Strange output when hitting the ground

Topics about the HYSPLIT trajectory model.
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khartig
Posts: 6
Joined: June 16th, 2020, 4:22 pm
Registered HYSPLIT User: Yes

Strange output when hitting the ground

Post by khartig » June 16th, 2020, 6:28 pm

I'm running HYSPLIT trajectories on Linux (compiled from source code, Last Changed Rev 1011), using data I've converted from the Community Atmosphere Model v4 to ARL with MeteoInfo. Many of my trajectories are close to the ground, so I expect some to hit ground, but I am confused by the output produced in the trajectory files and would like to know more about how "grounding" is determined. I've seen three different behaviors that I would like to understand:

1. Switch to NaN: sometimes, when the height is very low, all columns from the latitude column on will become NaN:

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     1     1    11     1    18     5     0    99   -25.0   44.440 -111.338      0.3    786.2    248.2   1864.3
     2     1    11     1    18     5     0    99   -25.0   46.052 -109.776      0.0    824.1    243.8   1517.5
     3     1    11     1    18     5     0    99   -25.0   46.920 -108.695      0.0    865.8    243.8   1154.2
     4     1    11     1    18     5     0    99   -25.0   38.079 -109.228    144.2    768.0    267.3   2018.2
     5     1    11     1    18     5     0    99   -25.0   40.467 -120.049   4855.3    433.6    234.7   1437.5
     1     1    11     1    18     4     0    99   -26.0   44.442 -111.374      0.8    786.3    248.6   1862.8
     2     1    11     1    18     4     0    99   -26.0   46.056 -109.825      0.0    823.5    244.4   1522.2
     3     1    11     1    18     4     0    99   -26.0   46.928 -108.785      0.3    864.7    244.3   1161.7
     4     1    11     1    18     4     0    99   -26.0   37.715 -109.474    109.2    773.8    267.9   1999.5
     5     1    11     1    18     4     0    99   -26.0   41.374 -120.266   4947.3    435.0    234.9   1324.2
     1     1    11     1    18     3     0    99   -27.0      NaN      NaN      NaN      NaN      NaN      NaN
     2     1    11     1    18     3     0    99   -27.0      NaN      NaN      NaN      NaN      NaN      NaN
     3     1    11     1    18     3     0    99   -27.0      NaN      NaN      NaN      NaN      NaN      NaN
     4     1    11     1    18     3     0    99   -27.0   37.374 -109.690     74.4    779.8    268.6   1982.3
     5     1    11     1    18     3     0    99   -27.0   42.310 -120.455   5040.4    436.7    234.9   1202.4
     1     1    11     1    18     2     0    99   -28.0      NaN      NaN      NaN      NaN      NaN      NaN
     2     1    11     1    18     2     0    99   -28.0      NaN      NaN      NaN      NaN      NaN      NaN
     3     1    11     1    18     2     0    99   -28.0      NaN      NaN      NaN      NaN      NaN      NaN
     4     1    11     1    18     2     0    99   -28.0   37.096 -109.923     43.7    784.9    269.2   1957.8
     5     1    11     1    18     2     0    99   -28.0   43.262 -120.624   5140.0    438.2    235.1   1093.9
2. Recovery from height of zero: in other cases, trajectories will sit at a height of 0.0 meters for many time steps without becoming NaN, and then recover and increase in height again

3. Row of asterisks: sometimes, the switch to NaN as the trajectory presumably hits the ground will be preceded by a row of asterisks (see trajectory 1 in sample_traj_asterisks.txt)

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     1     1    15    12    30    15     0    99   -21.0   28.243  -82.265     15.0   1024.5    285.9   -112.1
     2     1    15    12    30    15     0    99   -21.0   33.475  -84.965    111.1    988.4    274.9     82.0
     3     1    15    12    30    15     0    99   -21.0   33.758  -86.949    318.6    965.4    277.5     65.5
     4     1    15    12    30    15     0    99   -21.0   33.949  -88.400    672.7    928.3    277.8     33.7
     5     1    15    12    30    15     0    99   -21.0   44.433 -110.504   5582.3    377.4    237.2   1812.3
     1     1    15    12    30    14     0    99   -22.0*********  -82.368 ******** ******** ******** ********
     2     1    15    12    30    14     0    99   -22.0   33.505  -85.006    118.9    986.2    275.2     98.4
     3     1    15    12    30    14     0    99   -22.0   33.778  -87.046    324.1    964.5    277.5     67.0
     4     1    15    12    30    14     0    99   -22.0   33.954  -88.617    674.6    928.6    277.9     27.0
     5     1    15    12    30    14     0    99   -22.0   44.862 -112.152   5663.4    380.9    237.6   1696.1
     1     1    15    12    30    13     0    99   -23.0      NaN      NaN      NaN      NaN      NaN      NaN
     2     1    15    12    30    13     0    99   -23.0   33.547  -85.068    127.6    984.3    275.5    100.1
     3     1    15    12    30    13     0    99   -23.0   33.819  -87.158    329.9    963.8    277.6     66.3
     4     1    15    12    30    13     0    99   -23.0   33.970  -88.828    677.2    929.1    278.0     20.6
     5     1    15    12    30    13     0    99   -23.0   45.156 -113.749   5758.5    386.9    238.4   1501.9
     1     1    15    12    30    12     0    99   -24.0      NaN      NaN      NaN      NaN      NaN      NaN
     2     1    15    12    30    12     0    99   -24.0   33.603  -85.154    137.3    982.4    275.7    102.3
     3     1    15    12    30    12     0    99   -24.0   33.881  -87.284    335.7    963.1    277.6     66.3
     4     1    15    12    30    12     0    99   -24.0   33.995  -89.033    680.2    929.4    278.1     14.6
     5     1    15    12    30    12     0    99   -24.0   45.332 -115.290   5822.3    392.6    239.3   1337.5
What leads to these three different output behaviors? I would attach files with examples, but the post interface says the board attachment quota has been reached and won't let me.

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