| 1. |
- Azua-Bustos, Armando, et al.
(författare)
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Aeolian transport of viable microbial life across the Atacama Desert, Chile : Implications for Mars
- 2019
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Ingår i: Scientific Reports. - : Springer. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Here we inspect whether microbial life may disperse using dust transported by wind in the Atacama Desert in northern Chile, a well-known Mars analog model. By setting a simple experiment across the hyperarid core of the Atacama we found that a number of viable bacteria and fungi are in fact able to traverse the driest and most UV irradiated desert on Earth unscathed using wind-transported dust, particularly in the later afternoon hours. This finding suggests that microbial life on Mars, extant or past, may have similarly benefited from aeolian transport to move across the planet and find suitable habitats to thrive and evolve.
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| 2. |
- Bhardwaj, Anshuman, et al.
(författare)
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Martian slope streaks as plausible indicators of transient water activity
- 2017
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Slope streaks have been frequently observed in the equatorial, low thermal inertia and dusty regions of Mars. The reason behind their formation remains unclear with proposed hypotheses for both dry and wet mechanisms. Here, we report an up-to-date distribution and morphometric investigation of Martian slope streaks. We find: (i) a remarkable coexistence of the slope streak distribution with the regions on Mars with high abundances of water-equivalent hydrogen, chlorine, and iron; (ii) favourable thermodynamic conditions for transient deliquescence and brine development in the slope streak regions; (iii) a significant concurrence of slope streak distribution with the regions of enhanced atmospheric water vapour concentration, thus suggestive of a present-day regolith-atmosphere water cycle; and (iv) terrain preferences and flow patterns supporting a wet mechanism for slope streaks. These results suggest a strong local regolith-atmosphere water coupling in the slope streak regions that leads to the formation of these fluidised features. Our conclusions can have profound astrobiological, habitability, environmental, and planetary protection implications
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| 3. |
- Durán, Pablo, et al.
(författare)
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Meso-microscale coupling for wind resource assessment using averaged atmospheric stability conditions
- 2019
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Ingår i: Meteorologische Zeitschrift. - : Schweizerbart science publishers. - 0941-2948 .- 1610-1227. ; 28:4, s. 273-291
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Tidskriftsartikel (refereegranskat)abstract
- A methodology to couple Numerical Weather Prediction (NWP) models with steady-state Computational Fluid Dynamic (CFD) models for wind resource assessment applications is proposed. NWP simulations are averaged according to their atmospheric stability and wind direction. The averaged NWP simulations are used to generate the initial and boundary conditions of the CFD model. The method is applied using one year of Weather Research and Forecasting (WRF) simulations at the Honkajoki wind farm in Finland and validated by Sonic Detection and Ranging (SODAR) measurements at the site. It is shown that coupled simulations reproduce a more realistic shear for heights above 150 m. In terms of estimated energy production, there is not a big difference between coupled and standalone models. Nevertheless, a considerable difference in the horizontal wind speed patterns can be seen between the coupled and non-coupled approaches. The WRF model resolution has only a small influence on the coupled CFD results.
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| 4. |
- Fonseca, Ricardo, et al.
(författare)
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A surface temperature and moisture intercomparison study of the Weather Research and Forecasting model, in‐situ measurements and satellite observations over the Atacama Desert
- 2019
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Ingår i: Quarterly Journal of the Royal Meteorological Society. - : John Wiley & Sons. - 0035-9009 .- 1477-870X. ; 145:722, s. 2202-2220
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Tidskriftsartikel (refereegranskat)abstract
- Good knowledge of the environmental conditions of deserts on Earth is relevant forclimate studies. The Atacama Desert is of particular interest as it is considered tobe the driest region on Earth. We have performed simulations using the WeatherResearch and Forecasting (WRF) model over the Atacama Desert for two week-longperiods in the austral winter season coincident with surface temperature and relativehumidity in-situ observations at three sites. We found that the WRF model generallyoverestimates the daytime surface temperature, with biases of up to 11◦C, despitegiving a good simulation of the relative humidity. In order to improve the agree-ment with observed measurements, we conducted sensitivity experiments in whichthe surface albedo, soil moisture content and five tuneable parameters in the NoahLand Surface Model (namely soil porosity, soil suction, saturated soil hydraulic con-ductivity, thebparameter used in hydraulic functions and the quartz fraction) areperturbed. We concluded that an accurate simulation is not possible, most likelybecause the Noah Land Surface Model does not have a groundwater table that maybe shallow in desert regions. The WRF-predicted land surface temperature is alsoevaluated against that estimated from the Moderate Resolution Imaging Spectrora-diometer (MODIS) instrument. While at night the satellite-derived and ground-basedmeasurements are generally in agreement, during the day MODIS estimates aretypically lower by as much as 17◦C. This is attributed to the large uncertainty inthe MODIS-estimated land surface temperatures in arid and semi-arid regions. Thefindings of this work highlight the need for ground-based observational networksin remote regions such as the Atacama Desert where satellite-derived and modelproducts may not be very accurate.
