McIDAS-X User's Guide
Version 2023.1

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UACROSS

Plots a vertical cross section of upper-air data.


Format

UACROSS loc1 . . locN [keywords]


Parameters

loc1 . . locN

two or more locations to include in the cross section; each location can be specified as a 4-character station ID (e.g., KINL), a 5-digit station ID number (e.g., 72747), or a latitude/longitude pairing enclosed in single quotes (e.g.,'48.5 93.3' or '48:30:10 93:18:40'); see the Remarks for information about how the specified locations and other keywords are used to select and plot datapoints in the cross section


Data Selection Keywords
(Point and Grid)

DATaset=

point or grid dataset(s) to use in the cross section; use the mand sig format for point datasets and grid_dataset format for grid datasets; the default is for point datasets as described below so you must specify this keyword to use a grid dataset; see the Remarks for information about the differences in datapoint selection with point data and grid data

 

mand sig

point dataset(s) containing the mandatory- and significant-level data to use in the cross section; must also specify SIG=YES if you want significant levels included with the mandatory levels; currently only IRAB/IRSG and RAOB/RSIG schema point datasets can be used (mand default=RTPTSRC/UPPERMAND; sig default=RTPTSRC/UPPERSIG if mand =RTPTSRC/UPPERMAND and SIG=YES, otherwise sig default=NONE)

 

grid_dataset

grid dataset containing the grids to use in the cross section

DAY=

date of grids or observation date in point file; valid formats include YYYYDDD, YYYY/MM/DD and DD/MON/YYYY where YYYY, DDD, MM and DD are integers and MON is 3 or more letters, e.g., JAN or JANUARY (default=current for point data; no default for grids)

TIMe=

time of grids or observation time in point file (for point data, default=0 if current time is between 0 UTC and 11:59 UTC, otherwise default=12; no default for grids)

MODe=

I

interactive mode that uses the navigation of the current frame and the mouse to select locations for the cross section; you can select between 2 and 13 locations; see the Remarks for information about how the selected locations and other keywords are used to find and plot datapoints in the cross section; MODE=I is valid only if locations are not specified in the loc1 . . locN parameters (default=I if no locations are specified in loc1 . . locN)

 

N

non-interactive mode where the cross section's locations are selected with the loc1 . . locN parameters (default=N if locations are specified in loc1 . . locN)

CORridor=

YES size[units]
use corridor(s) of the specified size to select datapoints for the cross section; a corridor is a rectangular region with a line running down the middle that connects the beginning and ending locations and a width equal to 2 times the size specified in this keyword; use size and/or the EXCLUDE or INCREMENT keyword to increase or decrease the number of datapoints in the cross section; run command CU LIST to list the valid units; see the Remarks for additional information about corridors

 

 

NO size [units]
do not use corridor(s); thus only the 3+ locations specified in loc1 . . locN or located with MODE=I are included in the cross section; for CORRIDOR=NO the size value and units specify the maximum radius from each location (selected with MODE=I or specified in loc1 . . locN) to use to find an endpoint; the closest datapoint within the radius is selected as the endpoint; if no datapoints are within the radius, UACROSS fails (default=YES 250[KM] if two locations are selected with MODE=I or are specified in loc1 . . locN; default=NO 250[KM] if 3 or more locations are selected or specified)

 

PRAnge=

min max

pressure levels, in mb, at top and bottom of diagram, respectively (default=100 1050)


Point-Only Data Selection Keywords

EXClude=

stn1 . . stnN

stations to exclude from the cross section; up to 8 stations may be excluded; each station can be specified as a 4-character station ID (e.g., KINL) or a 5-digit station ID number (e.g., 72747); this keyword is useful for re-running commands that select more stations than desired and/or include questionable data

SIG=

NO

do not include data from significant-level dataset specified in DATASET keyword; use only its mandatory-level dataset (default)

 

