1.3 shortwavb.aml

This AML enables the user to calculate direct clears-sky short-wave radiation for a terrain of choice (Kumar et al., 1997) using a batch job mode. There is no difference to the coding of shortwavc.aml, except that shortwavb.aml has no user interface. Rather, the necessary parameters are passed when starting the AML. It might be appropriate to read the instructions for shortwave.aml and for shortwavc.aml first. The usage of the routine is as follows:
 
&r shortwavb  <dem>  <out>  <lat>  <dstart>  <dend>  <timeint>


where: trn = the DEM grid; out  = is the radiation output grid; dem = file name of DEM; out = base name of outgrid file names; lat = latitude of study site (DEM) in decimal degrees; dstart = the start day (in Julian day; dend = the time interval in minutes to calculate sun positions (used for interpolating the energy budget; timeint = the time interval in minutes to calculate sun positions (used for interpolating the energy budget.

If dend is set equal to dstart then a single day is calculated with this routine. .

All the other requirements are the same as for running the shortwavc.aml
 

Modifications:

  • This AML had to be adjusted to a bug in ArcInfo 8.0.2, where the raise to fractional powers causes the program to crash. This reported bug is supposed to be fixed for AI 8.2. Calvin Tolkamp proposed an interim "fix", which is included in this version. Attention: This "fix" has been updated Sept. 14th, 2000!
  • Lattitudes exceeding ± 66° caused the original code to crash. This flaw has been fixed on Sept. 26th 2002.
  • The original code (SHORTWAVE.AML) does not properly initialize, and checks for the file instead of . Thus, if there are remaining temporary grids left in the run directory, the code crashed. The flaw has been fixed in Oct. 7th, 2003.
     
     
     

    General specifications of the AML:

    Command: &r shortwavb  <parameters>    (at GRID or ARC prompt)
    Required input: DEM
    Output units: kJ/m2/time period
    Solar constant used: 1.367 kW/m2
    Transmittance used: 0.8 (max for vertical beam)
    Elevat. lapse rate for trans. None
    Minimum calculation step: 1 day
    Speed of calculations: Very fast due to parsimonious programming
    Flexibility of the routine: Medium; can’t go beyond 1 day
    User interface: Limited, but simple and easy
    Known errors:  -
    Corrections 9/14/2000: Adjustments to bug in ArcInfo 8.0.2
    Programmer N.E. Zimmermann
    L. Kumar (original base code of shortwave.aml)
    Download: shortwavb.aml,       (use: "save link as"; download all 3 files)
    Contact: niklaus.zimmermann @ wsl.ch

     

    References:

    Kumar, L., Skidmore, A.K. and Knowles, E., 1997. Modelling topographic variation in solar radiation in a GIS environment. International Journal for Geographical Information Science, 11(5): 475-497.
     
     

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    Last Updated: 4/25/04
    By Niklaus E. Zimmermann