This study involving both observations and simulations furthers our understanding of water transport in the Martian northern polar region, a critical component of the global water cycle, and explores strengths and weaknesses in simulations of the polar atmosphere. Observations of the northern polar winter by the Mars Climate Sounder (MCS) onboard the Mars Reconnaissance Orbiter show extensive water ice clouds over the polar ice cap throughout the 300-3 Pa (similar to 10-50 km) vertical column within the vortex during the entire winter season. The observations also indicate that the vortex evolves throughout its depth on a broad range of timescales, from sub-diurnal to seasonal. Time sequences of these data together with results from a Mars global circulation model and Ensemble Mars Atmosphere Reanalysis System reanalysis (EMARS) are used to study the evolution of the winter polar atmosphere and to examine dynamic mechanisms for transporting water across the vortex boundary. Model simulations and reanalysis show a similar temperature structure to observations, although they struggle to reproduce some of the detailed features such as the extent of polar warming above the vortex and the magnitude of the temperature minima inside the vortex. The free run simulation also fails to capture the vertically distributed water ice cloud due to a general absence of transport across the vortex boundary. EMARS results, with assimilated MCS temperatures, show a greater amount of water entering the vortex at pressures below 200 Pa, leading to a more vertically extended cloud within the vortex and improving agreement with observations. This study explores the winter atmosphere of the northern polar region of Mars and examines how winds move water into this region, which is important for understanding the cycling of water between the atmosphere and the Martian ice caps. The study uses both spacecraft observations of the atmosphere (from which we can infer temperature, dust, and water ice clouds), along with computer simulations that are guided by observations (from which we get greater space and time coverage, and gain additional insights on winds and water vapor). The Martian polar vortex, which serves as a boundary to the polar regions, varies considerably on sub-daily, daily, and seasonal time scales. Computer simulations that are guided by observations show a greater transport of water by the wind at higher altitudes, which is consistent with the greater vertical extent of water ice clouds in winter polar regions, as seen in observations. Similarities and differences between observations and model simulations are also discussed, which motivate future modeling to better represent water transport into the vortex aloft and therefore a better depiction of the water cycle. Improved Mars Climate Sounder (MCS) observations reveal a complex northern winter polar vortex evolving on multiple timescales Water enters the northern winter polar vortex in the middle atmosphere (10-50 km) on Mars, forming a vertically extended ice cloud Agreement of model and observed ice cloud distribution in the north polar region is improved by assimilation of temperature observations

Electrical system operators utilizing wind energy production need accurate wind power forecasts to prepare for changes in power production. To understand the forecast problem and sources of forecast uncertainty, a climatology of the region of interest is needed. For Shagaya Renewable Energy Park in Kuwait, seasonal and diurnal wind patterns and the atmospheric phenomena that cause them are identified using observations from meteorological towers, surface weather stations, and wind turbines. A setup conducive to shamals increases hub-height wind speed by up to 3 m s-1 from May to August and thereby increases power production of the Shagaya wind turbines by 24%, in a season with higher energy demand for cooling homes and businesses. Near sunset, wind speed ramps up and remains faster throughout the night due to the prevalent nocturnal low-level jet. Wind speed ramps back down after sunrise when the nocturnal boundary layer is eroded by convective turbulence, which leads to more short-term fluctuations in wind speed and wind power during the day. Given knowledge on these seasonal and diurnal cycles of short-term and long-term wind power variability, wind power has clear potential to meet a significant portion of Kuwait's energy needs.

Determining how global dust storms originate and develop is one of the major challenges of Martian meteorology. We model the 2018 global dust storm using the Ensemble Mars Atmosphere Reanalysis System (EMARS), combining satellite observations with a Mars global climate model via data assimilation. A reanalysis is a valuable data set for this investigation because it is anchored to the real Martian atmosphere by temperature and dust observations, and the model provides full 4D coverage of wind fields, which are not directly observed and are key to assessing advection. Dust was observed to encircle the northern hemisphere early on in the storm's development. This encirclement could be caused by either the formation of new lifting centers along the path of observed encirclement or the advection of dust from active lifting center(s) elsewhere. Results from EMARS, including particle advection from inferred EMARS winds, provide evidence that the aforementioned dust encircling Mars's northern hemisphere may come from the initial lifting center of the storm, near Chryse Planitia. We propose that dust from the initial lifting center of the storm was entrained into the Martian Hadley circulation, with the assistance of the thermal tides, and then entrained into the northern hemisphere westerly jet. Plain Language Summary About once every three Martian years, or about once every five Earth years, a global dust storm envelops most of Mars, lasting for months. The 2018 global dust storm discussed in this paper began near the solar-powered rover Opportunity. The large amount of dust in the air during a global dust storm can reduce sunlight so much that the Opportunity rover lost power during the 2018 storm, resulting in end of mission. Despite the effect dust has on movement of Martian air, little is known about how global dust storms form and grow. Scientists have historically considered two features of growing global dust storms to be important. One is the existence of multiple locations on Mars where dust is lifted high into the air from the surface. The other is the spreading of dust around Mars, forming a dust ring in the Martian air. We investigate the spreading by combining satellite observations with computer simulations using basic physics equations applied to air. Early in this storm's growth, dust spread eastward and formed a ring around Mars's northern hemisphere. Our computer simulations suggest that dust may have been lifted from one region near Opportunity and moved around the planet by wind.