YES

include data from significant-level dataset specified in DATASET keyword


Grid-Only Data Selection Keywords

FDAy=

forecast day of grids to use in cross section; calculated by adding a grid's fhour to its day and time, e.g., a grid with day=2000300, time=12 and fhour=72 has fday=2000303; use with FTIME to select a specific forecast day and time; you cannot use FDAY with the FHOUR keyword

FHOur=

forecast hour of grids to use in cross section; you cannot use FHOUR with the FDAY or FTIME keyword

FTIme=

forecast time of grids to use in cross section; calculated by adding a grid's fhour to its time, e.g., a grid with time=12 and fhour=18 has ftime=6 on the following day; use with FDAY to select a specific forecast time and day; you cannot use FTIME with the FHOUR keyword

GPRo=

projection of grids to use in cross section, e.g., MERC, PS, LAMB, EQUI

INCrement=

row col

grid point sampling increment for rows and columns; use this keyword and the CORRIDOR keyword to increase or decrease the number of grid points that can be used as datapoints in a cross section corridor; see the Remarks (row default=5; col default=row)

SRC=

source of grids to use in cross section, e.g., ETA, GFS, MDX


Parameter Selection and Display Keywords

PARam=

par1 [unit1] . . parN [unitN]
list of up to 10 parameters to plot and their output units (default=THA[K]); the valid parameters are DIR, MIX, P, RH, SPD, SPDE, SPDN, SPDS, SPDZ, T, TD, TE, THA, THE, THW, TV, TW, U, V, WINDB, Z; see table in Remarks for parameter descriptions, their default units, and their defaults for the CINT, COLOR, DASH, LINT, LSIZE, and SMOOTH keywords

 

CINt=

c1 . . cN

contour interval for each PARAMeter; specify 0 to let UACROSS compute a reasonable interval, a value greater than zero to select your own value, or the name of a string that contains up to 64 values (default=value specified for corresponding parameter in UACROSS.* text file - see table and paragraphs before and after it in the Remarks)

COLor=

c1 . . cN

graphics color level for each PARAMeter (default=value specified for corresponding parameter in UACROSS.* text file - see table and paragraphs before it in Remarks)

DASh=

d1 . . dN

contour dash mode for each PARAMeter; specify one of the following values for each PARAMeter:
ALL - dash all contours
NONE - do not dash contours
NEG - dash negative contours only
POS - dash positive contours only
(default=value specified for corresponding parameter in UACROSS.* text file - see table and paragraphs before it in Remarks)

LINt=

l1 . . lN

contour label interval for each PARAMeter; the value must be greater than 0; the value 1 means label every contour, 2 means label every other contour, etc. (default=value specified for corresponding parameter in UACROSS.* text file - see table and paragraphs before it in Remarks)

LSIze=

l1 . . lN

contour label height, in pixels, for each PARAMeter (default=value specified for corresponding parameter in UACROSS.* text file - see table and paragraphs before it in Remarks)

SMOoth=

s1 . . sN

contour smoothing factor for each PARAMeter; the range is 3-50; larger numbers produce smoother contours (default=value specified for corresponding parameter in UACROSS.* text file - see table and paragraphs before it in Remarks)


Other Output Keywords

EG=

NO

do not erase graphics frame before plotting (default=YES)

GCOlor=

bg land tlab blab datapt p map path
graphics color level of cross section components
(default=8 8 3 X 3 8 1 3), where:

 

bg

background borders, vertical lines and tic marks

 

land

land surface

 

tlab

top label identifying beginning and ending datapoints

 

blab

bottom label identifying plotted parameters; the default color for each parameter's label is the value specified in the COLOR keyword for that parameter

 

datapt

datapoint labels at bottom of diagram

 

p

pressure labels on left side of diagram

 

map

inset map, when requested with MAP=YES keyword

 

path

cross section path and datapoint markers on map

 

note: you can specify 0 to omit (not draw) any component

IDLabel=

NUMbers

display 5-digit ID numbers of plotted stations at bottom of cross section; valid only with point data (default for point data)

 

NAMes

display 4-character IDs of plotted stations at bottom of cross section; valid only with point data

