# how to apply non-standard day conditions to the Standard Atmosphere?

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#### Buckeye

##### Well-Known Member
TRF Supporter
Modeling gurus:

The simulators apply launch site conditions (temp, pressure, latitude, sometimes humidity) to the US Standard Atmosphere model. I am trying to duplicate that, for the troposphere only. I've Googled the hell out of this, and the best I can figure to do is:

1. Compute the standard atmosphere as a function of altitude, using standard sea level T0 = 288.15 K and P0 = 101325 Pa. I am using the hydrostatic equations here:

https://en.wikipedia.org/wiki/Density_of_air

2. Then, simply apply the difference between the launch site T,P and T0, P0 to the results as a constant offset. Use the corrected T,P vs. altitude to then compute density, speed of sound, etc.

With this method, I can duplicate this calculator with the temperature deviation:

https://www.digitaldutch.com/atmoscalc/index.htm

I assume the same would apply to pressure deviation, but I can't find any calculators that do that.

Am I on the right track?

The only really accurate way to handle this is with measured data because the air column can deviate quite a lot from the standard model and there is no way to predict that deviation from just ground level measurements. Short of performing those measurements yourself, the best you can hope for is to find sounding data from a site/time close to the launch.

I fiddled around with use sounding data to correct RDAS data.

The only really accurate way to handle this is with measured data because the air column can deviate quite a lot from the standard model and there is no way to predict that deviation from just ground level measurements. Short of performing those measurements yourself, the best you can hope for is to find sounding data from a site/time close to the launch.

I fiddled around with use sounding data to correct RDAS data.

That sounding data is pretty cool. Thanks. Sure, actual sounding measurements are best. I am just trying to figure out how RS, OR, RA account for local ground-level conditions in the standard model equations.

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