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MPA: Meridian Photometer Array


 

Where_is_the_data

The location of data does not need to be known when using any of the MPA baseline software. A routine, FIND_MPA (see Software), is called by GET_PARAM (see Software) and looks for data in all the usual places (see BETA, below). In addition a caller may have data in another directory. This may be made known to the program by defining the logical D$OTHER_BETA. There are two levels of processed data on the system, ALPHA and BETA data. Most of the software requires BETA data, but if not available, and ALPHA data is, the access routine GET_BETA will create BETA data "on-the-fly". Provided of course the code can find the Alpha data. Here FIND_MPA also looks for the data in all the usual places (see ALPHA, below). If the Alpha data is in a different directory, this must be made known to the program by defining the logical D$OTHER_ALPHA. Additional information available: ALPHA BETA CAMPAIGN SOFTWARE This help file contains information on programs and subroutines related to the MPA, and provides help on how to use or run the code. In general, this help (except for the example) is an excerpt of the header in the source code of the mainline program or subroutine in question, but this source code is not routinely made available to the general user. The source code header always contains the most up to date information on the program. Sometime in the future, this header will always be a available as a corresponding .DOC file in MPA$SOFT. On-line help is also available for most public MPA software. This is called up from help files with the filetype .QUE located in [CANHELP.MPA], usually at time of parameter entry (see GET_PARAM). Executable images of these programs are located in MPA$EXE. The .OBJ files of the subroutines are found in MPA$SOFT:MPALIB.OLB, MPA$SOFT:STARLIB.OLB, the source code of data structures are located in MPA$SOFT:INCLUDE_FOR.TLB. Plotting programs are all written in IDL2 (except for those that have not been converted yet!). These are found in MPA$EXE. The support routines are in MPA$SOFT:MPA_IDL.TLB. Where mainline programs need to be linked locally, a .BLD file to link the program is provided. Additional information available: DARK_TIME GET_MPA GET_PARAM GET_BETA MPA_DATA PLOT_BETA RASTER READ_BETA

Cloud_Index

Estimation of Cloud Cover using MPA data.

F. Creutzberg, 30-JUL-1992

In the MPA data, cloud cover is estimated from the shape of the background channel scans, on the assumption that when the sky is clear, the measured brightness near the horizons is greater than the zenith brightness (van Rhijn effect); conversely, when the sky is overcast, the zenith brightness is greater than that near the horizons (Rayleigh or Mie scattering). There is a smooth monotonic change in going from the horizon to the zenith and back to the other horizon at least in a full meridian scan. This holds fairly well also for the binned data that constitute the MPA scans.

A number of factors can contribute to the failure of this strategy. If the filters are not pure background filters (and none of them are!), there will be enhanced emission where there is aurora during clear skies and in locations near the zenith when it is overcast and we donot have a simple second degree polynomial brightness curve. The same is true if the moon is crossing or near the scanner meridian. If we have broken cloud this concept also breaks down. So in short, an index for the cloud cover is a three-valued parameter: GOOD, BAD, DON'T KNOW.

We have to expand on this a little, because we have two background channels, which behave differently in situations where the concept breaks down. So for this reason we have created a four-valued index where the fourth value is PERHAPS (CAUTION), the case where one channel indicates clear sky and the other does not.

The cloud index described here is computed on a scan by scan basis. There are other ways of getting a handle of the degree of cloud cover. At switch-on/off the sky brightness often gives a positive indication of the presence of clouds based on the above criteria. At turn-on, clear skies show a decaying brightness which produces a << profile (darkest in the zenith), while a cloudy sky produces a >> profile (directions reversed at turn-off). Broken cloud often produces a skewed wave pattern, while high cirrus or ice crystals often cause "weeping", a spreading of the intensity towards the horizons where well confined arc boundaries would be expected. When aurora is active we expect to see structure, often moving equatorward or poleward. This may get washed out when haze is present. Bright arcs above the clouds show up as a bright band near the zenith. Extensive motion does not show up much, if at all. Another common feature is streaky bands running from horizon to horizon, particularly visible in H-Beta. H-Beta is a very low level emission and is very sensitive to haze. It is also corrected for background and the presence of such bands probably indicates cirrus drifting accross the meridian.

