Using the Hydro-Estimator in McIDAS

Bob KuligowskiNOAA/NESDIS Center for Satellite Applications and

Research (STAR)

Outline

I. Brief McIDAS Background

II. Hydro-Estimator Basics

III. Running the Hydro-EstimatorA. Preparing the data fields

B. Running the algorithm

C. Examining the results

Appendix: Basic McIDAS Commands

Brief McIDAS Background

• Man-computer Interactive Data Access System—used to display and analyze satellite data (GEO and LEO)

• Supports both line commands and a programming language similar to FORTRAN 77

• Information and online documentation: http://www.ssec.wisc.edu/mcidas/

• To run, just type mcidas from a terminal window. A command screen and display screen should appear.

McIDAS Programs

• McIDAS has a programming language that is virtually identical to FORTRAN 77.

• Programs are kept in the mcidas/src directory and have a .pgm suffix instead of .f or .for.

• Special subroutines and library functions are used to read and write McIDAS data files, but ASCII and binary file formats are also supported

• Programs are compiled using the command fx program l –vendor which compiles program.pgm and places an executable program.k in the mcidas/bin directory.

Outline

I. Brief McIDAS Background

II. Hydro-Estimator Basics

III. Running the Hydro-EstimatorA. Preparing the data fields

B. Running the algorithm

C. Examining the results

Appendix: Basic McIDAS Commands

Hydro-Estimator Basics

• Manual techniques for estimating rainfall from satellite cloud-top temperatures have existed for >30 years

• The Auto-Estimator was the first-generation automated technique at NESDIS; the Hydro-Estimator (HE) replaced it in 2002.

• Both techniques related rainfall rate to cloud-top temperature as estimated in 10.7-µm GOES imagery:– Colder clouds are raining heavily;– Warmer clouds are raining lightly or not at all.

200 250 290T (K)

Tb=230 K

Tb=224 K

Tb=212 KTb=200 K

Illustration of the IR signal from different rainfall intensities

290200 250T (K)

CumulonimbusTb=200 K

NimbostratusTb=240 K

CirrusTb=205 K

Exceptions to the Rule...

Hydro-Estimator Basics

• Simple use of 10.7-µm brightness temperatures leads to missing of warm, stratiform rain and incorrect designation of cold cirrus as raining clouds—a major problem with the original Auto-Estimator

• The HE considers the temperature relative to the surrounding pixels using the relationship Z=(µ-T)/ σ– µ is the mean temperature of the nearby cloudy pixels– σ is the standard deviation of the temperature of the nearby

cloudy pixels– Pixels colder than their surroundings (positive Z) are assumed to

be convective updrafts and hence producing rainfall– Pixels as warm as or warmer than their surroundings (negative

Z) are presumed to be convectively inactive

Illustration of the HE Rain-No Rain Differentiation

290200 250T (K)

Tb < Tb

Rain

Tb ≥ Tb

No Rain

Tb < Tb

Rain

Tb ≥ Tb

No Rain

Hydro-Estimator Basics• Satellite imagery alone does not contain all the

information needed for evaluating rainfall. Numerous processes occur below the clouds, including– Evaporation of raindrops– Enhancement or reduction of rainfall by terrain-induced upslope /

downslope

• Numerical Weather Prediction (NWP) model forecast fields are used to derive correction factors:– Precipitable water: enhance rain rates in high-PW areas; reduce

in low-PW areas– Relative humidity: reduce rain rates in dry (low-RH) areas– Convective equilibrium level temperature; regions with values

above 213 K have their rain rates enhanced– 850-hPa winds interfaced with digital topography: enhance rain

rates in upslope regions and reduce them in downslope regions

Rain rate as a function of brightness temperature and precipitable water in the Hydro-Estimator

“Convective Core” rainfall “Non-core” rainfall

PW (mm)

PW (mm)

Reduction in rain rate as a function of relative humidity in the Hydro-Estimator

Tpre≤235 K?

Find Tmin in surrounding 101x101 box

Zi=(μ-Tadj)/ σ for r1, r2

Zi>0?

RR1>0? RR=SQRT(RR12+RR2

2)RR=RR2

RH=RH-0.01*SQRT(RR-10)

RRi=[RRc*Z2+RRn*(1.5-Z)2]/[Z2+(1.5-Z)2

RRi=0

Y

N

NRR=0

Y

Done

Done

N Y

Preliminary EL, ORO, PWAdjustments (T10.7Tpre)

r1=250-Tmin; 30≤r1≤50r2=15

Compute μ, σ for r1 and r2

Replace Tpre with Tadj

GOES T10.7 Eta TEL ORO Eta PW

i=1,2

Eta RH

RR=RR-25*(0.85-RH)-0.35(0.6-RH)-0.5(0.4-RH)(only negative components are used)

TEL<270 K? Tadj=T10.7

TEL-min(T(Z1=1.0), T10.7)<10 K?

