Implementation of Bessel's method for solar eclipses prediction in the WRF-ARW model

Abstract

Abstract. Solar eclipses are predictable astronomical events that abruptly reduce the incoming solar radiation into the Earth's atmosphere, which frequently results in nonnegligible changes in meteorological fields. The meteorological impacts of these events have been analyzed in many studies since the late 1960s. The recent growth in the solar energy industry has greatly increased the interest in providing more detail in the modeling of solar radiation variations in numerical weather prediction (NWP) models for the use in solar resource assessment and forecasting applications. The significant impact of the recent partial and total solar eclipses that occurred in the USA (23 October 2014) and Europe (20 March 2015) on solar power generation have provided additional motivation and interest for including these astronomical events in the current solar parameterizations.Although some studies added solar eclipse episodes within NWP codes in the 1990s and 2000s, they used eclipse parameterizations designed for a particular case study. In contrast to these earlier implementations, this paper documents a new package for the Weather Research and ForecastingAdvanced Research WRF (WRF-ARW) model that can simulate any partial, total or hybrid solar eclipse for the period 1950 to 2050 and is also extensible to a longer period. The algorithm analytically computes the trajectory of the Moon's shadow and the degree of obscuration of the solar disk at each grid point of the domain based on Bessel's method and the Five Millennium Catalog of Solar Eclipses provided by NASA, with a negligible computational time. Then, the incoming radiation is modified accordingly at each grid point of the domain.This contribution is divided in three parts. First, the implementation of Bessel's method is validated for solar eclipses in the period 1950-2050, by comparing the shadow trajectory with values provided by NASA. Latitude and longitude are determined with a bias lower than 5 × 10 −3 degrees (i.e., ∼ 550 m at the Equator) and are slightly overestimated and underestimated, respectively. The second part includes a validation of the simulated global horizontal irradiance (GHI) for four total solar eclipses with measurements from the Baseline Surface Radiation Network (BSRN). The results show an improvement in mean absolute error (MAE) from 77 to 90 % under cloudless skies. Lower agreement between modeled and measured GHI is observed under cloudy conditions because the effect of clouds is not included in the simulations for a better analysis of the eclipse outcomes. Finally, an introductory discussion of eclipse-induced perturbations in the surface meteorological fields (e.g., temperature, wind speed) is provided by comparing the WRF-eclipse outcomes with control simulations.

Transition Zone Radiative Effects in Shortwave Radiation Parameterizations: Case of Weather Research and Forecasting Model

“…The Advanced Research WRF (WRF-ARW) is a state-of-the-art open source mesoscale atmospheric model, developed by National Center for Atmospheric Research (NCAR) for both research and numerical weather prediction purposes (Powers et al, 2017). This model, which is probably the most popular meteorological (it also has a climatic version) model worldwide, has the capability to be used for a wide range of applications, such as real-time numerical weather prediction, data assimilation, parameterized-physics research, regional climate simulations, air quality modeling, atmosphere-ocean coupling, and idealized simulations (Blossey et al, 2013;Doubrawa et al, 2018;Jimenez et al, 2016;Lin et al, 2015;Moeng et al, 2007;Montornès et al, 2016;Wang et al, 2009;Yamaguchi & Feingold, 2012;Zhong et al, 2016). In addition, it can be ran at different domains and offers various options for parameterization of convective processes, turbulent transports, evolution of surface temperature and soil moisture, and soil-air interactions (Ruiz-Arias et al, 2013;Skamarock et al, 2008).…”

Restoring the top-of-atmosphere reflectance during solar eclipses: a proof of concept with the UV absorbing aerosol index measured by TROPOMI

“…5, is plotted against r. Solar limb darkening is most significant at the shortest wavelengths, for which the difference between the hot centre and relatively cooler limb is most pronounced (see also Fig. 5 of Ockenfuß et al, 2020). Figure 6 is a sketch of the lunar disc occulting the solar disc during an annular solar eclipse.…”

“…They showed that the error in the solar irradiance close to total obscuration may become 30 % at 1500 nm and 60 % at 310 nm if solar limb darkening is not taken into account. Emde and Mayer (2007), Kazantzidis et al (2007), and Ockenfuß et al (2020) performed extensive 3-D radiative transfer modelling of total solar eclipses, taking into account solar limb darkening. Their work gives insight into the spectral behaviour of sunlight reaching a ground sensor located in or close to the total Moon shadow and the importance of the various 3-D radiative transfer components.…”

The Total Solar Eclipse of 2017: Meteorological Observations from a Statewide Mesonet and Atmospheric Profiling Systems

“…To further explore the impacts of the 2017 total solar eclipse and for comparison with observations, the WRF Model (Skamarock et al 2008), version 3.7.1, was utilized. This version was specifically adapted for the study of the evolution of the atmosphere during solar eclipses (Montornès et al 2016). A 30-h simulation from 0000 UTC 21 August to 0600 UTC 22 August 2017 was conducted with and without the presence of the eclipse (i.e., without and with solar forcing, respectively).…”