Irradiance is a measure of the power of solar energy received per unit area, typically expressed in watts per square meter (W/m²). It quantifies how much sunlight hits a specific surface, which is important for applications like solar energy generation and climate studies. This measurement can vary based on factors such as time of day, weather conditions, and the angle of the sun. Understanding irradiance helps in optimizing the performance of solar panels and assessing the impact of sunlight on ecosystems and agriculture.