I

1) 87-100

)4

Everitt JH Hipps LE lant community response [0

d Management and Water

spheric Science 19 189 smiddot_middot-an energy combination m

height Boundary-Layer

felation determination of n and Drainage in the 21 5t 60S-tiJ6 1985 Evaluation of an ~ement In Advances in ces in Evapotranspiration

m fluxes in the atmospheric itions Journal of Applied

enee characteristics over a inhomogcneities of surElce

dary-Layer Meteorology 8

mined by one-dimensional

exchange rates Boundaryshy

terrain Boundary-Layer

y and the budgets of shear

Journal of Arid

Environments Journal of Arid Environments 57 (2004) 101-115

wwwclseviercomlocatejnlabryjarc

Origin of winter precipitation in the central coastal lowlands of Saudi Arabia

Hans-Jorg Barth Frank Steinkohl InsfiliI fllr (ieowophi( Lei1rslUhlfilr Physiscre Ceouraphil Ul1iversiTy ( RCflll1shllry

Regel1shurl 93IJ53 CermltIlmiddot

Received 16 December 2002 received in revised form 22 April 2003 accepted 6 May 2003

Abstract

The area under investigation is situated at the Gulf coast in Saudi Arabia north of Jubail Industrial City The region is characterized by a Mediterranean climate regime displaying a hot and dry summer season and a cooler winter period with rainfalL The analysis of regional climate data was based on the measurements of three weather stations during three winter periods For further analysis GMS 5(col) IR and MET5j7 IR satellite images were used in order to locate tracks of cyclones and cloud formations During the observation period four different types of precipitation occurred (I) cyclones from the Mediterranean Sea (2) convection cells (3) the fonnation of new cyclonic depressions in front of the Zagros Mountains above Iraq and eastern Iran (4) currents from equatorial areas in Sudan and Ethiopia The study demonstrates that apart from the well-known Mediterranean depressions there are at least three more characteristic weather situations which may provide rain for the Eastern Province of Saudi Arabia

2003 Elsevier Ltd All rights reserved

Keyords Precipitation 1 iddlc East Iran Low-pressure systems Climate

1 Introduction

In the coastal lowlands of the Eastern Province of Saudi Arabia rain is almost exclusively confined to the winter period between October and Jay Many authors deal with the climate of Eastern Saudi Arabia in one or the other way However regarding the winter precipitation only few of them present information more

Corresponding author Tel + 49-941-943-3606 fax j- 49-941-943-4004 E-mail address hans-joergbarth(ageographicuni-regensburgdc (I-I-J Barth)

0140-1963103$ - sec front maller 2003 Elsevier Ltd All righls reserved doi 101 016SOI40-1963(03)0009J-0

102 H-J Barrh F Seinkohll Journal of Arid Environments 57 (2004) 101middotmiddotl5

detailed than the general statement that most events are related to Mediterranean depressions Detailed analysis of preeipitation events is so far not available The meteorological data of three weather stations combined with the analysis of satellite images indicate that the origin of winter precipitation within the study area is more manifold Our analysis demonstrates that apart from Mediterranean depressions there are at least three more characteristic weather situations which may provide rain for the Eastern Province of Saudi Arabia These additional weather patterns have never been described on an analytical level before Therefore the results of this study are of substantial significance towards a better understanding of the climatic pattern in the Middle East Studies like this are a perquisite for successful modeling of the future climate development on a regional scale

2 General description of the study area

The study area is located at the Arabian Gulf coast north of Jubail Industrial City and covers about 900 km2 of terrestrial area (Fig I) It is part of the central coastal lowland of the Eastern Province of Saudi Arabia The relief is weak although some

4905 E 4915 4925 4935

z V N N

v

N

v o N

RASAZ-ZAuR

50 52 54

IRAN

~ LOCATION

bullbull ~ ltTUD( OF THe ARfA

_~middot-Juball

ltabian Gu

UAE OMAN

4905 E 4915 4925 4935

Fig I Location of the study arca and the weather stations

N N

v

N

z V o N

H-J B

limestone exposUl common Genera extensive sand 5

stabilized by vegei

1999) The Eastern Pt

Precipitation is cc spatial occurrence ranges from 44 m] Dhahran is 26c C 1987)

3 Methods

The three autom Germany) are distr (Abu Kharuf stati climate (eastern til I) The third statio embayments of the The weather stati pressure (all in a h height of lOm) and collects 10-min me is transferred to processing was can MS Excel softwar between 199394 and 2000 to 2001 from the historical area = left7htmlamp1 700ampe 0 (0804 thermal infrared Bernhard M uhr Germany) (http (0 11 000-310401

4 Results

During the peri occurred (Table 1) four described typ

s 57 (2004) Wf-ll5

re related to Mediterranean 5 is so far not available ombined with the analysis er precipitation within the mstrates that apart from nore characteristic weather Province of Saudi Arabia described on an analytical of substantial significance

in the Middle East Studies future climate development

mh of lubailindustrial City is part of the central coastal elief is weak although some

4935

her stations

H -1 Barth F Steinkohl I Journal of Arid Environments 57 (2004) 10 -115 103

limestone exposures in the form of minor escarpments and small domes are quite common General features in the topography of the study area are flat and extensive sand sheets and widely rolling inactive dune systems These are stabilized by vegetation and therefore they are referred to as fossil dunes (Barth 1999)

The Eastern Province belongs to the arid part of the SUbtropical desert belt Precipitation is confined to the winter season and varies in amount as well as in spatial occurrence The long-term average annual rainfall in Dhahran is 754mm and ranges from 44mm (1970) to 3298mm (1982) The average annual temperature in Dhahran is 26c C with extreme values of 48degC in summer and lOC in winter (MEPA 1987)

