Over 18 years of satellite data from Multi-Angle Imaging Spectroradiometer (MISR) and 14 years from Global Navigation Satellite System-radio occultation (GNSS-RO), with ERA5 reanalysis temperature profiles, are used to assess the co-variability of cloud and thermodynamic properties of the Northeast Pacific subtropical marine boundary layer. Low cloud top height (CTH) inferred from MISR and planetary boundary layer height (PBLH) inferred from GNSS-RO are well-correlated spatially for all seasons when seasonally-varying mid-latitude grids (temperature at 700 hPa < 4°C) are removed (r=0.83), or when vertical velocity at 500 hPa (ω500) indicates descent (r=0.74). The temporal correlation of PBLH and CTH is highest in the stratocumulus region (r=0.72), with the CTH versus PBLH slope close to one for heights between 0.8 km and 1.6 km of the time series. Seasonal sea-surface to 700 hPa lapse rate (LR) is spatially related with PBLH and more strongly with CTH, and ω500 modulates seasonal CTH-LR relationships. The impact of El Niño Southern Oscillation (ENSO) through teleconnections on the PBL structure is also characterized, with maximum deseasonalized temperature anomalies near or above PBL top (near the surface) during La Niña (El Niño), with CTH, PBLH, and LR anomalies largest during the strong 2015-2016 El Niño. Temperature anomalies above the PBL lead CTH’ and PBLH’ by 15 and 18 months, respectively, just under half the time scale of the periodicity of an Ocean Niño Index mode (~3.1 years), suggestive of the role of atmosphere-to-ocean exchange manifesting in a deepening PBL during warm ENSO.

The recently selected VERITAS and EnVision missions will fly with X and Ka Band telecommunications channels, permitting dual band radio occultations of the Venus atmosphere. While signal absorption measurements during S and X Band radio occultations of Venus in the past have been used to retrieve vertical abundances of H2SO4 vapor as a function of latitude, Ka Band links have yet to be employed to sound the neutral atmosphere. Laboratory measurements and propagation models of the Venus atmosphere suggest that H2SO4 cloud aerosols/vapor and SO2 absorb radio signals differently between X and Ka bands, permitting inversion of their abundance profiles down to the attenuation limit near 45 km. Such measurements would be of great value to the study of Venus atmospheric chemistry and dynamics. While the bulk abundance of SO2 at the cloud base has been inferred from microwave/infrared radiometry and from X Band occultations, Ka Band measurements could be used to derive vertically resolved profiles at the deepest altitudes yet, spanning a region where the abundance of SO2 changes by several orders of magnitude. Vertical profiles of lower cloud bulk density could also be achieved at higher resolution than any prior remote measurements. This presentation will discuss approaches to retrieving H2SO4 vapor/aerosol, and SO2 abundances using dual X/Ka Band radio occultations of the Venus neutral atmosphere. H2SO4 vapor can be retrieved with very high accuracy, surpassing that of prior single frequency occultations. Due to the relatively low (high) X (Ka) Band opacity of both SO2 and H2SO4 aerosols, retrievals of these species from dual band occultations are highly degenerate. To improve accuracy, we find that it is necessary to incorporate the results of chemical and dynamical modeling as prior information. At lower latitudes and in regions of high abundance, preliminary results suggest retrievals of SO2 profiles can be accomplished within 15-20% uncertainty. This error increases at higher latitudes, where models of cloud bulk density span a wider range of predictions. We compare the effects of various assumptions on the accuracy of the resulting retrievals, and discuss prospects for coupling a chemical/dynamics model to the retrieval process.

The atmospheric measurements made by the six Mars orbiters in operation (as of July 2020) significantly improved our understanding of the Martian weather and climate. However, while some of these orbiters will reach their lifetime, innovative and cost-effective missions are requested - not only to guarantee continued observation but also to address potential gaps in the existing observing network. Inspired by the success of the two Mars Cube One (MarCO) satellites we have established a mission concept, which is based on a series of cubesats, carried to Mars and injected into a low-Mars orbit as secondary payload on a larger orbiter. Each cubesat will be equipped with the necessary features for cross-link radio occultation (RO) measurements in X-band. Intelligent attitude control will allow for maintaining the cubesats in a so-called “string-of-pearls” formation over a period of about 150 solar days. During this period, a series of RO experiments will be carried out with the larger orbiter for up to 180 measurement series per day. Due to the specific observation geometry, we will obtain a unique set of globally distributed cross-link occultations. For processing of the observations, tomographic principles are applied to the RO measurements for reconstruction of high-resolution 2D temperature and pressure fields of the lower Martian atmosphere. The obtained products will give an insight into various unresolved atmospheric phenomena - especially of those which are characterized by distinct horizontal gradients in pressure and temperature, e.g. as observed at the day-night terminator, during dust storms, or over complex terrain.

Radio occultation (RO) can provide high vertical resolution thermodynamic soundings of the planetary boundary layer (PBL). However, sharp moisture gradients and strong temperature inversion lead to large refractivity () gradients, and often cause ducting. Ducting results in systematically negative RO -biases due to a non-unique Abel inversion problem. Using 8-year (2006-2013) Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) RO soundings and collocated European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-I) data, we confirm that the large lower tropospheric negative -biases are mainly located in the subtropical eastern oceans, and quantify the contribution of ducting for the first time. The ducting-contributed -biases in the northeast Pacific (160°W~110°W; 15°N~45°N) are isolated from other sources of -biases using a two-step geometric-optics simulation. Negative bending angle biases in this region are also observed in COSMIC RO soundings. Both the negative refractivity and bending angle biases from COSMIC soundings mainly lie below ~2-km. Such bending angle biases introduce additional -biases to those caused by ducting. Following the increasing PBL height from the southern California coast westward to Hawaii, centers of maxima bending angles and -biases tilt southwestward. In areas where ducting conditions prevail, ducting is the major cause of the RO -biases. Ducting-induced -biases with reference to ERA-I comprise over 70% of the total negative -biases near the California coast where strongest ducting conditions prevail, and decrease southwestward to less than 20% near Hawaii.