The subroutine (BG_LSQ) which computes the cloud indices does a least squares fit (2nd order polynomial) to the two background channels of each MPA scan and returns two background cloud indices and a composite cloud index.

The channel cloud index is a positive number which can assume five values: 1 - Clear: A significant second order constant >0; no rejected observations. 8 - Cloudy: A significant second order constant <0; no rejected observations. 2 - Marginal Viewing: A significant second order constant >0 after rejecting 1 or 2 observations in 1 cycle. 4 - Indeterminate: No significant second order or first order constant. 0 - No Valid Data to asses cloud index with. The Composite Index is evaluated as follows. Two indices the same (value I), CI = I C, O, !, ?, N One index 8, the other 2, 4 CI = 8 O the other 1 CI = 4 ? One index 1, the other 2 CI = 2 ! the other 4, 8 CI = 4 ? One index 2, the other 4 CI = 2 ! where C = Clear, O = Overcast, ! = Caution, ? = Don't Know, N = No Data In MPA RASTER plots, the cloud index is displayed in a color bar or grayscale bar. The colour values are assigned as follows.

        0     White       White          No Data
        1     Green       White          Clear
        8     Red         Black          Cloudy
        2     Yellow      Light Grey     Caution
        4     Orange      Dark Grey      Don't Know

BIN_ANGLES

The step tables for the mirror driver of the four MPA are set up to provide data bins 0.5° wide, centered every even 0.5° for the low altitude emissions (4861Å, 5577Å, 4709Å) and bins 1.0° wide, centered every even 1.0° for the high altitude emisision (6300Å). The angles on which these computations are based, those of the bin centres, are shown together with the angles of the "Northern" and "Southern" bin boundaries. They are based on a mirror step size of 0.225° (1600 steps per revolution). The field of view of the instruments is 4°.

Rankin_110

      Azimuth and Elevation Angles for RANKIN at 110.0 km
       BIN  Northern Bin Edge Southern Bin Edge     Bin Centre
        1     3.200   10.800    3.200   12.600    3.200   11.700
        2     3.200   12.825    3.200   14.850    3.200   13.838
        3     3.200   15.075    3.200   17.775    3.200   16.425
        4     3.200   18.000    3.200   21.825    3.200   19.913
        5     3.200   22.050    3.200   27.675    3.200   24.862
        6     3.200   27.900    3.200   36.450    3.200   32.175
        7     3.200   36.900    3.200   50.625    3.200   43.763
        8     3.200   51.300    3.200   73.575    3.200   62.438
        9     3.200   74.700  183.200   77.625    3.200   88.537
       10   183.200   76.725  183.200   53.550  183.200   65.137
       11   183.200   52.875  183.200   38.250  183.200   45.563
       12   183.200   37.800  183.200   28.800  183.200   33.300
       13   183.200   28.575  183.200   22.725  183.200   25.650
       14   183.200   22.500  183.200   18.450  183.200   20.475
       15   183.200   18.225  183.200   15.300  183.200   16.763
       16   183.200   15.075  183.200   12.825  183.200   13.950
       17   183.200   12.600  183.200   11.025  183.200   11.813

