THE WINDS.

  

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year in the opposite direction. They are in real-
ity huge land and sea breezes, caused by the dif-
ference in temperature between the warmer and
colder halves of the year. They occur mainly in
the regions of the trades, and are in reality trade
winds which have been turned out of their course
by the unequal heating of land and water.

During winter, in either hemisphere, the oceans,
being warmer than the land, cause a greater
regularity in the trades; but during summer, the
tropical continents become intensely heated, and
their powerful ascending currents cause the equa-
torial currents to blow toward the heated areas
as surface winds, and thus displace the trades.
The interval between the two monsoons is gener-
ally characterized by calms, suddenly followed by
furious gales, that may blow from any quarter.

250. Monsoon Regions.—There are three well-
marked regions of monsoons—the Indian Ocean,
the Gulf of Guinea, and the Mexican Gulf and
Caribbean Sea. The first is the largest and most
distinctly marked.

Monsoons of the Indian Ocean.—Here the
trades are deflected by the overheating of the
continents of Asia, Africa, and Australia.

    
  
   
  
  
  
   
  
   
  
 
   
   
  
  
  
  
    
 
    
   
   
 
 
   
  
 
 
 
 
 
 
      
         
       
 
 

In the northern hemisphere the north-east trades prevail
with great regularity over the Indian Ocean during the
cooler half of the year: from October to April, but during
the warmer half: from April to October, the heated Asiatic
continent deflects the trades, and the equatorial currents
prevail from the south-west. The same winds also pre-
vail south of the equator, on the western border of the
ocean, along the eastern coast of Africa as far south as
Madagascar.

In the southern hemisphere, in the south-eastern portion
of the ocean, the south-east trade is similarly deflected by
the Australian continent. Here the winds blow south-
east during the southern winter, and north-west during
its summer.

Monsoons of the Gulf of Guinea.—Here the
north-east trades are deflected by the intensely
heated continent of Africa. The south-west sum-
mer monsoon blows over the land as far inland
as the Kong Mountains.

Monsoons of the Mexican Gulf and Caribbean
Sea.—In this region the north-east trade winds
are deflected by the overheating of the Missis-
sippi Valley.. The Northers of Texas, which are
cold winds blowing for a few days at.a time over
the Texan and Mexican plains, may be considered
as connected with the winter monsoons.

Besides the preceding well-marked regions, nearly all
the coasts of the continents in and near the tropics have
small monsoon regions, as, for example, the western coasts

of Mexico, the eastern and western coasts of South Amer-
ica, and the western and northern coasts of Africa,

 

 

   

251, Desert Winds.—The rapid heating and
cooling of deserts make them great disturbers
of the regular system of winds. Currents al-
ternately blow toward and from the heated area.
The latter are intensely hot and dry.

The Etesian Winds During summer the barren
soil of the Desert of Sahara, becoming intensely
heated, causes strong north-east winds to blow
over the Mediterranean Sea. These are called
the Etesian winds, and continue from July to
September; they are strongest during the day-
time.

Hot Desert Winds.—F rom the Sahara a period-
ical wind, called the Harmattan, blows on the south-
west, over the coasts of Guinea; on the north, the
Solano blows over Spain, and the Sirocco blows
over Southern Italy and Sicily. Though some-
what tempered during their passage across the
Mediterranean, these winds dre still exceedingly
hot and oppressive.

From the deserts of Nubia and Arabia in-
tensely hot, dry winds blow in all directions over
the coasts of Arabia, Nubia, Persia, and Syria.
These winds are known under the general name
of the simoom or samiel. From their high tem-
perature and the absence of moisture, they often
cause death from nervous exhaustion.

During the prevalence of the simoom, particles of fine
sand are carried into the atmosphere and obscure the light
of the sun. Becoming intensely heated, these particles,
by their radiation, increase the temperature of the air,

 

 

 

 

 

 

Fig. 86. “Sand Storm in the Desert,

which sometimes rises as high as 120° or 130° Fahr. When
powerful winds prevail, dense clouds of sand are carried
about in the atmosphere, producing the so-called sand
storms. The sand-drifts which are thus formed constantly
change their position.