15.07.2015   EuroSun2008-13

Experimental data. Ground measurements

In this study, we used one year (2005) of global irradiance measurements from 14 stations located in the Sierra Nevada Natural Park, in Hueneja (Granada, Spain). The stations are equipped with LICOR 200-SZ pyranometers, with a sample frequency of 2.5 minutes. In addition, we utilized a DTM with 100 m resolution containing the area where the stations are located, and provided by the local government Junta de Andalucia. Table 1 shows the characteristics of the stations and Figure 1 shows their location inside the studied area.

1.1. Meteosat Images

The satellite images used in this work cover a period of time convergent with the information from the pyrometers. These are images of high resolution and correspond to the visible channel of the satellite METEOSAT-7 (HRI-VIS) and they have been registered by the PDUS (Primary Data User Station) station located in the Department of Renewable Energies of the CIEMAT (DER-CIEMAT).

Station ID

Lat [°]

Long [°]

Altitude

[m]

Slope

[°]

Azimuth

[°]

1

37°08’52"

2°58’34"

1659

10

150

2

37°08’50"

2°58’29"

1669

14

192

3

37°08’47"

2°58’17"

1619

13

177

4

37°08’05"

2°58’25"

1558

9

116

5

37°08’58"

2°58’13"

1565

5

83

6

37°08’58"

2°58’02"

1532

11

152

7

37°08’59"

2°58’56"

1505

3

82

8

37°08’48”

2°58’45"

1467

19

180

9

37°08’47”

2°58’54"

1449

19

85

10

37°08’22"

2°58’36"

1305

5

40

11

37°08’25”

2°58’25"

1292

15

68

12

37°08’29”

2°58’32"

1300

8

106

13

37°08’31 "

2°58’16"

1188

0

—

14

37°08’34”

2°58’20"

1091

6

153

 

image128

Fig. 1 . Position of the stations in the studied area.

 

The METEOSAT is located in a geostationary orbit of longitude 0°. The principal element of detection of the satellite is the sensor MVIRI (Meteosat Visible and Infrared Imager), a radiometer of high

 

definition that constitutes the principal subsystem of the METEOSAT. In case of the images corresponding to the visible channel the field of instantaneous vision, according to the angular amplitude of the sensor and of the orbital distance of the satellite, is 2.5 km in the nadir or point of the subsatellite (latitude=0°, longitude= 0 °). Due to the terrestrial curvature this magnitude increases according to the distance to the point of the subsatellite (for the studied zone approximately 3.5 km).

Подпись: Longitude C) Fig. 2. A.Meteosat image (© 2005 EUMETSAT). B. Iberian Peninsula. C. Subimage used in this study and location of the radiometric stations.

Every pixel of the image has a value of brilliance, registered by the satellite, on the grey scale of 0-255 (8 bits). The 14 stations are located in four different pixels of the image, as shown in Figure 2.