Tadj=0.9*(213 - TELadj

TELadj=min(TEL+min(T(Z1=10), T10.7))/2, Tmin)

Tadj=0.6*(213-TELadj)

Y

N

NY

Tadj>210? Tadj=max(Tadj-ORO/2,210)

Tadj=Tadj-ORO

PW>1.5?

DPW=1.5-PWDPW=2.5*(1-PW)

Tadj=max(Tadj+DPW, 210)

PW>2.0? DPW=2*(2-PW)

Tadj>210?

YY

Y

NN

Compute “core” RRc via function fit(RRc@210K=RR’ in/hr; RRc@240K=0.5 in/hr)

Compute “non-core” RRn with 12 mm/h cap:RRn=min(RR’*(250-Tadj)/5,RRc/5)

RR’=25.4*(1-DPW/10)

N

Eta TEL

GOES T10.7

ORO

Eta PW

Outline

I. Brief McIDAS Background

II. Hydro-Estimator Basics

III. Running the Hydro-EstimatorA. Preparing the data fields

B. Running the algorithm

C. Examining the results

Appendix: Basic McIDAS Commands

Sample Hydro-Estimator Run

• Different from operational HE in that we will use pre-made adjustment files

• Necessary inputs:– Current GOES band 4– NAM EQL (convective equilibrium level in K)– NAM precipitable water (PW in hundredths of inches)– NAM mean relative humidity (percent) from the lower

third of the NAM vertical domain– Orographic correction (ORO; NAM 850-hPa winds

interfaced with digital topography)– Dummy file with all values=100

Sample Hydro-Estimator Run

• Necessary Programs (again, a reduced set):– zenitcor.pgm: Corrects for limb cooling at high

satellite zenith angles• zenitcor IN OUT

– parcormercir.pgm: Corrects for parallax• parcormercir IN OUT

– rainsplitiso.pgm: Produces rain rate estimates• rainsplitiso GOES OUT PW RH EQL RH ORO DUM

Getting Started—Get the Files

• Create a local directory for yourself and cd to it• Access ftp.orbit.nesdis.noaa.gov via

anonymous ftp• cd /aftp/pub/smcd/emb/bobk/HE• ls (directory listing)• prompt• binary• mget * (download the files into your local directory)• bye (to exit), and then uncompress the files

(uncompress *.Z)

Getting Started—Data Files

• Copy the following files into mcidas/data, assigning your own set of AREA numbers to the new files:– goes12.2006.171.17mm.Z (pick 1 of the 3): GOES Imager

band 4 for 17mm UTC 20 June 2006 (Julian day 171)– 0606201200EQL.Z: NAM-derived convective equilibrium level

temperature for 1200 UTC 20 June 2006– 0606201700PW_.Z: NAM PW for 1700 UTC 20 June 2006– 0606201700RH_.Z: NAM RH for 1700 UTC 20 June 2006– 0606201200ORG.Z: NAM-derived orographic correction for

1200 UTC 20 June 2006– DUM.Z: a dummy file used to fill an unused slot

• Use the standard copy command; e.g., cp goes12.2006.171.1701.Z mcidas/data/AREA5001.Z

Getting Started—Data Files• From your McIDAS command line, first reproject each

of your AREA files onto a common grid using the IMGREMAP command. The grid projection, coverage, resolution, etc. do not matter as long as you are consistent. A suggestion:

IMGREMAP LA.1001 LA.2001 LAT=40 95 PRO=MERC RES=4 SIZ=ALL

• Make sure you use different destination AREA numbers for each one! You may want to write them down for reference.

• Display a few images to see the difference before and after remapping.

Getting Started—Source Code• Copy the following files into mcidas/data:

– latitudeerror– zenitherror

• Copy the following programs into mcidas/src:– zenitcor.pgm: Corrects for limb cooling at high

satellite zenith angles– parcormercir.pgm: Corrects for parallax– rainsplitiso.pgm: Produces rain rate estimates

• Compile each program using fx name l –vendor, where name does NOT have the .pgm suffix.

HE—Zenith Angle Correction• To correct for limb darkening of the GOES

imagery, use ZENITCOR sarea darea– sarea is the source AREA file number (your

remapped GOES band 4 file)– darea is the destination AREA file number

• Display the image and compare it to the original; it should appear slightly warmer, especially in northern portions of the image

HE—Parallax Correction• To correct for parallax in the GOES imagery, use PARCORMERCIR sarea darea– sarea is the source AREA file number (your limb-

corrected GOES band 4 file)– darea is the destination AREA file number

• Display the image and compare it to the original; the clouds should have shifted to the east (toward 75 W) and south (toward the equator)

HE—Rain Rate Estimation• To create the rain rate images, use RAINSPLITISO goes darea pw eql rh oro dum– goes is the AREA file number of your limb- and

parallax-corrected GOES band 4 file– darea is the destination (output) AREA file number– pw is the reprojected PW AREA file number– eql is the reprojected EQL AREA file number– rh is the reprojected RH AREA file number– oro is the reprojected ORO AREA file number– dum is the reprojected dummy AREA file number

• Run it and look at the output, using the WSI.ET enhancement table (see next page).

