147

Trends in Orographic Rainfall over the Fertile CrescentAkiyo YATAGAI
Faculty of Life and Environmental Science, University of Tsukuba
1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japanemail: akiyo@ies.life.tsukuba.ac.jp

Abstract
The author presents a precipitation climatology and its trend over the mountainous areas of the Middle
East using the dense network rain-gauge observation data gathered by the APHRODITE project. Coastal andorographically induced precipitation zones are found in semi-arid regions, and those patterns are consistent
with those observed by the Precipitation Radar of the Tropical Rainfall Measuring Mission.
The author then uses 34-year monthly precipitation data over Turkey, Israel and Iran to show seasonal
precipitation trends. There is a strong and significant decreasing trend over Turkey and Israel in winter,
especially in January. Trends over Turkey differ from month to month, while general trends over Iran differ
little from season to season. On the other hand, Iran has orographically characterized trends. Trends areaffected by the mountain ridges and slopes of the Taurus, Anatolian, Zagros, Erboz and other ranges.
Then she compares the trends at thirteen high stations paired with low stations under the same synoptic
conditions for the winter season. Most station pairs showed decreasing trends in the ratio of precipitation at
the high stations to that at the low stations. Exceptional cases, which showed increasing trends in the ratio,
were observed in the easternmost part of the Taurus Mountains (north of Syria) and in the northwestern part ofTurkey.
Key words: Middle East, mountain climate, orographic precipitation, paleo-climate, precipitation trend

1. Introduction
Quantitative measurement of precipitation is important in water management as well as climate study. Hence,tremendous efforts have been made to develop grid precipitation data for the last two or three decades. Satellite
observations can be used to estimate precipitation. However, accurate measurements of precipitation over land
from satellite observations are particularly difficult.
Hence, the collection and analysis of precipitation datausing rain gauges have been urged (Xie et al., 2007;
Yatagai et al., 2009). Moreover, rain-gauge data have an
advantage of long-term data archives created for use indiscussing climatic trends.
However, in the process of making a rain-gauge based
product, characteristic features of rainfall distribution
such as small-scale orographic patterns are sometimes
smoothed out. As is described below, long-term trends inprecipitation in mountainous regions are very important
to ascertain, especially in arid/semi-arid regions.
Mountain water resources are important in arid/semiarid regions, and quantitative estimations of orographic
precipitation are critically important to climate change
studies, including model simulation studies, in relation to
the global warming issue. Recently, the amounts ofprecipitation and water resources and their trends overGlobal Environmental Research
15/2011:147-156
printed in Japanthe East Mediterranean and part of the Middle East havebecome a concern since most climate models simulate adecreasing trend in future precipitation under global
warming scenarios (IPCC, 2007; Milly et al., 2005;
Nohara et al., 2006; Kitoh et al., 2008) and evidence has
been reported showing a trend of decreasing precipitation
over the Middle East (Alpert et al., 2002, 2006; Bolle
2003, Zhang et al., 2005; Yatagai, 2005).
However, no detailed trend has yet been clarified over
the Middle East, especially for the mountainous regions,because of a lack of assembled data (Adam et al., 2006).
National data for the Middle East are neither wellassembled nor available to the international researchcommunity (Zhang et al., 2005); hence, the global dataset
and global analysis have yet to clarify the distribution
pattern of precipitation in the region and its seasonalchanges and trends.
A recent rain-gauge collection (Yatagai et al., 2008)
indicated a crescent-shaped rainfall area over the Middle
East, which corresponded to the ancient Fertile Crescent.
Roughly speaking, the crescent-type distribution of
precipitation is due to mountains (Zagros, Anatolian
Plateau) and coastal hills along Israel and Syria. This
orographic rainfall is a water source for rivers such as the
Tigris, Euphrates and Jordan River, so orographic rainfallof the Fertile Crescent was critical in ancient times as©2011 AIRIES148

