Simulated Climatology of a General Circulation Model With a Hydrologic Cycle

To investigate the impacts of anthropogenic global warming on tropical cyclone (TC) activity, climate simulations were conducted under the present, and CO 2 -warmed conditions, using the National Center for Atmospheric Research Community Climate Model version 2. The CO 2 -warmed condition includes doubled atmospheric CO 2 concentration, and about 1 C of tropical sea surface temperature (SST) warming. Simulated TCs were objectively selected from twice daily instantaneous outputs during an eight-year time integration period of each simulation. The changes associated with global warming were examined in terms of the frequency of occurrence, and mean intensity of TCs.The frequency of global TC occurrence remains unchanged in response to the CO 2 -induced warming. Although the hydrologic cycle is generally enhanced in the warmed climate, increased precipitation does not necessarily make a great impact on TC activity. This unchanged global TC frequency seems to coincide with almost neutral variations in the zonally-averaged moist instability in the tropics. However, there is some uncertainty in the model regarding the treatment of physical processes that control moisture distributions in the middle to lower troposphere. On the regional scale, the CO 2 -induced changes in TC occurrence were generally not statistically significant. TC intensities were enhanced over warmed SST regions in the western Pacific, which contribute to the significantly increased mean intensity of global TCs.

Section: Overview Of Ccm2mentioning

confidence: 99%

Implications of Anthropogenic Climate Change for Tropical Cyclone Activity: A Case Study with the NCAR CCM2.

Tsutsui

2002

“…regions from Oort and Chan (1977), values over northern hemisphere by Oort and Peixoto (1974) and the results of numerical experiments of the hemispheric general circulation model by Manabe, et al (1970). North America in general is comparable with the area in this study in terms of the horizontal dimensions and the density of the upper-air network.…”

Section: Kinetic Energy Balance Of the Asian Wintermentioning

confidence: 99%

“…It should be noted that these two regions are of similar magnitude in size, have about the same latitudinal span and have the subtropical jets over their eastern ends. However, the mean quantities for the northern hemisphere from the diagnostic study by Oort and Peixoto (1974) and from numerical experiments by Manabe, et al (1970) in Table 2 are only about 25 % of the values over the continental areas.…”

Section: Kinetic Energy Balance Of the Asian Wintermentioning

confidence: 99%

Energetics of Winter Synoptic Features Over East Asia

Chan

1983

Energetics characteristics over Siberia, Northeastern Asia , China and Japan Sea are studied with two winter's upper air data.The Siberia region, which is frequently occupied by a surface high pressure and an upper anticyclonic flow, shows destruction by cross-isobaric flow and negative dissipation of kinetic energy in the winter mean balance of kinetic energy . The Northeastern Asia and Japan Sea areas, which are frequently occupied by a surface low and an upper cyclonic flow, show generations and dissipations of kinetic energy. From the comparison of the regional balances of kinetic energy, the upper atmosphere over the China and Japan Sea regions together with the adjacent oceanic areas may be considered as the most energetically active area over the northern hemisphere in winter.The studies of kinetic energy budgets for various flow patterns show that with the exception of Siberia, the kinetic energy generation, outflow and dissipation are associated with the cyclonic type flows. Even though the flow patterns over the China and Japan Sea regions are predominantly cyclonic, their kinetic energy budgets show extremely intense transformation in comparison with that of an average cyclonic flow over other regions in this study or over North America.

“…In large-scale models, cumulus convection is essentially subgrid-scale process and the collective effects of the nonresolyable convective process on the grid-scale should be properly represented in terms of the resolvable fields with some closure assumptions. Cumulus parameterization schemes used in large-scale models can be categorized into three groups: the moist convective adjustment scheme (Manabe et al,1965;Betts, 1986;Betts and Miller, 1993), the moisture convergence scheme (Kuo, 1965(Kuo, , 1974Anthes, 1977) and the mass-flux scheme (Arakawa and Schubert, 1974;Tiedtke, 1989;Hack, 1994).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of the GCM-Simulated Large-Scale Structures to Two Cumulus Parameterizations

Baik

Takahashi

1995

To examine the sensitivity of the simulated large-scale structures to the Betts-Miller and the ArakawaSchubert cumulus parameterizations, a series of 6-month integrations are performed using the CCSR/NIES atmospheric general circulation model with a horizontal triangular resolution of 21 and 20 vertical levels. The model results are time-averaged for the last three months, that is, June-July-August mean. Comparisons between the simulations using the Betts-Miller scheme and the Arakawa-Schubert scheme indicate that although the simulated large-scale structures are generally similar to each other, there are some noticeable differences. These include the temperatures in the middle and upper troposphere at mid-latitudes in the northern hemisphere, the location of the maximum convective heating in the tropical deep connective region, the convective heating/cooling in the boundary layer, the precipitation distribution pattern over the tropical western Pacific and the vertical profile of the vertical turbulent heat transport. Sensitivity experiments with different adjustment parameters in the Betts-Miller scheme show that the precipitation distribution pattern over the tropical western Pacific is very sensitive to the adjustment time scale and stability weight as well as the saturation pressure departure. It is also shown that the partition between the convective precipitation and the large-scale precipitation is most sensitive to the saturation pressure departure.