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| 5. |
- Fonseca, Ricardo, et al.
(författare)
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High-Resolution Dynamical Downscaling of Re-Analysis Data over the Kerguelen Islands using the WRF Model
- 2019
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Ingår i: Journal of Theoretical and Applied Climatology. - : Springer. - 0177-798X .- 1434-4483. ; 135:3-4, s. 1259-1277
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Tidskriftsartikel (refereegranskat)abstract
- We have used the Weather Research and Forecasting (WRF) model to simulate the climate of the Kerguelen Islands (49° S, 69° E) and investigate its inter-annual variability. Here, we have dynamically downscaled 30 years of the Climate Forecast System Reanalysis (CFSR) over these islands at 3-km horizontal resolution. The model output is found to agree well with the station and radiosonde data at the Port-aux-Français station, the only location in the islands for which observational data is available. An analysis of the seasonal mean WRF data showed a general increase in precipitation and decrease in temperature with elevation. The largest seasonal rainfall amounts occur at the highest elevations of the Cook Ice Cap in winter where the summer mean temperature is around 0 °C. Five modes of variability are considered: conventional and Modoki El Niño-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), Subtropical IOD (SIOD) and Southern Annular Mode (SAM). It is concluded that a key mechanism by which these modes impact the local climate is through interaction with the diurnal cycle in particular in the summer season when it has a larger magnitude. One of the most affected regions is the area just to the east of the Cook Ice Cap extending into the lower elevations between the Gallieni and Courbet Peninsulas. The WRF simulation shows that despite the small annual variability, the atmospheric flow in the Kerguelen Islands is rather complex which may also be the case for the other islands located in the Southern Hemisphere at similar latitudes.
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| 6. |
- Fonseca, Ricardo Morais, et al.
(författare)
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MARSWRF Prediction of Entry Descent Landing Profiles : Applications to Mars Exploration
- 2019
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Ingår i: Earth and Space Science. - : John Wiley & Sons. - 2333-5084. ; 6:8, s. 1440-1459
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we use the Mars implementation of the Planet Weather Research and Forecasting model, MarsWRF, to simulate the Entry, Descent and Landing (EDL) vertical profiles from six past missions: Pathfinder, Mars Exploration Rovers Opportunity and Spirit, Phoenix, Mars Science Laboratory Curiosity rover and ExoMars 2016 (Schiaparelli), and compare the results with observed data. In order to investigate the sensitivity of the model predictions to the atmospheric dust distribution, MarsWRF is run with two prescribed dust scenarios. It is concluded that the MarsWRF EDL predictions can be used for guidance into the design and planning stage of future missions to the planet, as it generally captures the observed EDL profiles, although it has a tendency to underestimate the temperature and overestimate the density for heights above 15 km. This could be attributed to an incorrect representation of the observed dust loading. We have used the model to predict the EDL conditions that may be encountered by two future missions: ExoMars 2020 and Mars 2020. When run for Oxia Planum and Jezero Crater for the expected landing time, MarsWRF predicts a large sensitivity to the dust loading in particular for the horizontal wind speed above 10‐15 km with maximum differences of up to ±30 m s‐1 for the former and ±15 m s‐1 for the latter site. For both sites, the best time for EDL, i.e. when the wind speed is generally the weakest with smaller shifts in direction, is predicted to be in the late morning and early afternoon.
