Latitude land distribution

Significant economies of computation are possible in systems that consist of a one-dimensional chain of identical reservoirs. Chapter 7 describes such a system in which there is just one dependent variable. An illustrative example is the climate system and the calculation of zonally averaged temperature as a function of latitude in an energy balance climate model. In such a model, the surface temperature depends on the balance among solar radiation absorbed, planetary radiation emitted to space, and the transport of energy between latitudes. I present routines that calculate the absorption and reflection of incident solar radiation and the emission of long-wave planetary radiation. I show how much of the computational work can be avoided in a system like this because each reservoir is coupled only to its adjacent reservoirs. I use the simulation to explore the sensitivity of seasonally varying temperatures to such aspects of the climate system as snow and ice cover, cloud cover, amount of carbon dioxide in the atmosphere, and land distribution. 

The Miocene land distribution is compared with the present land distribution in Figure 7-24. There has been an increase in land fraction at the South Pole since the Miocene, a decrease in middle latitudes in the South-... 

The net terrestrial sink of —0.7 Pg C yr is not evenly distributed either. The comparison by Gurney et al. (2002) showed net terrestrial sinks of 2.4 0.8 PgC yr and 0.2PgCyr for northern and southern mid-latitude lands, respectively, offset to some degree by a net tropical land source of 1.2 1.2PgCyr Errors are larger for the tropics than the nontropics because of the lack of sampling stations and the more complex atmospheric circulation there. 

Fig. 7-4. Specified distributions of land fraction, land cloud cover, and ocean cloud cover as functions of the sine of latitude. Also plotted is the albedo calculated for these values of land and cloud and for the temperatures of Figure 7-6. Negative values of SIN(LATITUDE) correspond to the Southern Hemisphere.

The differences between the hemispheres are largely the result of different distributions of land as a function of latitude. 

The observed distribution of atmospheric C02 and oxygen/nitrogen ratios show that the land sink of carbon prevails in northern and middle latitudes over the ocean sink. In tropical latitudes, considerable emissions of C02 to the atmosphere as a result of the Earth s resources being exploited can be observed. 

Particle emissions resulting from natural processes should be roughly distributed according to the relative amounts of land and ocean areas in various latitudinal bands. Assuming this, natural amissions are estimated to be a function of latitude, based on the amount of land and water distributed in various latitude zones. When this is done for the northern hemisphere and compared with an estimated zonal distribution of pollutants based on Figure 3, the relative contribution of pollutant sources to atmospheric aerosol concentrations as a function of latitude is estimated. 

Ozone loss over the Arctic has been less dramatic than that over the Antarctic, mainly because the different distribution of land and sea in the Northern Hemisphere allows for only a weak vortex over the Arctic. There is more mixing of air with that from lower latitudes and temperatures do not become low enough for routine formation of polar stratospheric clouds. In years when the Arctic has been cold enough for cloud formation similar ozone destruction has been observed, but for less prolonged periods than over Antarctica. Trends in ozone over the rest of the globe have been small compared to those of the Antarctic, or even Arctic, and are quantified in section 2.4.1. 

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