Akiyo YATAGAI

well as at present and in the future. Issar and Zohar(2004) described paleo-climate studies over the Middle
East. In spite of much archaeological evidence, there arefew descriptions of climate zones and those that exist are
based on limited data. To investigate historical trends inthe orographic rainfall over such a region seems to be aworthy endeavour for interpreting various kinds of proxy
data in the future. Hence, I show the seasonal patterns ofprecipitation distribution and their trends over the
crescent-shaped orographically-induced rainfall areawith long-term ground-observation precipitation datacollected in Turkey, Israel and Iran.
The object of this study is to display seasonal precipitation over the Middle East and to study the trends in
orographically induced precipitation regions. Since
winter is a main precipitation season in this area, I
concentrate on winter precipitation in this paper.

2. Data and Precipitation Climatologythat confirms a similar maximum on the precipitation
map based on rain gauges (upper panel).
Figure 2 (upper) shows the winter (DecemberFebruary) pattern of precipitation. It resembles theannual one (Fig.1), and the crescent shape of the precipitation distribution is clear in winter. To illustrate thegeneral air flow and hydrological conditions, the water
vapour flux pattern for winter is also shown in Fig. 2(lower). In the Middle East domain, generally speaking,moisture comes from the west, and the Mediterranean
Sea and Arabian Sea show divergence. In winter, relatively strong moisture convergence is observed around
Iraq and the eastern Black Sea. The orographic rainfall
discussed above is due to western or southwestern moisture converging in and around the mountainous terrain.
Since a moisture flow pattern based on precipitation does
not always correspond to the mean moisture flow pattern,
especially over arid/semi-arid regions (Yatagai &Yasunari, 1998), further investigation using daily precipitation/and circulation fields is expected in the future.

2.1 Data
The precipitation dataset used in this study is similar
to that used by Yatagai et al. (2008). Although wecollected daily precipitation data throughout the
APHRODITE project <http://www.chikyu.ac.jp/precip/>,
here I only use monthly precipitation data. Since trend
analysis is the main purpose of this study, I used only
quality-controlled long-term data series.
As complementary data, I also use rainfall patterns
determined from Tropical Rainfall Measuring Mission(TRMM) satellite observations and water vapour transport computed using the European Centre for Mediumrange Weather Forecasts (ECMWF) 15-year reanalysis(Gibson et al., 1997) from a previous study (Yatagai,2003).
2.2 Climatology
Figure 1 shows a gauge-based annual precipitation
climatology over the Middle East (Yatagai et al., 2008).
A clear crescent-shaped pattern is observed throughIsrael, part of Syria, southeastern Turkey, northernmost
Iraq and western Iran. As shown in the orography map(Figure 1, bottom), the orographic precipitation is due tomoisture transported mainly from the west. The moisturepattern of winter is presented in Fig. 2. There are strong
precipitation zones to the south of the Caspian Sea(northern Iran), around the Black Sea and in western
Turkey. These wet zones are mainly due to adjacentinland sea water.
The middle panel of Fig. 1 is a composite chart of the
10-year average of the annual mean precipitation rate as
determined by the precipitation radar (PR) on board theTRMM. Radar can depict the character of orographic
rainfall. (north of 36°N is not shown since the coverageof the TRMM/PR does not extend that far). There is clear
orographic precipitation along the Zagros Mountains(western Iran) and precipitation maxima occur along theeastern Mediterranean coast. The TRMM/PR patternshows a weak maximum at the centre of Saudi Arabia

Fig. 1 Top: Annual precipitation climatology (mm/year) derived
using a rain-gauge network (Yatagai et al., 2008).
Middle: Annual precipitation pattern derived from ten
years of observations (1998-2007) by the Precipitation
Radar on board the TRMM (3A25 monthly product).
Bottom: Orography (m).

Trends in Orographic Rainfall over the Fertile CrescentFig. 2 a) Winter (December-February) precipitation climatology(mm/3months) defined by Yatagai et al. (2008).
b) Vertically integrated winter-mean water vapour flux
(mm·m/s) and its divergence (kg/m2·s).
Unit vectors of the water vapour flux are shown on themaps. Red to light green indicates divergence and violet toblue to green indicates convergence.

