-Corbari C, Ravazzani G, Mancini M. A distributed thermodynamic model for energy and mass balance computation: FEST-EWB. Hydrol. Process. 2011; 25: 1443–1452. -Corbari, C., Mancini, M. (2014), Calibration and validation of a distributed energy water balance model using satellite data of land surface temperature and ground discharge measurements, Journal of hydrometeorology, 15, 376-392

Chiara Corbari, Marco Mancini Politecnico di Milano, Milano, Italy

chiara.corbari@polimi.it, www.FEST.POLIMI.it

Calibration and validation of distributed models at basin scale generally refer to external variables, which are integrated catchment model outputs, and usually depend on the comparison between simulated and observed discharges at the available rivers cross sections, which are usually very few. However distributed models allow an internal validation due to their intrinsic structure, so that internal processes and variables of the model can be controlled in each cell of the domain. In particular this work investigates the potentiality to control evapotranspiration and its spatial and temporal variability through the detection of land surface temperature (LST) from satellite remote sensing. This study proposes a methodology for the calibration of distributed hydrological models at basin scale using remote sensing data of land surface temperature.

The distributed energy water balance model, Flash–flood Event–based Spatially–distributed rainfall–runoff Transformation - Energy Water Balance model (FEST-EWB) will be calibrated in the Upper Po river basin (Italy) closed at the river cross section of Ponte della Becca with a total catchment area of about 38000 km2. The model algorithm solves the system of energy and mass balances in term of the representative pixel equilibrium temperature (RET) that governs the fluxes of energy and mass over the basin domain. This equilibrium surface temperature, which is a critical model state variable, is comparable to the land surface temperature (LST) from satellite. So a pixel to pixel semi-automatic calibration procedure of soil and vegetation parameter is presented through the comparison between the model internal state variable RET and the remotely observed LST. A similar calibration procedure will also be applied performing the traditional calibration using only discharge measurements. 130 diurnal and nocturne LST MODIS products are compared with FEST-EWB land surface temperature over the 4 years of simulation from 2000 to 2003 where meteorological and hydrological ground data are available.

ABSTRACT

Ptot=R+ETeff+D+(θt+1-θt)*Z Soil water balance

Energy balance

FEST-EWB model solves the system of energy and mass balances in term of a representative equilibrium temperature (RET) that governs the fluxes of energy and mass

FEST-EWB: Flash – flood Event – based Spatially – distributed rainfall – runoff Transformation – including Energy - Water Balance

Distributed hydrological model calibration through satellite land surface temperature and discharge data

DEM  Soil  Parameters  

Vegeta2on    Parameters  

Snow    Dynamics  

Spa2al  interpola2on:  Thiessen,  IDW  

Defini2on  of    river  network  

Subsurface  rou2ng  

Surface  flow  rou2ng  

Hydrograph  

Percola2on   Surface  Runoff  

Input  

Output  

LEGEND  

Process  

Internal    variable  

groundwater  

Lakes  and  reservoires  

LST  SM  

Energy  fluxes  

Meteorological  data  

S0 Sd

St αSt L

0LiΛ

E H

25 July 9:30 UTC AIRBORNE LST AHS

Δx= 5 m °C

3 km

3 km

HETEROGENEUS AREA: 65% of cultivated lands at Barrax are dryland (67% winter cereals, 33% fallow) and 35% irrigated land (75% corn, 15% barley/sunflower, 5% alfalfa, 5% onions and other vegetables).

Soil paramters are calibrated minimizing the difference between observed and simulated LST

EC1: camelina EC2: vineyard

EC3: reforestation

before calibration After calibration

MAE (%) MD(AHS - FEST-EWB) (°C)

MAD(°C) RMSD MAE (%)

MD(AHS - FEST-EWB)

(°C) MAD RMSD

9.5 0.7 3.4 4.6 3.4 -0.9 1.5 2.1

RET FEST-EWB_not calibrated

RET FEST-EWB calibrated

...with different configurations…

Energy budget closure 82 % (Van der Tol et al., 2015)

not calibrated calibrated

MAD (W m-2) MAE (%) MAD (W m-2) MAE (%)

Rn 20 3.5 10 3 G 180 55 98 26 H 50 26 33 13 LE 100 70 12 17

H e LE are compared considering eddy covariance footprint (Hisie et al. 2000; Corbari et al., 2015)

25 July 9:30 UTC

ENERGY FLUXES LOCAL VALIDATION

CONCLUSIONS Solving the energy budget on land surface temperature allows to use this variable as internal control of hydrologic simulations. It can be promising tool to calibrate the soil and vegetation parameters of

the distributed water balance model complementary to the traditional comparison based on discharge measurements.

TOCE  

BORMIDA  

MAGGIA  

SESIA  

TICINO  

ORBA  

BELBO  STURA  DI  DEMONTE  

PO   SCRIVIA  

TANARO  

MAGGIORE  LAKE  

PADDIES

Toce at Candoglia

CALIBRATION: comparison among FEST-EWB & MODIS LST

6000 N pixels

3000

MODIS

FEST-EWB

1- originali 2-ksat modified ( °C )

LST

3-ksat, depth 4-ksat, depth, bc, rs min

+ - RET (° C)

Pixel base calibratiob

2000 – 2003, 130 MODIS LST images with cloud coverage percentage less then 30%

Mean absolute difference 1.8 °C,

RMSE 3.4 °C

Mean average over pixels of the absolute difference between RET and LST-

MODIS

Autocorrelation function

6 july 2000 13:00

Volume Error (calibrated Q) = 3.2 % Volume Error (calibrated LST+Q) = -0.14 %

Nash (calibrated Q) = 0.90 Nash (calibrated LST+Q) = 0.87

J.  Dooge(  1986)  observing    internal  state  variables  of  hydrologic  model    (  θ)        

TradiNonal  calibraNon  on  point  measurements  (observed  discharge,local  soil  moisture  or  evapotranspiraNon)  

calibrated  Not  calibrated  

Each  pixel  is  mul.plied  by  a  local  factor  which  depends  on  the  temperature  matrix  differences  

Soil  parameters:  same  spa.al  distribu.on  

FEST-­‐EWB  

MODIS  

calibrated  Not  calibrated  

SUPERFICIAL  Soil  parameters:  Increased  spaNal  variability  

!T (.) =Min(RET (.)"LST (.))!Q=Min(Qobs "Qsim)

Each  pixel  is  mul.plied  by  a  common  factor  which  depends  on  discharge  differences  

Hydrological  model  calibraNon  with  distributed  informaNon:  satellite  images  of  land  surface  temperature  (LST)  

Is  it  reasonable  to  use  evaporaNon  flux  “measures”  similarly  to  discharge  measurements?  

PIXEL  to  PIXEL  calibraNon  on  satellite  LST  

Basin scale: UPPER PO river basin (Italy)

Agricultural scale: Barrax (2012 experiment)

Laboratory scale: lysimeter

DIMENSIONS Length, width =1.5 m height =1.0 m Weight = 956 kg without soil Weight about 4700 kg with soil

PIXEL BY PIXEL CALIBRATION BY COMPARING AIRBORNE AND FEST-EWB LST

The energy water balance hydrological model calibration

Calibration of soil paramters regulating surface processes

Calibration of soil paramters regulating sub-surface processes

CALIBRATION: comparison among FEST-EWB & ground discharge

Before calibration

Combined LST and Q calibration leads to good agreement with observed discharge (volume) and also SM (evapotranspiration) better spatial distribution

measured

Fully equipped to measure all the process of the hydrological cycle

FEST-EWB model