A high-performance atmospheric radiation package: With applications to the radiative energy budgets of giant planets

Abstract

A High-performance Atmospheric Radiation Package (HARP) is developed for studying multiplescattering planetary atmospheres. HARP is an open-source program written in C++ that utilizes high-level data structure and parallel-computing algorithms. It is generic in three aspects. First, the construction of the model atmospheric profile is generic. The program can either take in an atmospheric profile or construct an adiabatic thermal and compositional profile, taking into account the clouds and latent heat release due to condensation. Second, the calculation of opacity is generic, based on line-by-line molecular transitions and tabulated continuum data, along with a table of correlated-k opacity provided as an option to speed up the calculation of energy fluxes. Third, the selection of the solver for the radiative transfer equation is generic.The solver is not hardwired in the program. Instead, based on the purpose, a variety of radiative transfer solvers can be chosen to couple with the atmosphere model and the opacity model.We use the program to investigate the radiative heating and cooling rates of all four giant planets in the Solar System. Our Jupiter's result is consistent with previous publications. Saturn has nearly perfect balance between the heating rate and cooling rate. Uranus has the least radiative fluxes because of the lack of CH4 and its photochemical products. Both Uranus and Neptune suffer from a severe energy deficit in their stratospheres. Possible ways to resolve this issue are discussed. Finally, we recalculate the radiative time constants of all four giant planet atmospheres and find that the traditional values from (Conrath BJ, Gierasch PJ, Leroy SS. Temperature and Circulation in the Stratosphere of the Outer Planets. Icar. 1990;83:255-81) are significantly overestimated.

Uranus in Northern Midspring: Persistent Atmospheric Temperatures and Circulations Inferred from Thermal Imaging

“…Polar aerosols could also potentially explain the slightly warmer summer temperatures at the poles in the lower stratosphere seen the Voyager data . If this was due to solar heating, such changes would only be expected from the radiative-dynamical model of Conrath et al (1990) if radiative time constants were significantly shorter than even those of Li et al (2018) at stratospheric heights. This could potentially be caused by unaccounted presence of absorbing aerosols.…”

“…If variations in the seasonal albedo are related to changes in temperatures-whether through changes in condensation, subsidence, or convective stability-these temperature changes are not apparent in our upper tropospheric or stratospheric data. Li et al (2018) computed radiative time constants as short as a decade near the polar cloud tops (Sromovsky et al 2019), but the variation of cloud layer temperatures have yet to be measured. We have shown that radiative time constants at higher altitudes are either longer than expected or mixing can effectively dampen seasonal temperature changes.…”

Ice Giant Circulation Patterns: Implications for Atmospheric Probes

“…This result would be changed if a latitude-dependent absorbing aerosol were present (see Section 2.1), but the small magnitude of the temperature differences due to Uranus' small haze opacity should result in a weak annual-mean meridional circulation, with a low-latitude cell of rising motion between 10 − 30 • in both hemispheres and subsidence at the equator. Li et al (2018) calculated updated estimates of the radiative heating/cooling rates, using modern estimates of temperature and hydrocarbon profiles. The rates at Uranus are much smaller than at Neptune because Uranus has the coldest atmosphere and the least stratospheric methane (and resulting photochemical products).…”

“…Furthermore, photolysis of CO and CO 2 can lead to secondary peaks of hydrocarbon production at higher altitudes . The spatial distribution of these stratospheric species control the local radiative balance (ethane and acetylene are excellent coolants, but their efficiency leads to a stratospheric energy crisis, e.g., Li et al 2018) and the condensation of thin stratospheric haze layers in the 0.1-30 mbar range (Rages et al 1991;Romani et al 1993;Moses and Poppe 2017;. Aerosol layers of water, benzene, CO 2 , acetylene, ethane and propane are just some of the various condensed layers that might be expected at these low temperatures.…”

“…At even higher altitudes, an upward motion in the summer hemisphere and downward motion in the winter hemisphere is known as the solsticial mesospheric circulation, and is primarily driven by gravity waves. Wave propagation and breaking on the Ice Giants may be a key mechanism for energy transport to partially resolve the stratospheric and thermospheric energy crises, where solar heating alone is insufficient to explain the high temperatures (Herbert et al 1987;Stevens et al 1993;Li et al 2018;Melin et al 2019). So wave-driven circulations might be at work in giant planet stratospheres, in addition to thermally-driven Hadley-like circulations such as those modelled by Conrath et al (1990), who predicted mid-latitude rising and equatorial subsidence on Uranus.…”