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| 7. |
- Fonseca, Ricardo, et al.
(författare)
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Planetary Boundary Layer and Circulation Dynamics at Gale Crater, Mars
- 2018
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Ingår i: Icarus. - : Elsevier. - 0019-1035 .- 1090-2643. ; 302, s. 537-559
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Tidskriftsartikel (refereegranskat)abstract
- The Mars implementation of the Planet Weather Research and Forecasting (PlanetWRF) model, MarsWRF, is used here to simulate the atmospheric conditions at Gale Crater for different seasons during a period coincident with the Curiosity rover operations. The model is first evaluated with the existing single-point observations from the Rover Environmental Monitoring Station (REMS), and is then used to provide a larger scale interpretation of these unique measurements as well as to give complementary information where there are gaps in the measurements.The variability of the planetary boundary layer depth may be a driver of the changes in the local dust and trace gas content within the crater. Our results show that the average time when the PBL height is deeper than the crater rim increases and decreases with the same rate and pattern as Curiosity's observations of the line-of-sight of dust within the crater and that the season when maximal (minimal) mixing is produced is Ls 225°-315° (Ls 90°-110°). Thus the diurnal and seasonal variability of the PBL depth seems to be the driver of the changes in the local dust content within the crater. A comparison with the available methane measurements suggests that changes in the PBL depth may also be one of the factors that accounts for the observed variability, with the model results pointing towards a local source to the north of the MSL site.The interaction between regional and local flows at Gale crater is also investigated assuming that the meridional wind, the dynamically important component of the horizontal wind at Gale, anomalies with respect to the daily mean can be approximated by a sinusoidal function as they typically oscillate between positive (south to north) and negative (north to south) values that correspond to upslope/downslope or downslope/upslope regimes along the crater rim and Mount Sharp slopes and the dichotomy boundary. The smallest magnitudes are found in the northern crater floor in a region that comprises Bradbury Landing, in particular at Ls 90° when they are less than 1 m s−1, indicating very little lateral mixing with outside air. The largest amplitudes occur in the south-western portions of the crater where they can exceed 20 m s−1. Should the slope flows along the crater rims interact with the dichotomy boundary flow, which is more likely at Ls 270° and very unlikely at Ls 90°, they are likely to interact constructively for a few hours from late evening to nighttime (∼17-23 LMST) and from pre-dawn early morning (∼5-11 LMST) hours at the norther crater rim and destructively at night (∼22-23 LMST) and in the morning (∼10-11 LMST) at the southern crater rim.We conclude that a better understanding of the PBL and circulation dynamics has important implications for the variability of the concentration of dust, non-condensable and trace gases at the bottom of other craters on Mars as mixing with outside air can be achieved vertically, through changes in the PBL depth, and laterally, by the transport of air into and out of the crater.
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| 8. |
- Fonseca, Ricardo, et al.
(författare)
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Wind Forecasts for Rocket and Balloon Launches at the Esrange Space Center Using the WRF Model
- 2018
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Ingår i: Weather and forecasting. - : American Meteorological Society. - 0882-8156 .- 1520-0434. ; 33:3, s. 813-833
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Tidskriftsartikel (refereegranskat)abstract
- High-altitude balloons and rockets are regularly launched at the Esrange Space Center (ESC) in Kiruna, Sweden, with the aim of retrieving atmospheric data for meteorological and space studies in the Arctic region. Meteorological conditions, particularly wind direction and speed, play a critical role in the decision of whether to go ahead with or postpone a planned launch. Given the lack of high-resolution wind forecasts for this remote region, the Weather Research and Forecasting (WRF) Model is used to downscale short-term forecasts given by the Global Forecast System (GFS) for the ESC for six 5-day periods in the warm, cold, and transition seasons. Three planetary boundary layer (PBL) schemes are considered: the local Mellor-Yamada-Janjic' (MYJ), the nonlocal Yonsei University (YSU), and the hybrid local-nonlocal Asymmetric Convective Model 2 (ACM2). The ACM2 scheme is found to provide the most skillful forecasts. An analysis of the WRF Model output against the launch criteria for two of the most commonly launched vehicles, the sounding rockets Veículo de Sondagem Booster-30 (VSB-30) and Improved Orion, reveals probability of detection (POD) values that always exceeds 60% with the false alarm rate (FAR) generally below 50%. It is concluded that the WRF Model, in its present configuration, can be used to generate useful 5-day wind forecasts for the launches of these two rockets. The conclusions reached here are applicable to similar sites in the Arctic and Antarctic regions.
