Validation data

Validation of model results both for the downward fluxes reaching the surface of the Earth and the outgoing fluxes at TOA is only possible through comparison with ground-based measurements at specific sites for the downward fluxes, and with satellite measurements for the outward fluxes. Table 8.3 summarizes a sample of validation data sets that are available.

Table 8.3 Validation data sets. Fluxes at the top of the atmosphere (TOA) are outgoing to space. Fluxes are both longwave and shortwave.

Dataset

Description

Years

Time resolution

Spatial resolution

Coverage

BSRN

Surface fluxes

92-

01

minute-daily

Point location

Global

Synoptic data

GEBA

Surface fluxes

84-

-97

mean monthly

Point location

Global

ERBE

TOA Fluxes

85-

89

mean monthly

2.5° x2.5°

Global

ERBS-NS

TOA Fluxes

85-

-99

mean monthly

5° x5°

60°S-60°N

Table 8.4 Global Energy Balance Archive surface fluxes. Volume corresponds to the amount of data stored as at 2002.

Code

Name

Instrument

Volume

2

Direct solar radiation

pyrrheliometer

2700

3

Diffuse solar radiation

pyranometer with shading device

10000

1

Global solar radiation

pyranometer up-facing

180000

5

Reflected solar

pyranometer down-facing

3300

16

Absorbed solar radiation

difference of 1 and 5

5000

4

Albedo

quotient of 5 and 1; albedometer

3800

19

Circumglobal radiation

spherical pyranometer

500

6

Incoming longwave radiation

pyrgeometer up-facing

1900

7

Outgoing longwave radiation

pyrradiometer down-facing

1000

8

Longwave net radiation

difference of 6 and 7

800

9

Radiation balance

net radiometer

21000

17

Total outgoing radiation

sum of 5 and 7

30

14

UV radiation

broadband UV instrument

300

10

Sensible heat flux

aerodynamic method

300

11

Latent heat flux

aerodynamic method or lysimeter

800

18

Sensible and latent heat flux

sum of 10 and 11

20

difference of 9 and 12

12

Subsurface heat flux

thermistors or heat plates

300

13

Latent heat of melt

measurement of water-equivalent

60

of snow before melt or of

ablation of glacier ice

8.3.1 Global energy balance archive

The Global Energy Balance Archive (GEBA) contains quality checked monthly means of surface energy fluxes. Data have been extracted from periodicals, monographs, data reports, and unpublished manuscripts. GEBA sites are distributed all over the world. Table 8.4 lists the surface energy flux data that are stored in the GEBA database.

Table 8.5 Basic radiation measurements of BSRN stations.

Quantity

Accuracy

Direct SW Diffuse radiation

Downwelling LW radiation 5% (10 W m-2) Upwelling LW radiation 5% (10 W m~2)

8.3.2 Baseline radiation network

BSRN has records of solar and atmospheric longwave radiation, along with surface and upper-atmospheric observations. BSRN stations are located in a variety of climates. The stations have to follow specific observational and calibration procedures, resulting in standardized data of very high accuracy. The data provided also have very high temporal resolution (minutes). The basic measurements that exist for all BSRN certified stations include: global (solar) radiation, direct solar radiation, diffuse sky irradiance and downward longwave radiation (see Table 8.5).

Some stations also have measurements that include: direct solar spectral radiation at the WMO specified A and SA, synoptic measurements (wind, temperature, dew point, cloud amount and type determined by experienced observers), radiosonde data (vertical distribution of temperature and water vapour), cloud base height, water-vapor vertical distribution and total ozone amount. They also give height for low plus middle clouds (when there is collocation with synoptic stations). There are currently 36 operational BSRN stations around the world, 9 of which are located in Europe. Radiosonde data exist for 16 of the stations, eight of which have data since 1992. Table 8.6 lists the names and locations of the 36 BSRN stations. Sample long-term data from the Sahara station of Tamanrasset are given in Table 8.7.

