From bhaberle@mail.arc.nasa.gov Wed Jun 9 17:04 PDT 1999 Received: from mail.arc.nasa.gov (pony1.arc.nasa.gov [143.232.48.201]) by hellas.arc.nasa.gov (8.9.1/8.9.1) with ESMTP id RAA18934 for ; Wed, 9 Jun 1999 17:04:56 -0700 (PDT) Received: from [128.102.218.33] (rmhaberle.arc.nasa.gov [128.102.218.33]) by mail.arc.nasa.gov (8.8.7/8.8.7) with ESMTP id RAA17243 for ; Wed, 9 Jun 1999 17:04:06 -0700 (PDT) Message-Id: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Date: Wed, 9 Jun 1999 17:04:08 -0800 To: bridger@hellas.arc.nasa.gov From: Robert Haberle Subject: Words for Catalog Content-Type: text/enriched; charset="iso-8859-1" Content-Length: 11330 Status: RO X-Status: PalatinoMars GCM=20 Climate Catalog Description & Content PalatinoThe catalog consists of graphs and tables of GCM output that emphasize the climate of Mars and how it varies with season. The purpose of the catalog is to provide PSG members a ready reference tool for use during the mission itself. The intent is to provide a climate context for the interpretation of MGS mapping data as they are received. Clearly, since these simulations are based mostly on Viking data, revision will be necessary as new data are acquired. This is particularly true of global surface elevation which is not well known at the present time. Nevertheless, it should be useful to have some estimate of what we might expect the Martian climate system to be like. The simulations the catalog is constructed from use the Smith and Zuber (1996) long wavelength topography, Consortium Data surface thermal inertia and albedo, and a new boundary layer scheme as described in Haberle et al. (1999). Two annual simulations were performed: one with a dust visible optical depth of 0.3, and one with a dust visible optical depth of 1.0. The optical depth 0.3 simulation is designated (our nomenclature) "Run 98.04"; the optical one simulation is designated "Run 98.27". In both simulations the dust is horizontally uniform and does not change with time. However, its concentration does fall off quasi-exponentially with height as shown in Figure 1. Above 50 km, dust is virtually absent. This assumed vertical distribution also does not change with time. Clearly, a dust distribution fixed in time and space is unrealistic and this will no doubt be a major reason for discrepancies between the GCM and observations. But again, at this point we are not trying to make accurate predictions. Instead, we want to provide a starting point for making comparisons, and gain some experience in interacting with potential users. At the end of the mission, we plan to redo these simulations using MOLA topography, TES/MOC dust & water ice distributions, and an updated version of the model radiation code with improved dust optical properties based on Viking, Pathfinder, and MGS observations. The catalog runs were carried out with a horizontal resolution of 7.5=B0 in latitude, 9.0=B0 in longitude, and with 30 vertical layers. The model top is at the 0.005 Pa level (~12 scale heights). The mean pressure and height of the midpoint of each model layer is given in Table 1. The heights are computed assuming a constant scale height of 10 km and are therefore approximate. The total amount of CO2 in the atmosphere-cap system is 788 Pa. The polar cap properties (albedo and emissivity) were taken from Hourdin et al. (1995) and produce a seasonal variation in daily mean surface pressure in reasonable agreement with Viking Lander data. In constructing the catalog, we divide the Mars year into 12 periods ("seasons") beginning with Ls=3D0 and continuing every 30=B0 of Ls thereafter. For each of these seasons we compute averages of temperature, wind, surface pressure, and surface stress. The averages are either time averages, or time and zonal averages (i.e., averages around a latitude circle). Standard deviations and variance fields are also included. Time averages for each period are based on 30 sols of simulated data centered on each of the Ls subdivisions (0=B0, 30=B0, 60=B0, =2E... ). This was done so as not to wash out features which change rapidly with time such as the Hadley cells at the equinoxes. Note, however, that the time averaging does wash out the diurnal cycle. Table 2 lists the output provided for each season in the order they appear in the catalog.=20 Each of the figures listed in Table 2 can also be accessed on the enclosed CD. When opening the CD two folders appear: RUN98_04 and RUN98_27. These correspond to the optical depth 0.3 and 1.0 runs, respectively. Within each of these folders are twelve subfolders labeled "XXX_YYY" where XXX can be 0P3 or 1P0 (optical depth 0.3 or 1.0), and YYY is the three-digit Ls seasonal index (e.g., 090 is Ls=3D90=B0). Within each of these subfolders are the corresponding gif (GIF), text (TXT), and postscript (PS) file for each of the figures listed in Table 2. The GIF and PS files are graphical displays (in color), while the TXT files are provided for digital access to the numbers making up the figure. This should be useful for comparing the catalog results with observations.