 

LALO

display latitude/longitude pairings of plotted stations at bottom of cross section; valid with point or grid data (default for grid data)

GRA=

graphic frame number to display cross section (default=current)

LABel=

'text' color line ele size
text, color, location & size for cross section label, where:

 

'text'

label's text; 80 characters maximum; specify X without quotes for default text (default=computed)

 

color

graphics color level of label (default=3)

 

line

beginning TV line to write label (default=lower-left corner of frame; line number depends on frame size)

 

ele

beginning TV element to write label (default=20)

 

size

pixel size of characters drawn (default=8)

 

note: if you specify this keyword, the default top and bottom labels (which identify beginning and ending datapoints, and plotted parameters, respectively) are not drawn

LIStinfo=

YES

list detailed station information (ID number, ID name, station name, state, country, latitude, longitude and elevation) of each station in text frame; valid only when using point data, i.e, not valid with grids

 

NO

do not list detailed information; list only the ID number (default)

MAP=

NO

do not draw a map showing the cross section (default)

 

YES

draws a map in the upper-right corner of the frame showing the cross section location, datapoints, and path as determined by the SPACING keyword

 

YES 'command'
draws a map using the MAP command specified in 'command' and draws the cross section datapoints and path as determined by the SPACING keyword; use this option to override the map domain and/or frame location that MAP=YES draws; the defaults for the 'command' are the same as in the MAP command except for the LIN and ELE keywords, which default to the upper-right corner like the default MAP=YES output
Examples:

1. MAP=YES 'MAP MID X LALO'
draws a map of the Midwest with lat/lon lines instead of the default map computed by UACROSS

2. MAP=YES 'MAP MID X LALO LIN=300 450 ELE=10 210'
draws the same map but places it in the location specified with the LIN and ELE keywords instead of the upper-right corner of the frame

SPAcing=

NORMAL

spaces datapoints in the diagram using the normalized distances along the cross section axis; i.e., the distance between datapoints on the diagram is proportional to the distance between where their lines perpendicular to the axis intersect the axis; if you also draw a map using the MAP keyword, the cross section path is drawn along the axis

 

ACTUAL

spaces datapoints in the diagram according to their actual distances from each other, not the normalized distances along the axis; if you also draw a map using the MAP keyword, the cross section path is drawn from datapoint to datapoint, in a zig-zag pattern as defined by the datapoint locations; this option is not recommended if grid data is used and CORRIDOR=YES is specified (default=ACTUAL if three or more locations and CORRIDOR=NO are specified, otherwise default=NORMAL)


Remarks

UACROSS plots contoured vertical cross sections of meteorological parameters using point or grid data. Use the DATASET keyword to specify the point or grid dataset, and keywords like TIME, DAY and FHOUR and SRC to narrow the search to more specific data. The cross section requires upper-air data from three or more datapoints. A datapoint is an observation location in a point file, or a grid point location in a grid. The datapoints are found using the locations specified in the loc1 . . locN parameters or the geographic points selected interactively with the mouse when MODE=I. The six paragraphs below explain how datapoints are selected and plotted in the cross section.

If you use point data and specify station IDs in loc1 . . locN, UACROSS uses the data only at those stations. That is, it will NOT look for data at a nearby station if the specified station didn't report data. Therefore, UACROSS will fail if any of the specified stations don't have data at the requested time.

If you use grid data, or use point data and specify latitude/longitude locations in loc1 . . locN or interactively choose locations with MODE=I, UACROSS selects the datapoint closest to each location if it's within the size value in the CORRIDOR keyword. Therefore, the lat/lons specified in loc1 . . locN or locations chosen with MODE=I do NOT have to exactly match those of stations in a point file or grid points in a grid.

If you specify only two locations in loc1 . . locN or select only two locations with MODE=I, they are used to find the beginning and ending datapoints (endpoints) of the cross section. The beginning datapoint is plotted on the left end and the ending datapoint is plotted on the right end of the diagram. Datapoints within the corridor defined by the endpoints and the size value in the CORRIDOR keyword are included in the cross section unless they're excluded by the program because they're too close to another datapoint or are excluded by the EXCLUDE or INCREMENT keywords.

