Atmospheric radiative forcing at the MSL landing site during the 2018/Mars Year 34 global dust storm

In situ measurements by the Mars Science Laboratory (MSL) mission during the 2018/Mars Year 34 global dust storm [1] provide a unique opportunity to estimate the atmospheric radiative forcing (QLW) under extremely dusty conditions. This forcing is expected to dominate the surface energy budget under such conditions [2], thus driving the near-surface thermal environment.

First, we plan to use measurements of ground temperature (Tg) by the Rover Environmental Monitoring Station (REMS) as an upper boundary condition to solve the heat conduction equation applied to the soil [3]. The solution to this equation is the vertical profile of the subsurface temperature, from which the net heat flux into the ground (G) can be obtained. This flux, in turn, can be expressed as G = QSW(1-a) + QLW - σɛTg4 - QH - QE, where QSW is the downwelling shortwave radiation, α is the surface albedo, QLW is the downwelling longwave radiation from the atmosphere (i.e., the atmospheric radiative forcing), σɛTg4 is the surface upwelling longwave radiation, ɛ is the surface emissivity, QH is the sensible heat flux, and QE is the latent heat flux. Second, we plan to use REMS measurements of UV flux, Tg and air temperature to calculate QSW, QH, and QE [3]. Finally, we plan to obtain the atmospheric radiative forcing as QLW = G - QSW(1-a) + σɛTg4 + QH + QE.

Determination of QLW under dusty conditions provides an excellent opportunity to validate dust radiative parameters [2], and to compare its values with future measurements by the Thermal Infrared Sensor of the Mars Environmental Dynamics Analyzer onboard Mars 2020 [4,5].

[1] Guzewich, S. D., et al (2019), GRL, 46.1: 71-79. [2] Savijärvi, H., et al (2019), Curiosity observations and column model integrations for a martian global dust event, Icarus (under revision). [3] Martínez, G. M., et al. (2014), JGR, 119.8: 1822-1838. [4] Rodriguez-Manfredi, J. A., et al (2014), LPSC. Vol. 45. [5] Pérez-Izquierdo, J., et al. (2018), Measurement 122: 432-442.