3 Methods

The three automatic weather stations (Adolf Thies GmbH amp Co KG G6ttingen Germany) are distributed in a way that the terrestrial climate of the coastal lowlands (Abu Kharuf station at 27deg2228N 49deg lO21E) as well as the maritime Gulf climate (eastern tip of Abu Ali Island at 27deg1805N 49deg41561E) is recorded (Fig I) The third station represents the climate of the intertidal areas within the shallow embayments of the disseeted coastline at Mardumah Bay (27deg0735~ 49deg3336E) The weather stations are permanently recording air temperature humidity air pressure (all in a height of 2 111 above the surface) wind direction wind speed (in a height of 10 m) and precipitation (in a height of I m) The data logger (Thies DL 15) collects IO-min mean values based on readings in 10 s intervals Eventually the data is transferred to a personal computer via memory card (256 kilobytes) Data processing was carried out with a personal computer and Unisoft (THIES) as well as MS Exeel software The data analyzed has been collected in the winter periods between 199394 199495 and 200001 For the whole period from 1993 to 1995 and 2000 to 2001 satellite images of the MET5 IR satellite were made available from the historical archive of EUMErSAT (httpwwweumetsatdeenjindexhtml area left7htmlampbody = jendpsjarchivejhistorichtmlampa 720ampb = Iampc = 700ampd 700ampe 0 (080402raquo For the winter period of 20002001 additionally thermal infrared images of MET7 lR and GMS5 (col) IR were recorded by Bernhard Muhr (Metereological Department of the University of Karlsruhe Germany) (httpwww-imkphysikuni-karlsruhede- muehr IFmmeSa tindex_dhtml (011 000-310401raquo

4 Results

During the period of investigation at least four different types of precipitation occurred (Table 1) Precipitation events which could not be attributed to one of the four described types were classified as others

104 H -J Bartil F Steil1koll1 Journal of Arid Environments (20(4) 101-115 I -1 Banh

Table I Types and number of precipitation events

1000 Precipitation type 199311994 19941995 20002001 Total 800

Mediterranean depressions 4 3 3 10 Formation of new low-pressure cells 3 5 2 10 Convection 2 3 4 9 Currents from Sudan Ethiopia 5 I 7 Others o I 2 3

Fig 2 Meditcrranean low-pressure systcm between January 5th and 8th 200 I [satellite images from MET fR (httpiwww-imkphysikuni-karlsruhe de ~ muehrmiddotframcSatindcx_dhtml)j

41 lvfedilerranean depressions

Due to the southward shift of the global pressure belts in winter time (northern hemisphere)_ Atlantic cyclones breaking free from the sub-polar low-pressure belt move eastward across the Mediterranean Sea In most cases these depressions dissipate influenced by stronger low-pressure centers further to the north or highshypressure cells further to the east If the Mediterranean low-pressure center is not hindered on its eastward way it enters the mainland via the Near East and Iraq occasionally crossing Northern Saudi Arabia and Kuwait (Fig 2b) In such cases precipitation may reach the eastern part of Saudi Arabia High temperature gradients between different air masses may bring squall lines and thunderstorms with brief torrential rains and gale-force winds

The depression displayed in Fig 2a moved eastward above the Mediterranean Sea crossing IsraeL Syria and the southern part of Iraq by January 7th (Fig 2b) Due to convection above the Middle East cloud formation increased (Fig 2c) At midday on January 7th the air pressure dropped significantly in the study area (Fig 3) with south-western winds Clouds covered the sky and prevented radiation which is reflected in the relatively high night temperatures (Fig 3) In early morning on January 8th thunderstorms aecompanied by intensive precipitation passed the arca The total precipitation of this event (on January 8th) at the Abu Kharuf weather

600

400

250

P 200

150

100

50

00

Fig J Air pressure temp station from January 7 lint

station was 145mm patchy distribution pH ceased at 8 pm Beca remained low during

42 Cycfoyenesis wes

The situation leadi] Iranian Zagros MOl mountains and follol The development of ~ steps

I Warm air masses lt

The latent heat w temperature gradie high-pressure zone (Fig 4B warm air more distant to ea

105 IS 57 (20(14) ]O]-Il5

995 20002001 Total

I 10 2 10 4 9

7 2 3

1000

800

600

400

250

200

150

100

50

00

I07 Jan 2001 I I08 Jan 2001 I I09 Jan 2001 I

30

J-----~~jj----_f_-_J------__t 10220 mb

10200

10180

10160

10140

10120

10100

iIHIII_IIiMHllllMllIi- 1 0080

th 200 I [satellite images from MET ieLdhtmllj

Its in winter time (northern sub-polar low-pressure belt )st cases these depressions rther to the north or highshylow-pressure center is not

ia the Near East and Iraq ait (Fig 2b) ] n such cases -rabia High temperature nes and thunderstorms with

jove the Mediterranean Sea nuary 7th (Fig 2b) Due to sed (Fig 2c) At midday on Ie study area (Fig 3) with vented radiation which is 3) ]n early morning on ~cipitation passed the area t the Abu Kharuf weather

H-J Barth F Steinkohll Journal of Arid Environments 57 (2004) 101 middotlJ5

I-temperature --air pressure

Fig 3 Air pressure temperature precipitation and relative humidity al the Maniumah Bay weather station from January 7 unlil 9 in 200 I

station was 145 mm and at the Mardumah Bay station 341 mm displaying the patchy distribution pattern typical for arid regions With rising air pressure the rain ceased at 8 pm Because of cold winds from north-western directions temperatures remained low during the next day despite a clear sky and sunshine

42 (vcloyenesis Irest ojthe Zaqros Mountains

The situation leading to the formation of a new low-pressure cell in front of the Iranian Zagros Mountains is characterized by moist air forced to cross the mountains and following colder air masses coming from north-western directions The development of such a low-pressure center is described by the following three steps

I Warm air masses are forced to rise because of the Zagros Mountains (Fig 4A) The latent heat which is released by the condensation processes decreases the temperature gradient with height The result of this situation is the formation of a high-pressure zone above the mountain range in elevations higher than 6000 m (Fig 4B warm air masses are less dense than cold air and therefore the isobars are more distant to each other than above colder air to the west which inevitably

=

H-i Barth[06 H-i Bartlz F Steinkohll Journal oArid Environmel1ls 57 (201M) OJ- 5

u)

(Bl pressure gradient IFI

Fig 4 (A) Air masses rising because of the Zagros Mountains (B) High-pressure ridge above the Zagros Mountains low-pressure zone in the north-west of the mountain range

leads to a pressure gradient in the height) Corresponding an upper low-pressure trough is located above the colder air masses in the north-west

2 The high isobars (above 6000 m) between the low-pressure trough and the highshypressure ridge display a convergence zone in the south-west and a divergence zone in the north-east (Fig 5) Ageostrophic mass transfer within the divergence zone leads to a surface pressure fall north-west of the high-pressure ridge (Fig 5 west of the Zagros Mountains)

3 Because of the surface low (north-west of the mountains) a cyclonal vortex is initiated (anti-clockwise) This vortex supports the rise of air in front of the Zagros Mountains which increases condcnsation there The release of latent heat then increases the high-pressure ridge above the mountains (as illustrated by Fig 48) This results in an increase of the pressure gradient between the high air masses (above 6000 m) causing an increase of the divergence and the ageostrophic mass transfer which finally leads to a further pressure fall in the surface low (see Fig 6)