If you specify 3 to 13 locations in loc1 . . locN and CORRIDOR=YES, or you select 3 to 13 locations with MODE=I and specify CORRIDOR=YES, multiple corridors are used and the first and second locations are used to find the endpoints for the first corridor, the second and third locations are used to find the endpoints for the second corridor, etc. Datapoints within each corridor defined by its endpoints and the size value in the CORRIDOR keyword are included in the cross section unless they're excluded by the program because they're too close to another datapoint or are excluded by the EXCLUDE or INCREMENT keywords.

If you specify 3 to 13 locations in loc1 . . locN and CORRIDOR=NO, or you select 3 to 13 locations with MODE=I and specify CORRIDOR=NO, corridors are not used, so only the datapoints for each location are included in the cross section. The datapoints are plotted from left to right on the cross section.

Although up to 25 datapoints can be included when CORRIDOR=YES is specified, a more practical limit is 15 or less. To decrease the number of datapoints, specify a smaller size value in the CORRIDOR keyword and/or larger row and col values in the INCREMENT keyword (which is valid only with grid data). For example, INC=8 6 allows datapoints to be selected only at grid points in every eighth row and every sixth column within the specified CORRIDOR. Longer and/or wider corridors often require larger INCREMENT values to keep the number of datapoints to 15 or less. The most uniform distribution of datapoints along a corridor is obtained by setting INC=1 and keeping the size value in CORRIDOR as small as necessary to reject neighboring grid points without excluding the anchoring endpoints. Use the SPACING keyword to specify how the sounding at each datapoint is projected onto the cross section.

The default units and keyword values for each parameter specified in the PARAM keyword are stored in the text files UACROSS.USER, UACROSS.SITE, and UACROSS.CORE. The .USER file overrides the .SITE file, which overrides the .CORE file. This order of precedence allows you to define your preferred defaults in your .USER file. The .CORE file is supplied with McIDAS-X and should not be modified. To create a .USER or .SITE file, copy the .CORE file from ~mcidas/data to your $HOME/mcidas/data directory (or another MCPATH directory) and edit the values as needed.

The table below lists the contents of the UACROSS.CORE file, which includes the parameters that can be specified in the PARAM keyword, their default units, and their default values for the CINT, COLOR, DASH, LINT, LSIZE, and SMOOTH keywords. Default units enclosed in parenthesis cannot be changed. Otherwise the units can be changed with the PARAM keyword and/or by creating and modifying a UACROSS.USER or UACROSS.SITE file as described above. Likewise, the other values can be changed with their corresponding keywords and/or in UACROSS.USER or UACROSS.SITE.

  Default Values  
Param Unit CINt COLor DASh LINt LSIze SMOoth Description
DIR (degrees) 90 1 ALL 1 6 20 wind direction
MIX (G/KG) 2 4 ALL 1 6 20 mixing ratio
P MB 50 8 NONE 2 6 20 pressure
RH (%) 5 8 NONE 2 6 20 relative humidity
SPD KTS 5 2 NONE 1 6 20 wind speed
SPDE KTS 5 2 NEG 1 6 20 enhanced wind normal to cross section
SPDN KTS 5 2 NEG 1 6 40 wind normal to cross section
SPDZ (1/S) 5 2 NEG 1 6 20 vertical wind shear
T C 5 5 NEG 2 6 20 temperature
TD C 5 4 NEG 2 6 20 dewpoint temperature
TE K 5 5 NEG 2 6 20 equivalent temperature
THA K 5 5 NEG 2 6 20 potential temperature
THE K 2 5 NEG 2 6 20 equivalent potential temperature
THW K 1 4 NEG 2 6 20 wet bulb potential temp.
TV K 5 5 NEG 2 6 20 virtual temperature
TW K 5 4 NEG 2 6 20 wet bulb temperature
U KTS 5 2 NEG 2 6 20 easterly wind component
V KTS 5 3 NEG 2 6 20 northerly wind component
WINDB (barb) n/a 7 n/a n/a 12 n/a windbarb: flag=25mps(~50kts)
long barb=5mps(~10kts) short barb=2.5mps(~5kts)
Z M 2000 1 NEG 2 6 20 height from surface

