ఱ‫⅔ܨ‬٬ဢ⅚௖ࡽैဥ

2The Air-Sea Interaction‫ނ‬സఱ‫ڠ‬ఱ‫֭ڠ‬ၑ‫شݪࡄڠ‬Masanori Konda
Kyoto University

2.1 ఱ‫͂ܨ‬٬ဢ͈έͻȜΡΨΛ·

Feedback between Ocean and Atmosphereఱ‫ܨ‬٬ဢ‫͈ۼ‬ೄ୪എ̈́෎ȟ‫׋‬൲ၾ͈࢐۟
Heat and momentum exchange between the ocean and atmosphereఱ‫ܨ‬੏۪͈ߐ൲
Atmospheric circulationާࠫ෎Condensation heatஆ෎Ȫ૊อĪ‫ح‬෎ȁ
Latent heat (Evaporation)٬࿂‫أ‬ഽȁ႖‫ݕ‬ȁ

Heatingచၠ‫ڰ‬൲Convective activity

ఱܰ࿅੏۪Large scale circulation٬ષ໓
Ocean winds

٬࿂໓؊ႁWind stress΀·ζϋ࿶௣
Ekman transport໓଼੏۪Wind-driven circulation

Sea surface temperatureCooling଎ġġġ2.1.1 ఱ‫ܨ‬٬ဢ‫͈ۼ‬௖ࡽैဥ͈‫ٽ‬ැ଎ईࣣ௄ࠁ଼ً೾ͥ͢ͅ٬࿂‫أ‬ഽ͈་‫ا‬
Change of the sea surface temperature by throughthe mixed layer processesఱ‫͞ܨ‬٬ဢ̞̹͂̽౷‫ݩ‬ၠఘ͈‫׋‬൲͈΀ΥσΆȜ࡙͉ఊု̥͈ͣ༶ৣ΀ΥσΆȜ̳́ȃজ̹̻̦୆‫̳ͥڰ‬చၠ࠷Ȫ౷ນ̷̥̤ͣ͢12km͈̯͈ࣞ‫ۼ‬ȫ͉́Ȃఊု̥͈ͣ༶ৣ΀ΥσΆȜ̴͉͘٬ဢͬ‫̥ͣ̀͛أ‬Ȃ૊อ෎͞ࡐ෎̱͂̀ఱ‫ͅܨ‬࿶௣̯̳ͦ͘ȃ̷ͦ̽̀͢ͅߐ൲̯̹̯̰ͦ̈́͘͘ΑΉȜσ͈ఱ‫׋͈ܨ‬൲Ȫ໓ȫ̽̀͢ͅȂࣽഽ͉ນ௄ັ߃͈٬ဢ͈‫׋‬൲͜ߐ൲̯͈̳ͦͥ́ȃ٬ဢ͈ນ௄͉ͅ‫أ‬ഽ͞‫؂‬໦͉͕͖֚೰̜́ͥईࣣ௄̦໦ື̱̞̳̦̀͘Ȃईࣣ௄͈କ‫͉أ‬٬ષ໓͞૊อ͈‫ͬޣג‬਋̫̯̀ͣͅ་‫̥̳̱ͣ͘ا‬Ȃఱ‫͂ܨ‬٬ဢ͉΀ΥσΆȜͬ࢐̷̸̱ࣣ̠̭͈۟͂̽̀ͦͦ͢ͅ‫׋‬൲ͬ֋঵̱̞̭̳̀ͥ͂̈́ͤ͘ͅȃ̭͈̠̈́͢௖ࡽैဥ̽̀͢ͅ୆̲̹ఱ‫͂ܨ‬٬ဢ͈ධཤ੏۪̽̀͢ͅ೩֌ഽ̥ͣࣞ֌ഽ̥࢜̽̀ͅఉ̩͈෎̦࿶௣̯̭͉ͦͥ͂Ȃ౷‫̦࢓ܨ͈ݩ‬஠ఘഎͅ‫͈̭̜̥͂ͥ́͞ؤ‬ఱ̧̈́ါ֦͈̜͌͂̾́ͥ͂ࣉ̢̞̳ͣͦ̀͘ȃ٬ષ໓͉၄ၠ΀ΥσΆȜ͈٬ဢ͈͒࿶௣͂Ȃ૊อͥ͢ͅྟഽέρΛ·Αͬ୆̵̲̯̭ͥ͂́Ȃ٬ဢईࣣ௄͈อోͅ‫ܙ‬ဓ̱̞̳̀͘ȃ̷͈ࠫ‫ض‬Ȃठ͍૊อͥ͢ͅఱ‫حܨ‬෎̦୆̲̭ͥ͂ͥ͢ͅέͻȜΡΨΛ·ΏΑΞθ̦֋঵̯̞͈̳ͦ̀ͥ́ȃ૗ș̈́ΑΉȜσ͈٬ဢ෎࿶௣
Oceanic heat transport at various scales

