Good bye!!Cold tropopause

気候物理コアモデル改良サブグループ

渡辺真吾

?

What’s cold bias?

• JJA Temperature biases

-10 +10

Underestimation of shortwave heating rate?• Shortwave heating rate [K/day] in

the tropics (10S-10N) ; Jan

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UMUM

GSM/JMAGSM/JMA

New radiation codemstrnX (radX)

• Newer release of HITRAN (HIgh-resolution TRANsmission molecular absorption database) HITRAN`92 ⇒ HITRAN`00

• Highly optimized integration scheme for K-distribution method

Improvement in the shortwave heating rate• Shortwave heating rate [K/day] in

the tropics (10S-10N) ; Jan

mstrn8mstrn8

UMUM

GSM/JMAGSM/JMA

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• Temperature profiles in the tropics (10S-10N); January

ERA40ERA40

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mstrnXmstrnX mstrnX_noGWDmstrnX_noGWD

Meridional structure?

• JJA Temperature biases

-10 +10

Moist / Dry biases

• JJA humidity biases [%difference]

-100 +100

Summary #.1

• The cold tropopause has been caused by shortcomings of the previous radiation code.

• Temperature and humidity biases were significantly reduced.

• Some tuning parameters (e.g., GWD) must be re-concerned.

How about lower resolution models?

• JJA Temperature biases

-10 +10

• JJA Temperature biases

-10 +10

Moist / Dry biases

• JJA humidity biases [%difference]

-100 +100

Cloud water distribution

• JJA cloud water [kg/kg]

0 5x10-5

Why cold & moist biases are still significant in T21L40?

• Lower vertical resolution near the tropopause (dZ=~1.5 km)

• Lower horizontal resolution; 5.6• Insufficient GWD?• Physical processes (all parameters

are tuned for T106+full physics)