Rankin_230

      Azimuth and Elevation Angles for RANKIN at 230.0 km
       BIN  Northern Bin Edge Southern Bin Edge     Bin Centre
        1     3.200   10.800    3.200   12.600    3.200   11.700
        2     3.200   12.825    3.200   14.850    3.200   13.838
        3     3.200   15.075    3.200   17.775    3.200   16.425
        4     3.200   18.000    3.200   21.825    3.200   19.913
        5     3.200   22.050    3.200   27.675    3.200   24.862
        6     3.200   27.900    3.200   36.450    3.200   32.175
        7     3.200   36.900    3.200   50.625    3.200   43.763
        8     3.200   51.300    3.200   73.575    3.200   62.438
        9     3.200   74.700  183.200   77.625    3.200   88.537
       10   183.200   76.725  183.200   53.550  183.200   65.137
       11   183.200   52.875  183.200   38.250  183.200   45.563
       12   183.200   37.800  183.200   28.800  183.200   33.300
       13   183.200   28.575  183.200   22.725  183.200   25.650
       14   183.200   22.500  183.200   18.450  183.200   20.475
       15   183.200   18.225  183.200   15.300  183.200   16.763
       16   183.200   15.075  183.200   12.825  183.200   13.950
       17   183.200   12.600  183.200   11.025  183.200   11.813

Gillam_110

        Azimuth and Elevation Angles for GILLAM at 110.0 km 
        BIN Northern Bin Edge Southern Bin Edge Bin Centre 
        1     9.200  10.800     9.200 12.375     9.200 11.588 
        2     9.200  12.600     9.200 14.850     9.200 13.725 
        3     9.200  15.075     9.200 18.000     9.200 16.538 
        4     9.200  18.225     9.200 22.050     9.200 20.138 
        5     9.200  22.275     9.200 28.125     9.200 25.200 
        6     9.200  28.350     9.200 37.350     9.200 32.850 
        7     9.200  37.800     9.200 52.650     9.200 45.225 
        8     9.200  53.325     9.200 76.725     9.200 65.025 
        9     9.200  77.850   189.200 73.575   189.200 87.862 
        10  189.200  72.675   189.200 50.625   189.200 61.650 
        11  189.200  49.950   189.200 36.225   189.200 43.088 
        12  189.200  35.775   189.200 27.450   189.200 31.613 
        13  189.200  27.225   189.200 21.600   189.200 24.413 
        14  189.200  21.375   189.200 17.550   189.200 19.462 
        15  189.200  17.325   189.200 14.625   189.200 15.975 
        16  189.200  14.400   189.200 12.375   189.200 13.387 
        17  189.200  12.150   189.200 10.575   189.200 11.363
 

Gillam_230

      Azimuth and Elevation Angles for GILLAM at 230.0 km
       BIN  Northern Bin Edge Southern Bin Edge     Bin Centre
        1     9.200   10.800    9.200   12.375    9.200   11.588
        2     9.200   12.600    9.200   14.850    9.200   13.725
        3     9.200   15.075    9.200   18.000    9.200   16.538
        4     9.200   18.225    9.200   22.050    9.200   20.138
        5     9.200   22.275    9.200   28.125    9.200   25.200
        6     9.200   28.350    9.200   37.350    9.200   32.850
        7     9.200   37.800    9.200   52.650    9.200   45.225
        8     9.200   53.325    9.200   76.725    9.200   65.025
        9     9.200   77.850  189.200   73.575  189.200   87.862
       10   189.200   72.675  189.200   50.625  189.200   61.650
       11   189.200   49.950  189.200   36.225  189.200   43.088
       12   189.200   35.775  189.200   27.450  189.200   31.613
       13   189.200   27.225  189.200   21.600  189.200   24.413
       14   189.200   21.375  189.200   17.550  189.200   19.462
       15   189.200   17.325  189.200   14.625  189.200   15.975
       16   189.200   14.400  189.200   12.375  189.200   13.387
       17   189.200   12.150  189.200   10.575  189.200   11.363

