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value of ©,. The temporal coverage of 
the ERS  Scatterometer is variable 
because it cannot work at the same 
time as the Synthetic Aperture Radar 
(SAR) ; which is also part of the 
payload of ERS -1 and ERS-2. The 
maximum number of ©, measurements is 
about ten, but in some months no 
measurements were acquired at all. For 
the production of soil moisture maps 
it was required that at least two O0, 
measurements are available. 
3.1. Mediterranean Climate 
The major part of the Iberian 
Peninsula is under the influence of 
the Mediterranean climate. The 
northern-west coast is relatively 
humid due to the prevailing westerlies 
from the Atlantic ocean. The 
Mediterranean climate is unique among 
the climate types because its annual 
precipitation cycle has a wet winter 
and a dry summer (Strahler and 
Strahler, 1996). This | precipitation 
Cycle is in general well reflected in 
Figure 2. Some problem areas exist in 
the South-east of Spain where 
repeating patterns of high soil 
moisture values occur during the 
summer / months: (July, August). ‘As a 
comparison with rainfall observations 
has shown these high values do not 
reflect local rainfall ‘events. The 
reasons for this phenomenon are 
unknown. Luckily, these patterns are 
very localised in space and time. 
Also year to year differences are well 
reflected in Figure 2. In the period 
1991 to 1995 a drought persisted over 
large regions of the Iberian 
Peninsula. Especially 1995 was a 
critical year. For example, due to 
water shortages the total area of 
irrigated maize fields in Andalucia 
was 7861 ha in 1995 which is only 
about 28 $ of the irrigated area in 
1996 (Source: Boletin Mensual de 
Estadistica, Ministerio de 
Agricultura, Pesa y Alimentacion). 
Wheat yield in 1995 in the Andalucia 
(southern Spain) and Extremadura 
(south-western Spain) was less than 40 
*$ of the long term average. This very 
low yields were caused by little 
rainfall in winter 1994/95 in this 
Intemational Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998 
region as correctly depicted in the 
soil moisture maps from October 1994 
to May 1995. The drought ended in the 
period from November 1995 to January 
1996 when persistent rainfall 
replenished the soil profile. Also 
this can be observed in Figure 2. 
3.2. Wet-Dry Tropical Climate 
Soil moisture maps of south-western 
Mali (2°W-12°W, 10°N-17°N) are shown in 
Figure 3. This region" is part^of'^ the 
Sahel and is under the influence of a 
wet-dry tropical climate. A very dry 
season at low sun alternates with a 
very wet season at high‘ sun. ‘This 
precipitation pattern is caused by the 
movement of the Intertropical 
Convergence Zone (ITZ). In spring ‘the 
ITZ moves northward as depicted in 
Figure 3. The highest rainfall amounts 
are normally observed in August 
(Strahler and Strahler, 1996) and the 
Soil moisture maps suggest that in 
early September the soil wetness is at 
its maximum. Some rainfall might still 
occur .in "October ‘but. the soil is 
already drying. In December the soil 
surface has completely dried out and 
remains. dry: until the next rainy 
season. In the upper-right part of the 
Mali maps a wet spot remains visible 
till well into December. This is the 
Central Delta of the Niger. Figure 3 
suggests that rainfall was most 
abundant in 1994 followed by 1995. 
1993 and 1992. It is interesting to 
note that total cereal production 
(sorghum, millet, maize, rice, etc.) 
followed the same trend: 2276000 tons 
in 1994, 2219000 tons in 1995, 2086000 
tons in 1993, and 1717000 tons in 1992 
(source: FAO). 
3.3. Moist Continental Climate 
As a last example soil moisture maps 
of Hungary are presented in Figure 4. 
Only the maps for the months March to 
November are shown because based 
solely on ERS Scatterometer data it is 
not possible to decide whether the 
ground was snow covered or not or 
whether the ground was frozen or not. 
Also in November and March there might 
be snow on the ground and the ground 
575