The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beijing 2008 
Figure 7-a shows surface soil moisture (black), with the yearly 
mean reproduced for all years (orange), for a location near 
Sainshand, southeast Mongolia. The difference between the 
surface moisture and the mean is shown in figure 7-b. Rainfall-, 
snow and temperature information has been available from 
ground stations (7-c). Figure 8-d depicts the total precipitation 
in mm (black line) and the number of rainy days per year (pink 
line). It can be noted that after the data gab from 2001-2005 (7- 
a, 7-b) the surface moisture signal is much lower than during 
the measuring period before. The decrease is not sensor related. 
This behaviour could be observed from numerous locations in 
eastern Mongolia (which also all show a decrease in the number 
of rainy days and precipitation in mm), such as the stations in 
Bajndelger and Barum-Urt, while other areas in other countries 
show a completely different behaviour. 
vWWVWVWAW 
-UÄ М.л M як JJL JiL-JLi, álu «*&$...; Ш »J, м. 
ÂTJt 
°i 
ÌÌ. 
1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 
Figure 7: Surface soil moisture development for a station near 
Sainshand, Inner Mongolia, a) surface moisture (black) and 
long term mean (orange), b) difference between the two, c) 
ground station information d) precipitation and number of rainy 
days. 
4. CONCLUSION 
Usually, the derivation of trends, analyzed under the scope of 
climate change phenomena or related studies is performed on 
time series of 20+ years. One could thus argue that the TU 
Wien soil moisture time series is not yet long enough to derive 
meaningful trends. However, previous studies, anomaly 
analyses and the finding of this study indicate that the soil 
moisture time series processed by TU Wien has a large 
potential for long term trend analyses. It is the only time series 
of its kind existing since 1992. Results presented within 
grassland- and savannah-dominated areas clearly indicate 
regions, which have become drier or wetter over time. These 
findings could be verified through available in-situ data for a 
few selected sites. Currently the ERS-Scatterometer based time 
series is being extended and reprocessed with first data derived 
from the METOP Advanced Scatterometer (Ascat). Therefore, 
the extension and continuity of the time series based on two 
sensors is guaranteed. Even though spatial coverage is not 
always global, and temporal gaps do exist, the time series 
allows for the observation of short term trends, and the 
detection of the onset of probable long term trends. Furthermore, 
the time series clearly reflects all global deviating events such 
as strong droughts, floods, or El Niño events. We propose to 
investigate the TU Wien dataset further, focussing on medium- 
to long-term trend analyses and frequency analyses of 
anomalous events. 
ACKNOWLEDGEMENTS 
The authors thank Klaus Scipal (ECMWF) for many valuable 
ideas and comments. 
Figure 8 shows a similar plot for a location in Northeast 
Australia near Palmerville. According to this figure there is a 
slight increase in surface moisture especially since 1998 (8-b: 
curve is starting to slightly move upwards compared to the 
zero-line) However, this is only a shorter phenomenon, which 
can not be further observed after 2001 (no data). 
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