149

Fig. 3 Linear trends of winter and monthly (December, January
and February) precipitation for the period of 1971–2004.
Blue dots indicate increasing trends while red dots indicate
decreasing trends. Black open circles indicate the time series
to be beyond the 5% significant level according to the t-test.

3. Precipitation Trends
Here I discuss mainly winter precipitation trend patterns. Figure 3 shows seasonal precipitation and wintermonth trends during 1971-2004 over Turkey, Israel and
Iran. Since the periods of data coverage differ with thedataset and stations, I only used stations at which morethan 30 years of data were available for the period of
1971-2004. For winter precipitation, I added December
precipitation of the previous year to the summation ofthat of January and February. I applied the t-test to detect
trends.
There are general decreasing trends in winterthroughout Turkey, Israel and most of Iran. Significant
decreasing trends can be seen in the northern part of Iran.
In the Middle East domain, generally speaking, moisturecomes from the west. Interestingly, trends for the three
winter months over Turkey and Israel vary, whereas there
is more uniformity over Iran. There are strong increasing
trends in the south of Turkey in December and in the west
in February. In Iran, there are decreasing trends in thewest and along the Caspian Sea throughout the winter.

Interestingly, the trends differ along the Zagros mountainchain. There is an increasing trend along the western
foothills, decreasing trend along the western slopes of theZagros, and increasing trend in central Iran (east of theZagros).
From a macroscopic view, one can see that the trend
patterns are not sporadic but they show the same signals
in some regions of 300 - 1,000 km horizontal scaleof orographically characterized region. For example,
batches of the same trend signals are found in the following regions: west of the Taurus Mountains (January),
Anatolia (January), along the Caspian Sea (winter), thewestern part of Turkey (winter), and upper reaches of the
Tigris and Euphrates (winter).
As mentioned before, it is important to investigate thetrends and dominant factors of interannual variation inprecipitation in elevated places, especially for places
where there is an influx of precipitation into an arid
region. Dominant factors of international variability havebeen investigated in the arid region of China and adjacent150

Akiyo YATAGAI

mountains, and interannual variation modes which are
related to both highlands and lowlands have been foundto show larger amplitude than that of a mode whichshows independent variabilities between highlands andthe lowlands (Yatagai, 2007). The trend results shown
here are consistent with those of previous studies.
Namely, in general, the trend signals are the same in highand low places where the same large-scale moisture flowor synoptic systems affect their precipitation amounts.
3.1 Regional analysis of trends in orographic
precipitation
It is important to clarify whether trends at relatively
high stations, which are considered to be more important
as water resources, are increasing or not. Hence, here I
will examine the trends in pairs of high and low places
which show similar international variation signals which

eliminate such large-scale variability.
I selected some regions where batches of the same
trend signals appeared with respect to the orography.
Figure 4 shows four regions (A-D) I will discuss in thenext few figures (Figs. 5-8).

Fig. 4 Map of major mountains and close-up areas to be shown insubsequent figures. Color represents altitude (m).

A1 January

A2 January

A3 January

A1 winterFig. 5 Map of Region A (Taurus Mountains) shown in Fig. 4. Colours showing elevation are the same as in Fig. 6. Contours
are drawn every 1,000 m. Numbers in the map are stations used in this study. A1, A2 and A3 are the station pairs along
the mountains. Red circles show higher stations and blue circles show lower stations.
The upper graphs of A1, A2 and A3 show January precipitation of each year, in which closed (open) circles show
precipitation data of higher (lower) stations and straight (dashed) lines show linear trends of higher (lower) stations.
“Ratio” means the precipitation ratio of high station vs. low station, and the straight line shows the trend of this ratio.

