T20 Only: T20 THB World Development Step 4 Climate & T20 World Map

[snrdg082102]

Hello all,

Can someone please provide an example of how to determine a world's climate using THB 1e 3rd printing p. 376?

 

[aramis]

Ok...
Starting on page 372 of the PDF (which is what I have)...

Step 1, yeah there's a star system here.

Step 2, I roll 2d6, get a 4, so that's a single star.

Step 3 Red Dwarf. Temp mod is +2... (note that positive mods here are COOLER stars). Size V.

Step 4 Automatically color M, as it's a RD. So it's M_ V. Rolling a d10, I get a 9... so M9 V (sometimes written M9v). M is a +2 temp mod.

Step 5 Gas Giants. Roll 12 - not a one.

Step 6 Planetoids. Roll 10 - again, none. So, everything there is solid bodies.

Step 7 Lots of data...
Minimum orbit is 0 (because RD is main sequence color M)
hab zone is orbit 0 (Main sequence type M)

So we also run the standard gen for the mainworld...
and get E-75A535-9 ... a backwater noplace. And it's breathable, so it goes in Orbit 0, the hab zone.
Orbit 0 is temp mod –4. (from the table on 374).
Star is +2.
So climate is 1d20+2-4=17–2 = 15
And 15 is Frozen. So all that water is ICE!!! (We can assume the high albedo is why it's cold - it's not absorbing much of the light.)

The second planet is going to be in orbit 1 and have an orbit mod of –2, plus the stellar mod of +2, for +0.


Some other things we can extrapolate from this particular hell world...
The equatorial equinox temps are averaging no higher than –10°C by day, and –30°C at night (due to the thin atmosphere). (That's comparable to a Fairbanks, Alaska winter - at the equinox and equator.) Given that I want to keep it reasonably habitable - I pick that the average is really the least bad case for the roll...
Polar temps will average –71°C by day, and –91°C by night...

Axial Tilt roll is 10°... so we get +10° in summer and –15° in winter...

So, a table...

	Summer	Spring/Fall	Winter
90°	-61/-81	-71/-91	-86/-106
75°	-53/-73	-63/-83	-78/-98
60°	-46/-66	-56/-76	-71/91
45°	-28/-48	-48/-68	-63/-83
30°	-21/-41	-41/-61	-56/-76
15°	-16/-36	-26/-46	-41/-61
0°	-1/-21	-11/-31	-

Note that the winter polar is actually going to be pretty much all night temps... and right on the edge of CO2 frost in 0.5 ATM.

That's what the climate data generated gives... and here's the part not listed... interpreting it.
There will be some interesting water effects... given the half-atmosphere, water will be either solid or vapor... And the melt/boil point is about –30°C... at surface.

I can't find a good phase diagram for CO2, but extrapolating from several outside the regimes we want... the poles will have winter CO2 frosting....

Lovely place to be FROM...

If we want to make it even worse, note that it will have sub-ice oceans, especially if there's any orbital eccentricity...



http://acmg.seas.harvard.edu/people/faculty/djj/book/bookchap1-26.gif - O2 phase table

 

[snrdg082102]

Hello aramis,

Something in the post from 4/17/16 at [FONT=arial,helvetica] 07:33 AM is not allowing the quote feature to work in either IE or Firefox.

Next, thank you for the explanation of how to determine Step 4 Climate in T20 THB Chapter 16.

I have a little set-back in the spreadsheet I'm building which is delaying my study of your example, however per my hardcover copy of T20 THB 1e 3rd printing a result of 15 is Frigid not Frozen. The link to the [/FONT][FONT=arial,helvetica][FONT=arial,helvetica]ERRATA for the TRAVELLER’S HANDBOOK 1e, 1st Printing Current as of June 4, 2003 held here on COTI provided by savage replaced Step 4 with the material in my THB hardcover.

Hopefully, I'll be back soon with either the I got the idea or to ask more questions.

Again thank you for the help.


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[snrdg082102]

Hello all,

I am back and have put together a Mongoose Traveller CRB 1e System Generation spreadsheet as well as getting back to T20 THB Chapter 16 World Development Step 4 Climate.

I"m at the point that I am trying to follow the example that aramis has provided, unfortunately I'm not sure about the wording of the rules on p. 376.

"*At 30° latitude. Add +0.5 °C every 1° south of 30° latitude, and subtract -0.5 °C every 1° north of 30° latitude. Using the T20 World Map add +5°C for every hex row below row 4 and subtract -5° for every hex row above row 4."

I think that T20 World Map row 4 is 30° latitude.

Hopefully, I'm on the right track, but if possible can someone please let me know if I am on track or out to lunch?

 

[aramis]

Ct and t20 use a 21 row tall map... 180°/21=~8.57° per row

Note that the tropics are (by definition) as many degrees as the axial tilt, as they are defined by direct overhead sun at noon during some point of the year.

Map row 4 north is about 25.8° to 31.4° north. On some worlds, this is tropical. On others, sub-tropical. .. but other factors determine if the climate is what we think of as tropical... tropical mars is still cold and dry, albeit above water boiling at that pressure....

 

[snrdg082102]

Hello aramis,

The web gremlins are not allowing me to use the quote feature again and I can not seem to find the post number so I'll being responding without them hoping to get everything covered.

1. In the example from 4/17/2016 07:33 AM I seem to be having an issue with the process so I'll work my way through here using T20 THB 2002 3rd printing hardcover.

