Session 2: LSA-SAF evapotranspiration: files, format and applications

Application of remote sensing data for drought monitoring Introduction to EUMETSAT Land SAF products Wednesday November 13, 2013 Session 2: LSA-SAF evapotranspiration: files, format and applications

1. The LSA SAF evapotranspiration products 2. Definitions of evapotranspiration variables 3. Applications

1. The LSA SAF evapotranspiration products Variables and quality information The file structure and format How to access the files Examples of time series retrieval 2. Definitions of evapotranspiration variables 3. Applications

Instantaneous ET LSA-SAF MET ET (mm/h) for 2010/10/29 at 12:00 UTC Associated quality flag (-)

Instantaneous ET LSA-SAF MET Surface type Quality input data Overall quality

Daily cumulated ET LSA-SAF DMET a) DMET (mm/day) b) Percent of missing values for every pixel 0 5 0 100 (mm/d) (%)

Units m 3.ha -1.day -1 l.s -1.ha -1 MJ.m -2.day -1 mm.day -1 10 0.116 2.45

How to access the files?

How to read the files? Free softwares, eg :HDFview (http://www.hdfgroup.org) Commercial softwares (matlab, idl, ) The files are compressed with bzip2 (http://www.bzip.org). When downloaded, you should uncompress with bunzip2

Visualize data with HDFview (http://www.hdfgroup.org) Evapotranspiration values (array) Quality flag (array) This software allows: - Visualize images - Visualize values - Histograms - Save images in other formats (.jpg, bmp, gif,.)

Visualize data with HDFview Vizualization with different color panels Attribute of dataset

Read files with matlab Datasets attributes

3 datasets for the hdf5 file Daily evapotranspiration Information on the data: attributes

Read the HDF5 file (dataset ET) with hdf5read Step 1: use «hdf5read», specifying the dataset to read Step 2: T is an array of integers. You should divide by the scaling factor.

Select a point based on its geographical coordinates

Step 1: choice of the point (Ex.: 15.05 N, 10 W) Step 3: divide by scale factor Step 2: read file lat-long Step 4: compute the distance between point and pixels Meteosat Distance = lat + long Chosen point corresponds distance minimum

ET in mm/hr Quality flag

Extraction of a time series

Clear sky day Clouds passing over According to the table in the product user manual (PUM) Nominal quality Below nominal quality Poor quality

Daily values

Filter the daily values on the basis of the number of observation used

1. The LSA SAF evapotranspiration products 2. Definitions of evapotranspiration variables 3. Applications

Natural Evapotranspiration (ET) = Actual evapotranspiration (AET) = Real evapotranspiration (ETR) Evaporation of natural surfaces + plant transpiration Potential Evapotranspiration (PET) Maximum evapotranspiration for a given climate and continuous vegetated surface (no hydric stress) Reference Evapotranspiration (ET0) Used for agricultural irrigation management (FAO standard). Evapotranspiration (can be potential) of a well-watered grass patch. Crop Evapotranspiration (ETc) Optimum evapotranspiration of a given crop (productivity not affected by hydric stress).

For crops Daily Evapotranspiration PET (ETc) ET0 AET A year For a given crop: ETc = Kc x ET0

Kc locally calibrated or tabulated (FAO) Kc Kc, mid Kc, end Kc, ini Initial growing season Midseason Late season A year Usually, KC curves follows Leaf Area Index. ETc = Kc x ET0 PET - AET = Water deficit

1. The LSA SAF evapotranspiration products 2. Definitions of evapotranspiration variables 3. Applications Monthly composites over hydrological basins Application in agricultural yield monitoring: examples Application in drought monitoring: examples

Monthly composites over hydrological basins West Africa basin Nile basin Monitoring ET over large basins on monthly/seasonal basis South Atlantic coast basin Congo basin (m/month) J F M A M J J A S O N D Monthly average (mm/d) ET over the Nile river basin for 2010

Monthly composites over hydrological basins Oder river basin Vistula river basin

Monthly composites over hydrological basins A M F M J Monthly ET over Vistula river basin year 2011 J A S O J D N [mm]

Agricultural yield monitoring Crop monitoring: dry matter productivity (DMP) From GLOBAM project (Sepulcre-Canto et al., 2012) DMP Soil moisture regulator Solar radiation Without W With W

Meteorological drought monitoring Meteorological drought occurs when there is a prolonged period of below average precipitation, which creates a natural shortage of available water.

Meteorological drought monitoring Drought index (%) = AET PET AET DMET product (LSA-SAF daily ET) PET LSA-SAF ET algorithm, but removing hydric stress Drought index is computed daily on each grid cell, and can be averaged over the entire region of interest.

Meteorological drought monitoring Rhin river basin Danube river basin

Meteorological drought monitoring Comparison between Et/Eto obtained in France in spring 2011 and 2012 11-20/05/2011 21-31/05/2011 1-10/06/2011 11-20/05/2012 21-31/05/2012 1-10/06/2012 >1 0.8-1 0.6-0.8 0.4-0.6 0.2-0.4 0-0.2 (From Sepulcre-Canto et al., Potential of LSA-SAF for drought monitoring Eumetsat conference 2012)

Agricultural drought monitoring Agricultural drought This type of drought occurs when there isn t enough moisture to support average crop production on farms or average grass production on range land. Although agricultural drought often occurs during dry, hot periods of low precipitation, it can also occur during periods of average precipitation when soil conditions or agricultural techniques require extra water.

Agricultural drought monitoring AET - PET = Water deficit LSA-SAF DMET PET computed by a model or ETc = Kc x ET0 FAO-56 equation e.g. download on european commission Agri4cast Makking equation ET0 = cmak x e.g. estimated with LSA-SAF products (available in LSA-SAF in a near future) D D+g x Rs

Agricultural drought monitoring LSA-SAF FVC Fundulea, Romania PET Zhiten, Bulgaria LSA-SAF DMET

Agricultural drought monitoring Fundulea, Romania Zhiten, Bulgaria Winter wheat flowering Maize silking

Extraction of water by irrigation monitoring

Extraction of water by irrigation monitoring 2011-06-24, DMET Irrigated areas: water used from reservoirs. Extraction from reservoirs= ET regional ET irrigated. It can be compared to optimum practice to survey the excess of irrigation.

Contact: nicolas.ghilain@meteo.be