18
E. Raschke
25oDlownward longwave radiation [Wm· 2 ]
225
:
_ _
• :~ 4 • . : : : : : ,
o 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
UTe [h]
Upward longwave radiation [Wm- 2 ]
::~C:'::Y: 200
•
175
150
•
o 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
UTe [h]
Reflected shortwave radiation [Wm-2]
UO~ ~~~~r-~'-~~i~~'-r·-.~--r-~'-~·-r~~i~~~~'--r-.~ o 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
UTe [h]
80D~ownward shortwave radiation JWm- 2 ]
~g
~
o
i
I ~
o
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
UTe [h]
Figure 1.10: Comparison of surface radiation fluxes which have been retrieved from the conventional analyses and from passive satellite data with measured values over the Arctic ice (from
Kornblueh, 1995, private communication), where cloud bases have additionally been measured
with lidar.
analyses of the precipitation over oceans are not worse than the estimates made from the very
recent satellite measurements (e.g.: Huffmann et aI., 1995), since the latter are based on many
assumptions and require steady validation.
1.6.1 Ground-based gauge measurements
The various operational and often also community-owned or commercial networks over continental areas are in many cases not very reliable due to systematic errors of the different rain
gauge types and their exposition, which have been investigated and some corrections (amounting in some cases up to recommended 20% increase of the measured values!) are suggested
(e.g.: Sevruk, 1982). Legates' (1995) and Hulme's (1995) summaries of such analyses are quite
discouraging in this respect, since the present ground-based networks might be the only means
to "calibrate" other precipitation data derived from radar and satellite measurements. Despite
of such uncertainties, they are at present the only means to search for expected trends or variations in the amount and patterns of precipitation. Some recent trend analyses by Hulme (1995)
E. Raschke
25oDlownward longwave radiation [Wm· 2 ]
225
:
_ _
• :~ 4 • . : : : : : ,
o 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
UTe [h]
Upward longwave radiation [Wm- 2 ]
::~C:'::Y: 200
•
175
150
•
o 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
UTe [h]
Reflected shortwave radiation [Wm-2]
UO~ ~~~~r-~'-~~i~~'-r·-.~--r-~'-~·-r~~i~~~~'--r-.~ o 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
UTe [h]
80D~ownward shortwave radiation JWm- 2 ]
~g
~
o
i
I ~
o
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
UTe [h]
Figure 1.10: Comparison of surface radiation fluxes which have been retrieved from the conventional analyses and from passive satellite data with measured values over the Arctic ice (from
Kornblueh, 1995, private communication), where cloud bases have additionally been measured
with lidar.
analyses of the precipitation over oceans are not worse than the estimates made from the very
recent satellite measurements (e.g.: Huffmann et aI., 1995), since the latter are based on many
assumptions and require steady validation.
1.6.1 Ground-based gauge measurements
The various operational and often also community-owned or commercial networks over continental areas are in many cases not very reliable due to systematic errors of the different rain
gauge types and their exposition, which have been investigated and some corrections (amounting in some cases up to recommended 20% increase of the measured values!) are suggested
(e.g.: Sevruk, 1982). Legates' (1995) and Hulme's (1995) summaries of such analyses are quite
discouraging in this respect, since the present ground-based networks might be the only means
to "calibrate" other precipitation data derived from radar and satellite measurements. Despite
of such uncertainties, they are at present the only means to search for expected trends or variations in the amount and patterns of precipitation. Some recent trend analyses by Hulme (1995)