Star system generation
Step 1: Star system present check
Step 2: Solo star check
Step 3: Red Dwarf; Size D; Temp Mod +2
Step 4: Spectral Class M; Color Red; Temp Mod +2
Step 5: No gas giants present check
Step 6: no planetoid belts present check
Step 7: Red Dwarf Class M Minimum orbit: 0 (zero) and Habitable zone: Orbit 0 check. If the main world has been determined place in habitable zone unless the atmosphere is 0, 1, or 10+.
Steps 8 and 9 skipped

World Development
Step 0: Parent star already generated as a single star so the world is orbiting the main world.
Step 1: World Orbit for main is the habitable zone of Orbit 0 Temp Mode -4
Step 2: World Size 7
Step 3: World Atmosphere 5
Step 4: World Climate:

Roll 1d20 + Star Size Red Dwarf V Temp Mod 2 + Star Classification M Temp Mod 2 + World Orbit 0 Temp Mod -4 Orbit=

1d20 = 17 + Star Size Red Dwarf V Temp Mod 2 + Star Classification M Temp Mod 2 + World Orbit 0 Temp Mod -4 Orbit=

1d20 = 17 + 4 -4 = 17

World Climate Table 16 or greater Frozen -41°C or lower at 30° latitude.

From this point onward, if not earlier, I'm lost on how to put everything else together.

2. T20 World Map IS Form 8.2 Row 4 = 30° latitude.

Thank you for confirming that Row 4 is roughly 30° latitude.

Hopefully I'll have the remainder of Step 4 figured out before the next reply.

 

[aramis]

Hello aramis,

The web gremlins are not allowing me to use the quote feature again and I can not seem to find the post number so I'll being responding without them hoping to get everything covered.

1. In the example from 4/17/2016 07:33 AM I seem to be having an issue with the process so I'll work my way through here using T20 THB 2002 3rd printing hardcover.

Star system generation
Step 1: Star system present check
Step 2: Solo star check
Step 3: Red Dwarf; Size D; Temp Mod +2
Step 4: Spectral Class M; Color Red; Temp Mod +2
Step 5: No gas giants present check
Step 6: no planetoid belts present check
Step 7: Red Dwarf Class M Minimum orbit: 0 (zero) and Habitable zone: Orbit 0 check. If the main world has been determined place in habitable zone unless the atmosphere is 0, 1, or 10+.
Steps 8 and 9 skipped

World Development
Step 0: Parent star already generated as a single star so the world is orbiting the main world.
Step 1: World Orbit for main is the habitable zone of Orbit 0 Temp Mode -4
Step 2: World Size 7
Step 3: World Atmosphere 5
Step 4: World Climate:

Roll 1d20 + Star Size Red Dwarf V Temp Mod 2 + Star Classification M Temp Mod 2 + World Orbit 0 Temp Mod -4 Orbit=

1d20 = 17 + Star Size Red Dwarf V Temp Mod 2 + Star Classification M Temp Mod 2 + World Orbit 0 Temp Mod -4 Orbit=

1d20 = 17 + 4 -4 = 17

World Climate Table 16 or greater Frozen -41°C or lower at 30° latitude.

From this point onward, if not earlier, I'm lost on how to put everything else together.

2. T20 World Map IS Form 8.2 Row 4 = 30° latitude.

Thank you for confirming that Row 4 is roughly 30° latitude.

Hopefully I'll have the remainder of Step 4 figured out before the next reply.

It helps to have form IS-8 handy - that's the world mapping icosaheral projection.

To get mean daytime temp for a location, look at its row - don't think in degrees of longitude. For each row, adjust that by how many rows of hexes away from row 4, hotter towards row 1, cooler towards row 11.
To find nighttime temps, apply the mod by atmosphere type.

Seasonal variation then adjusts those.

A more realistic system would also moderate the distance between daytime high and nighttime low for places adjacent to liquid water. (water has a much higher specific heat that air per unit volume...)

From that point, the rest is extrapolation based upon some basic chemistry and physics...

 

[snrdg082102]

Hello aramis,

It helps to have form IS-8 handy - that's the world mapping icosaheral projection.

To get mean daytime temp for a location, look at its row - don't think in degrees of longitude. For each row, adjust that by how many rows of hexes away from row 4, hotter towards row 1, cooler towards row 11.
To find nighttime temps, apply the mod by atmosphere type.

Seasonal variation then adjusts those.

A more realistic system would also moderate the distance between daytime high and nighttime low for places adjacent to liquid water. (water has a much higher specific heat that air per unit volume...)

From that point, the rest is extrapolation based upon some basic chemistry and physics...

This is interesting the web gremlins have decided to allow me the use of the quote feature. When I tried to quote Post 5 from May 2nd, 2016 at 03:53 AM the reply widow opened up blank.

Anyway, I did not figure out the rest of Step 4 before this post which did appear to get me past the road block. I used both the T20 IS Form 8.2 and match most of the table you created in Post 2 of the thread. I have given up trying to recreate your table.

Under the World Climate Table, T20 THB 2002 3rd printing hardcover p. 376 there is the following directions:

"*At 30° latitude: Add +0.5°C every 1° south of 30° latitude, and subtract -0.5°C every 1° north of 30° latitude."

Using 15° bands the temperature is adjusted by ±7.5°C.

The temperatures for latitudes between 60° to 90°, with the exception of adding 0.5°C to 75° latitude, in my table match up.

The Spring/Fall temperatures, again there is a 0.5°C difference, match for 30° and 45° latitude also match.

My Latitude 15° numbers are
Summer Day/Night: -23.5°C/-43.5°C
Spring/Fall Day/Night: -33.5°C/-53.5°C
Winter Day/Night: -48.5°C/-68.5°C

My Latitude 0° numbers are
Summer Day/Night: -16°C/-36°C
Spring/Fall Day/Night: -26°C/-46.5°C
Winter Day/Night: -41°C/-61°C

I'm not sure where I went off the tracks.