital water reservir fr all the plants buffering their water cnsumptins in perid with rain water supplies are lesser than their requests. In additin, drught in nt nly a temprary lack f rain but als ccurs when the sil misture decreases cnsiderably, and crps and natural plant cmmunities suffer due t insufficient water availability. Therefre, great effrts have been made t estimate sil misture using sil water balance mdel frced with realistic precipitatin and ther atmspheric data (grund bservatin, numerical weather predictin, etc.) t be used as direct indicatr t assess the drught nset, duratin and severity. The aim f this indicatr is t prvide an instantaneus assessment f the tp sil water cntent as mdeled by LISFLOOD acrss Eurpe. The LISFLOOD mdel was develped in JRC in regards t the Eurpean Fld Alert System (EFAS). The sil water cntent can be used as direct indicatr fr determining the start and duratin f drught cnditins. In fact, the sil water cntent expressed as water ptential (pf) prvide an assessment f the plants difficulty t extract water frm the sil matrix (pf varies between 0, when saturated, and 7, when extremely dry) r, in ther terms, f the sil water availability fr the plant s needs. The sil water cntent is als bviusly related t the plant bimass accumulatin (grss primary prductin) in many envirnment were the water availability is the main limiting factr (dry, semiarid, arid). 1. Prduct The sil water ptential is ne f the utput parameters f the LISFLOOD mdel. Gegraphic cverage: Eurpean cntinent Spatial scale: 5 km Tempral scale: daily calculated based n grund bservatin update with 2 days f delay as f the real time and extended fr 7 days with ECWMF numerical weather frecast Data surce: Natinal Mete Office, JRC-MARS elabratin and ECMWF numerical weather frecast Frequency f data cllectin: daily 2. Methdlgy 2.1 Calculatin f Sil Misture The LISFLOOD mdel is a hydrlgical rainfall-runff mdel that is capable f simulating the hydrlgical prcesses that ccur in a catchment. LISFLOOD has been develped by the flds grup f the Natural Hazards Prject f the Jint Research Centre (JRC) f the Eurpean Cmmissin

3 The fllwing figure gives an verview f the structure f the LISFLOOD mdel. P = precipitatin; Int = interceptin; EW int = evapratin f intercepted water; D int = leaf drainage; ES a = evapratin frm sil surface; T a = transpiratin (water uptake by plant rts); INF act = infiltratin; R s = surface runff; D 1,2 = drainage frm tp- t subsil; D 2,gw = drainage frm subsil t upper grundwater zne; D pref,gw = preferential flw t upper grundwater zne; D uz,lz = drainage frm upper- t lwer grundwater zne; Q uz = utflw frm upper grundwater zne; Q l = utflw frm lwer grundwater zne; D lss = lss frm lwer grundwater zne. Basically, the mdel is made up f the fllwing cmpnents: a 2-layer sil water balance sub-mdel sub-mdels fr the simulatin f grundwater and subsurface flw (using 2 parallel intercnnected linear reservirs) a sub-mdel fr the ruting f surface runff t the nearest river channel a sub-mdel fr the ruting f channel flw (nt shwn in the Figure) The prcesses that are simulated by the mdel include snw melt (nt shwn in the Figure), infiltratin, interceptin f rainfall, leaf drainage, evapratin and water uptake by vegetatin, surface runff, preferential flw (bypass f sil layer), exchange f sil misture between the tw sil layers and drainage t the grundwater, sub-surface and grundwater flw, and flw thrugh river channels. Grundwater strage and transprt are mdelled using tw parallel linear reservirs. The upper zne represents a quick runff cmpnent, which includes fast grundwater and subsurface flw thrugh macr-pres in the sil. The lwer zne represents the slw grundwater cmpnent that generates the base flw. Cncerning the land use and calculatin f the effective rainfall as well as the actual evaptranspiratin, the LAI is calculated frm remte sensing data (NDVI). Several years f NDVI are used and averaged; a fixed lk-up table f LAI in each 5 km pixel is prduced n daily time step. Rting depth is linked with LAI and it is changing accrding t phenlgical phase

4 2.2 Calculatin f Anmalies The anmalies are calculated as the fllwing: where is the Sil Misture f the day t f the current year and, is the lng-term average and δ is the standard deviatin, bth calculated fr the same perid t ver the available time series ( ). Accrding t the definitin the Anmaly present values expressed as units f standard deviatin. 2.3 Calculatin f Frecasted trend The frecasted values are calculated ver the ECMWF numerical weather frecast. In practice, the LISFLOOD mdel ges n the calculatin f the sil misture since the last bservatin up t 7 fllwing days. The frecast prvides the tendency during the cming days in terms f pf variatin between the last day f simulatin n the bserved data (t 0 ) and the day t The sil misture map and the anmaly, as well as, the frecast maps prvide infrmatin n spatial distributin f the sil water cntent and its evlutin alng the time. Each day the EDO mapserver autmatically update the sil misture values ver the last grund bservatin available and the weather frecast The sil misture map as well as the Anmaly map culd prvide a prxy infrmatin n the pssible presence f drught cnditins in case f pf values bigger than r/and in case f large deviatins frm the lng term average cnditins. Of curse, the presence f real water stressing cnditins depends n the specific plant resistance and capacity t water extractin frm the sil matrix. At the same time pf values lwer than 2 culd be cnsider as indicatr f sil water excess. 1. Strength & weaknesses [+] The daily update and the use f weather frecast give cntinuus infrmatin n the simulated status f the sil misture and the spatial extensin f the area affected by drught r under risk. Mrever, the analysis f the time series allws t estimate the duratin and the severity f drught. [-] The generalizatins and the scientific assumptin (sil physic, land use, canpy cver, mete data interplatin, etc.) embedded in the sil water balance mdel, and at the same time, the calibratin f the mdel culd prduce in sme case large apprximatin f the real sil misture and prgressive divergence with the real cnditins - 4 -

5 De R, A., Wesseling,C., Van Deursen, W. Physically based river basin mdelling within a GIS: the LISFLOOD mdel. Hydrl. Prcess. 14, (2000) Laguardia, G., Niemeyer S. (2007) Twards a sil misture-based drught index. Gephysical Research Abstracts, Vl. 9, 06714, Laguardia, G., Niemeyer S. (2008) On the cmparisn between the LISFLOOD mdelled and the ERS/SCAT derived sil misture estimates. Hydrl. Earth Syst. Sci. Discuss., 5, , 2008 M, Xinggu, Pappenberger, Flrian, Beven, Keith, Liu, Suxia, De R, Ad and Lin, Zhnghui(2006) 'Parameter cnditining and predictin uncertainties f the LISFLOOD-WB distributed hydrlgical mdel', Hydrlgical Sciences Jurnal, 51: 1, Van Der Knijff, J. M., Yunis, J. and De R, A. P. J.(2010) 'LISFLOOD: a GIS-based distributed mdel fr river basin scale water balance and fld simulatin', Internatinal Jurnal f Gegraphical Infrmatin Science, 24: 2, , First published n: 24 Nvember 2008 Van Der Knijff, and De R, A. P. J.(2008) LISFLOOD Distributed Water Balance and Fld Simulatin Mdel : Revised User Manual. JRC Scientific and Technical reprt - 5 -