Radiation energy budgets of the Earth and of the region of the Aegean Sea

The radiation energy budgets are referred to:

a) the inflow of solar radiation (insolation) towards the Earth's atmosphere and surface,

b) the outflow of the Earth's (infrared/ longwave) radiation from the top of the atmosphere to the space and

c) transmission (scattering, convection, diffusion, reflection, evaporation), absorption or re-emission of radiation energy (solar or Earth's) among the surface of the Earth, the atmosphere and the top of the atmosphere.

I had seen that there where radiation energy budgets for the whole planet (e.g. from NASA). However there where very few radiation energy budgets for certain places, at least in a simple image/ figure. Furthermore I couldn't find simplified information about the seasonal variance in radiation energy budgets. It is very important to know the seasonal fluctuations if we want to have a better understanding of a region's climate. The annual average values could be deceiving. For instance, in Larissa (Greece) the average annual temperature is 15,8 ^oC, but through the winter season and the summer season the mean temperature is 6,2 ^oC and 26,3 ^oC correspondingly. Furthermore we have daily fluctuations of the climatic characteristics (weather) which are also very important for the understanding of the climate.

I had the idea to make a figure of the radiation energy budget for the region of the Aegean Sea, like the figure NASA gives for the whole planet (http://science-edu.larc.nasa.gov/energy_budget/pdf/ERB-poster-combined-update-3.2014.pdf). Thus, I managed to make figures of radiation energy budget for the Aegean Sea in an annual base, but also for every season (winter, spring, summer, autumn). I do not know how reliable and scientifically correct is this effort but, for me, regardless all that, it was a chance to learn (and to discover) some things.

In every figure that I submit there is a summary of the most important information that I think someone can export by studying it.

In the end of this work, I present the sources (bibliography) which I used.

There is also an annex where I explain the methodology I used to make all these radiation energy budgets.

How to make a sundial

Several types of sundials exist. In this article guidance is given in order to make two types of sundials:

1. Equatorial sundial, and
2. Analemmatic sundial.

There is also a manual written about how to use the sundials and read the time properly.

The figures you are going to see apply for places in the Northern Hemisphere of the Earth. However, directions will be given in order to apply also for places in the Southern Hemisphere.

Let’s begin…:

Day length and sun’s trajectory over the sky (from an observer on Earth)

                                                                                                          Last updated: April 2020

It all started when I attended a professor’s lecture about the big ecosystems (biomes) on Earth: tundra, tropical rainforests, taiga, savanna, forests of temperate zone, deserts, mediterranean vegetation, and others. It was pointed out how temperature and humidity are crucial factors for the development of these biomes. As for the factor of temperature, various regions of the earth receive different amounts of the sun’s energy around the year. Even at the same region there are seasonal variations of sun’s energy distribution. During the summer the sun is higher in the sky (sun rays fall more vertically) compared to the winter. In the northern hemisphere sun rises from south-east and north-east during winter and summer correspondingly. And sets to the south-west and north-west respectively. In the northern hemisphere (latitudes > 23.5^o) the sun’s trajectory over the sky has south orientation. In the southern hemisphere (latitudes > 23.5^o) the sun’s trajectory over the sky has north orientation. At latitudes close to the equator (< 23.5^o north or south) the sun’s trajectory over the sky has north orientation during some days or months and south orientation during the rest (days or months) of the year. Day length is longer during the summer season and shorter during the winter season. As we approach the poles of the earth, day length has greater variations. For example, at regions on the equator the sun is 12 hours above the horizon, every day, throughout the year. Near the North (or South) Pole, for several months the sun does not set (it is above the horizon) and again for several months over the year the sun is below the horizon!