A self-energising process starts which leads in the end to a complete low-pressure system (including warm and cold front) with the extent to influence the weather of

~

the northern and co cold front may bring the satellite images il the Zagros Mountail

On 7th of Februar East (Fig 7a) Due t next day Cloud fo the rising air After I following 2 days the related to this vorte station on 10th of FI before 9th of Febrlllt higher temperatures After the low-pressu cold north-western overall reduced rela

111 57 (2004) 101-115

igh-pressure ridge ahove the Zagros ge

rlding an upper low-pressure north-west essure trough and the highshyl-west and a divergence zone r within the divergence zone Jressure ridge (Fig 5 west of

ltains) a cyclonal vortex is rise of air in front of the ~ The release of latent heat ountains (as illustrated bv adient between the high air gence and the ageostrophic fall in the surface low (see

0 a complete low-pressure o influence the weather of

H -J Barth F Seillkolz I Journal 0 Arid bnvironmenll 57 (2004) f() J- I 15 107

IRAN

[H]-~ SAUDI

ARABIA

I j

200 km

ageostrophic mass transfer

Fig 5 Divergence ahove north-western Iran

the northern and coastal lowlands of Saudi Arabia The warm front as well as the cold front may bring precipitation with their typical characteristics Fig 7 displays the satellite images illustrating the formation of a new low-pressure cell in front of the Zagros Mountains

On 7th of February 200 I moist air from the Mediterranean Sea crossed the Near East (Fig 7a) Due to convection cloud formation increased above Iraq during the next day Cloud formation in front and above the Zagros Mountains indicate the rising air After passing through the described steps explained in 1-3 during the following 2 days the cyclonal spin of the vortex was visible (Fig 7d) The cloud band related to this vortex lead to 19 mm of precipitation at the Abu Kharuf weather station on 10th of February (Fig 8) The air pressure fell gradually during the days before 9th of February The cloud cover prevented radiation and therefore lead to higher temperatures during the night between the 9th and 10th of February (Fig 8) After the low-pressure center moved eastward on the II th of February relatively cold north-western winds prevailed resulting in low temperatures at night and an overall reduced relative humidity

i

lOS H-J Burtli F Steinkohll Journal (f Arid EI1Firo1l11cnts 57 (2004) ()j-115

SAUDI

-

ARABIA

IRAN

-

j

200 km

J cyclonal spin of low pressure center (near the surface)

fig 6 Sur[ite low-pressure cell generated west of the northern Zagros Mountain range due to dynamic prOCf-SCS

43 Convection

Thermal convection of air may lead to precipitation events if the air carries enough moisture and the convection is of such an intensity that condensation is sufficient The convection cell has to reach a height of more than 10 km because repeated freezing is needed to increase the size of the droplets and ice grains in such a way that they are large enough not to evaporate before reaching the ground This sort of precipitation is local and usually of short duration The cxample from 21 sl of March 200 I demonstrates the cloud formation due to thermal convection (see Fig 9)

Usually more effective are rainfalls associated to convection combined with frontal thunderstorms This happens when cool air masses from northern directions are being lead against unstable moist air masses coming from sOllthern directions Thermal convection serves as a trigger effect to release a spontaneolls updraft fed by latent heat energy This for example happened between the 8th and 9th of November 2000 (Fig 10) when after the passage of a low-pressure cell cold air entered the Arabian Peninsula from north-western directions At the same time warm and moist

H-J BUrl

Fig 7 Formation of a 200l [satellite images f

index_dhtmIJ]

air penetrated cent] formation during t the afternoon (Fig temperatures in the several intensive ra cllm ulonim bus diss still thunderstorm temperatures than

44 Currents from

These high curr eastern direction a(

109 fills 57 f20(4) 101-115

IRAN

IlM1 I

I

-

200 km

)f low pressure he surface)

ros MOllntain range dllc 0 dynamic

vents if the air carries enough 11 condensation is sufficient lan 10 km because repeated ice grains in such a way that

rIg the ground This iort of example from 21 sl of March convection (see 9) convection combined with

ses from northern directions g from southern direetions spontaneous updraft fed by he 8th and 9th of 0Jovember Ire cell cold air entered the same time warm and moist

H-J Barh F Stcillwhll journal (Arid Emironmeilfs 57 (2()04) 101 115

Fig 7 Formation ora new low-pressure cell in front oCtile Zagros lvlollntain range from Fehrllary 7-10 20l) I isalelille images from MET 7 I R (httpwww-imkphysikuni-karbruhedei~ muchrFramcSat indccdhrml))

air penetrated central Saudi Arabia from the south-east This lead to intensive cloud formation during the 8th of November ( 10) The first rain showers occurred in the afternoon (Fig II) The high cumulonimbus clouds (visible because of the cold temperatures in the infrared satellite image) persisted during the night and provided several intensive rain showers (Fig II) In the late morning (9th of November) the cumulonimbus dissipated and by noon also the rain stopped Above Iran there were still thunderstorms visible The next day temperatures than before this convectional st

was clear with orm

significantly lower

44 Currents Fom Sudan and Ethiopia

These high currents transport air masses from Sudan and Ethiopia in northshyeastern direction across the Arabian Peninsula towards Iran This is clearly visible in

=

H-i Barth[06 H-i Bartlz F Steinkohll Journal oArid Environmel1ls 57 (201M) OJ- 5

u)

(Bl pressure gradient IFI

Fig 4 (A) Air masses rising because of the Zagros Mountains (B) High-pressure ridge above the Zagros Mountains low-pressure zone in the north-west of the mountain range

leads to a pressure gradient in the height) Corresponding an upper low-pressure trough is located above the colder air masses in the north-west

2 The high isobars (above 6000 m) between the low-pressure trough and the highshypressure ridge display a convergence zone in the south-west and a divergence zone in the north-east (Fig 5) Ageostrophic mass transfer within the divergence zone leads to a surface pressure fall north-west of the high-pressure ridge (Fig 5 west of the Zagros Mountains)

3 Because of the surface low (north-west of the mountains) a cyclonal vortex is initiated (anti-clockwise) This vortex supports the rise of air in front of the Zagros Mountains which increases condcnsation there The release of latent heat then increases the high-pressure ridge above the mountains (as illustrated by Fig 48) This results in an increase of the pressure gradient between the high air masses (above 6000 m) causing an increase of the divergence and the ageostrophic mass transfer which finally leads to a further pressure fall in the surface low (see Fig 6)

