GENERATION OF SYNTHETIC SATELLITE IMAGES OF MARS DUST STORMS BASED ON RADIATIVE TRANSFER MODELS AS A SEQUENTIAL APPLICATION OF THE MARSWRF DUST CYCLE. This thesis is submitted as partial fulfillment of the requirements for the degree Master of Science in Space Science. Dust is a fundamental component of the Martian atmosphere; it plays a crucial role in the planet's climate system and atmospheric variation.
The imagery is generated by passing selected variables from the MarsWRF output through the DISORT model, which is used to calculate the top-of-the-atmosphere reflectance for a given band. The results of this project are consistent with the real cases of satellite images of Martian dust storms. MarsWRF model run shows a global dust storm.. shows the change in surface dust on a local scale.. shows 3 separated regional dust storms.. shows the expansion of regional dust storm to a global scale event.. shows the effect of the Global scale dust storm event on the planet .
Introduction
Overview
Statement of the Problem
Additionally, we may utilize synthetic satellite imagery in connection with upcoming/future satellite missions to Mars and their data exploration.
Research Objectives
Relevant Literature
- Dust Cycle
- Dust Devils
- Optical Depth
- Seasonal Variability
- Local and Regional Storms
- Global Storms
- Mars Topography
- Effect of Dust on the Martian Atmosphere
- Albedo
- Studying the Atmosphere and Forecasting the Storms
- Synthetic Satellite Images
In order to understand the behavior of the Martian atmosphere, an in-depth knowledge of the dust cycle is required (Gebhardt et al., 2020). Normally, there is always a background dust haze in most parts of the lower atmosphere, except in the winter polar vortex (Kass et al., 2016). Differences in temperature between the surface and the air regulate the available energy to drive potential dust formation (Montabone et al., 2005).
In general, dust devils were observed to occur in all seasons in both hemispheres (Cantor et al., 2006). Peak activity occurs when solar radiation peaks with large sensible heat fluxes (Gebhardt et al., 2020); this happens. However, despite the complexity of the Martian atmosphere, there are preferred periods and regions that are generally repeatable from one year to the next (Kass et al., 2016).
Large dust storms are unlikely, while local dust storms may still occur (Gebhardt et al., 2020). Unlike other storms, the interannual sequence of occurrence of global storms is irregular (Montabone et al., 2020). Global storms develop during the dust season on Mars, the southern spring and summer (Bertrand et al., 2020).
We can say with some certainty that there is a strong relationship between the distribution of dust storms and the topography in the northern hemisphere (Cantor et al., 2001). The steep topography of the western and southern basin rims is where the storms likely grew (Chow et al., 2018). Meteorological observations of the last three global dust storms (MY25, MY28, MY34) showed an impressive effect on atmospheric temperatures (Montabone et al., 2020).
Flaugergues noted yellow clouds obscuring surface albedo features; these clouds were subsequently identified as dust storms (Cantor et al., 2001).
Methods
- About the Model
- Model Variables
- The Radiative Transfer Model DISORT
- The Model Modules
- T15 Mid-level Atmospheric Temperature
This version of the model has a dust cycle but no water cycle, so there are no water cloud effects, just dust clouds. Based on the characterization of the dust optical depth, we can gain insight into the behavior of dust on the planet.; this will help us determine the exact time and location of the dust event. According to Stamnes et al. 1988), the discrete ordinate algorithm can be used for radiative transfer calculations from the UV to the radar range.
Based on the modules of the model, we can proceed to the next step by selecting the related parts of the model DISORT and building on them to develop our program with a selected variable from MarsWRF output files. Vertically resolved optical depth, used from the output data from MarsWRF and set to a spectral wavelength of 670 nm. The radiation module contains data structures to hold the radiation variables, the incident solar radiation at the top of the atmosphere and the emission of thermal radiation.
The loop will run in steps of 2 degrees due to the model's horizontal resolution across latitude and longitude. The input data about the altitude must be reversed, as the DISORT's convention assumed that the altitude starts from the top of the atmosphere, and it must decrease. The final result is the UU variable, which is the average intensity of the output array.
It represents the reflectance of the top of the atmosphere for each longitude and latitude. The study by Gebhardt et al. 2020) was focused on 10 years, with the first model year discarded due to model spin-up.
Results and Discussions
Dust Optical Depth
In his research, Gebhardt labeled four surface dust-lifting regions at equatorial latitudes, named SCP (south of Chryse Planitia), N-HB (northern Hellas Basin), S-HB (southern Hellas Basin), and N-OM (north of Olympus). To put away). 39 the atmosphere at all longitudes and from 50°N to the South Pole 90°S, with an optical depth value generally greater than 3 over most of the planet and greater than 5.8 in the dust collection centers. Finally, the global dust storm enters the decay phase in sol 550 at Ls 291°; Almost no dust is lifted and dust from the atmosphere begins to settle.