BIN_LATITUDES

Rankin_110

     Geodetic and Geomagnetic Coordinates for RANKIN at 110.0 km
       BIN  GD Lat   GD Lon    EDFLat EDFLon      L      INLat
        1   66.838  268.455    74.49  339.30    20.46    77.22
        2   66.333  268.374    73.99  339.23    19.05    76.75
        3   65.854  268.299    73.50  339.17    17.92    76.33
        4   65.363  268.226    73.00  339.11    16.84    75.89
        5   64.860  268.153    72.51  339.05    15.79    75.42
        6   64.358  268.083    72.00  339.01    14.88    74.97
        7   63.855  268.017    71.50  338.96    14.00    74.49
        8   63.353  267.951    71.00  338.92    13.25    74.05
        9   62.851  267.889    70.49  338.88    12.52    73.58
       10   62.354  267.829    70.00  338.84    11.86    73.12
       11   61.854  267.771    69.50  338.81    11.26    72.66
       12   61.351  267.714    69.00  338.78    10.70    72.19
       13   60.854  267.660    68.50  338.75    10.18    71.73
       14   60.351  267.607    68.00  338.72     9.63    71.19
       15   59.846  267.555    67.50  338.69     9.24    70.79
       16   59.334  267.504    67.00  338.67     8.82    70.32
       17   58.840  267.456    66.51  338.65     8.44    69.86

Rankin_230

  Geodetic and Geomagnetic Coordinates for RANKIN at 230.0 km
       BIN  GD Lat   GD Lon    EDFLat EDFLon      L      INLat
        1   70.178  269.095    77.90  339.84    35.19    80.28
        2   69.394  268.927    77.11  339.66    30.67    79.58
        3   68.608  268.771    76.32  339.51    26.84    78.86
        4   67.761  268.614    75.47  339.36    23.65    78.11
        5   66.853  268.458    74.57  339.23    20.69    77.28
        6   65.905  268.307    73.62  339.12    18.24    76.44
        7   64.917  268.162    72.64  339.01    16.10    75.55
        8   63.905  268.023    71.63  338.92    14.29    74.64
        9   62.878  267.893    70.61  338.83    12.72    73.70
       10   61.862  267.773    69.61  338.77    11.42    72.77
       11   60.850  267.660    68.61  338.71    10.31    71.83
       12   59.860  267.557    67.64  338.67     9.39    70.94
       13   58.914  267.464    66.71  338.63     8.61    70.06
       14   58.000  267.379    65.82  338.60     7.94    69.21
       15   57.123  267.301    64.97  338.57     7.38    68.39
       16   56.280  267.229    64.15  338.55     6.89    67.61
       17   55.507  267.166    63.40  338.53     6.50    66.89

Gillam_110

     Geodetic and Geomagnetic Coordinates for GILLAM at 110.0 km
       BIN  GD Lat   GD Lon    EDFLat EDFLon      L      INLat
        1   60.364  266.664    68.00  337.48     9.63    71.20
        2   59.867  266.483    67.50  337.29     9.18    70.72
        3   59.352  266.303    66.99  337.11     8.74    70.23
        4   58.855  266.135    66.50  336.93     8.35    69.75
        5   58.360  265.970    66.00  336.78     8.03    69.33
        6   57.857  265.809    65.50  336.63     7.64    68.79
        7   57.348  265.650    65.00  336.47     7.32    68.31
        8   56.844  265.497    64.49  336.33     7.02    67.81
        9   56.338  265.348    63.99  336.20     6.73    67.32
       10   55.837  265.204    63.49  336.06     6.47    66.83
       11   55.332  265.063    63.00  335.94     6.22    66.35
       12   54.827  264.924    62.49  335.82     5.98    65.86
       13   54.322  264.790    62.00  335.71     5.76    65.36
       14   53.807  264.656    61.49  335.59     5.54    64.86
       15   53.302  264.529    60.99  335.49     5.34    64.36
       16   52.805  264.406    60.51  335.39     5.16    63.88
       17   52.313  264.287    60.02  335.29     4.99    63.39

