From: redden@ttidca.TTI.COM (John Redden) Newsgroups: rec.games.frp Subject: Other Suns : 19 Date: 12 Oct 90 14:11:20 GMT Reply-To: redden@ttidca.tti.com. (John Redden) Organization: Citicorp/TTI, Santa Monica ------------------ OS.19 ---------------------------------------- This is being posted to the net by myself for Niall Shapero. Others Suns is copyright by Niall Shapero. This gaming material is distributed on a shareware basis. If you do not use the material you owe the author nothing. If you do use it please pay him what you think it is worth at a fair price becasue it took a damn lot of work to develop and playtest. The USmail address is: Niall Shapero 2536 Short Ave Los Angeles CA 90066 USA Those of you with modems can dial into his BBS using this phone number: (213)822-6729 Please email any comments to my electronic mailing address and I will pass them on to Niall. ---------------- end of preamble ------------------------------------------- ICE WORLD I (PART 5 OF 28) Hard Pack Snow: Hard pack is the term used in the rules to refer to "old" snow, which has accumulated on previous days. The weight of new snow compacts the older snow, producing a potentially slick base. Each day, new snow from the previous day becomes hard pack if the temperature does not rise high enough to permit melting. If hard pack snow is present under spotty snow cover, movement is more difficult for both vehicles and walking person- nel. By the time snow becomes deep, however, underlying hard pack is no longer relevant. Limitations on Snow and Ice: If a world has no water vapor (values for "S" in the planetary atmosphere equation between 0.56 and 0.32), then snow and ice are obviously not going to be present. Cryogenic worlds, like pluto, may well have hydrogen "ice" on the surface, but in these rules we are assuming basically terrestrial type oxygen-nitrogen atmos- phere worlds WEATHER Several tables elsewhere in this booklet can be used to establish weather conditions. They were prepared for use on terrestrial type worlds; the Referee should feel free to modify these tables to cover unusual or extreme conditions on specific worlds in his campaign. Snowfall is based on humidity, which is in turn derived from the general cloudiness of the area. Every day, the Referee should roll for cloudiness percentage (on 1D100). Reading across from the result, the Referee finds a Cloudiness Factor and a Humidity Factor for the world (the Snow Cover Chance is used, as described earlier, only when creating initial terrain conditions; daily weather changes do not randomly alter the snow cover). Use of the "Cloudiness Factor" is covered in a later section. The Humidity Factor gives the chance for snowfall. Every eight hours (three times per day) the Referee should roll 1D100 and compare the result to the Humidity Factor. If the roll is less than the number shown, snow will fall during that period of time. Should the temperature be above freezing, rain will fall instead of snow. The three Snow Storm tables are used to determine the intensity, duration, and nature of the snowfall once it is established that a snow storm is taking place. Roll first on Table I for the intensity, using 1D10. The result describes the snow fall rate and accumulation, and gives a die modifier to be applied to the roll on the second table. A roll on 1D10 is then made on Table II to determine the number of hours that snow will fall. Another 1D10 roll is made and Table II used to determine type of snow (wet or powder). Snowfall may continue for more than one 8 hour period. If a storm is determined to last all the way through a given period, no new roll for snow storms is made. If it is to end in a given period, new rolls are made, and the current storm duration is extended by that of any new storm that might occur. New cloudiness ranges should be determined every 24 hours, though in some cases they will not influence the day's weather. For the sake of convenience, itast. Once the storms end, however, new areas en- tered should only have the snow cover that is established from the terrain determination process, and no more. The Referee, however, should feel free to make any modifications in procedures or results that seem reasonable for a given world or situation. Additional tables to provide for wider variations between worlds or climate zones can be developed, or elaborate rules for movement and behavior of storm fronts and the like could be introduced. The basic procedures here, however, are quite sufficient to simulate the most important aspects of snow storms in the game. Cloudiness and Visibility: Clouds may serve to make navigation difficult, or to inhibit the effective use of aircraft or space- craft. Visibility is determined from the Cloudiness and Humidity chart. First roll 1D100 once every 8 hours to determine the percent cloud cover. Roll 1D100 again and if the result is less than or equal to the Cloudiness factor, there is a low overcast. When the sky is overcast, navigation without