Synthetic Satellite Images of Mars Dust Events
- Small (Local) Dust Storms
- Regional Dust Storms
- Expansion From Regional to Global
- Global Dust Events
The surface albedo was included as an input in the model, as shown in Figure 11 in the changes of the surface CO2 ice. In that case, the interpretation of the satellite images of Mars should take into account the effects of the surface reflectance. For a clear assessment of the dust storm in the images, the MarsWRF CDOD plots are provided.
The Hellas Basin is the main surface area of dust upwelling during this storm; the dust cloud started in the south of the basin and reached the north by the end of the storm duration. The intensity of the regional storm (b) in sol 397 is clearly shown in the CDOD plot, while in the synthetic image it appears blurred and covered by atmospheric dust raised in the equatorial region. It is primarily a decrease in the intensity of baroclinic transitional waves between Ls 230° and Ls 300°.
The dust settles and settles back to the surface until it re-forms and re-grows as regional dust storms at Ls 270° in Fig. 12(c) , an intense early-stage regional dust storm before the emergence of a global dust storm. From the image, the storm appears to cover most of the latitude, but it started and spread at equatorial latitudes south of Chrysa Planitia, as clearly shown in the CDOD plot. From the synthetic satellite imagery in Figure 13, it is not easy to observe the surface change and dust movement during the development of a regional to global storm.
These images provide a clear and general view of the state of the planet during a global dust storm. Under these circumstances, the planet is completely shrouded in dust, blocking the view of the surface.
Synthetic Satellite Images with Zero Dust
Differences can be apparent between synthetic images and CDOD plots when comparing the same sol in terms of dust extent and spread. For this, isolating and removing atmospheric dust as input and generating zero-dust images will clearly identify how far albedo affects the images, verifying that the model produces reasonable results. A clear color gradient can be appreciated in Figure 16, which compares the two cases: (a) images without atmospheric dust and (b) regular images with atmospheric dust. The model mainly consists of main groups responsible for building results; 1) Rayleigh arrays, 2) Dust arrays and 3) surface reflectance.
The exclusion of dust information means that the images on the left represent upper-atmosphere Rayleigh scattering and surface reflection. The images on the left are quite similar to the albedo map Figure 6 in section (1.4.8), but notably all three images in (a) have the same pattern of spatial distribution of values regardless of changes in the surface CO2 ice, especially (2,3) both are the same. The reason is that the surface reflectance is the same throughout the MY, unlike the dust distribution.
Although the dust activity in b(1) occupied only a limited number of places in Hellas and Argyre, the image appears brighter in the equatorial region from 40 N to 40 S, about the same extent as the surface reflectance. The b(2) was the maximum phase of the global dust storm, and the atmosphere was already completely covered with dust, so the albedo effect only appears as a high reflection from the north pole. Whereas the clear image of atmosphere b(c) clearly shows the impact of the surface albedo, as no dust is lifted in the CDOD image (not shown), and the maximum opacity is about 0.5.
Still, the synthetic image appears brighter than expected, as if pointing to the existence of dust activity.
Conclusion
Martian years are only simulated years of the model itself; they did not simulate or represent a particular year or day of Mars. The EXI instrument is a radiation-resistant multiwavelength camera that provides images of the Martian atmosphere. We can take advantage of the observation and detected EXI data to obtain images of recent dust storm events in selected wavelength bands, then match them with synthetic satellite images plotted under the same conditions and wavelength.
This procedure can help in the analysis of real and synthetic satellite imagery and derive the characteristics of atmospheric dust coverage and storm characteristics in general. Simulation of the 2018 global dust storm on Mars using the NASA Ames Mars GCM: a multitracker approach. Fully interactive and high-resolution simulations of the Martian dust cycle with the MarsWRF model.
Characterization of dust radiation feedback and refinement of the horizontal resolution of the MarsWRF model to 0.5 degree. Improved discrete ordinate solutions in the presence of an anisotropically reflective lower bound: upgrades to the DISORT computing tool. A first assessment of the impact of the postulated orbit-spin coupling on Martian dust storm variability in fully interactive dust simulations.
Investigating the nature and stability of the Martian seasonal water cycle with a general circulation model. Impact of resolution on the dynamics of the Martian global atmosphere: Varying resolution studies with the MarsWRF GCM.
