An analytical model for spatially varying clear-sky CO2 forcing

<p>Instantaneous clear-sky CO2 forcing is known to vary significantly over the globe, but the climate factors which control this are not well understood. Building upon the work of Wilson (2012), we build a first-principles, analytical model for CO2 forcing which requires as input only the temperatures at the surface and roughly 20 hPa, as well as column relative humidity. This model quantitatively captures global variations in clear-sky CO2 forcing, and shows that the meridional forcing gradient is predominantly due to the meridional surface temperature gradient, with modulation by water vapor. In particular, the Simpsonian behavior of water vapor emission implies an upper bound on CO2 forcing (with respect to surface temperature) which is realized in the present day tropics.</p>

Download Full-text

Colour changing material for the estimation of flue gas radiation on the miniature gas turbine surface

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/14644207211045520 ◽

2021 ◽

pp. 146442072110455

Author(s):

Mahalingam Arulprakasajothi ◽

Pegyyem Lokaiah Rupesh ◽

Hitesh Kumar Rana ◽

Kariappan Elangovan

Keyword(s):

Fluid Dynamics ◽

Temperature Gradient ◽

Surface Temperature ◽

Gas Turbine ◽

Turbine Blade ◽

Flue Gas ◽

Dynamics Simulation ◽

Blade Surface ◽

Numerical Validation ◽

Surface Temperature Gradient

The gas turbine is being used in the applications of the aircraft propulsion system and land-based power generating systems more effectively. The manufacturers should optimise the temperature of the gas turbine engine components to enhance the life span of the components. The present research work concentrates on determining the surface temperature gradient on the fabricated turbine blades using a colour changing paint based on temperature attained on the surface. A calibration database has been created, and the surface temperature has been detected based on the available colour contours on the blade surface using human vision. An image processing algorithm has also been proposed for accurate temperature measurement on the blade surface. The obtained surface temperature using colour changing paint multi-colour change 350-8 has been calibrated with the conventional measurement technique IR thermography for experimental validation. A computational fluid dynamics simulation model of the turbine blade has been simulated to predict the surface temperature of blades using analysis systems fluid dynamics for numerical validation. The experimental and numerical validation results have shown a nominal value of error, which proves that the surface temperature gradient can be easily predicted with the help of temperature indicating paint using the proposed algorithm. The study has been extended further to evaluate the amount of emissive power radiated by the flue gas on the turbine blade surface based on the temperature and the wavelength of the colour obtained for the health monitoring of the blade.

Download Full-text

What Controls the Mean East–West Sea Surface Temperature Gradient in the Equatorial Pacific: The Role of Cloud Albedo

Journal of Climate ◽

10.1175/jcli-d-13-00255.1 ◽

2014 ◽

Vol 27 (7) ◽

pp. 2757-2778 ◽

Cited By ~ 29

Author(s):

N. J. Burls ◽

A. V. Fedorov

Keyword(s):

Temperature Gradient ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Walker Circulation ◽

Equatorial Pacific ◽

Sea Surface ◽

Sea Surface Temperature Gradient ◽

The Mean ◽

East West ◽

Surface Temperature Gradient

Abstract The mean east–west sea surface temperature gradient along the equator is a key feature of tropical climate. Tightly coupled to the atmospheric Walker circulation and the oceanic east–west thermocline tilt, it effectively defines tropical climate conditions. In the Pacific, its presence permits the El Niño–Southern Oscillation phenomenon. What determines this temperature gradient within the fully coupled ocean–atmosphere system is therefore a central question in climate dynamics, critical for understanding past and future climates. Using a comprehensive coupled model [Community Earth System Model (CESM)], the authors demonstrate how the meridional gradient in cloud albedo between the tropics and midlatitudes (Δα) sets the mean east–west sea surface temperature gradient in the equatorial Pacific. To change Δα in the numerical experiments, the authors change the optical properties of clouds by modifying the atmospheric water path, but only in the shortwave radiation scheme of the model. When Δα is varied from approximately −0.15 to 0.1, the east–west SST contrast in the equatorial Pacific reduces from 7.5°C to less than 1°C and the Walker circulation nearly collapses. These experiments reveal a near-linear dependence between Δα and the zonal temperature gradient, which generally agrees with results from the Coupled Model Intercomparison Project phase 5 (CMIP5) preindustrial control simulations. The authors explain the close relation between the two variables using an energy balance model incorporating the essential dynamics of the warm pool, cold tongue, and Walker circulation complex.

Download Full-text