A self-energising process starts which leads in the end to a complete low-pressure system (including warm and cold front) with the extent to influence the weather of

~

the northern and co cold front may bring the satellite images il the Zagros Mountail

On 7th of Februar East (Fig 7a) Due t next day Cloud fo the rising air After I following 2 days the related to this vorte station on 10th of FI before 9th of Febrlllt higher temperatures After the low-pressu cold north-western overall reduced rela

111 57 (2004) 101-115

igh-pressure ridge ahove the Zagros ge

rlding an upper low-pressure north-west essure trough and the highshyl-west and a divergence zone r within the divergence zone Jressure ridge (Fig 5 west of

ltains) a cyclonal vortex is rise of air in front of the ~ The release of latent heat ountains (as illustrated bv adient between the high air gence and the ageostrophic fall in the surface low (see

0 a complete low-pressure o influence the weather of

H -J Barth F Seillkolz I Journal 0 Arid bnvironmenll 57 (2004) f() J- I 15 107

IRAN

[H]-~ SAUDI

ARABIA

I j

200 km

ageostrophic mass transfer

Fig 5 Divergence ahove north-western Iran

the northern and coastal lowlands of Saudi Arabia The warm front as well as the cold front may bring precipitation with their typical characteristics Fig 7 displays the satellite images illustrating the formation of a new low-pressure cell in front of the Zagros Mountains

On 7th of February 200 I moist air from the Mediterranean Sea crossed the Near East (Fig 7a) Due to convection cloud formation increased above Iraq during the next day Cloud formation in front and above the Zagros Mountains indicate the rising air After passing through the described steps explained in 1-3 during the following 2 days the cyclonal spin of the vortex was visible (Fig 7d) The cloud band related to this vortex lead to 19 mm of precipitation at the Abu Kharuf weather station on 10th of February (Fig 8) The air pressure fell gradually during the days before 9th of February The cloud cover prevented radiation and therefore lead to higher temperatures during the night between the 9th and 10th of February (Fig 8) After the low-pressure center moved eastward on the II th of February relatively cold north-western winds prevailed resulting in low temperatures at night and an overall reduced relative humidity

i

lOS H-J Burtli F Steinkohll Journal (f Arid EI1Firo1l11cnts 57 (2004) ()j-115

SAUDI

-

ARABIA

IRAN

-

j

200 km

J cyclonal spin of low pressure center (near the surface)

fig 6 Sur[ite low-pressure cell generated west of the northern Zagros Mountain range due to dynamic prOCf-SCS

43 Convection

Thermal convection of air may lead to precipitation events if the air carries enough moisture and the convection is of such an intensity that condensation is sufficient The convection cell has to reach a height of more than 10 km because repeated freezing is needed to increase the size of the droplets and ice grains in such a way that they are large enough not to evaporate before reaching the ground This sort of precipitation is local and usually of short duration The cxample from 21 sl of March 200 I demonstrates the cloud formation due to thermal convection (see Fig 9)

Usually more effective are rainfalls associated to convection combined with frontal thunderstorms This happens when cool air masses from northern directions are being lead against unstable moist air masses coming from sOllthern directions Thermal convection serves as a trigger effect to release a spontaneolls updraft fed by latent heat energy This for example happened between the 8th and 9th of November 2000 (Fig 10) when after the passage of a low-pressure cell cold air entered the Arabian Peninsula from north-western directions At the same time warm and moist

H-J BUrl

Fig 7 Formation of a 200l [satellite images f

index_dhtmIJ]

air penetrated cent] formation during t the afternoon (Fig temperatures in the several intensive ra cllm ulonim bus diss still thunderstorm temperatures than

44 Currents from

These high curr eastern direction a(

109 fills 57 f20(4) 101-115

IRAN

IlM1 I

I

-

200 km

)f low pressure he surface)

ros MOllntain range dllc 0 dynamic

vents if the air carries enough 11 condensation is sufficient lan 10 km because repeated ice grains in such a way that

rIg the ground This iort of example from 21 sl of March convection (see 9) convection combined with

ses from northern directions g from southern direetions spontaneous updraft fed by he 8th and 9th of 0Jovember Ire cell cold air entered the same time warm and moist

H-J Barh F Stcillwhll journal (Arid Emironmeilfs 57 (2()04) 101 115

Fig 7 Formation ora new low-pressure cell in front oCtile Zagros lvlollntain range from Fehrllary 7-10 20l) I isalelille images from MET 7 I R (httpwww-imkphysikuni-karbruhedei~ muchrFramcSat indccdhrml))

air penetrated central Saudi Arabia from the south-east This lead to intensive cloud formation during the 8th of November ( 10) The first rain showers occurred in the afternoon (Fig II) The high cumulonimbus clouds (visible because of the cold temperatures in the infrared satellite image) persisted during the night and provided several intensive rain showers (Fig II) In the late morning (9th of November) the cumulonimbus dissipated and by noon also the rain stopped Above Iran there were still thunderstorms visible The next day temperatures than before this convectional st

was clear with orm

significantly lower

44 Currents Fom Sudan and Ethiopia

These high currents transport air masses from Sudan and Ethiopia in northshyeastern direction across the Arabian Peninsula towards Iran This is clearly visible in

111 57 (2004) 101-115

igh-pressure ridge ahove the Zagros ge

rlding an upper low-pressure north-west essure trough and the highshyl-west and a divergence zone r within the divergence zone Jressure ridge (Fig 5 west of

ltains) a cyclonal vortex is rise of air in front of the ~ The release of latent heat ountains (as illustrated bv adient between the high air gence and the ageostrophic fall in the surface low (see

0 a complete low-pressure o influence the weather of

H -J Barth F Seillkolz I Journal 0 Arid bnvironmenll 57 (2004) f() J- I 15 107

IRAN

[H]-~ SAUDI

ARABIA

I j

200 km

ageostrophic mass transfer

Fig 5 Divergence ahove north-western Iran

the northern and coastal lowlands of Saudi Arabia The warm front as well as the cold front may bring precipitation with their typical characteristics Fig 7 displays the satellite images illustrating the formation of a new low-pressure cell in front of the Zagros Mountains