Fig. 2.1.1 Schematic view of the interaction between
ocean and atmosphere

The shortwave solar insolation provides the energy that drives the geophysical fluids including
ocean and atmosphere. In the troposphere (which ranges from the Earth's surface to a height of12km) where we live, radiation energy warms the ocean surface before transferring to the atmospherethrough sensible heat and the latent heat of evaporation. This force drives atmospheric circulations at
various scales. In turn, the wind drives ocean circulation. Wind and evaporative cooling at the sea
surface affect the temperature in the ocean mixed layer, where the temperature and the salinity arealmost uniform. This important feedback system plays a major role in maintaining the geophysical fluid
motion through the exchange of energy between ocean and atmosphere. The calm global climate isattributable to meridional heat transport by oceanic and atmospheric circulation. The oceanic wind
contributes to the mixed layer processes through the input of turbulent energy and also through thedensity flux caused by evaporative cooling. As a result, the feedback system starts again, heating theatmosphere by evaporation at the sea surface.

112.2 ٬࿂‫أ‬ഽ͂٬ષ໓͈ාș་൲

Interannual Variation of Sea Surface Temperature and Ocean Wind
Mean Sea Surface Temperature in Dec. 2002ಿ̞শ‫̹̫̥ͬۼ‬ఱ‫͂ܨ‬٬ဢ͈௖ࡽैဥ͈ࠫ‫ض‬Ȃ࡛ह͈౷‫̤ͅݩ‬̞͉̀କ‫͞أ‬໓͈̤̤̥̈́͘໦ື͉͕͖໹࣑ેఠͅో̱̞̳̀͘ȃ႕̢͊Ȃ٬࿂‫أ‬ഽ͉೩֌ഽ֖͈‫أ‬ഽ̦̩ࣞȂࣞ֌ഽ̈́ͥ̾ͦ̀ͅͅ‫أ‬ഽ̦‫̳̞̦̀̽͘ئ‬ȃ̱̥̱Ȃ̩͢ࡉͥ͂Ȃཤఊ໹ဢ͈൐໐͞ཤఱୌဢ͈̠̈́̓͢ͅȂ൝‫أ‬஌̦ධཤͅ০͛ͅ߹̞̞̀ͥအঊ̦ࡉ̳ͣͦ͘ȃ̭͈̠̈́͢໦ື͉̜ͥ೾ഽȂ٬͈ၠͦ໦ືͬ฽‫̞̱̀͘ד‬̳ȃ֚๔٬࿂‫أ‬ഽ̦̞͈͉ࣞͼϋΡΥΏͺఉോ٬֖́Ȃ̭̭͈ࣞ‫أ‬֖͉౰କίȜσ͂ࡤ̞͊ͦ̀̀Ȃཟօ໓ͥ͢ͅ଑̧‫̽͢ͅض̵࢘ܙ‬̀֋঵̯̞̳ͦ̀͘ȃ෎ఝఊ໹ဢ൐໐͉ͅ႖କ୳͂͊ͦͥ͢೩କ‫أ‬֖̦୤ൽͅ‫̀̽״‬൐ୌͅ‫̳̞͍̀͘װ‬ȃ٬ષ໓௸͈໦ື͜൳အͅඅಭഎ̈́໦ື̱̞̳ͬ̀͘ȃಎ֌ഽ֖́໓௸̦‫͉͈̞ޑ‬Ȃ̭͈֌ഽఝͅ๱ુͅ‫̞ޑ‬೩‫ܨ‬գ͂ࣞ‫ܨ‬գ̦໦ື̱̞̭̀ͥ͂ͬ฽‫̳̞̱̀͘ד‬ȃ̹͘ȂͼϋΡΥΏͺఉോ٬֖͉̈́̓́౷ນັ߃́ఱ‫̦ܨ‬ਓ௵̱̞̹̀ͥ͛ͅȂ໹޳എͅ೩໓௸̞̳̈́̽̀͘ͅȃ

60
45
30
150-15-30
-45
-60
45
0

390
69180

1215-135
18-90
21-45

24

27

30

33 [qC]