instruments is impossible for characters or vehicles on the ground. Air vehicles must fly in "Nape Of the Earth" mode (NOE) to maintain visual contact with the ground -- and are fully subject to ad verse ef- fects of wind and weather when doing so. At high speeds, modifi- ers must be applied to the appropriate skill (piloting or vehicu- lar operations) to avoid accidents in NOE mode. Pilots may avoid risk and fly above cloud level, but they lose visual con tact with the ground. They must descend below the cloud cover to land, risking local weather problems as they do so. Vehicular situations are discussed more fully in a later section of the booklet. ICE WORLD I (PART 6 OF 28) TEMPERATURE The basic mean day temperature of a world is given in the tables in book 2 of Other Suns. This temperature represents the mean day temperature found at 30o north or south latitude on the planet. On a typical Terrestrial planet, the mean day temperature de- clines at a rate of 1.5oC per degree of latitude north of 30o North or south of 30o South latitude. On a world with a mean day temperature of 25oC (298 Kelvin) the mean day temperature at 76o N latitude would be -44oC. Moving inward from the 30o latitude line towards the equator, temperatures increase at a basic rate of 1oC per two degrees of latitude shift. At the equator, a world with a mean day tempera- ture of 25oC (298 Kelvin) would have a mean day temperature of 40oC. Axial Tilt also affects a world's temperature variations. Axial tilt for a Terrestrial world is (8D6-8) degrees (this yields tilts of from 0 to 40 degrees, with 20o being average -- Earth has an axial tilt of 23o). Once the axial tilt has been deter- mined, two other factors are established: the tropical bands, and the rate of temperature variation enjoyed by the world. The tropical bands are set at the lines of latitude north and south of the equator equal to the axial tilt itself; thus, on Earth, the tropical zone runs between 23o N and 23o S latitude. Within this band there are no seasonal variations. Outside the tropics, apply the following seasonal temperature modifiers: Summer: Add 0.6oC per degree of axial inclination. Winter: Subtract 1oC per degree of axial inclination. By way of example, our sample world, with a mean day temperature of 25o has an axial tilt determined to be 17o. At 30o N latitude, the temperature varies from 8oC in winter to 35oC in summer. At 76o N latitude this figure ranges from a winter low of -71oC to a summer high of -34oC. These basic steps -- base temperature, modifications for latitude and modifications for axial tilt and season -- enable the Referee to determine the expected local temperature for any point on the globe for any time of year. Once this temperature has been established, additional modifiers are applied to cover specific situations that may arise in the course of the game. Altitude: Temperatures derived from the steps above are for sea level. For every 200 meters elevation above sea level, tempera- ture decreases by 1oC. Daytime: The temperature derived from the previous steps can be determined to be for early evening (just after sunset). In the course of the day, temperatures will slowly increase to a maximum temperature, then fall to this "daytime" temperature just after sunset. Roll 1D10 and divide the result by the atmospheric pres- sure of the planet; this amount is added to the local temperature (as modified by altitude) to yield the daytime high. The actual temperature will increase evenly over the hours between sunrise and mid-afternoon (halfway between mid-day and sunset), then decrease to the "daytime" temperature at dusk. Nighttime: The opposite effect occurs at night. Roll 1D10, divide by the atmospheric pressure, and subtract this value from the local temperature to find the low temperature for the night. Again, the actual change should be spread over the time from sunset to one hour before dawn; the temperature gradually in- creases from this low value to the standard local temperature at dawn. Referee's note: It should be remembered that rotational periods vary from world to world and, moreover, planets with extreme axial tilt will have a diurnal cycle wherein a single "day" can be six months long, even if the rotation period is close to twenty-four hours. Add the possibility of tidally locked worlds where the sun never shines on half the globe and the result is a wide variation in how these day/night temperature changes should be applied. Temperature Effects: Variations in temperature have three major effects: on the environment, on equipment, and on characters themselves. When the temperature is above freezing, snowfall becomes rainfall and snow already on the ground begins to melt. Melting is an uneven process, but a workable rule of thumb is to remove 1D6 x 1 millimeter of snow cover per hour per 5 degrees C. Should rain fall on melting snow, treat a moderate storm as adding 10 degrees C to the temperature, a heavy storm 20 degrees. ICE WORLD I (PART 7 OF 28) WIND