Trends in Orographic Rainfall over the Fertile Crescent3.1.1 Taurus Mountains (Region A)
It is expected that more stable results may be available if we treat seasonal trends rather than monthly trends.
However, monthly trend patterns in the winter season
differed very much from one to the next (Fig. 3). Hence, I
show the January trend pattern along the Taurus Mountains, where I found significant decreasing trends inJanuary. Figure 5 (upper map) shows stations in Region
A for which there are 30 years of data from the period
1975-2004.
I selected station pairs within each orographicallycharacterized region where stations showed similar trend
signals with the following criteria: 1) The distance
between the pair of stations was less than approximately
100 km (1 degree). 2) The lower elevation station was
located in the (dominant) windward direction from thehigher elevation station. (I used Fig. 1 and other climatological figures.) Here I refer to the two stations in a pairas the high station and the low station. 3) The correlation
coefficients between the high station and low station
were very high (around 0.9 or higher).
In Figure 5 I show only three pairs (A1, A2 and A3)
but actually I investigated more stations by taking thecorrelation coefficients at each pair of stations for
1975-2004. Table 1 shows a summary of the location
information (longitude, latitude and altitude) and correlation coefficients and trends in January. I calculated theratio (Ro) of precipitation at the high station to that of the
low station, and the linear trend of Ro. Graphs includedin Fig. 5 show trends of station pairs (A1, A2 and A3) for
January and the trend of A1 for the winter season
Table 1

151

(December, January and February (DJF)). Each uppergraph shows the precipitation amount and trend and eachlower graph shows Ro=(precipitation at high station)/(precipitation at low station) and its trend.
As we saw previously, all six stations shown in Fig. 5
showed a decreasing trend for January. However, Ro
showed a decreasing trend in A1 and A2 but an increasing trend in A3. That means decreasing trends at highstations relative to low stations were observed at A1 andA2.
Next I show the results for the winter season (DJF). A
summary is given in Table 2. Plots of precipitation and
Ro at the A1 pair in winter are given in the right-bottom
corner of Fig. 5.
Ro in winter at A1 showed a weak decreasing trend,
although the amplitude in Ro was smaller than in January.
Ro in winter at A2 showed a decreasing trend and that of
A3 showed an increasing trend as summarized in Table 2,
which was consistent with the results of January itself.
Comparing the correlation coefficients between Table 1(January) and Table 2 (winter), the correlation of thewinter season always showed a higher value than that ofJanuary. Hence, I will mainly argue for the winter season.
3.1.2 Western Turkey (Region B)
Figure 6 shows the pattern of Region B, shown in
Fig. 4, enlarged. To select the station pairs, I took into
account the distance between the two stations, winddirection (moisture transport) and elevation. I selected
station pairs that showed very high correlation coefficients (larger than 0.9) in winter. I did not write about

Station pairs and their locations. Correlation coefficients, trends at each station, trends of Ro (precipitation at highstation/precipitation at low station) for January. Red numbers in the Ro trend indicate a decreasing trend in Ro. C1 is not shownsince it is the same as A4.

Pair
A1 (high)
A1 (low)
A2 (high)
A2 (low)
A3 (high)
A3 (low)
B1(high)B1(low)B2(high)B2(low)B3(high)B3(low)B4(high)B4(low)
B5(high)B5(low)C2(high)C2(low)C3(high)C3(low)C4(high)C4(low)C5(high)C5(low)
D1(high)D1(low)

Station ID
17864
17240
17754
17800
17261
17978
17292
17924
17742
17180
17676
17116
17704
17700
17725
17704
17768
17804
17847
17874
17740
17776
17880
17285
99015940732

Longitude (deg.)
38.08
37.77
39.10
38.65
37.38
37.12
28.37
28.68
27.18
26.88
29.08
29.07
29.50
28.63
29.97
29.50
38.92
38.75
38.28
39.45
41.70
41.07
44.02
43.73
50.73
50.67

Latitude (deg.)
30.45
30.55
33.00
32.93
37.07
36.72
37.22
36.97
39.12
39.07
40.13
40.18
39.55
39.58
39.42
39.55
39.07
38.80
39.77
38.13
39.37
38.97
38.05
37.58
36.86
36.90

