In addition to the faculty, graduate students are a key part of the community. In addition, the data show that the midlatitude westerlies extend poleward from the indicated MGCM locations.
Chapter 1 Preface
In my study of the Martian atmosphere, I examine how the atmosphere changes on several different time scales. They concentrate on the processes that affect the atmosphere over the age of the solar system.
Chapter 2 Sputtering Model
Introduction
While solar wind particles can remove H, they are estimated to disperse only an amount of C02 corresponding to the current atmosphere at the age of Mars. The difference in mass between the solar wind particles and the mass of the atmosphere makes the transfer of momentum and energy very inefficient.
Theory
Energetic exospheric o+ ions were considered a possible source of heavier particles [Tombrello, 1982, Watson, 1980), but the actual fluxes were not determined until Luhmann and colleagues [Luhmann and Kozyra, 1991, Luhmann et al., 1992) is not modeled. they. This process is called indirect solar wind-induced sputtering, and it is much more effective than direct sputtering in removing C02 and other heavy species.
Mars
Model
Once the model knows where the collision occurs, it determines the species of the target. Given the location and target species for the collision, the model determines the results of the collision.
M odel R esults
In the lower part of the table are several rows that calculate the total C, 0 and N yields. The energy of the impacting ion is distributed into four categories while the model is running (Table 2.4).
Discussion
In addition, it is quite likely that some water is still stored on the planet. In this case, both estimates use the same shock currents but differ in the model calculation of dispersion efficiency.
There are three sources of error in calculating the total amount of atmosphere lost. The error in the Monte-Carlo model, the error in the model parameters and the error in the calculation of the impact fluxes.
2. 6 Conclusion
If a planet's magnetic field is strong enough to prevent the solar wind from interacting with the planet's ionosphere, the sputtering will not occur. Although a magnetic field may have kept sputtering from removing the full rv 0.8 bar of C02, sputtering still played a role in the evolution of the Martian atmosphere.
Bibliography
- Intr oduction
- Martian Carbon "Cycle"
Other processes play an important role in determining how the atmosphere evolves throughout the planet's history. The atmosphere is the main exchange center with which all other reservoirs communicate.
0 Regolith
Organic ? Carbonate
The polar cap is the C02 frost (and ice) that has condensed out of the atmosphere at the poles. Since most of the atmosphere is C02, the history of the atmosphere is actually the history of carbon. Thus, understanding the history of carbon provides an understanding of the overall history of the atmosphere.
Starting with an atmosphere of 0°/00 (and assuming it is infinite), the c513C valley of the carbon removed by the various processes is shown.
Fractionation Effects
Sputtering
Carbonate Frost and Outgassing
Numerical Simulation
The following section provides an overview of the model and addresses key issues. For convenience, the size of the atmosphere (and other reservoirs) is measured in bar CO2 (as surface pressure). This rapidly removes most of the CO2 from the atmosphere and the current vapor equilibrium condition is reached.
The first is a simple constant flux model where the carbonate deposition is independent of the model time and chosen to ensure that the desired amount of carbonate is formed.
Results
Increasing the size of any of the three reservoirs will decrease the final 613C value (for example, B or K). The final 613C is strongly influenced by the timing of the carbonate deposition (and thus the difference between 0 and P). The controlling factors are the sputter fractionation (set by the sputtering model) and the isotopic composition of the regolite reservoir as it is created.
The later it is created, the higher it is, so increasing the size of the current regolith reservoir (causing later atmospheric collapse) is most effective.
3. 6 Discussion
Conclusion
Unfortunately, the 813C of the atmosphere is not sensitive to the amount of carbonate deposited, but primarily reflects the extent to which Rayleigh distilled the carbon by sputtering. A modest (rv 100 mbar) amount of C02 must be stored in a reservoir that can isotopically exchange with the atmosphere on moderate time scales. Over the last 3.5 Gyr or so, scattering has removed much, but not all, of the atmosphere left by the collapse.
This leads to the current state where a small regolith and polar reservoir remains from the collapsed atmosphere.
Appendix 3.A
Computat ional M odel
3.A.l Mass Calculation
Chapter 4 Data Assimilation Methodology
- Introduction
- Theoretical Background
- Assimilation Resources
Global dynamical fields can be used to obtain climatological means for the data season. This is usually done by using observations as a guide for changing the state of the model. The second state is the state of analysis and is the result of a process of complete assimilation.