On 7th of February 200 I moist air from the Mediterranean Sea crossed the Near East (Fig 7a) Due to convection cloud formation increased above Iraq during the next day Cloud formation in front and above the Zagros Mountains indicate the rising air After passing through the described steps explained in 1-3 during the following 2 days the cyclonal spin of the vortex was visible (Fig 7d) The cloud band related to this vortex lead to 19 mm of precipitation at the Abu Kharuf weather station on 10th of February (Fig 8) The air pressure fell gradually during the days before 9th of February The cloud cover prevented radiation and therefore lead to higher temperatures during the night between the 9th and 10th of February (Fig 8) After the low-pressure center moved eastward on the II th of February relatively cold north-western winds prevailed resulting in low temperatures at night and an overall reduced relative humidity

i

lOS H-J Burtli F Steinkohll Journal (f Arid EI1Firo1l11cnts 57 (2004) ()j-115

SAUDI

-

ARABIA

IRAN

-

j

200 km

J cyclonal spin of low pressure center (near the surface)

fig 6 Sur[ite low-pressure cell generated west of the northern Zagros Mountain range due to dynamic prOCf-SCS

43 Convection

Thermal convection of air may lead to precipitation events if the air carries enough moisture and the convection is of such an intensity that condensation is sufficient The convection cell has to reach a height of more than 10 km because repeated freezing is needed to increase the size of the droplets and ice grains in such a way that they are large enough not to evaporate before reaching the ground This sort of precipitation is local and usually of short duration The cxample from 21 sl of March 200 I demonstrates the cloud formation due to thermal convection (see Fig 9)

Usually more effective are rainfalls associated to convection combined with frontal thunderstorms This happens when cool air masses from northern directions are being lead against unstable moist air masses coming from sOllthern directions Thermal convection serves as a trigger effect to release a spontaneolls updraft fed by latent heat energy This for example happened between the 8th and 9th of November 2000 (Fig 10) when after the passage of a low-pressure cell cold air entered the Arabian Peninsula from north-western directions At the same time warm and moist

H-J BUrl

Fig 7 Formation of a 200l [satellite images f

index_dhtmIJ]

air penetrated cent] formation during t the afternoon (Fig temperatures in the several intensive ra cllm ulonim bus diss still thunderstorm temperatures than

44 Currents from

These high curr eastern direction a(

109 fills 57 f20(4) 101-115

IRAN

IlM1 I

I

-

200 km

)f low pressure he surface)

ros MOllntain range dllc 0 dynamic

vents if the air carries enough 11 condensation is sufficient lan 10 km because repeated ice grains in such a way that

rIg the ground This iort of example from 21 sl of March convection (see 9) convection combined with

ses from northern directions g from southern direetions spontaneous updraft fed by he 8th and 9th of 0Jovember Ire cell cold air entered the same time warm and moist

H-J Barh F Stcillwhll journal (Arid Emironmeilfs 57 (2()04) 101 115

Fig 7 Formation ora new low-pressure cell in front oCtile Zagros lvlollntain range from Fehrllary 7-10 20l) I isalelille images from MET 7 I R (httpwww-imkphysikuni-karbruhedei~ muchrFramcSat indccdhrml))

air penetrated central Saudi Arabia from the south-east This lead to intensive cloud formation during the 8th of November ( 10) The first rain showers occurred in the afternoon (Fig II) The high cumulonimbus clouds (visible because of the cold temperatures in the infrared satellite image) persisted during the night and provided several intensive rain showers (Fig II) In the late morning (9th of November) the cumulonimbus dissipated and by noon also the rain stopped Above Iran there were still thunderstorms visible The next day temperatures than before this convectional st

was clear with orm

significantly lower

44 Currents Fom Sudan and Ethiopia

These high currents transport air masses from Sudan and Ethiopia in northshyeastern direction across the Arabian Peninsula towards Iran This is clearly visible in

i

lOS H-J Burtli F Steinkohll Journal (f Arid EI1Firo1l11cnts 57 (2004) ()j-115

SAUDI

-

ARABIA

IRAN

-

j

200 km

J cyclonal spin of low pressure center (near the surface)

fig 6 Sur[ite low-pressure cell generated west of the northern Zagros Mountain range due to dynamic prOCf-SCS

43 Convection

Thermal convection of air may lead to precipitation events if the air carries enough moisture and the convection is of such an intensity that condensation is sufficient The convection cell has to reach a height of more than 10 km because repeated freezing is needed to increase the size of the droplets and ice grains in such a way that they are large enough not to evaporate before reaching the ground This sort of precipitation is local and usually of short duration The cxample from 21 sl of March 200 I demonstrates the cloud formation due to thermal convection (see Fig 9)

Usually more effective are rainfalls associated to convection combined with frontal thunderstorms This happens when cool air masses from northern directions are being lead against unstable moist air masses coming from sOllthern directions Thermal convection serves as a trigger effect to release a spontaneolls updraft fed by latent heat energy This for example happened between the 8th and 9th of November 2000 (Fig 10) when after the passage of a low-pressure cell cold air entered the Arabian Peninsula from north-western directions At the same time warm and moist

H-J BUrl

Fig 7 Formation of a 200l [satellite images f

index_dhtmIJ]

air penetrated cent] formation during t the afternoon (Fig temperatures in the several intensive ra cllm ulonim bus diss still thunderstorm temperatures than

44 Currents from

These high curr eastern direction a(

109 fills 57 f20(4) 101-115

IRAN

IlM1 I

I

-

200 km

)f low pressure he surface)

ros MOllntain range dllc 0 dynamic

vents if the air carries enough 11 condensation is sufficient lan 10 km because repeated ice grains in such a way that

rIg the ground This iort of example from 21 sl of March convection (see 9) convection combined with

ses from northern directions g from southern direetions spontaneous updraft fed by he 8th and 9th of 0Jovember Ire cell cold air entered the same time warm and moist

H-J Barh F Stcillwhll journal (Arid Emironmeilfs 57 (2()04) 101 115

Fig 7 Formation ora new low-pressure cell in front oCtile Zagros lvlollntain range from Fehrllary 7-10 20l) I isalelille images from MET 7 I R (httpwww-imkphysikuni-karbruhedei~ muchrFramcSat indccdhrml))

air penetrated central Saudi Arabia from the south-east This lead to intensive cloud formation during the 8th of November ( 10) The first rain showers occurred in the afternoon (Fig II) The high cumulonimbus clouds (visible because of the cold temperatures in the infrared satellite image) persisted during the night and provided several intensive rain showers (Fig II) In the late morning (9th of November) the cumulonimbus dissipated and by noon also the rain stopped Above Iran there were still thunderstorms visible The next day temperatures than before this convectional st

was clear with orm

significantly lower

44 Currents Fom Sudan and Ethiopia

These high currents transport air masses from Sudan and Ethiopia in northshyeastern direction across the Arabian Peninsula towards Iran This is clearly visible in