Altitude (m)
1160
997
1010
969
855
638
646
24
53
3
1878
100
834
639
969
834
953
808
1000
700
1715
1365
2400
1728
79
-20

R
0.905
0.924
0.945
0.901
0.935

Trend
-2.338-0.895-1.233-0.864-9.631-0.353-3.993-1.807-2.082-1.276

Trend of Ro-9.71E-03-0.716-1.923-1.852-0.716-0.421-0.326-0.842-1.385

1.32E-02-4.65E-03
6.11E-03-2.02E-03-9.85E-03

0.676
0.854
0.817
0.818
0.931

-2.96E-03-1.90E-03-2.97E-02

0.599
0.547
0.786

-0.9990.646-2.20E-02

152

Akiyo YATAGAI

the results for B3 of January, since the correlation
coefficient was low (Table 1).
Decreasing trends in Ro are found the for the coastal
station pairs, B1 and B2. At both station pairs, somerecent years show more precipitation at the low station,and the Ro of B2 fell below 1 after the late 1980s.
A clear increasing trend in Ro is found at B3, where
differences in altitude as well as differences in precipitation amounts are large between the high station and thelow station. I chose this pair, which are aligned in anorth-south direction, since the wind from the Sea ofMarmara and from the Black Sea come to this mountain.
However, I may consider the local wind direction in the
future.
The high station of B4 (17704) is the same as low
station of B5. Both correlation coefficients at B4 and B5
are very high (larger than .95). However, for pair B4,
precipitation at the high station is less than at the low
station. Therefore, we need to be careful about interpreting the increasing trend of Ro in B4. On the other hand, at
station pair B5, the high station (17725) shows more
precipitation than the low station (17704), and the Ro of
B5 shows the largest decreasing trend among the station
pairs shown in Table 2.
There are more complicated moisture flow patterns
among the Region B pairs, namely, it might not be simply
westerly at B5 but the southerly mountain makes acomplicated moisture flow and convergence system there.
I won’t argue about the cause of increasing Ro at B3 andB4, since I cannot clarify the moisture transport andorographic precipitation system there.
Table 2

3.1.3 Upper reaches of the Tigris and Euphrates(Region C)
Then we move on to the northern part of the Fertile
Crescent, the upper reaches of the Tigris and Euphrates(Region C). In the map of Fig. 7, the station pair C1 isactually the same as pair A3. I showed the results of A3
January in Fig. 7 but not for the winter pattern. As shownin Table 2, an increasing trend in Ro is also found in thisseason.
A clear decreasing trend in Ro is observed at C2 inwinter. It is remarkable that the C1 (=A3) pair shows adifferent Ro trend signal from the surrounding station
pairs. C3 shows a very small decreasing trend in Ro,
however Ro exceeds 1 for the years 1986-1993 but falls
below 1 during the other years. We must consider the
local circulation, especially for the southerly mountainridge.
At station pairs C4 and C5, the high station has lessprecipitation than the low station. It is unclear from thisanalysis why the high station has less precipitation, as thehigh station might be located above the maximum
precipitation zone or there may be higher altitudes thanthe high station itself, and the high station observes rainfall from the airflow over such higher places. In any case,
we may distinguish the meaning of the decreasing trendof Ro at C4 and C5 from that of C2.
I checked the station pairs to the east of C5, but I
could not find a good pair in the Iranian region included
in Region C.

Same as Table 1 but for winter (DJF). Results for all Regions A, B and C are shown.