N is the total number of observations that will be assimilated during this update of the model.
4 .4 Assimilation Method
Assimiation Model
Observations ~ Differences Covariances
Assimilate Calculate
Step
Model
Gain Calculation
The primary goal of the assumptions was to enable the calculation of profits offline. We recover this part of the term later in the process by dividing all the differences by the total number of profiles in the time step, and so the term can be neglected here. Under the first assumption, the only variable part of the gains is the number and location of observations within each profile.
To make the gains time independent, we assume while computing them that each profile has exactly 13 points and that each is on one of the model layers.
Twinned Assimiation Model
I Observations II
Results
With the synthetic data, the "Truth" is known, so it is quite easy to measure the effectiveness of the assimilation technique. This figure compares the "Truth" (ie the source of the synthetic data) and the results of the assimilation run. The figure is comparable to figure 4.4 - the red line is again the inherent variation of the weather.
It is essentially the average of the squared fractional improvement of the analysis model (when compared to pure weather variability).
Pressure Deviation (sol 4.81)
Variations in the Method
All experiments were done with synthetic data based on TES observations. Since, during the narrow pass as well as during the extraction parts, the data density is much higher than the resolution of the MGCM, the averaging can reduce the computational load in the meantime. For each time step, all profiles within each subgrid box were averaged over each data pressure surface.
The process reduces the total number of profiles by about a third, as suspected, the long-distance parts of the orbit offer little opportunity for averaging.
Chapter 5 Assimilation of TES Data
5 .1 Introduction
TES Data
This shows the total number of TES profiles available for each 6 min time step of the MGCM. To ensure that the MGCM matches the actual observations, the MGCM was run with conditions as close as possible to those of the data. First, the season of the model initial states was identical to that of the data.
The same season was also used to build profits over the observation period.
Validating the Assimilation
Here, the solid line is the RMS temperature difference (DT) between two runs of the MGCM at the season of the data with different initial conditions. To determine whether the assimilation actually drives the model to the state of the Martian atmosphere, we use a second test. The other cases indicate the convergence of the two initial conditions as a result of the data assimilation.
The G value (see equation 4.7) for each dynamic variable from the assimilation of the TES data.
Results of Assimilating TES Data
For the first 12 sols, slightly higher values are better (and are more decoupled from the initial conditions), but then there is a change in the quality of the assimilation and the f = 0.075 case ends up being better over the whole period. Due to the limited temporal coverage, we only really sample one season and therefore cannot study the changes in Martian climatology over the seasons. The pressure field expresses the tides as "waves" along the equator, synchronized west of the sub-solar longitude.
The other possibility is that the radiative forcing from the model tides is too strong for the data to change.
5.4. 1 Baroclinic Waves
Note that there is some saturation in Figures 5.7 and 5.13 (and in the corresponding polar plots 5.8 and 5.14), primarily in the maps of the assimilation results. The second figure contains one of the assimilation cases and the corresponding MGCM initial state without assimilation. Furthermore, the two TES results (Figures 5.9 and 5.10) are very similar, especially in the phasing of the baroclinic waves.
This is also one of the regions where the two cases of assimilation are most similar.
Pressure Deviation (sol 3.50)
TES2
TES 1
Pressure Deviation (sol 17.25)
Pressure Deviation (sol 23.88)
Surface pressure deviation for each model point at sol 3.5, with and without assimilation. The bottom map is the MGCM run without assimilation with the same initial condition as the assimilation case. Surface pressure deviation for each model point at sol17.25, with and without assimilation.
Pressure Deviation (sol 23 .88)
Zonal Mean Climatology
Contour plot of the zonal mean temperature field, averaged over the 25 sols covered by the TES data. Contour plot of the zonal mean meridional velocity (V) averaged over the 25 sols covered by the TES data. The difference between the zonal mean temperature of the assimilated results and that of the MGCM without assimilation.
The difference between the zonal mean meridional winds from the assimilated results and those from the MGCM without assimilation.
5. 5 Conclusions
The jet core is actually slightly slower in the model assimilation results - -2 m/s contour above 0.2 mbar at 55N. The opposite side of the westerly jet, like the northern one, is expanded, but to a much lesser extent. The main effects of data assimilation on climatology occur in the northern mid- and polar regions.
Even with a dust load similar to the observations, the amplitude of the waves is larger than predicted by the MGCM.
