The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
1366 
sequence indicates that also this behavior is to be expected. 
Very differently appear the months September to November. 
Already in September it can be seen that most of the UK is 
much wetter than usual. Soils are by far not saturated (still some 
yellow areas below 50% soil moisture), however, according to 
expectations this month should be drier. In October soil 
moisture values are high. The anomaly sequence again indicates 
“wetter than normal” conditions for the whole country. The 
same applies for November - the month when soils were so 
saturated that all buffer capacity had diminished and increased 
surface runoff lead to severe floods. Comparing the two time 
intervals (Jan-Mar and Sept-Nov) it can clearly be seen that the 
anomaly time series could support the prediction of future soil 
moisture saturation situation and flood danger. 
4 
A 
4 
4 
4 
4 
4 
4 
4 
-JB 
4 
4 
à 
« 
§k 
4 
Ti 
4 
4 
Á 
m 
m 
Js 
Figure 4: Upper sequence: Soil moisture between 0-100% 
saturation (dark brown to dark blue), lower sequence: soil 
moisture anomalies with respect to the long term mean of the 
specific month (grey: no deviation, yellow: drier than expected, 
blue: wetter than expected) 
3.2 Time series long term trend analyses 
Witt amamal«« <Xi 1996 Mi. 
During time series processing the whole global soil moisture 
data set underwent the procedure described under subchapter 
2.2.. Thus, the percentage of wet anomalies and the percentage 
of dry anomalies had to be calculated for each month and all 
years. Figure 5 depicts the percentage of wet anomalies, which 
occurred during the month of July for the two years 1996 and 
1998. Pink areas indicate regions with no obvious deviations, 
while blue-green to yellowish-red tones indicate a large number 
of outstandingly wet measurements. In July 1996 most areas 
(except some parts of Mongolia and the western Sahel) show 
now obvious changes. In July of 1998 (a strong El Niño year) 
the whole Sahel zone, as well as larger parts of Australia, 
Central Asia, and the Great Plains show anomalous behaviour. 
Figure 6 shows the global trend for areas to become wetter 
(upper) or drier (lower). Based on figure 6 we can observe that 
there are some regions with very outstanding trends concerning 
soil moisture deviation from the mean and an increase in wet 
and dry anomalies. 
It is obvious that the northern part of Australia has become 
slightly wetter over time, as have parts of south-eastern Africa. 
Furthermore, Mongolia shows some very impressive trends, 
indicating that especially the eastern part of the country has 
become significantly drier over time. To investigate if these 
observations coincide with meteorological ground station 
measurements we analyzed precipitation-, temperature- and 
“number of rainy days” information from Australian and 
Mongolian stations. 
While the upper and lower figure 6 are mostly complementary 
(in areas , where the percentage of wet anomalies increase, the 
number of dry anomalies usually decreases), there are also 
some regions, where these complementarities cannot be 
observed. In these regions an increase of extreme events is 
likely. 
Figure 5: Percentage of wet anomalies for the month July in the 
years 1996 and 1998. 
Change in wet anomaly occurence (percent per year) 
■■■■■■■■■■■■■■■■■■■■ ll'i U ir 11 1 
2X> -1.0 0 1.0 2.0 
* m o «0 
Change In dry anomaly occurence (percent per year) 
20 t.0 O 1 a 20 
Figure 6: Global trend for areas to become wetter (upper) or 
drier (lower), respectively areas with an increase in wet or dry 
anomalies.