MARS WEATHER AND CLIMATE: AN ORBITAL CONSTELLATION FOR ATMOSPHERIC PROFILING AND SURFACE THERMOPHYSICS A. Kleinböhl, J. T. Schofield, D. M. Kass, S. Piqueux, D. J. McCleese, A. Spiga, S. J. Greybush, T. Navarro Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA; Synoptic Science, Altadena, CA; Sorbonne University, Paris, France; PennState, University Park, PA; University of California, Los Angeles, CA. (Armin.Kleinboehl@jpl.nasa.gov)

Data assimilation is carried out for the Martian atmosphere with the Mars Climate Sounder (MCS) retrievals of temperature, dust, and ice. It is performed for the period Ls = 180° to Ls = 320° of Mars Year 29 with the Local Ensemble Transform Kalman Filter scheme and the Laboratoire de Météorologie Dynamique (LMD) Mars Global Climate Model (GCM). In order to deal with the forcings of aerosols (dust and water ice) on atmospheric temperatures, a framework is given for multivariate analysis. It consists of assimilating a GCM variable with the help of another GCM variable that can be more easily related to an observation. Despite encouraging results with this method, data assimilation is found to be intrinsically different for Mars and more challenging, due to the Martian atmosphere being less chaotic and exhibiting more global features than on Earth. This is reflected in the three main issues met when achieving various data assimilation experiments: (1) temperature assimilation strongly forces the GCM away from its free‐running state, due to the difficulty of assimilating global atmospheric thermal tides; (2) because of model bias, assimilation of airborne dust is not able to reproduce the vertical diurnal variations of dust observed by MCS, and not present in the GCM; and (3) water ice clouds are nearly impossible to assimilate due to the difficulty to assimilate temperature to a sufficient precision. Overall, further improvements of Martian data assimilation would require an assimilation that goes beyond the local scale and more realism of the GCM, especially for aerosols and thermal tides.

The structure and evolution of the Martian polar vortices is examined using two recently available reanalysis systems: version 1.0 of the Mars Analysis Correction Data Assimilation (MACDA) and a preliminary version of the Ensemble Mars Atmosphere Reanalysis System (EMARS). There is quantitative agreement between the reanalyses in the lower atmosphere, where Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) data are assimilated, but there are differences at higher altitudes reflecting differences in the free-running general circulation model simulations used in the two reanalyses. The reanalyses show similar potential vorticity (PV) structure of the vortices: There is near-uniform small PV equatorward of the core of the westerly jet, steep meridional PV gradients on the polar side of the jet core, and a maximum of PV located off of the pole. In maps of 30 sol mean PV, there is a near-continuous elliptical ring of high PV with roughly constant shape and longitudinal orientation from fall to spring. However, the shape and orientation of the vortex varies on daily time scales, and there is not a continuous ring of PV but rather a series of smaller scale coherent regions of high PV. The PV structure of the Martian polar vortices is, as has been reported before, very different from that of Earth's stratospheric polar vortices, but there are similarities with Earth's tropospheric vortices which also occur at the edge of the Hadley Cell, and have near-uniform small PV equatorward of the jet, and a large increase of PV poleward of the jet due to increased stratification.

Airborne dust modifies the thermal structure of the Martian atmosphere. The Mars Climate Sounder (MCS) first revealed local maxima of dust mass mixing ratio detached from the surface, not reproduced by global climate models (GCM). In this paper, the thermal signature of such detached layers is detected using data assimilation, an optimal combination of a GCM and observations. As dust influences the atmospheric temperatures, MCS temperature profiles are used to estimate the amount of dust in the atmosphere. Data assimilation of only MCS temperature information reproduces detached dust layers, independently confirming MCS's direct observations of dust. The resulting analyzed state has a smaller bias than an assimilation that does not estimate dust. This makes it a promising technique for Martian data assimilation, which is intended to support weather forecasting and weather research on Mars.