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| 9. |
- Gebhardt, C., et al.
(författare)
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Characterizing Dust‐Radiation Feedback and Refining the Horizontal Resolution of the MarsWRF Model down to 0.5 Degree
- 2021
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Ingår i: Journal of Geophysical Research - Planets. - : John Wiley & Sons. - 2169-9097 .- 2169-9100. ; 126:3
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Tidskriftsartikel (refereegranskat)abstract
- In this study, three simulations by the Mars Weather Research and Forecasting (MarsWRF) model are compared: two 10 Martian Year (MY) 2° × 2° simulations with (i) fully radiatively‐active dust and (ii) a prescribed dust scenario, and a (iii) 1 MY 0.5° × 0.5° simulation with prescribed dust as in (ii). From comparing (i) and (ii), we found that the impact of dust‐radiation feedback is individually different for any region. The most striking evidence are major dust lifting activities to the south of Chryse Planitia (S‐CP) seen in (i) but not in (ii). By contrast, dust lifting and deposition on the southern slopes and inside the Hellas Basin are similar in both simulations. The latter, in turn, points towards a similar near‐surface atmospheric circulation. In (iii), the total global amount of wind stress lifted dust is by a factor of ∼8 higher than in (ii), with S‐CP being a major lifting region as in (i). Nonetheless, the surface dust lifting by wind stress in (iii) may be also reduced regionally, as seen at the peak of Elysium Mons because of its unique topography. The zonal mean circulation in (i) is generally of a comparable strength to that in (ii), with exceptions in global dust storm years, when it is clearly stronger in (i), in line with a dustier atmosphere. The differences in the zonal mean circulation between (ii) and (iii) are mostly at lower altitudes, and may arise due to differences in the representation of the topography.
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| 10. |
- Gebhardt, C., et al.
(författare)
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Fully Interactive and Refined Resolution Simulations of the Martian Dust Cycle by the MarsWRF Model
- 2020
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Ingår i: Journal of Geophysical Research - Planets. - : John Wiley & Sons. - 2169-9097 .- 2169-9100. ; 125:9
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Tidskriftsartikel (refereegranskat)abstract
- The MarsWRF model is set up with fully interactive dust at 5° × 5° and 2° × 2 resolution. The latter allows for a better representation of topography and other surface properties. An infinite reservoir of surface dust is assumed for both resolutions. For 5° × 5°, surface dust lifting by wind stress takes place over broad areas, occurring in about 20% of the model’s grid cells. For 2° × 2°, it is more spatially restricted, occurring in less than 5% of the grid cells, and somewhat reminiscent of the corridors Acidalia‐Chryse, Utopia‐Isidis, and Arcadia‐West of Tharsis. The onset times of major dust storms ‐ large regional storms or global dust storm events (GDEs) ‐ do not exhibit much inter‐annual variability, typically occurring at around Ls 260°. However, their magnitude does show significant inter‐annual variability ‐ with only small regional storms in some years, large regional storms in others, and some years with GDEs ‐ owing to the interaction between major dust lifting regions at low latitudes. The latter is consistent with observed GDEs having several active dust lifting centers. The model’s dust distribution is found to better agree with observation‐based albedo and dust cover index maps for the 2° × 2° run. For the latter, there is also significant surface dust lifting by wind stress in the aphelion season that is largely confined to the Hellas basin. It has a recurring time pattern of 2‐7 sols, possibly resulting from the interaction between mid‐latitude baroclinic systems and local downslope flows.
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