8.3.3 ERBE data

The Earth Radiation Budget Experiment (ERBE) data provide sufficient spatial, temporal and diurnal sampling to measure the radiation budget of the Earth. The Goddard Space Flight Center built the Earth Radiation Budget Satellite (ERBS) on which the first ERBE instruments were launched by the Space Shuttle Challenger in 1984. ERBE instruments were also launched on two National Oceanic and Atmospheric Administration weather monitoring satellites, NOAA 9 and NOAA 10 in 1984 and 1986. There are two types of instruments: (a) Scanner - comprising a set of three coplanar detectors (longwave, shortwave and total energy), all of which scan from one limb of the Earth to the other, across the satellite track (in its normal operational mode); (b) Non-scanner - comprising a

Table 8.6 BSRN operational stations

Station name

Sponsor

Latitude

Longitude

1

Ny Elesund, Spitsbergen (N)

Germany/Norway

78

° 56'

N

11°

57' E

2

Barrow, Alaska

USA

71

° 19'

N

156

° 36' W

3

Lerwick, Shetland Islands

Great Britain

60

08'

N

11' W

4

Toravere

Estonia

58

16'

N

26°

28' E

5

Lindenberg

Germany

52

13'

N

14°

07' E

6

Regina

Canada

50

12'

N

104

° 43' W

7

Camborne

Great Britain

50

13'

N

19'W

8

Palaiseau Cedex

France

48

43'

N

12' E

9

Rock Springs SURFRAD

USA

40

43'

N

77°

56' W

10

S. Great Plains ARM Ext. Facil. 13

USA

36

36'

N

97°

30' W

11

Fort Peck, SURFRAD, CO, Montana

USA

48

19'

N

105

° 06' W

12

Payerne

Switzerland

46

49'

N

57' E

13

Carpentras

France

44

03'

N

02' E

14

Albany New York

USA

42

42'

N

73°

50' W

15

Boulder SURFRAD, Co.

USA

40

08'

N

105

° 14' W

16

Bondville, Illinois

USA

40

04'

N

88 °

22' W

17

Boulder, Colorado

USA

40

03'

N

105

°00' W

18

Chesapeake Lt. Station

Virginia, USA

36

54'

N

75°

43' W

19

Desert Rock SURFRAD, PA

USA

36

39'

N

116

° 1' W

20

Billings, ARM/CART, OK

USA

36

36'

N

97°

31' W

21

Tateno

Japan

36

03'

N

140

° 08' E

22

Goodwin Creek, Mississippi

USA

34

15'

N

89°

52' W

23

Bermuda

USA

32

18'

N

64°

46' W

24

Sede Boqer

Israel

30

52'

N

34°

46' E

25

Solar Village, Riyadh

Saudi Arabia

24

55'

N

46°

25' E

26

Tamanrasset

Algeria

22

47'

N

31' E

27

Kwajalein, Marshall Islands

USA

43' N

167

° 44' E

28

Ilorin

Nigeria/USA

32' N

34' E

29

Momote, Manus Is. ARM PNG

USA

03' S

147

° 26' E

30

Alice Springs

Australia

23

' 48' S

133

° 53' E

31

Florianopolis

Brazil

27

32' S

48°

31' W

32

De Aar

South Africa

30

' 40' S

24°

00' E

33

Lauder

New Zealand

45

00' S

169

° 41' E

34

Syowa, Antarctica

Japan

69

00' S

39°

35' E

35

Georg von Neumayer, Ant.

Germany

70

39' S

15' W

36

South Pole, Antarctica

USA

90

• S

-

Table 8.7 Sample long-term (1991-1995) BSRN station solar radiation data from the Sahara station of Tamanrasset, Algeria (Source: World Radiation Data Center)

Tamanrasset

22°

47'

N,

5° 31' E

Source: WRDC

1377m(a.s.l.)

J

F

M

A

M J

J

A

SON

D

Annual

Global 177

214

237

259

256 253

272

247

225 209 184

156

224

Diffuse 30

40

60

85

101 97

83

83

80 53 37

36

65

set of five detectors, one measuring the total energy from the Sun, two measuring the shortwave and total energy from the entire Earth disk and two measuring the shortwave and total energy from a medium resolution area beneath the satellite.

The ERBE products include instantaneous time-sequenced instrument measurements, as well as monthly averaged regional, zonal, and global estimates of radiation budget parameters (S-2 Solar Incidence; S-4 Regional, Zonal, and Global Averages; S-4G Regional, Zonal, and Global Gridded Averages; S-7 Medium-Wide Field of View Non-scanner Data; S-8 Instantaneous Scanner and Nonscanner Data; S-9 Scanner Earth Radiant Flux and Albedo; S-10 Non-scanner Earth Radiant Flux and Albedo). From these products, one can use the scanner S4 satellite data (1984-1989) to validate model radiative fluxes at TOA, and the S-10N (WFOV NF edition 2) non-scanner data (1984-1999) to compare against TOA flux anomaly time series derived from LW and SW models. We note that there are new satellite data becoming available for the TOA fluxes from the Me-teosat Second Generation (MSG) GERB and SEVIRI instruments, CERES and the Terra and Aqua platforms (see also Chapter 10).

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