3.1 Temporal and zonal mean structure

In this subsection, we show the vertical profiles of radiative cooling rate and condensation heating rate at the equator and the latitudinal distributions of rainfall intensity obtained by the experiment with Kuo scheme.

Vertical profiles of radiative cooling and condensation heating

The temporal and zonal mean vertical profiles of radiative cooling and condensation heating at the equator of the cases with Kuo scheme are shown in the left and the right panel of Fig.3.1, respectively. When the smaller value of band absorption coefficient of the dry air is adopted, radiative cooling rate in the upper troposphere increases, and correspondingly the peak of condensation heating is located at the higher levels in the troposphere, as was expected.

We call case kuo-a (red lines in Fig.3.1), in which the condensation heating takes maximum in the lower troposphere, as "lower-level cooling experiment",, and case kuo-c (blue lines in Fig.3.1), in which the condensation heating takes maximum in the upper troposphere as "upper-level cooling experiment", and compare them in detail in the later subsections. In case kuo-d (light blue lines in Fig.3.1), the condensation heating is more enhanced in the upper levels than in kuo-c. However, we do not select this case kuo-d to be compared with case kuo-a, because the structure of the mean meridional circulation in kuo-d is too much different from that in case kuo-a, as is implied in the difference in the latitudinal distributions of zonal mean precipitation in these cases (Fig.3.3).

Fig.3.1: Temporal and zonal mean vertical profiles of radiative cooling rate (left panel) and condensation heating rate (right panel) at the equator, averaged from 1000 day to 1700 day of the experiment with Kuo scheme. Unit is [K s-1]. The band absorption coefficient of dry air is the largest for case kuo-a (red), is gradually decreased for cases kuo-con (black), kuo-b (yellowish green), kuo-c (blue), and is the smallest for kuo-d (light blue).

Zonal wind at the equator

The vertical profiles of the zonal and temporal mean zonal wind at the equator of the cases with Kuo scheme are compared in Fig.3.2. In the lower level cooling experiment (kuo-a), easterly wind strengthens from the lowest level to the middle troposphere. Wind speed reaches about 5 [m s-1] at the height of 2 [km] (σ=0.8) which is about the lower level of condensation layer of the atmosphere. In the upper level cooling experiment (kuo-c), on the other hand, zonal wind remains weak from the lowest level to the middle troposphere.

Fig.3.2: Temporal and zonal mean vertical profiles of zonal mean wind at the equator, averaged from 1000 day to 1700 day of the experiment with Kuo scheme. Unit is [m s-1]. Line colors indicate the same cases as Fig.3.1.

Precipitation

The latitudinal distributions of zonal and temporal mean precipitation of the experiment with Kuo scheme is shown in Fig.3.3. Except for case kuo-d, so-called "double ITCZ" structure is observed; two maxima of precipitation are located at around 7 degree north and south, and precipitation takes mimimum value at the equator. Case kuo-d, on the other hand, is characterized by the "single ITCZ" structure; precipitation takes a single maximum at the equator. Other aspects of general circulation for kuo-d, e.g., low latidude meridional circulation, the distribution of zonal mean zonal wind, etc., also differ from those for the other cases (the details are not presented here).

Fig.3.3: Temporally and zonal mean latitudinal distribution of precipitation, averaged from 1000 day to 1700 day of the experiment with Kuo scheme. Unit is [Kg m-2 s-1]. Line colors indicate the same cases as Fig.3.1.