# 1:1.2.2 Solar Radiation under Cloudless Skies When solar radiation enters the earth's atmosphere, a portion of the energy is removed by scattering and adsorption. The amount of energy lost is a function of the transmittance of the atmosphere, the composition and concentration of the constituents of air at the location, the path length the radiation travels through the air column, and the radiation wavelength. Due to the complexity of the process and the detail of the information required to accurately predict the amount of radiant energy lost while passing through the atmosphere, SWAT+ makes a broad assumption that roughly 20% of the extraterrestrial radiation is lost while passing through the atmosphere under cloudless skies. Using this assumption, the maximum possible solar radiation, $$H\_{MX}$$, at a particular location on the earth's surface is calculated as: $$H\_{MX} = 30.0E\_0\[{\omega T\_{SR} }\sin\delta \sin\phi+\cos\delta\cos\phi\sin(\omega T\_{SR})]$$ 1:1.2.7 where the maximum possible solar radiation, $$H\_{MX}$$, is the amount of radiation reaching the earth's surface under a clear sky ($$MJ m^{-2} d^{-1}$$). --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://swatplus.gitbook.io/io-docs/theoretical-documentation/section-1-climate/untitled/solar-radiation/1-1.2.2-solar-radiation-under-cloudless-skies.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.