Dead Sea Climate Change

Dead sea climate change Mesometeorology seminar Lecturer: professor Pinhas Alpert Roni Lapid 18.5.2009

Literature  RECENT CHANGES IN THE CLIMATE AT THE

DEAD SEA )P. Alpert, H. Shafir, D. Issahary 1997).  A MODEL SIMULATION OF THE SUMMER CIRCULATION FROM THE EASTERN MEDITERRANIEAN PAST LAKE KINNERET IN THE JORDAN VALLEY (P. Alpert, A. Cohen, J. Neumann, E. Doron 1982).  Encyclopedia of climate (367-373).

Outline Part I - background and overview  Historical survey of the last 80 years.  The general circulation in the dead sea and the inland//kinneret.  Modeling the breeze and the σ coordinates.  Pan evaporation. Part II – dead sea climate change  Measured indication for climate change.  3 D model for climate change investigation.  Summery.

Historical survey  The dead sea level was steady for many

years, but since the Dganya dam has built, the natural flow of the southern Jordan river reduced dramatically.

Rutenberg hydroelectric Power station

Historical survey  Damming the Yarmuch and the Jordan rivers

was the first anthropogenic change, but not the last, the Dead Sea Works company (Est. 1929) make a use in the water from the northern basin to produce a verity of minerals by evaporating water in the southern basin.

Historical survey  Mean sea level and area during the last 80 years

in meters under the sea level. Sea area

1999

1969

Sea level

1939

 today the lake lose more than

1m ∗ year −1

General circulation in the dead sea  The circulation in the dead sea is ruled by three

mesometeorological systems (the lake breeze and the sea breeze) and the one synoptic system (the etesian winds).  The interaction between those three systemsgoverning the local climate of the dead sea.  To understand better the circulation, we’ll use the techniques that Alpert at al (1982) developed for mesoscale systems.

Land lake breeze P-2δp ρ-δρ

P-δp

p▼

ρ▼ ρ

ρ

P

warm

ρ-δρ

P-2δp

P-δp P

cool

warm

Land lake breeze

:Baroclinic torque

B ∇ρ × ∇ p = ρ ρ3

H

L

L

Lake breeze L

The baroclinic torque accelerate the air toward the upper Area above lake, than the air decrease .To the surface of the lake Finally the air move from the Lake to the surrounding land

H

Lake breeze H

H

L

The etesian winds  The synoptic major system in the summer

known as the Persian through that cause north westerly winds in the Levant, called the etesian winds. 06:00

14:00

Sigma coordinate  Because of the complication of the bottom

boundary condition Philips (1957) introduced to “normalized pressure” or sigma coordinate.  the sigma coordinate is

defined by

p− p σ= p −p t

s

t

 where p is the air

pressure, and the subscripts s and t refer to the surface and top of the model. 11

The advantages of the σ coordinate n

It produce simple formulation for handling the lower boundary layer. n Allows for good depiction of continuous fields such as temperature advection and wind. (lee mountain slope) n The model can better define boundary layer processes such as low-level wind, turbulence etc. 12

The disadvantages of the σ coordinate 1. The coordinate surfaces slope steeply to follow steep mountains, 2. Horizontal derivative calculations yield errors in the vicinity of mountains, particularly for pressure gradient force 3. Errors increase as model resolution increases with mountain slopes being better represented.

13

D coordinates 2 X

Z

45 = X

X σ=

0

σ 1 σ=

0 X=

Pt=(σ=0)=750mb

Model for the inland breeze  In this section we will try to understand the

mechanism of breeze inland and its amplification.  Our motivation for Better understanding of the breeze mechanism, is to conclude about the dead sea circulation with this research realization.  For this reason we will use 2 D model with resolution of 4 km.

Model for the inland breeze  1. 2. 

The model is 2 dimensional and assume: Quasi hydrostatics. Steady large scale geostrophic wind. The model in (x,σ,t) coordinate system are: ∂p* φ − + F p p* +∂ t x∂ x σ

(1)

∂u ∂u ∂u =− u − σ + f − v( v −g) ∂t ∂x ∂ σ

(2)

∂v ∂v ∂v = −u −σ − f( u −ug ) +Fy ∂t ∂x σ ∂

∂φ (3) =− c pθ T ∂

θ

RT

x

Model for the inland breeze ∂θ ∂θ ∂θ = −u −σ + Fx ∂t ∂x ∂σ

(4) (5)

∂p* ∂ ∂ = − ( px u ) − ( pxσ ) ∂t ∂x ∂σ

(6)

∂p* ∂ p(*u ) =− ∫ dσ ∂t ∂ 0

(7)

