For atmospheric RTMs that allow user-defined atmospheric profiles (e.g., MODTRAN5), ALG implements a graphical user user interface to automate and facilitate the definition of new atmospheric profiles. Through this tool, the user has higher versatility on defining additional atmospheric models by introducing altitude-dependent profile data (e.g., temperature, H2O, O3) that is later formated and interpreted to be input in the atmospheric RTM.
When selecting atmospheric models as Key Input Variables in the LUT, the user will have available the RTM default atmopsheric profiles (e.g., MODEL for MODTRAN) and the User-defined atmospheric profile option. This last option allows users to introduce a larger number of discrete atmospheric profiles.
After introducing the User-defined as one of the atmospheric profile model values, a window will pop-up allowing users to automate the generation of user-defined atmospheric profiles in terms of the latitude and day-of-year.
Here, the user starts by introducing (1) the day-of-year (DOY, ∈[1,365]) and latitude (∈[0,90] deg) in the top-left table, and (2) the number of atmospheric profiles (N) on the corresponding text block. By clicking on the create profiles button (or press ↵), ALG will randomly generate N new atmospheric profiles associated with uniformly distributed DOY and latitude values between the user input min/max values. Then, ALG will perform a 2D interpolation (in DOY and latitude) from a set of reference atmospheric profiles. This process can be repeated as many times as desired with various input values of DOY and latitude.
Reference atmospheric model | Day-of-year | Latitude (deg) |
---|---|---|
Tropical (TRO) | 0 (year average) | <15 |
Mid-Latitude Summer (MLS) | 182 (June) | 45 |
Mid-Latitude Winter (MLW) | 1 (January) | 45 |
Sub-Arctic Summer (SAS) | 182 (June) | >65 |
Sub-Arctic Winter (SAW) | 1 (January) | >65 |
US Standard 1986 (USS) | 0 (year average) | 40 |
The interpolation of the reference profiles is done as follows:
If the latitude is <15 deg, the profiles are assigned to the reference TRO profile regardless the values of DOY and latitude.
If the latitude is ≥15 deg and <45 deg, the profiles are interpolated between the TRO, MLS and MLW based on the input DOY and latitude.
If the latitude is ≥45 deg and ≤65 deg, the profiles are interpolated between the MLS, MLW, SAS and SAW based on the input DOY and latitude.
If the latitude is >65 deg, the profiles are calculated by linear interpolation between SAS and SAW based on the DOY value.
Notice that only positive values of latitude are allowed since the northern and southern hemispheres are considered to behave in a similar manner. Notice also that the winter-spring-summer variations in the atmospheric profiles (DOY from 1 to 182) are the same as the summer-autumn-winter variations (DOY from 182 to 365), thus it is adviced to select DOY values from 1 to 182 to avoid repetitions of the atmospheric profiles.
The data associated to the reference atmospheric profiles is stored in Others/atmprofiles.h5 and, for each of the above default models, contains the following profiles. Further information about the default atmospheric profile models can be found in (Anderson et al., 1986).
Field name | Units | Dimensions | Description |
---|---|---|---|
doy | days | 6 × 1 | Day of the year associated to each default atmosphere model. |
latitude | deg | 6 × 1 | Latitude associated to each default atmosphere model. |
ZM | km | 50 × 1 | Altitude of each atmospheric layer, from 0 km to 120 km. |
T | K | 50 × 6 | Temperature of each atmospheric layer |
P | mbar | 50 × 6 | Pressure of each atmospheric layer |
CH4 | ppmv | 50 × 6 | CH4 content |
CO | ppmv | 50 × 6 | CO content |
CO2 | ppmv | 50 × 6 | CO2 content |
H2O | ppmv | 50 × 6 | H2O content |
HNO3 | ppmv | 50 × 1 | HNO3 content |
N2O | ppmv | 50 × 6 | N2O content |
NH3 | ppmv | 50 × 1 | NH3 content |
NO | ppmv | 50 × 1 | NO content |
NO2 | ppmv | 50 × 1 | NO2 content |
O2 | ppmv | 50 × 6 | O2 content |
O3 | ppmv | 50 × 6 | O3 content |
SO2 | ppmv | 50 × 1 | SO2 content |
The user can visualize the generated profiles graphically by selecting them (one or more) from the listbox and press the Plot selected button. This will display the profiles in a pop-up window, where the user can interact to select the different atmospheric gases in the profile.
In addition, the user can manually modify each individual profile by selecting the desired profile in the Select profile pop-up menu. This will automatically fill the table at the right with the generated profile, allowing the user to edit the values in each cell of the table. The user can also re-calculate an automatic generated profile by introducing the desired DOY and latitude values in the top-right text boxes.
Finally, the user can delete the generated profiles by selecting them (one or more) from the listbox and press the pressing the Delete selected button.
After pressing the Accept button, the new atmospheric profiles will be added on the Key Input Variables table. These user-defined atmospheric profiles will have a numeric value ≤ -1.
Anderson, G.P., Clough, S.A., Kneizys, F.X., Chetwynd, J.H. & Shettle, E.P. (1986), "AFGL Atmospheric Constituent Profiles (0-120 km).", AFGL-TR-86-0110, AD A175173.