1820 [m/s]Mean Sea Surface Wind in Dec. 2002

The sea surface temperature (SST) and the wind field over the oceans arealmost in a steady state due to the persistent air-sea global-interaction

60system. For example, SST is generally high at low latitudes, and low at

45

middle and high latitudes. However, careful inspection of SST distribution

135

30

demonstrates that some contours are not parallel to the latitude, such as in
the northeast Pacific and the north Atlantic. This meridional inclination of the15SST distribution should reflect to some extent the ocean currents. We see0the highest SST in the Indonesian archipelago, known as the 㵰warm water-15

pool,㵱 which is maintained by the Trade wind. In contrast, we also see a low-30

SST along the equator in the eastern tropical Pacific known as 㵰the cold-45

tongue.㵱 The map of the ocean wind in the figures demonstrates the typical
distribution in the boreal winter. The high wind speed in the mid latitudes-60

should reflect the marked stationary high and low pressures. The wind speed
is low over the Indonesian archipelago and the other notable atmospheric

4502904135
6180
810-135
12-90
14-45
16

convergence zones.
Land surface Data missing଎ġġġ2.2.1 AMSR-Eͥ͢ͅ2002ා12࠮͈࠮໹޳٬࿂‫أ‬ഽȪષ౲ȫ͂٬ષ໓௸Ȫ‫ئ‬౲ȫ͈஠‫ݩ‬໦ື
Fig. 2.2.1 Global distribution of monthly averaged SST and wind speed in December 2002 as observed by AMSR-E

12

7.3
Mean Sea Surface Temperature in Dec. 2003ఈ༷Ȃఱ‫͂ܨ‬٬ဢ̷͉͈௖ࡽैဥ̽̀͢ͅુͅ་൲̱̞̳̀͘ȃ٬ဢນ࿂͈କ‫أ‬໦ື͜ΈυȜΨσ̈́ΑΉȜσ́་‫̳̞̱̀͘ا‬ḁ̑̈́́͜΀σΣȜΣο࡛ય͉෎ఝఊ໹ဢ஠ఘ͈କ‫أ‬་‫ฺ̠ͬا‬ఱܰ࿅̈́་൲࡛ય̜́ͤȂఱ‫͂ܨ‬٬ဢ͈௖ࡽैဥ̦๱ુͅਹါ̈́൱̧̱ͬ
̞̭̦̀ͥ͂౶̞̳ͣͦ̀͘ȃ2002ා͉΀σΣȜΣο̦อ୆̱Ȃ̷͈ൃ͉ͅडେ‫̢̹̱ࠞͬ͘ܢ‬ȃ΀σΣȜΣο̦อ୆̱̥̹̈́̽2003
ා͈٬࿂‫أ‬ഽ໦ື͂๤‫̳͂ͥڛ‬Ȃ2002ා͉ྶ̥ͣͅ႖କ୳̦ࢃప̱
̞̀̀Ȃ൐໐́٬࿂‫أ‬ഽ̦̞̞̭̦̾ͤࣞ͂͜͢໦̥̳ͤ͘ȃ฽చͅୌ໐͉́٬࿂‫أ‬ഽ̦2003ාͅ๤͓̀೩̩̞̳̈́̽̀͘ȃฺ̭ͦ̽̀ͅȂ೩໓௸֖̦2002ා͉́൐໐ͅ֊൲̱̞̀ͥ߹̦࢜ࡉ̳ͣͦ͘ȃ̭͉ͦȂକ‫̞͈ࣞأ‬ႀ֖̦൐༷࢜ͅ֊൲̳̹ͥ͛ͅ෎ఝ֖͈ఱ‫͈ܨ‬ਓ௵ఝ͈ાਫ਼̦་֊̱̞̭̀ͥ͂ͬা̱̞̳̀͘ȃ

60
45
30
150-15-30-45-60
45
0390
6135
91801215-135
18-90
21-45

24273033 [qC]

Mean Sea Surface Wind in Dec. 2003

On the other hand, air-sea interaction changes both the ocean and the60

atmosphere. One of the most notable large-scale variations of the SST is the45

El Niño, which cause the SST over the equatorial Pacific to changeinterannually. The close air-sea interaction plays an important role in this30

phenomenon. El Niño began developing in spring of 2002, and reached its
15

mature phase in winter. A comparison of SST in 2002 with those in 2003,

0when El Niño did not occur, reveals a warmer SST in the eastern Pacific with-15

a suppressed 㵰cold tongue㵱 and lower SST in the western Pacific in 2002.

