4-4 Climate physics core model improvement subgroup
While setting development of all the ball air models used as the foundation of a final integrated model as a long-term target, it aims at development and offer of the air model united with the needs of each subgroup (partial integrated model).
It extends so that a middle atmosphere (the stratosphere and mesosphere) may be included on the basis of the air model of a symbiosis first division title, and it improves about the dynamics place and temperature place of the up troposhere-lower stratosphere, and steam distribution especially. Low temperature and steam excessive bias remarkable in this domain exist in the model of the present symbiosis first division title. This solution is an important subject from having the radiation legal force which the clouds or water vapour content near the tropopause cannot disregard, and the water vapour content of the high latitude lower stratosphere of winter-spring being important for generating of the polar stratospheric cloud leading to ozone layer depletion.
Since this affair is considered that expression of an air internal gravity wave with short calculation accuracy of radiation process and perpendicular wavelength is important, it is necessary to it to experiment by changing the perpendicular resolution of a model partly between 100m-1500m, and to investigate the response of the gravity wave simulated, or a temperature place and steam distribution. Now, the experiment of about 20 sets from which horizontal / vertical resolution differs by model top 80 km is conducted on the Earth Simulator.
As an example of an initial result, horizontal resolution shows the situation of the reproducibility of a temperature place when making perpendicular resolution fine with T21 (grid spacing 550 km grade), from the 1500 m grade of having been conventionally used by the middle atmosphere general circulation model to 200 m, though it was coarse in Fig. 6. The numerical value of these figures expresses that the result of a simulation is so good that the value of observational data is pulled and a value becomes small from the result of a simulation.
From this result, by making perpendicular resolution high shows that the low-temperature bias (temperature is low as compared with observation) near the tropopause (50-300 hPa) is improved from the lower stratosphere. With the increase in horizontal resolution, since a big computer resource is needed for the increase in perpendicular resolution, these experiments become possible for the first time using an Earth Simulator.
Fig. 6: East-and-west mean temperature bias in June : (a) perpendicular resolution 1500 m and (b) 500 m and (c) 200 m. (Unit: degree C) |
Horizontal / vertical resolution suitable as an integrated model is due to be discerned, improving a model in cooperation with a symbiosis first division title from now on. I want to cooperate also with the symbiosis third division title about the handling of numerical viscosity (turbulent diffusion) which is the loss process of the gravity wave of a sub grid scale again. In addition, the work which updates the perpendicular coordinate system of an air model from the conventional sigma coordinate system to a sigma-P hybrid coordinate system is also parallel, and it is expected that the reproducibility of the dynamics place near the tropopause will improve by this.