109 fills 57 f20(4) 101-115

IRAN

IlM1 I

I

-

200 km

)f low pressure he surface)

ros MOllntain range dllc 0 dynamic

vents if the air carries enough 11 condensation is sufficient lan 10 km because repeated ice grains in such a way that

rIg the ground This iort of example from 21 sl of March convection (see 9) convection combined with

ses from northern directions g from southern direetions spontaneous updraft fed by he 8th and 9th of 0Jovember Ire cell cold air entered the same time warm and moist

H-J Barh F Stcillwhll journal (Arid Emironmeilfs 57 (2()04) 101 115

Fig 7 Formation ora new low-pressure cell in front oCtile Zagros lvlollntain range from Fehrllary 7-10 20l) I isalelille images from MET 7 I R (httpwww-imkphysikuni-karbruhedei~ muchrFramcSat indccdhrml))

air penetrated central Saudi Arabia from the south-east This lead to intensive cloud formation during the 8th of November ( 10) The first rain showers occurred in the afternoon (Fig II) The high cumulonimbus clouds (visible because of the cold temperatures in the infrared satellite image) persisted during the night and provided several intensive rain showers (Fig II) In the late morning (9th of November) the cumulonimbus dissipated and by noon also the rain stopped Above Iran there were still thunderstorms visible The next day temperatures than before this convectional st

was clear with orm

significantly lower

44 Currents Fom Sudan and Ethiopia

These high currents transport air masses from Sudan and Ethiopia in northshyeastern direction across the Arabian Peninsula towards Iran This is clearly visible in

110 HJ Barth F Stdnkohll Journal of AriJ ~Enrironmel1ts 57 (2004) ]0 ~115

109 Feb2001 110 Feb 20011 ~b2001 I 1000

relative800 humidity in

600

400

031~~~-~Tl~

10170 mb

10160 250

~ 200 10150

10140 150 10130

10120 10110

10100 50 01 10090

100

IINLIldIIIINIt I 1008000 precipitation in mmilliilllIil~~Illllililmltll~l~ll~IiI~I111 10070

Fig 8 Air pressure temperature precipitation and relative humidity at the Abu Kharuf weather station from 9th to 11th of February 200 l

dark areas indicate cumulonimbus reaching

high altitudes

Fig 9 Formation or convection cells above the slUdy area 2 Jst or Manh 2001 between 900 am and 900 pm [satellite images from GMS5 (col) IR (httpfwwwmiddotimkphysikunimiddotkarlsruhede ~ muehrFrameSat inde)uLhIl1l1raquo)

satellite images due to the movement of continuous linear cloud bands (Fig 12) On their way across the Arabian Peninsula the cloud cover intensifies probably due to convection In several cases these clouds provide rain for the Eastern Province Such was the case at 25th of December 2000 Fig 13 displays the development between

HI Bar

Fig I(J Convergence of between 91 h and 10th ( convectional cells bUIld t (J9 11 the cumulonimbu sky and sunshine domi www-imkphysikuni-kar

24th of December a weather station

5 Discussion

It is the wide 81 lowlands of the Eas pressure systems (l 1981 Khalili 19l Batanouny 1987 1992 Barth 1998 Mediterranean dep only about 25 0

systems The formation (

Mediterranean cun cells Warm and m

111 renl 57 12(04) 101-115

11 Feb 20011

relative humidity in

-----__- 10170 mb

10160 10150 10140 10130 10120 10110 10100 10090 10080 10070

ty at the Abu Kharuf weather S[dUon

lark areas indicate nulonimbus reaching

high altitudes

Heh 2001 between 900 am and 900 ni-karlsruhcdcmiddot - muchr FrameSal

ar cloud bands (Fig 12) On r intensities probably due to If the Eastern Province Such ys the development between

H-J Burth F Steinkohll Journal of Arid Environments 57 2004 J IOlll5

dark areas indicate cumulonimbus reaching

high altitudes

Fig 10 Convergence of cold and warm air mmses results in intensive convection with rain showers between 9th and 10th of November 071 L2000 cold air entering northern Arabia 081 several convectional cclb build high cumulonimbus (note the low temperatures in the infrared sateliite image) 0911 the cumulonimbus dissipate in the study area thunderstorms arc still active in Iran 10J L clear sky and sunshine dominate the study area again [satellite images from GMS5 (col) IR (http www-imkphysikuni-karlsruhedei - muehrFrameSaliindcLd hlml )]

24th of December and the precipitation which amounted 05 mm at the Abu Kharuf weather station

5 Discussion

It is the wide spread impression that most rain events in the central coastal lowlands of the Eastern Province in Saudi Arabia are caused by Mediterranean lowshypressure systems (Beaumont et a 1976 Barth 1976 Orshan 1980 Taha et aL 1981 Khalili 1984 Siraj 1984 Walter and Breckle 1984 Evenari 1985 Batanouny 1987 Child and Grainger 1990 Mandaville 1990 Sheppard et a 1992 Barth 1998 Weischet and End1icher 2000) Our analysis proved that Mediterranean depressions are an important factor but it also demonstrated that only about 25 of all events can be attributed exclusively to thcse low-pressure systems

The formation of new low-pressure systems above Iraq may be influenced by Mediterranean currents but they cannot be regarded as Mediterranean low-pressure cells Warm and moist air masses forced to rise at the Zagros Mountains and colder

112 1I -f BII F SIrillkoh I Journal of Arid iomirolllJ1(ns 57 (201M i 101 f 15

1000 relative -l800 humidity in

400 200600 l--~~~-Qj~----1~------

l07 fJOV~200iJ I~~_~~EJ I~NOV 20J I Nov 20~JI

t____ bullbullbullbull__ ~ 300 10200

10190 250 10180

10170 200 10160

10150150

10140 10130100 10120 10110 10100

50

00 10090

--------------------__----] I-temperature --air pressureL__~~~~_~___~_~~_~~_

Fig II Air pressure temperature precipitation and relative humidity at the Mardumah Bay weather station from 7th to I (Jth of Novemher WOO

linear cloud band

I

Fig 11 Current from Ethiopia and Sudan (image from MET5 IR OX02199S 12 pm (http wwwclIllletsatdecnindcxhtmlarea left 7htl1llamphody endpsarchiwhistorichtmlampa 720ampb =

