H/(Q*-G) cannot be grater than 1 and has to show values 
between 0 and 1. 
Fig. 3 shows the 
image of the ratio H/(Q*.G) 
  
  
Ratio H/COx-G 
Nulla 20.7.9886 
  
J 
  
  
    
] Sohnee/bebaut 
|| Hasser 
  
  
  
| Xnklination < 2 
B o « TL 0. H.wert 
  
  
Fig. 3. Ratio H/(Q*-G) 
it can be seen, that the ratio value does in no case 
exceed the value 1,2, and that only for very few pixels the 
value is greater than 1,0. The high values are limited to 
the driest and most sunexposed sites (Storl, 1992, 1993, 
1994). 
As the pixels with values greater than 1.0 are without 
exception rocky places bare of vegetation, it can be 
assumed that the ground heat flux has been 
overestimated in these places. This might be true, as 
ground heat flux was calculated using the NDVI which 
shows unproportionally low values for these sites. 
It can be shown in detail, how the ratio lowers at all sites 
that were mapped as moist places in the field campaign 
(Storl, 1992, 1993, 1994). This has to be so, as soil 
moisture increases the radiation balance by triggering 
evopatranspiration. The pattern of the soil moisture index 
is well defined in the ratio image. 
9.4 Ratio (H+LE)/(Q*-G) 
The ratio (H+LE)/(Q*-G) theoretically should equal 1,0 in 
all places, if all energy budget terms were modeled with 
accuracy. 
666 
Fig. 4, showing the ratio image (H*LE)/(Q*-G), can be 
interpreted in the following way: 
The calculated value for Eq must be too high in all cases, 
where water supply is no longer granted, as the 
theoretical condition for Eq to be true is unlimited water 
supply. This condition, at the time of satellite overpass, is 
surely no longer given on the rocky, sparesly vegetated 
and sunexposed NE-slopes of mount Njulla. This would 
explain the values ranging up to 1,7 at these places. In 
this context, an interesting observation can be made: 
Looking at the sites that were mapped as moist patches, 
especially below leaking snow fields, it can be stated, 
that the values are very close to 1,0. It can be concluded, 
that the evapotransiration model holds for these sites, a 
water supply is not limited, and that the model for 
sensible heat flux produces good values, as the energy 
budget equation holds. This observation can be made at 
many representative sites mapped in the field campaign 
All surface types, for which Rouse and Stewart 
(Rouse/Stewart, 1972) declared equilibrium evaporation 
to be valid, show values very close to 1,0, as far as they 
are not obviously subject to water stress. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B7. Vienna 1996 
  
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