Local meteorological measurements

Methodology: Add first to reference/lowtran_driver.f, test, then integrate to Python

Card 1

• IM=1 as per p.42 s.3.3.2 of manual
• Model=0; itype=1; iemsct=0; imult=0
• M1-M6: still set to 0 to use JCHAR from 2C.1
• IMULT=0; tbound=0; salb=0; noprt=0

Card 2

• ISEASN = 1 spring/summer 2 winter/fall default of 0 for this type redirects to 1 spring/summer
• IHAZE=0 for now, could use 8 for worst case perhaps with VIS=...
• IVULCN = 0 (volcanic dust is for stratosphere only)
• ICLD=0 for now, no rain or clouds
• IVSA=0; VIS=0.; WSS=0.; WHH=0.; RAINRT=0.; GNDALT=0

Card 2A

clouds, not used p.29 s.3.2.2.1

Card 2B

visibility in clouds, not used p.30

Card 2C

is a fundamental part of this MODEL=0 scenario. ML and Card 2C1 interact.

I would like to start by having one or two layers, using real altitudes in case of unknown interaction with other parts of Lowtran.

• ML=1 (p.42 s.3.3.2 ML=1 since we are using horizontal path)
• IRD1=1 use Card 2C2 (where we input our meteorological measurements)
• IRD2=0 Don't use Card 2C3 for now.

Card 2C1

we use this card per p.42 s.3.3.2, and ML=1 so only one layer. For simulating observations at distinct heights, run Lowtran simulation multiple times from Python. Build array of results in Python for plotting & saving.

• ZMDL=0.05 layer altitude (kilometers)
• P= (from local measurements) layer pressure
• T= (from local measurements) layer temperature

Now we specify species. For this work, the most important are initially thought to be H20, C02 and O3. see Lowtran Manual p. 31 and Table 11A on p. 32. It appears that these important 3 have their own variables, and the other 8 of 11 species are passed as an array. I would guess the API is like this because earlier versions of Lowtran might have started with only the most important 3 or 4 species, but that's just a guess.

• WMOL array, length 8 (??)
• WH WATER VAPOR
• WCO2 CO2
• WO OZONE

Card 2C3

Aerosol/haze parameters -- not used for now.

Card 2D

Not used -- custom aerosol parameters

Card 2D1, 2D2: not used

Card 3

p.34 s.3.2.3

Card 3 is sets the viewing geometry: height, zenith angle et al. Since for our horizontal path itype=1, in this case we specify H1, RANGE and ignore H2, ANGLE, BETA and LEN.

• H1 observer height (km) is already in API
• RANGE=H1 (set yourself in driving program)
• R0=0. for default earth radius

Card 3A1, 3B1, 3B2 NOT USED

Card 4

Trivial change: set V1, V2, DV for our camera frequency range and desired resolution (finest resolution possible is 5 cm^-1)

Card 5

IRPT=0

I think initially that we will always leave IRPT=0 and just resend all the parameters since we have a small simulation. Even if we had a big simulation, it may be that 25 years after Lowtran7 was written, PCs are so much faster that we can avoid the complications and bug-invoking dangers of partially reusing computations.