Iampe = 700ampd 7()Oampe 0)

air coming from north-western directions cause dynamic processes which lead to the development of a low-pressure cell in the south-eastern parI of Iraq The antishyclockwise turn of this system accelerates the process and a fast increase of cloud

Jimiddotf 81

Fig 13 Linear cloud I [satellite images [ron

index_dht1111]

cover as well as tl pressure system is is important to ne systems in averal probability of rain attributed to these

Convection was Eastern Province ( (Barth 1976 Schy and Endlicher 20 not present infofl convection are m measured paramel the large-scale sitt period of investig

The precipitati Ethiopia are clear (Figs 12 and 13) relates precipitatic K halili (1984) att Red Sea without probably also to t of northern latitu dynamic processe improves the con eastward drifting open We hope t this subject

57 (201M) ()~ 115

_Nov 20001

Irelative I humidity in

10200 10190 10180 10170 10160 10150 10140 10130 10120 10110 10100 10090

at the Mardumah Bay weather

j band

fabian ninsula

Og021995 12 pm (http vehistorichlmlampa = 720ampb

cesses which lead to the )art of Iraq The anti shy fast increase of cloud

H~J Balth F Sleinkohil Journal lrArid EnrirOlllwllls 57 (2004) 101 15

Fig 13 Linear cloud band crossing the Arahian Peninsula hetween 24th and 25th of Decemher 20()O [satellite images from j1ET 7 lR (httpwww-imkphysiklIl11-karlsruhede ~muchrFramcSat indcxdhtml)j

cover as well as the formation of a cold front is the result As soon as the lowshypressure system is established it starts its usually eastward movement across Iran It is important to note that compared to Mediterranean low-pressure centers these systems in average prevail longer above Iraq and Iran which increases the probability of rain in the area of consideration About 25 of the rain events can be attributed to these processes

Convection was mentioned by only a few authors as a possible cause of rain in the Eastern Province of Saudi Arabia (Beaumont et al 1976 Siraj 1984) Some others (Barth 1976 Schy[ltma 1978 Walter and Breckle 1984 Mandaville 1990 Weischet and Endlicher 2000) only mention thunderstorms with heavy rainfall but they do not present information about their origin Precipitation events due to thermal convection are usually not difficult to recognize because they are local and the measured parameters such as wind direction and air pressure are independent from the large-scale situation Twenty-three percent of all rain events that occurred in the period of investigation were due to convection

The precipitation events that we attributed to the currents from Sudan and Ethiopia are clearly related to the linear cloud bands across the Arabian Peninsula (Figs 12 and 13) As far as we know only one publication (Khalili 1984) exists which relates precipitation events in the Eastern Province of Saudi Arabia to these currents Khalili (1984) attributes 225 of the rainfall in eastern Iran to currents from the Red Sea without further explanation They must be related to the anti-trades and probably also to the oscillating sub-tropic-let which is situated between 20 and 35 of northern latitude Large-scale oscillations of currents above 10 km height cause dynamic processes which may lead to pressure fall near the surface which in turn improves the conditions necessary to provide rain But the relation of these northshyeastward drifting almost linear cloud bands with the observed precipitation remains open We hope that our paper might initiate some work and discussion regarding this subject

I

- 114 H-J Barth F Steinkohll Journal 01 Arid Environments 57 (20()4) JO-JJ5

If the atmospheric warming and the induced global change continues the climatic pattern in the Arabian Peninsula region will also be affected Without the knowledge of thc present c1imatie situation and the conditions that lead to precipitation even complex simulations will not be able to calculate the future development In order to support the establishment of sustainable land use methods it is essential to be in a position where we can rely upon estimates regarding the development of the future climate in the Gulf area This study might contribute to the understanding of the climate in north-eastern Saudi Arabia Kuwait and Eastern Iraq Most scenarios computed within the last few years (Rahmstorf and Ganopolski J999 Karl and Trenberth 2002) show an increase of precipitation in the Middle East of about 100mmyear until 2100 due to the global warming Due to the results of our study we expect a higher increase of the annual precipitation especially at the windward side of the Zagros Mountains Low-pressure systems which establish themselves in front of the Zagros Mountains remain there for a significantly longer time than Mediterranean low-pressure cells which increases the probability of rainfall in the Gulf area Additionally higher global temperatures will increase the absolute humidity of the air which means that precipitation events do not increase in number but in intensity At higher temperatures the latent heat will also be increased~shya condition which supports the dynamic processes leading to the low-pressure system as described above Therefore these low-pressure systems might become more effective if the global warming continues

Acknowledgements

We are grateful to NCWCD Riyadh for making our studies possible Many thanks to H E Prof Dr Abdulaziz H Abuzinada who provided the possibility to

work in the Jubail Marine Sanctuary Many thanks to the manager of NCWCD in Jubail Mr Khalid Ali AI-Shaikh who with his great support made our studies in the Sanctuary possible Further we would like to thank Mr Ahmed Salah Abdul Aziz for collecting climatological data between 1993 and 1995 Further we want to thank Mr Bernhard Muhr from the Meteorological Department of the University of Karlsruhe (Germany) who kindly provided the MET 7 IRVIS and the GMS5 (col) IR satellite images

References

Barth HK 1976 Die Landesnatur In Blume H (Ed) Saudi Arabien Erdmann Verlag Tubingcn pp23-90

Barth H-J 1998 Sebkhas als Ausdruck von Landschaftsdegradation im Zcntralen Kustcnliefland der Ostprovinz Saudi-Arabicns Rcgensburger Gcographischc Schriften 29 279

Barth il-1 1999 Desertification in the Eastern Province of Saudi Arabia Journal of Arid Environments 43 399~41O

Balanouny KH J987 Current knowledge of plant ecology in the Arab Gulf countries Catena 14 291-316