The default contour interval for each parameter is taken from the appropriate UACROSS.* text file as described above the table. If you change the units of a parameter you may also want to change the contour interval as the defaults above are usually appropriate only for the default units. If you specify 0 for the contour interval, a value is calculated that produces a reasonable number of contours, usually between 10 and 20. In all cases the values will be adjusted slightly by the program to the nearest multiple of 1, 5, 10, 50, etc., consistent with the plot resolution.


Examples

UACROSS

This entry displays a cross section of potential temperature for locations selected interactively using the mouse. If two locations are selected, datapoints within a 500 km-wide corridor with endpoints at the two locations are selected. If three or more locations are selected, only the datapoint at or closest to (within 250 km) each location is selected.

UACROSS CORRIDOR=YES 150[MI] MAP=YES

This entry displays a cross section of potential temperature for locations selected interactively using the mouse. A 300 mile-wide corridor is computed for each pair of consecutively chosen locations (i.e., first and second, second and third, etc.). All datapoints within each corridor are plotted in the diagram unless they're excluded by the program because they're too close to another datapoint. A map is drawn in the upper-right corner showing the cross section location, datapoints and path.

UACROSS KMIA KBUF MAP=YES IDLABEL=NAMES PARAM=MIX THA SPD

This entry displays a cross section of mixing ratio, potential temperature and wind speed using the attributes defined for each parameter in the UACROSS.USER, .SITE or .CORE file. The cross section runs from Miami to Buffalo and includes datapoints within a 500 km-wide corridor between the two cities. The plotted stations are labeled with their 4-character IDs instead of their 5-digit ID numbers (e.g., KJAX instead of 72206). A map is drawn in the upper-right corner showing the cross section location, datapoints and path.

UACROSS KSLE KBOI 72672 KLBF PARAM=TD[F] SPDN[MPH] COLOR=2 3

This entry displays a cross section of dewpoint temperature and wind speed normal to the cross section. The units and graphics color levels specified in the command (F and 2 for TD; MPH and 3 for SPDN) override the settings in the UACROSS.* files. Because there are more than two locations specified and the default for the CORRIDOR keyword in this case is NO, only the four specified stations (Salem, Boise, Riverton, and North Platte) are included in the cross section.

UACROSS '38:40 09:10' 08221 07645 12843 UKKK MAP=YES CORRIDOR=YES LABEL='UACROSS across Europe' X 5 5 12

This entry displays a cross section of potential temperature for the five specified locations and the datapoints within the 500 km-wide corridors between each of pair of locations. As shown in this example, locations can be specified as latitude/longitude pairings enclosed in single quotes, 5-digit ID numbers or 4-character IDs. A map is drawn in the upper-right corner showing the cross section location, datapoints and path. The text UACROSS across Europe is plotted in graphics color level 3 and pixel size 12 near the top-left corner of the frame.

UACROSS KMIA KIAD MAP=YES DAY=#Y TIME=0 FHOUR=12 DATASET=RTGRIDS/ETA INCREMENT=2 2 CORRIDOR=YES 100[KM]

This entry displays a cross section of potential temperature between Miami and Washington, D.C. using the 12-hour forecast grids from today's 0 UTC run in the dataset RTGRIDS/ETA. The INCREMENT and CORRIDOR keywords work together to keep the number of grid points selected as datapoints to a reasonable limit of 15 or less. In this example, those keywords ensure that only grid points from every other row and column that are within 100 km of the axis from Miami to Washington D.C. are selected as datapoints. A map is drawn in the upper-right corner showing the cross section location, datapoints and path.


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