BIN_LATITUDES

Gillam_230

     Geodetic and Geomagnetic Coordinates for GILLAM at 230.0 km
       BIN  GD Lat   GD Lon    EDFLat EDFLon      L      INLat
        1   63.670  268.021    71.40  338.94    13.89    74.43
        2   62.899  267.677    70.64  338.55    12.72    73.70
        3   62.056  267.323    69.80  338.15    11.60    72.91
        4   61.202  266.982    68.95  337.79    10.62    72.11
        5   60.305  266.643    68.06  337.43     9.71    71.26
        6   59.351  266.305    67.12  337.09     8.87    70.36
        7   58.351  265.970    66.13  336.77     8.10    69.42
        8   57.333  265.647    65.14  336.47     7.41    68.44
        9   56.298  265.337    64.12  336.18     6.81    67.45
       10   55.271  265.047    63.11  335.93     6.28    66.47
       11   54.255  264.773    62.13  335.70     5.82    65.49
       12   53.264  264.520    61.16  335.49     5.41    64.53
       13   52.310  264.286    60.24  335.30     5.07    63.61
       14   51.382  264.069    59.33  335.14     4.76    62.71
       15   50.513  263.874    58.49  334.99     4.50    61.86
       16   49.705  263.698    57.71  334.86     4.28    61.07
       17   48.945  263.539    56.98  334.74     4.08    60.33

Pinawa_110

     Geodetic and Geomagnetic Coordinates for PINAWA at 110.0 km
       BIN  GD Lat   GD Lon    EDFLat EDFLon      L      INLat
        1   54.340  264.742    62.01  335.64     5.76    65.38
        2   53.814  264.635    61.50  335.56     5.54    64.86
        3   53.289  264.529    60.98  335.49     5.34    64.35
        4   52.793  264.432    60.50  335.42     5.16    63.86
        5   52.293  264.337    60.00  335.35     4.98    63.38
        6   51.779  264.242    59.50  335.29     4.81    62.88
        7   51.261  264.147    58.99  335.22     4.65    62.37
        8   50.750  264.056    58.49  335.16     4.50    61.87
        9   50.236  263.967    57.99  335.10     4.36    61.36
       10   49.727  263.880    57.50  335.05     4.22    60.85
       11   49.217  263.794    56.99  334.99     4.09    60.35
       12   48.707  263.711    56.50  334.95     3.97    59.85
       13   48.199  263.630    56.01  334.90     3.85    59.35
       14   47.683  263.549    55.51  334.85     3.74    58.84
       15   47.160  263.468    55.00  334.80     3.63    58.32
       16   46.655  263.392    54.51  334.76     3.53    57.83
       17   46.139  263.316    54.01  334.71     3.43    57.32

Pinawa_230

   Geodetic and Geomagnetic Coordinates for PINAWA at 230.0 km
       BIN  GD Lat   GD Lon    EDFLat EDFLon      L      INLat
        1   57.744  265.515    65.53  336.26     7.66    68.81
        2   56.936  265.319    64.74  336.10     7.16    68.04
        3   56.084  265.122    63.90  335.93     6.68    67.23
        4   55.236  264.933    63.08  335.80     6.26    66.43
        5   54.338  264.742    62.20  335.65     5.85    65.57
        6   53.369  264.546    61.26  335.51     5.45    64.63
        7   52.355  264.350    60.28  335.37     5.09    63.66
        8   51.328  264.160    59.28  335.24     4.75    62.67
        9   50.277  263.974    58.26  335.13     4.44    61.65
       10   49.233  263.798    57.26  335.02     4.16    60.64
       11   48.201  263.631    56.28  334.92     3.92    59.64
       12   47.197  263.474    55.32  334.83     3.70    58.65
       13   46.231  263.329    54.40  334.74     3.51    57.71
       14   45.294  263.194    53.51  334.68     3.34    56.79
       15   44.391  263.068    52.65  334.61     3.18    55.91
       16   43.564  262.955    51.87  334.55     3.06    55.10
       17   42.766  262.850    51.11  334.51     2.94    54.32
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