Insolation variation

Much of the variation in these time series for the past 700 kyr can be described by a combination of a 100 kyr cycle plus additional cycles with periods of 20 and 40 kyr. This result immediately suggests that the ice-age cycles are caused by variations in the amount and seasonality of solar radiation reaching the Earth (insolation), because the 20, 40, and 100 kyr periods of climate history match the periods of cyclic variations in Earth s orbit and axial tilt, line hypothesis that these factors control climate was proposed by Milutin Milankovitch in the early part of the 20th century and is widely known as "Milankovitch Theory." It is now generally accepted that the Milankovitch variations are the root cause of the important 20 and 40 kyr climate cycles. The 100 kyr cycle, however, proves to be a puzzle. The magnitude of the insolation variation at this periodicity is relatively trivial, but the 100 kyr cycle dominates the climate history of the last 700 kyr. Further,... 

I Serbian astronomer Milutin Milankovitch developed the astronomical hypothesis in 1938 by observing that glacial and interglacial periods were related to insolation variations caused by small cycles in the Earth s axial rotation and orbit about the Sun. 

Tilt variations also do not affect the annual total of solar energy received by the whole Earth, but do change the annual total for polar regions (simultaneously for both hemispheres). Tilt also affects the seasonal insolation at high latitudes, with greater tilt leading to warmer summers and cooler winters in both hemispheres. 

Eccentricity variations change the average Earth-sun distance such that annual insolation changes by approximately 0.2%, or 0.5 W/m at the Earth s surface (Crowley and North, 1991). This is small compared to the 10% seasonal changes associated with the other Milankovitch cycles. That a 100 kyr periodicity characterizes both the eccentricity and the glacial-interglacial... 

Over the past 220 000 years methane concentrations ranged between 350 and 750ppbv, compared to modem values in excess of 1700-1800 (Fig. 18-15). Over tens of millennia, methane variations appear to correspond to northern hemisphere insolation changes, correlate with Vostok paleotemperatures (Chappel-... 

Fig. 7-1. The annual average insolation and average zenith angle as a function of the sine of latitude. The zenith angle has been multiplied by a factor of 10 so that its variation can be seen. The sine of latitude is used as the ordinate in all of these plots because it reflects the relative surface area at each latitude.

Seasonal variation of insolation and zenith angle from subroutine SEASON... 

SEASON Program SEASON calculates seasonal variation of daily insolation from formulas in Sellers and Berger, 1978. Uses approximate expression for true anomaly... 

Seasonal variation of insolation and zenith angle from subroutine SEASON This program uses the new solver GAUSSD and SLOPERD All ice is suppressed in SHALBEDO nrow = 18 the number of equations and unknowns ncol = nrow + 1... 

Berger, A. L. 1978. Long-term variations of daily insolation and quaternary climate changes. J. Atmospheric Sci. 35, 2362-67. 

Latitudinal variations in insolation caused by differenoes in the angle at which the sun s radiation strikes Earth s surface. Source-. From Thurman, H. V. (1988). Introductory Oceanography, 5th ed. Merrill Publishing Company, p. 170. 

The latitudinal heat gradient in the atmosphere and ocean remains relatively constant over time despite the short-term and spatial variations in insolation. This steady state is maintained by the net transport of heat from low to high latitudes where it is radiated back into space. Atmospheric currents (winds) are responsible for about half of this meridional net transport of heat. The rest is accomplished by water movement in the... 

A careful examination of the curve shown in Fig. 3.49 shows a periodicity of approximately 100,000 years. Hays et al. (1976) argued that the main structure of the oxygen isotope record is caused by variations in solar insolation, promoted by... 

Nature-induced RF for the last century due to SC changes (including an indirect impact on the ozone layer) can be assumed to be 0.4 0.2Wm"2. Since total RF constitutes only about 1W m 2, the contribution of variations in extra-atmospheric insolation could play a substantial role. 

Inclination of the rotation axis with respect to the orbital plane (fluctuating within 22°-24.5°, with the present-day value 23.4° the average periodicity of variation constitutes 41,000 years and mainly affects high-latitude insolation). 

Insolation (the solar energy received by an area of 1 m2) varies with the geographic location, weather, orientation of the collectors, and with diurnal and seasonal weather variations. Solar power plants have been built on all five continents, mostly in the high-insolation areas near the equator. There are also plans to collect solar energy on artificial islands in the oceans and in other locations including space stations and solar satellites. 

The thermal solar farm operation will be optimum if it efficiently responds to both the variation in solar energy availability (insolation) and to both equipment limitations and market conditions. In order to do that, one of the first requirements is to determine the efficiency curves for each combination of equipment blocks as a function of load and then operate the system at that point. 

---