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20040607: importing and contouring data on GOES imagery (cont.)



>From: Owen Cooper <address@hidden>
>Organization: Aeronomy Laboratory/NOAA
>Keywords: 200406080008.i5808gtK000586 McIDAS SCHEMA Flexpart

Hi Owen,

>Last year you helped me contour pollution data onto GOES imagery using 
>the SCHEMA below, which was applied to a text file containing 3 columns, 
>latitude longitude and carbon monoxide concentration.

I actually remember :-)

>The SCHEMA has worked great but the one thing it's lacking is the time 
>stamp of the data.

I believe I made a comment about this at the time...

>I'd like to create a large data set for one month with a separate MD 
>file (containing carbon monoxde data for the USA) for each 3-hour time 
>period.  So there would be 8 files per day.

Why split the observations into different files for 3 hour chunks?
The most common approach would be to create a single file for each
day.

>I would then like to use 
>PTCON to display the data, but have a SELECT clause set up so that the 
>data can be retrieved by day and hour.

OK.

>Seeing as my MD files contain 
>point data at each 1x1 degree grid cell, does this mean each data point 
>has to have a day and time (which would make the files much larger)

No.  It could, but it doesn't have to.

>or 
>can I simply add the day and time to a header within the MD file that 
>applies to all data points?

Yes.

Your objective is to essentially create an MD file that has a lot of
similarities with a surface (METAR) MD file.  To illustrate my point,
here is a listing for the schema (ISFC) for a surface MD file:

LSCHE ISFC

NAME: ISFC  VERSION:  7  DATE: 1999085  TEXTID: "SURFACE HOURLY OBSERVATIONS
----        -------
   DEFAULT NUMBER OF ROWS:   72                        INTEGER ID: 0
                     COLS:   3500                   MISSING DATA VALUE:  
-2139062144
   REPEAT GROUP:  NUMBER OF REPETITIONS:   1
                      STARTING POSITION:  11
                                   SIZE:  25
   NUMBER OF KEYS IN ROW HEADER:     4
                     COL HEADER:     6   STARTING AT POSITION   5
                    DATA RECORD:    25   STARTING AT POSITION  11
                                  ----
                                    35 TOTAL

        KEY  SCALE UNIT     KEY  SCALE UNIT     KEY  SCALE UNIT
        ---- ----- ----     ---- ----- ----     ---- ----- ----
        TYPE   0            DAY    0   CYD      TIME   0   HMS
        NREC   0            ID     0   CHAR     LAT    4   DEG
        LON    4   DEG      ZS     0   M        ST     0   CHAR
        CO     0   CHAR     MOD    0            HMS    0   HMS
        CIGC   0            CC1    0            CC2    0
        CIGH  -2   FT       ZCL1  -2   FT       ZCL2  -2   FT
        VIS    1   MI       WX1    0   CHAR     WX2    0   CHAR
        T      2   K        TD     2   K        DIR    0   DEG
        SPD    1   MPS      GUS    1   MPS      PSL    2   MB
        PCP    2   IN       SNO    0   IN       PRE    2   MB
        P24    2   IN       WXC1   0   CODE     WXC2   0   CODE
        WXC3   0   CODE     WXC4   0   CODE
LSCHE: DONE


Notice the following about the ISFC schema (located in the file DCISFC):

- there are 4 keys per row:  TYPE, DAY, TIME, NREC

- there are 6 keys per column: ID, LAT, LON, ZS, ST, CO

- there are 25 keys for data

(Here CO is COuntry, not Carbon diOxide)

What you are proposing to create could look very similar to this:

- 2 keys per row: DAY, TIME

- 0 keys per column

- 3 data keys: LAT, LON, CO

(Here CO is Carbon diOxide, not COuntry)

If your data is hourly, the schema would have 24 rows.  If your data is
3-hourly, your schema would have 8 rows.

I think the schema would end up looking something like:


"       NAME    VSN     DATE    ID      TEXTID
"       ----    ---     ----    --      ------
SCHEMA  FLXP    2       04160   0       "FLEXPART CO CONCENTRATIONS

"KEY    SCALE   UNITS   DESCRIPTION
"---    -----   -----   -----------

ROWS    24              "24 ROWS 1 PER HOUR

  DAY        CYD         "YEAR AND JULIAN DAY (CCYYDDD)
  TIME       HMS         "NOMINAL TIME (HH0000)

COLUMNS 360             "DEFAULT # OF COLS

DATA                    "START OF DATA SECTION

LAT     4       DEG     "LATITUDE (DECIMAL DEG)
LON     4       DEG     "LONGITUDE (DECIMAL DEG)
CO      2       CON     "CO2 CONCENTRATION

ENDSCHEMA

>Thank you in advance for any ideas you can send my way.

You may have to play a little with the setup to get TXT2MD to work with
your input file.

Please let me know if anything is not clear.

Cheers,

Tom
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