=20 While it is not our intent here to discuss the results in detail there are some robust features of the catalog that will be worth looking for in the observations: (1) The pronounced seasonal variation in the thermal structure of the atmosphere and associated wind systems. At both solstices a pronounced polar vortex develops in the winter hemisphere which is characterized by a strong poleward decrease of temperature. In the summer hemisphere temperatures actually increase toward the pole. Indeed, the summer pole is actually the warmest region of the planet at solstice. The equinoxes tend to be more hemispherically symmetric, though there are some notable exceptions: at high latitudes where the polar caps have different latitudinal extents, and at low latitudes where one Hadley cell still dominates over the other. (2) The predominance of easterly winds in the tropics at all times of year. At the solstices they extend well into the summer hemisphere. Westerly winds characterize the winter polar regions with "jet streams" well in excess of 100 m/s.=20 (3) The hemispheric asymmetry in midlatitude weather systems. The model predicts vigorous weather systems in midlatitudes of the northern hemisphere from late-fall to early spring, but only weak systems by comparison in the southern hemisphere during the same seasons. (See surface pressure RMS time deviation maps). In the model, topography is suppressing the southern systems. (4) The highest surface stresses on the planet occur in the midlatitudes of the northern hemisphere during fall and winter. The region north of Tharsis is particularly breezy. In the southern hemisphere, the highest surface stresses occur along the western rim of the Hellas basin during southern fall and winter. ( 5) An upper atmosphere tropical "dipole" in the 2pm-2am temperature differences. This feature, presumably due to thermal tides, is present at all seasons and is flanked by weaker dipoles of opposite polarity during the equinoxes. REFERENCES: Haberle, R.M., M.M. Joshi, J.R. Murphy, J.R. Barnes, J.T. Schofield, G. Wilson, M. Lopez-Valverde, J. L. Hollingsworth, A.F.C. Bridger, and J. Schaeffer. (1999). General Circulation Model Simulations of the Mars Pathfinder Atmospheric Structure Investigation/Meteorology Data, J. Geophys. Res., In press. Hourdin, F., F. Forget, and O. Talagrand. (1995). The Sensitivity of the Martian Surface Pressure and Atmospheric Mass Budget to Various Parameters: A Comparison Between Numerical Simulations and Viking Observations, J. Geophys. Res., 100, 5501-5524. Smith, D.E., and M.T. Zuber. (1996). The Shape of Mars and the Topographic Signature of the Hemispheric Dichotomy, Science, 271, 184-188. =20 =46igure 1. The variation of the dust mixing ratio (normalized to the surface value) as a function of scale height. =20 Table 1: Mean pressures and heights of the midpoints of MGCM layers.Times PalatinoLayer Pressure, Pa Height Palatino1 .007 115 km 2 .011 110 km 3 .019 105 km 4 .034 99 km 5 .060 93 km This region not shown in Figures 6 .101 88 km 7 .177 82 km 8 .305 77 km 9 .522 71 km 10 .895 66 kmTimes Palatino11 1.54 61 km 12 2.65 55 km 13 4.57 50 km 14 7.67 45 km 15 12.7 40 km =09 16 20.9 35 km 17 34.4 30 km=09 18 56.7 25 km 19 93.4 20 km 20 154 15 km This region shown in Figures 21 242 10 km =09 22 344 6.5 km 23 440 4.0 km 24 524 2.3 km 25 588 1.1 km 26 626 490 m 27 644 192 m 28 652 81 m 29 655 26 m 30 657 5 m=09 =20 Table 2: CD file name (bold) and description of its contents.Times Palatino1. GLOBALS.TXT - Miscellaneous tabulated global & hemispheric quantities. 2. PS_XY.* - Time mean surface pressure (top) and surface pressure variance (bottom). 3. T2AM_YZ.* - Time and zonally averaged 2AM temperature (top), and 2AM temperature standard deviation (bottom). 4. T2PM_YZ.* - Time and zonally averaged 2PM temperature (top), and 2PM temperature standard deviation (bottom). 5. TDIFF_YZ.* - Time and zonally averaged temperature (top) and 2PM-2AM temperature difference (bottom). 6. TGEXT_XY.* - Mean minimum ground temperature (top) and mean maximum ground temperature (bottom). 7. TGLOC_XY.* - Mean 2AM ground temperature (top) and mean 2PM ground temperature (bottom).Times Times Palatino8. TUVAV_XY.* - Time mean temperature and horizontal wind at 3 mb (top) and at 0.5 mb (bottom). 9. UVLOC_XY.* - Mean 2AM surface wind (top) and 2PM surface wind (bottom). 10. UVSAV_XY.* - Time mean surface wind (top) and surface stress magnitude (bottom). 11. UV_YZ.* - Time and zonally averaged zonal (top) and meridional (bottom) wind. 12. WMS_YZ.* - Time and zonally averaged vertical wind (top) and mass stream function (bottom). =20 Notes on the latitude vs height (*_YZ.*) plots: (1) There is a black filled region near the surface and above it is a thick black dashed line. The filled region represents the zonally-averaged topography. The thick dashed line represents that altitude at which we begin to loose longitude grid points in constructing zonal (east-west) means because of topography.=20 (2) The zero altitude level is defined to be the 610 Pa level (6.1 mb). Thus, the topography moves up and down in these plots with season due to the CO2 cycle. (3) Only that part of the atmosphere below the 1 Pa level is shown. This is the region emphasized by TES and RS, and it is also the region where the MGCM is probably more credible. =20 ******************************************** Robert M. Haberle Space Science Division, MS 245-3 NASA/Ames Research Center Moffett Field CA 94035-1000 Phone: 650-604-5491 =46AX: 650-604-6779 E-mail: bhaberle@mail.arc.nasa.gov haberle@humbabe.arc.nasa.gov ********************************************