H-J

BeaumonL P Blak London

Child G Grainger Evenari 11 1985

Ecosystems of th Karl TR Trenbert

12-17 Khalili A 1984 Cli

the First Internati Mandaville JP 19~ MEPA 1987 Arabia

Arabian Gulf Ri Orshan G 1980 Tt

Ecosystems of thi Rahmstorf S Gano

climate model CI Schyfsma L 1978 C

Springer Vienna Sheppard C Price Siraj A 1984 Clima

F (Eds) Fauna Taha MF Harb S

K Arakawa H Elsevier Amsterd

Walter H Breckle Subtropischen Ze

WeischeL W Endlic Stuttgart

115 nls 57 (2004) lOl-115

change continues the climatic fected Without the knowledge lat lead to precipitation even Iture development In order to thods it is essential to be in a the development of the future ~ to the understanding of the Eastern Traq Most scenarios Oanopolski 1999 Karl and

in the Middle East of about ue to the results of our study n espeeially at the windward which establish themselves in ignificantly longer time than probability of rainfall in the s will increase the absolute nts do not increase in number teat will also be increasedshyng to the low-pressure system ystems might become more

our studies possible Manv to provided the possibility t~ the manager of NCWCD in support made our studies in lk Mr Ahmed Salah Abdul ld 1995 Further we want to Jartment of the University of IRVIS and the OMS5 (col)

lbien Erdmann Verlag Tiibingen

n im Zentralen Kiistentieftand der n 29 279

Ibia Journal of Arid Environments

Arab Gulf countries Catena 14

H-J Barlh F Steinkohl Journal of Arid Environments 57 (2004) JOJ-115

Beaumont P Blake GJ Wagstaff JM 1976 The Middle East-A Geographical Study Wiley London

Child G Grainger J 1990 A plan to protect areas in Saudi Arabia lCWCD Report Riyadh Evcnari M 1985 The desert environment In Evenari M -loy-Meir I Goodall DW (Eds)

Ecosystems of the World 12 A Hot Deserts and Arid Shrublands Elsevier Amsterdam pp )-22

Karl TR Trcnberth KE 2002 Mensch und Klima Spektrum del Wissenschaften Klima-Dossier 1 12-17

Khalili A 1984 Climatological conditions and wind patterns over the Persian Gulf In Proceedings of the First International Conference on the Impact of Oil Spill in the Persian Gulf Theran pp 188-222

Mandaville JP 1990 Flora of Eastern Saudi Arabia Kegan parI Inl London MEPA 1987 Arabian Gulf an assessment of biotopes and coastal zone management requirements for the

Arabian Gulf Riyadh Orshan G 1980 The deserts of the Middle East In Evenari M Noy-Meir I Goodall DW (Eds)

Ecosystems of the World 12 B Hot Deserts and Arid Shrublands Elsevier Amsterdam pp 1-28 Rahmstorf S Ganopolski A 1999 Long term warming scenarios computed with an efficient coupled

climate model Climate Change 43 353-367 Schyfsma E 1978 Climate In Al-Sayari SS ZiitlI (Eds) Quaternary Period in Saudi Arabia Vol 1

Springer Vienna New York pp 3144 Sheppard C Price A Roberts C 1992 Marine Ecology of the Arabian Region London Siraj A 1984 Climate of Saudi Arabia climatological features of Saudi Arabia In Biittiker W Krupp

F (Eds) Fauna of Saudi Arabia Vol 6 Pro Entemologica Basle pp 32-53 Taha MF Harb SA Nagib MK Tantawy AH 19R I The climate of the Near East In Takahashi

K Arakawa H (Eds) Climates of Southern and Western Asia World Survey of Climatology Vol 9 Elsevier Amsterdam pp 183-229

Walter H Breckle SW 1984 Okologie der Erdc Vol 2 Speziclle Okologie der Tropischcn und Subtropischen Zoncn Stuttgart

Weischct W Endlicher W 2000 Regionale Klimatologie Teil2 Die Alte Welt-Europa Afrika Asicn Stuttgart

115 nls 57 (2004) lOl-115

change continues the climatic fected Without the knowledge lat lead to precipitation even Iture development In order to thods it is essential to be in a the development of the future ~ to the understanding of the Eastern Traq Most scenarios Oanopolski 1999 Karl and

in the Middle East of about ue to the results of our study n espeeially at the windward which establish themselves in ignificantly longer time than probability of rainfall in the s will increase the absolute nts do not increase in number teat will also be increasedshyng to the low-pressure system ystems might become more

our studies possible Manv to provided the possibility t~ the manager of NCWCD in support made our studies in lk Mr Ahmed Salah Abdul ld 1995 Further we want to Jartment of the University of IRVIS and the OMS5 (col)

lbien Erdmann Verlag Tiibingen

n im Zentralen Kiistentieftand der n 29 279

Ibia Journal of Arid Environments

Arab Gulf countries Catena 14

H-J Barlh F Steinkohl Journal of Arid Environments 57 (2004) JOJ-115

Beaumont P Blake GJ Wagstaff JM 1976 The Middle East-A Geographical Study Wiley London

Child G Grainger J 1990 A plan to protect areas in Saudi Arabia lCWCD Report Riyadh Evcnari M 1985 The desert environment In Evenari M -loy-Meir I Goodall DW (Eds)

Ecosystems of the World 12 A Hot Deserts and Arid Shrublands Elsevier Amsterdam pp )-22

Karl TR Trcnberth KE 2002 Mensch und Klima Spektrum del Wissenschaften Klima-Dossier 1 12-17

Khalili A 1984 Climatological conditions and wind patterns over the Persian Gulf In Proceedings of the First International Conference on the Impact of Oil Spill in the Persian Gulf Theran pp 188-222

Mandaville JP 1990 Flora of Eastern Saudi Arabia Kegan parI Inl London MEPA 1987 Arabian Gulf an assessment of biotopes and coastal zone management requirements for the

Arabian Gulf Riyadh Orshan G 1980 The deserts of the Middle East In Evenari M Noy-Meir I Goodall DW (Eds)

Ecosystems of the World 12 B Hot Deserts and Arid Shrublands Elsevier Amsterdam pp 1-28 Rahmstorf S Ganopolski A 1999 Long term warming scenarios computed with an efficient coupled

climate model Climate Change 43 353-367 Schyfsma E 1978 Climate In Al-Sayari SS ZiitlI (Eds) Quaternary Period in Saudi Arabia Vol 1

Springer Vienna New York pp 3144 Sheppard C Price A Roberts C 1992 Marine Ecology of the Arabian Region London Siraj A 1984 Climate of Saudi Arabia climatological features of Saudi Arabia In Biittiker W Krupp

F (Eds) Fauna of Saudi Arabia Vol 6 Pro Entemologica Basle pp 32-53 Taha MF Harb SA Nagib MK Tantawy AH 19R I The climate of the Near East In Takahashi

K Arakawa H (Eds) Climates of Southern and Western Asia World Survey of Climatology Vol 9 Elsevier Amsterdam pp 183-229

Walter H Breckle SW 1984 Okologie der Erdc Vol 2 Speziclle Okologie der Tropischcn und Subtropischen Zoncn Stuttgart

Weischct W Endlicher W 2000 Regionale Klimatologie Teil2 Die Alte Welt-Europa Afrika Asicn Stuttgart