-30

Simultaneously, the region with low wind, representing the atmospheric
convergence at the surface level, moved eastward in 2002. This indicated a-45

strong air-sea coupling, and it shifted both the anomalously high SST and-60

the atmospheric convergence zone to the east.
45
0

290
4

135
6180
8

10-135
12-90
14-45
16

18

20 [m/s]

Land surface Data missing଎ġġġ2.2.2 AMSR-Eͥ͢ͅ2003ා12࠮͈࠮໹޳٬࿂‫أ‬ഽȪષ౲ȫ͂٬ષ໓௸Ȫ‫ئ‬౲ȫ͈஠‫ݩ‬໦ື
Fig. 2.2.2 Global distribution of monthly averaged SST and wind speed in December 2003 as observed by AMSR-E13

2.3 έυςΘ٬ၠĮι΅Ώ΋სၠ֖͈́ཛྷఱ̈́෎༶੄
Large Heat Release over the Florida Current and the Gulf StreamέυςΘ٬ၠࣱ͉ಲ͂൳̲̠͢ͅఱဢ͈ୌ‫ͅ܅‬୪̱̀ၠͦͥ‫̞ޑ‬٬ၠ́ୌ‫ٮޏ܅‬ၠ͂ࡤ͊ͦȂ೩֌ഽ̥ͣಎ֌ഽ͈͒ఱၾ͈෎ͬ࿶௣̳ͥ࿨‫ͬڬ‬౜̞̳̽̀͘ȃι΅Ώ΋სၠ̷͉͈௽ၠ̳́ȃ٬ၠષ́٬࿂‫أ‬ഽ̦ਔս̩ͤࣞ͢͜Ȃஆ෎έρΛ·Α̦අͅఱ̧̞̭̦͂໦̥̳ͤ͘ȃ̭͉ͦȂ‫أ‬ഽ̦̩ࣞ̈́ͥ͂ఱ‫ܨ‬ಎͅ‫̧͈̭͚ͥ́͂܄‬କ૊‫ܨ‬ၾ̦‫ࠣͅݢ‬ఉ̩̈́ͤȂ૊อ̦ͤ͢‫ڰ‬อ̥̳̈́ͥͣ́ͅȃ႕̢͊Ȃ
500W/m2͈ஆ෎έρΛ·Α͉କ‫̦֚أ‬ώ࠮‫ͅۼ‬ນ࿂̥ͣ100ḿ͘
࿩3ɋC͜‫̬ͥͦͣئ‬ၾͅ௖൚̷̳̭̥͈ͥ͂ͣ͜෎༶੄ၾ̦ཛྷఱ́
̜̭̦ͥ͂໦̥̳ͤ͘ȃ༷֚Ȃ٬࿂‫أ‬ഽͅࡐಠͅࡉͣͦͥ‫أ‬ഽஜ஌͂٬ષ໓͈໦ື̥ͣȂ̭͈٬֖́අͅఱ̧̈́૊อ̦̭̞͈͉ܳ̽̀ͥ೩֌ഽ̥ͣ‫̀ͦ͊׋‬̩ͥࣞକ‫͈أ‬କ͂ൃ‫̞ޑ͈ܬ‬٬ષ໓͈‫̳̥̦̭̜ͤͩ͂ͥ́͘ޣג‬ȃ( a ) AMSR-E Sea Surface Temperature on Dec. 03, 2003

( b ) AMSR-E Sea Surface Wind on Dec. 03, 2003

38383636343432323030282826

26-84-80-76-72

14-68-64-84

34 [qC]

24-80-76

0-72

-68

-64

20 [m/s]10( c ) AMSR-E Latent Heat Flux on Dec. 03, 2003

The Florida Current is a strong western boundary current similar to theKuroshio, and the Gulf Stream is its extension. The figure shows an area of
extremely large latent heat flux just over the warm current. The rapid
increase of evaporation over the warm SST is attributable to the nonlinear

3836increase of water vapor capacity in the atmosphere, proportional to thetemperature. A cooling of 500W/m2 in latent heat flux would decrease the34

temperature of the ocean from the surface to a depth of 100m by 3qC in one
month, indicating the magnitude of the thermal effect of the strong meridional
flow.

