Cumulus convection parameterization and numerical modelling of moist atmospheres

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:6927377

Renno, N O

A hydrological cycle is explicitly included in a one-dimensional radiative-convective equilibrium model which is coupled to a swamp surface and tested with various cumulus convection schemes: the Moist Convective Adjustment scheme, the Kuo scheme, the GISS Model scheme, the GISS Model II scheme, and the Emanuel scheme. The results show that when the flux of incoming solar radiation is above a critical value-dependent on the choice of the cumulus convection scheme-equilibrium is not possible (a runaway greenhouse occurs). When the atmosphere's relative humidity is kept fixed at climatological values, the runaway greenhouse is inhibited. While the mass flux schemes produce an abrupt runaway greenhouse-which occurs through a finite amplitude instability generated by the interaction of infrared radiation fluxes with detrained water vapor at the level of neutral buoyancy-the other schemes produce a smooth transition to the runaway greenhouse. The author's results show that the Moist Convective Adjustment scheme breaks down when the runaway greenhouse is approached, and that the various cumulus schemes tested produce a decrease in the relative humidity of the middle-upper troposphere when the atmosphere's CO[sub 2] content is doubled. These schemes are not consistent with each other since they not only lead to different critical solar forcing for a runaway greenhouse to occur, but also produce very different water vapor profiles in the equilibrium atmosphere and have different lapse-rate feedbacks. The atmospheric water vapor content and the sensitivity of the equilibrium temperature to changes in the solar forcing, as well as the critical solar forcing in order of the runaway greenhouse to occur, depend crucially on the microphysics of cumulus convection. A physically-based cumulus convection scheme is of crucial importance in climate simulations, and a poor cumulus convection scheme can produce artificial sensitivities in numerical simulations of moist atmospheres.

• Research Organization: Massachusetts Inst. of Tech., Cambridge, MA (United States)
• OSTI ID: 6927377
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540120* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (1990-)
CLIMATE MODELS
CLIMATIC CHANGE
CONVECTION
EARTH ATMOSPHERE
ENERGY TRANSFER
GREENHOUSE EFFECT
HEAT TRANSFER
HEATING
HUMIDITY
HYDROLOGY
MASS TRANSFER
MATHEMATICAL MODELS
METEOROLOGY
ONE-DIMENSIONAL CALCULATIONS
SOLAR HEATING
TROPOSPHERE