Solar constant

About: Solar constant is a research topic. Over the lifetime, 967 publications have been published within this topic receiving 29647 citations.

A Comprehensive Global Model of Broadband Direct Solar Radiation for Solar Cell Simulation

Abstract: For any system that uses solar cells as either the primary or secondary power source, estimation of broadband direct solar radiation is n ecessary for simulation of the output power of the solar cells and the consequent performance of the system. This paper provides a comprehensive semi-physical and semi-empirical model of broadband direct solar radiation that includes the effects of the time of day, date of year, aerosol, global monthly precipitable water, operating altitude, operating l atitude, operating longitude, and solar array surface angles. This model is executed for fi ve cities in the United States and the results are compared with the corresponding recorded data. Nomenclature n d = day number of the year, ranging from 1 on Januar y 1 to 365 on December 31 0 E = eccentricity correction factor of the earth’s or bit t E = equation of time, hour I = intensity of solar radiation on arbitrarily orie nted planes, 2 W/m n I 0 = intensity of the extraterrestrial normal solar r adiation, 2 W/m SC I = extraterrestrial normal solar radiation constant , 2 W/m e L = local longitude, degree s L = longitude of the standard meridian for the local time zone, degree m = optical air mass act m = actual optical mass v act m , = actual optical mass in the vertical direction r

ACRIM total solar irradiance satellite composite validation versus TSI proxy models

Abstract: The satellite total solar irradiance (TSI) database provides a valuable record for investigating models of solar variation used to interpret climate changes. The 35-year ACRIM TSI satellite composite was updated using corrections to ACRIMSAT/ACRIM3 results derived from recent testing at the Laboratory for Atmospheric and Space Physics/Total solar irradiance Radiometer Facility (LASP/TRF). The corrections lower the ACRIM3 scale by ~5000 ppm, in close agreement with the scale of SORCE/TIM results (solar constant ~1361 W/m^2). Relative variations and trends are not changed. Differences between the ACRIM and PMOD TSI composites, e.g. the decadal trending during solar cycles 21-22, are tested against a set of solar proxy models, including analysis of Nimbus7/ERB and ERBS/ERBE results available to bridge the ACRIM Gap (1989-1992). Our findings confirm: (1) The validity of the TSI peak in the originally published ERB results in early 1979 during solar cycle 21; (2) The correctness of originally published ACRIM1 results during the SMM spin mode (1981-1984); (3) The upward trend of originally published ERB results during the ACRIM Gap; (4) The occurrence of a significant upward TSI trend between the minima of solar cycles 21 and 22 and (5) a decreasing trend during solar cycles 22-23. Our findings do not support: (1) The downward corrections to originally published ERB and ACRIM1 results during solar cycle 21; (2) A step function sensitivity change in ERB results at the end-of-September 1989; (3) the validity of ERBE's downward trend during the ACRIM Gap or (4) the use of ERBE results to bridge the ACRIM Gap. Our analysis provides a first order validation of the ACRIM TSI composite approach and its 0.037%/decade upward trend during solar cycles 21-22. Thus, solar forcing of climate change may be a significantly larger factor than represented in the CMIP5 general circulation climate models.

Solar Radiant Energy and its Modification by the Earth and its Atmosphere

Abstract: The sun is the principal source of the energy which, by devious means, becomes the internal, potential, and kinetic energy of the atmosphere. The solar irradiation of a unit horizontal surface at the outer limits of the earth’s atmosphere can be evaluated, at least in relative units, from astronomical and trigonometrical considerations [61]; thus on a relative scale, the diurnal and seasonal variations of this solar irradiation above the atmosphere are known. On the average, variations similar to these occur also at the earth’s surface, and the associated diurnal and seasonal changes in atmospheric temperature are commonplace knowledge [52].

Alternate approach to the analysis of solar photometer data.

Abstract: The standard technique of analyzing solar photometer data to determine atmospheric optical depth and the spectral solar constant is shown to inadvertently weight the data unequally. A new approach is proposed which equally weights all the data. Assuming that the deviations of the data points result from real random variations of optical depth during the period of the measurements, this latter approach is shown to yield more reliable results.

A suite of user-friendly global climate models: Hysteresis experiments

Abstract: A hierarchy of global spectral circulation models is introduced ranging from the shallow-water system via the primitive-equation dynamical core of the atmosphere to the Planet Simulator as a Global Climate Model (GCM) of Intermediate Complexity (MIC) which can be used to run climate and paleo-climate simulations for time scales up to ten thousand years or more in an acceptable real time. The priorities in development are set to speed, easy handling and portability with a modular structure suitable for problem-dependent configuration. Adaptions exist for the planetary atmospheres of Mars and of Saturn’s moon Titan and are being extended. Common coupling interfaces enable the addition of ocean, ice, vegetation models and more. An interactive mode with a Model Starter and a Graphical User Interface (GUI) is available to select a configuration from the available model suite, to set its parameters and inspect atmospheric fields while changing the models’ parameters on the fly. This is especially useful for teaching, debugging and tuning of parameterizations. An updated overview of the model suite’s features is presented based on the Earth-like climate model Planet Simulator with mixed-layer ocean introducing static and memory hysteresis in terms of a parameter sweep of the solar constant and CO2 concentrations. The static hysteresis experiment demonstrates that the solar constant varying by 20% reveals warm and snowball Earth climate regimes depending on the history of the system. This hysteresis subjected to a thermodynamic analysis shows the following features: i) Both climate regimes are characterized by global mean surface temperature and entropy growing with increasing solar constant. ii) The climate system’s efficiency decreases (increases) with increasing solar constant in present-day warm (snowball) climate conditions. iii) Climate transitions near bifurcation points are characterized by high efficiency associated with the system’s large distance from the stable regime. Memory hysteresis evolves when changing the direct atmospheric radiative forcing which, associated with a well-mixed CO2 concentration, modifies the planetary thermodynamic state, and hence the surface temperature. The hysteresis effected by different CO2 change rates is analysed: i) The response is due to infrared cooling (for constant temperature lapse-rate) which, in turn, is related to the surface temperature through the Stefan-Boltzmann law in a ratio proportional to the new infrared opacity. Subsequent indirect effects, that are water-vapour-greenhouse and ice-albedo feedbacks, enhance the response. ii) Different rates of CO2 variation may lead to similar transient climates characterized by the same global mean surface temperature but different values of CO2 concentration. iii) Far from the bifurcation points, the model’s climate depends on the history of the radiative forcing thus displaying a hysteresis cycle that is neither static nor dynamical, but is related to the memory response of the model determined by the mixed-layer depth of the ocean. Results are supported by a zero-dimensional energy balance model.