∂p* ∂ ∂ = − ( px u ) − ( pxσ ) ∂t ∂x ∂σ

1

T ( K )= 3 0 0 − 0 .00 65 z S

G

+

E [ 11 .7 9 sin( + y 0 .376 − 5 1 ( 1.87+)sin 39 ysin(1.1 4 ) + 5 .73 ( sin 2 y) 0.2

0.6 1−) ].2

Initial conditions TEMP[ C]

 The integration

  

17

700

22

starts at 08:00 750 800 LST. 850 The model assume 900 950 inversion layer in 1000 930-900 [mb] layer. At Z=0 we put T=300 K and p=1000 mb. There is no horizontal gradient pressure. Without friction the geostrophic wind is: barometric pressure [mb]



12

Vg = (u g , vg ) = (3, −1)m ⋅ s −1

27

32

Model’s realization

Penetration Of the sea Breeze front Vertical wind cm/sec*2 cm/sec*4

Lake Kinneret

Model’s realization Temperature profile ) In point 8 km from the sea (a ):And above lake Kinneret (b

Wind speed calculated :and observed

Model’s realization • The amplification of the wind in the lake Kinneret occurs due to three mean reasons: 1. The penetration of the breeze front lead to sudden rise in the air pressure which increase the pressure gradient: The coast 2. The lake breeze that flaw up slope, delay the westerly sea breeze, this delay cause Lake center an “outbreak” of the sea breeze when the east (lake breeze) wind weakening. 3. The cool sea breeze is more density, and accelerate below the warm air that exist above lake Kinneret.

Visual explanation for the strong wind in the kinneret continuity consideration Cause wind acceleration Inversion layer

Moist cold air

Lower Galilee Mountain

Acceleration due to down lifting

Dry Warm air

Pan evaporation  Measuring the evaporation rate of the lake is

not a simple task, many variables affect the rate of the evaporation and make it hard to estimate.  The most persists way to estimate the evaporation rate, called: pan evaporation, which makes a use with a large pan that simulating the environment of the water source.

Pan evaporation  Empyrean studies showed from observations that the E = C (ew − ea ) )shaw, 1993( formula of evaporation is

where E is the evaporation rate, C- is a factor that incorporates the effect of the wind speed, barometric pressure and other variables such as exposure. is the saturation water vapor pressure at the SST. ew is the vapor pressure of the air  eAnother studies showed the formula a

E = 0.771(1.465 − 0.0186 B )(0.44 + 0.11w)(ew − ea ))Rohwer, 1931(

.where w is the wind speed and B the barometric pressure

Part II Dead sea climate change Yearly pan evaporation at Sdom

)Mean evaporation (cm

Mean evaporation per month at Sdom

month

Explanation to the increase in pan evaporation  As we can see, the increase in pan evaporation is a

solid fact, but why it happens?  The reason for that change derived from the decreasing area of the dead sea weakening of the its breeze decrease of the RH and increase in the air temperature tending pan evaporation to increase.  This process reach is maxima during the spring when temperature gradient between the lake and land tend to increase.

Other climate variables changing

D model for the dead sea climate 3 change  After we all become convinced in the recent

changes of climate variables in the dead sea, we would like to use a mesoscale model to investigate the further climate changes in the dead sea.  For that reason, a 3 dimensional model based on the MM4 run for 24 hours in the early summer in order to find those implications.

Model boundary conditions  The model assume this physical parameters:

Model boundary conditions  The model contain

47 grid point distributed to 34 points at the Northern basin and 13 points at Southern basin.  The model was run for 3 different sea level condition:

No sea

Present sea

Full sea

model results for climate variables Full sea No sea Present sea full sea’ minus‘ ’present sea ‘

Distribution of the wind vector Present sea

June 1987 12 UTC 17

”Full sea” minus “present sea“

Surface Temperature change A

B

•Temperature interval: 2 Cº in A. 1 Cº In B.

Relative humidity change A

B

 The interval is:

5% in A. 2% in B.  We can see significant decrease at the southern basin.

Sea breeze

ze e e Br

Past breeze interaction

t n o fr

Lake breeze

Br ee ze

fro nt

Sea breeze

present breeze interaction

Lake breeze

summery  Both model and observations agree for climate

change in the dead sea.  The climate change effected by the decreasing area of the dead sea area, which weakening the lake breeze.  The lake breeze that temperate the climate of the dead sea become less affective, due to early penetration of the sea breeze front.  The sea breeze flow down slope in interval of 1300 m and warming adiabatically.

summery  Reducing the temperate component, increase

the temperature and the pan evaporation, and decrease the relative humidity and the wind speed.  Summarize all the information we have about the dead sea climate, lead us to consciousness that the dead sea is tending to fast process of desertification.

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