Pair
A1 (high)
A1 (low)
A2 (high)
A2 (low)
A3 (high)
A3 (low)
B1(high)B1(low)B2(high)B2(low)B3(high)B3(low)B4(high)B4(low)
B5(high)B5(low)C2(high)C2(low)C3(high)C3(low)C4(high)C4(low)C5(high)C5(low)
D1(high)D1(low)

Station ID
17864
17240
17754
17800
17261
17978
17292
17924
17742
17180
17676
17116
17704
17700
17725
17704
17768
17804
17847
17874
17740
17776
17880
17285
99015940732

Long. (deg.)
38.08
37.77
39.10
38.65
37.38
37.12
28.37
28.68
27.18
26.88
29.08
29.07
29.50
28.63
29.97
29.50
38.92
38.75
38.28
39.45
41.70
41.07
44.02
43.73
50.73
50.67

Lat. (deg.)
30.45
30.55
33.00
32.93
37.07
36.72
37.22
36.97
39.12
39.07
40.13
40.18
39.55
39.58
39.42
39.55
39.07
38.80
39.77
38.13
39.37
38.97
38.05
37.58
36.86
36.90

Alt. (m)
1160
997
1010
969
855
638
646
24
53
3
1878
100
834
639
969
834
953
808
1000
700
1715
1365
2400
1728
79
-20

R
0.972
0.967
0.980
0.972
0.945
0.935
0.959
0.962
0.977
0.949
0.965
0.923
0.882

Trend
-0.878-0.289-0.947-0.3540.736-0.327-1.013-0.402-1.656-5.19E-04-1.126-1.100-0.298-0.963-1.238-0.298-0.529-3.68E-02-1.920-1.650-0.276
0.233
0.316
3.173
-2.654-0.571

Trend of Ro-2.20E-03-5.98E-03
4.26E-03-1.20E-03-5.23E-03
4.49E-03
1.79E-03-9.21E-03-6.54E-03-1.15E-03-2.08E-03-2.41E-04-7.92E-03

Trends in Orographic Rainfall over the Fertile Crescent

153

Fig. 6 Same as Fig. 5 but for Region B (west Turkey) in the winter season.

3.1.4 Along the Caspian Sea (Region D)
There are significant decreasing trends along the
Caspian Sea, to the north of the Erboz Mountains. It is avery interesting place in terms of prominent orographic
precipitation, but no idealized station pairs are foundbetween the mountains and foothills. However, I chose
D1, where there was a difference in altitude (highstation = 70m, low station = – 20m). The correlation coefficient of this pair is relatively lower than the others I
have shown (= 0.882), as seen in the results of this station
pair in Fig. 8. A clear decreasing trend of Ro is found at
this station pair.
I have checked station pairs north of the Persian Sea
and Zagros Mountains, since they show a regional trend
structure. However, it is difficult to find a good station
pair according to my criteria described above, so I do notshow the results for other parts of the Iranian domain.

3.1.5 Discussion
In this study, to select the station pairs, I considereddifferences in altitude and avoided choosing pairs thatstraddled big mountain chains. I considered regions
characterized by similar trend patterns and selected pairs
with very high correlation coefficients. Hence, it should
be pointed out that most station pairs show decreasing
trends in Ro except for some regions.
If we view the locations more locally, sometimes both
high stations and low stations may exist in small valleys
and/or on small mountains forming a pair. Hence, thisanalysis is too rough to discuss the micro-physical effectthat should be examined with regard to the same cloudsystem. We should carefully consider it, but there may aneed for more station networks with long-term observations and idealized station pairs or for other methods
together with this type Ro analysis.

154

Akiyo YATAGAI

Fig. 7 Same as Fig. 4 but for Region C (southeast Turkey). C1 is not shown, since it is the same as A4.

The “Fertile Crescent,” famous in archaeology, runs
from the Jordan Valley northwards through inland Syria,
into southeastern Turkey, then eastwards throughnorthern Iraq, and finally southeastward along the Zagros
foothills of western Iran (Bellwood, 2005). It is a zone ofgentle gradients with comparatively moist and fertile
alluvial soil, thus it is also called the cradle of civilization.
The Fertile Crescent is flanked to its south by desert andto its north and east by high mountains, hence, precipitation there is extremely important as a feed source forrivers and groundwater in the desert area, including
Mesopotamia, the land in and around the Tigris andEuphrates Rivers.
In spite of its importance, as we saw in Fig. 3, winterprecipitation has shown decreasing trends over mostparts of the Fertile Crescent. In the station-pair analysis,