32
30

On the other hand, the strong temperature front and the strong wind
prevailing in this region indicate that the warm water carried by the strong
meridional current and the strong wind in the winter both contribute to the2826

significant levels of latent heat flux.
-84

0-80-76-72

500-68-641000 [W/m2]
Land surface Data missing଎ġġġ2.3.1 AMSR-Eͥ͢ͅ2003ා12࠮3඾͈ͺις΃൐‫̫̤֖ͥͅ܅‬Ȫaȫ٬࿂‫أ‬ഽȂȪbȫ٬ષ໓௸ȂȪcȫஆ෎έρΛ·Α͈໦ືFig. 2.3.1ȁSnapshots from AMSR-E on the east coast of America on December 3, 2003 depicting (a) SST, (b) wind speed, and (c) latent heat flux

14

2.4 ൃ‫͈ܬ‬൐Ώ΢٬͈૊อၾ͈་‫ا‬Gradual Increase of Evaporation in the East China Sea in Winter( a ) AMSR-E Latent Heat Flux on Dec. 20, 2003

( b ) AMSR-E Sea Surface Temperature on Dec. 20, 2003

( c ) AMSR-E Sea Surface Wind on Dec. 20, 2003

( d ) AMSR-E Water Vapor Pressure on Dec. 20, 2003

3838383836363636343434343232

323230303030282828282626262624242424222222220350

700 [W/m2] 8

1930 [qC]010

20 [m/s]01530 [hPa]଎ġġġ2.4.1ȁAMSR-Eͥ͢ͅ2003ා12࠮20඾͈൐Ώ΢٬̤̫ͥͅȪaȫஆ෎έρΛ·ΑȂȪbȫ٬࿂‫أ‬ഽȂȪcȫ٬ષ໓௸ȂȪdȫ٬ષକ૊‫ܨ‬գ͈໦ືȪaȫࣱ͈࿦֣͉ȂQuikSCAT൏शSeaWindsͥ͢ͅ൳඾͈٬ષ໓α·ΠσȃFig. 2.4.1ȁSnapshots from AMSR-E in the East China Sea on December 20, 2003 depicting (a) latent heat flux, (b) SST, (c) wind speed, and (d) water vapor pressure.
Black arrows in (a) indicate wind vector in the same day observed by SeaWinds on QuikSCAT.

ൃ‫͈ܢ‬඾ུਔ༏֖͉́Ȃఱၘ̥͈ͣ႖̹̩‫͈ܨߗ̹̞ۋ‬଑̧੄̱͂Ȃ̷ͦͥ͢ͅ٬ષ͈‫ڰ‬อ̈́૊อ̦අಭഎ̳́ȃ̭̦͂ͧȂ૊อ͉ౙͅ‫̹̞ۋ‬໓̦଑̞̹̺̫͉́‫ڰ‬อ̵̭ܳͤͭ͘ͅȃఱၘ̥ͣ଑̧੄̳‫͉ܨߗ̹̞ۋ‬Ȃ̴͘Ȃ౰̥̞٬କ̽̀͢ͅ੭șͅ‫ͬأܨ‬ષઌ̵̯̥̀ͣ੝͛̀บอഎ̈́૊อ̧̭̱̳ͬ֨ܳ͘ȃ2003ා͈12࠮20඾͈۷௶ΟȜΗ̥͉ͣȂఱၘ̥͈ͣ‫̞ޑ‬଑̧੄̱̦൐Ώ΢٬஠ఘ́‫̴̥̥̞ͣͩ͜ͅޑ‬Ȃ600W/m2͈͜૊อ̦̭͈͉ܳͥ߇ਗධ༷̜̭̦́ͥ͂໦̥̳ͤ͘ȃ̹͘Ȃ٬࿂͈କ૊‫ܨ‬գ͈໦ື̥͉ͣȂ‫ߗ̹̞ۋ‬‫̦ܨ‬૊อ̽̀͢ͅ੭șͅ‫ح‬෎̯ͦ̀৔ഽͬષ̬̞̩̀အঊ̧̦͉̽ͤ͂ࡉ̳ͣͦ͘ȃThe strong blowout of the cold, dry atmosphere from the continent is a typical phenomenon in thewinter near Japan, and it causes strong evaporation downstream. However, the dry atmosphere itself
is not enough to cause active evaporation. Before it is able to cool the sea surface by evaporation,
the cold, dry atmosphere must first be warmed by the sea surface, becoming a warm, dry
atmosphere that can contain a large amount of water vapor. It is obvious from the December 20,
2003 data that maximum evaporation occurs south of Kyushu, even though the strong blowout isprevailing over the East China Sea. The distribution of water vapor near the sea surface clearly
demonstrates that the humidity of the atmosphere increases in proportion to the enhanced
evaporation in the downstream winds.

15