stations A3, C1, C2, C3, C4 and C5 belonged to the
Fertile Crescent region. Interestingly A3 and C1, exceptionally showing decreasing trends in Ro, belong to thenorthwest part of the Fertile Crescent.
The horizontal resolution of climate models has
become finer and finer, and it could simulate a crescentshape of precipitation (Kitoh et al., 2008, Kitoh &Arakawa, 2011). However, representation of theorographic precipitation around the Fertile Crescent isstill a challenging issue (Kitoh & Arakawa 2011).
Climate models are expected to be used for paleo-climate
interpretation, but observational facts and precise analyses of precipitation are primarily important to the interpretation of archaeological proxy records. The beginningand the transition of agriculture and civilization musthave been regulated by temperature and precipitation. In

Trends in Orographic Rainfall over the Fertile Crescent155

future hydro/agricultural conditions of the Crescentregion, it is primarily important to understand thequantitative precipitation distribution and its local
changes associated with global change. Further investigations are needed, considering detailed orography andwind/rainfall systems of that region.

Acknowledgements
I appreciate Prof. Daniel Rosenfeld for his stimulatingsuggestions and fruitful discussions throughout the“Desert to Monsoons” Conference and at the beginningof this study.
This research is part of “Asian Precipitation–Highly
Resolved Observational Data Integration Towards the
Evaluation of the Water Resources (APHRODITE),” andis supported by the Global Environment Research Fund
(GERF-B062/A0601) of the Ministry of the Environment,
Japan. This work was supported by a Grant-in-Aid
for Scientific Research (No. 1674027) from the Japan
Society for the Promotion of Science.
References

Fig. 8 Same as Figure 4 but for Region D(along the Caspian Sea).

this arid/semi-arid region, changes in the location of the
precipitation zone, including in altitudinal zones, according to global climate change are often a critical issue
affecting agriculture.

4. Summary
I have presented winter precipitation trends for
Turkey, Israel and Iran using 34-year monthly precipitation data. There was a strong and significant decreasing
trend in winter over Turkey and Israel, especially inJanuary. Trends over Turkey differed greatly from month
to month, while those over Iran did not differ so muchfrom season to season. On the other hand, Iran has
orographically characterized trends. I showed wintertrend patterns, and found orographically characterized
trend patterns (groups) on the 300 - 1,000 km scale.
Then I compared the trends at 13 station pairs of highstations and low stations under the same synoptic conditions for winter in western and southern Turkey andalong the Caspian Sea. Most station pairs showeddecreasing trends in Ro, which is the ratio of the
precipitation at the high station to that at the low station.
The exceptional cases, which showed increasing trendsin Ro were observed in the easternmost part of the Taurus
range (north of Syria) and in the northwest part of Turkey,
which is a part of the Fertile Crescent. In order to understand the archaeologically important era and to predict

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Akiyo YATAGAI
Dr. Akiyo YATAGAI is a climatologist and a
researcher at the Faculty of Life and Environmental Sciences, University of Tsukuba. She
received her Doctor of Philosophy in 1996 fromthe Graduate School of Geoscience, University ofTsukuba. She was a Researcher at the Earth
Observation Research Center, National Space Development Agency from1995 to 2001, and contributed to the Tropical Rainfall Measuring Mission(TRMM) and Global Energy and Water Cycle Experiment (GEWEX). She
was an Assistant Professor at the Research Institute for Humanity andNature (RIHN), Kyoto from 2002 to 2011. She has been a part time lecturer
at the Disaster Prevention Research Institute, Kyoto University, Meiji
University and the Faculty of Maritime Sciences, University of Kobe. She
was a Principal Investigator of the Asian Precipitation – Highly Resolved
Observational Data Integration Towards Evaluation of water resources(APHRODITE) project for 2006 – 2011, funded by the Global Environment Research Fund, Ministry of the Environment, Japan. The
APHRODITE daily grid precipitation data throughout Asia are widely usedby the international research community.

(Received 27 October 2011, Accepted 26 December 2011)