HE—Adding a Color Bar• Copy the files WSI.ET and WSI75.ST to mcidas/data

• On the same frame where the HE is displayed, type BAR SU=WSI750 ORI=HOR RAN=0 75 LIN=5

• This will add a color bar to your display. Note that EG will not get rid of it; you have to use ERASE.

HE—Experimentation• One more useful command is IMGOPER, which can be

used to make additive or multiplicative adjustments to the values in IMAGE files

• IMGOPER sdataset1 . . sdatasetn ddataset [keywords]– sdataset1…n are the input datasets– ddataset is the destination dataset– Keywords:

• ACO=c adds a constant c to all data• ADD adds the corresponding pixels in each dataset; to subtract,

include COEF=-1• MULT multiplies the corresponding pixels; to divide, include POW=-1;

to multiply by different factors, use POW=a b c d, etc. where a…d are multiplication factors.

• MCO=d multiplies all data by a constant d

• Try IMGOPER on a file and use IMGPROBE to examine the results. Then try those new files as HE inputs to see what happens!

Appendix: Basic McIDAS Commands

McIDAS Command Line Basics

• McIDAS displays in ALL CAPS when the “Caps Lock” is OFF and vice versa

• Arrow keys scroll the screen up and down, but…• Only the current command is visible; use <shift-

7> (&) to recall previous commands• Use the arrow keys to move across the

command line to edit it– Default is to replace text– Toggle <Insert> to insert intead of replace

McIDAS Commands—DSINFO

• Lists data on local and remote servers• DSINFO type group

– type = type of data (GRID, IMAGE, NAV, POINT, or TEXT)

– group = group name– DATALOC LIST lists all of the available groups and

their IP addresses

• DSINFO ALL displays all of the available data sets

• DSINFO ALL group displays all available data sets in a particular group

McIDAS Commands—IMGCOPY

• Copies image data from one dataset to another. • IMGCOPY sdataset ddataset [keywords]

– sdataset = source dataset group and position– sdataset = destination dataset group and position

• Typically one copies into the local data directory, where sdataset is given as LOC/AREA.# (or just LA.#), where # is a number up to 9999.

• These files can be also be viewed outside of McIDAS in the mcidas/data directory.

• Try IMGCOPY GER/GENHEM04I4 LA.# SIZE=ALL.

McIDAS Commands—IMGCOPY

• Important IMGCOPY keywords:– LAT=lat lon, where lat and lon are the latitude

and longitude (degrees, with west longitude as a POSITIVE value) of the region of interest, specified either as• PLA=ULEFT: lat lon is the upper left of the region;• PLA=CENTER: lat lon is the center of the region (DEFAULT)

– SIZ=line ele, where the height (line) and width (ele) are given in pixels

• NOTE: the DEFAULT value is 480 640• SIZ=ALL will copy the entire image

McIDAS Commands—IMGLIST

• Lists the properties of the image• IMGLIST dataset epos [keywords]

– dataset is the same as before (e.g., LA.#)– If using local data, you can use epos to specify the

top end of range of data files to be listed (e.g., IMGLIST LOC/AREA.7670 7679)

– The keyword FORM=EXP gives a detailed listing

• Try IMGLIST LA.# FORM=EXP on the image you copied earlier.

McIDAS Commands—IMGDISP

• Graphically displays a McIDAS data file• IMGDISP dataset frame [keywords]

– dataset is the same format as before– frame is the McIDAS graphic frame number.

McIDAS can hold displays in multiple frames at once for making loops, etc. The default value is the frame you are currently displaying, which should be frame 1.

• You can either display a file on the server or a file in your local directory.

• Display the file you just copied using IMGDISP LA.#

McIDAS Commands—IMGDISP

• Some keywords of interest:– LAT=lat lon, where lat and lon are the latitude and

longitude (degrees, with west longitude as a POSITIVE value) of the region of interest, specified either as• PLA=ULEFT: lat lon is the upper left of the region;• PLA=CENTER: lat lon is the center of the region

– MAG=lmag emag, where lmag is the magnification in the line (y) direction, and emag is the magnification factor in the element (x) direction. Both values should be integers, with positive values blowing up the image and negative values blowing down the image

McIDAS Commands—EU

• Enhancement Utility (color enhancements)• EU LIST lists all of the color enhancement

tables that are available along with their directory locations

• EU REST name bframe eframe applies enhancement table name.ET to frames bframe through eframe.– Note that the .ET suffix is optional.– Note that bframe and eframe are optional; default is

the frame currently being displayed.

• Look at the available enhancement tables and apply one or more to your displayed image.

McIDAS Commands—MAP

• Display a map background and/or lat/lon lines• MAP map color1 LALO color2 [keywords]

– map=map background. Options include:• NA=North America’s coastal boundaries

• H=North America’s political boundaries

• L=World’s coastal boundaries

• POLI=World’s political boundaries

• Note: MUST include the keyword DOM=YES to make the map match the image projection!

• LALO option draws lat/lon lines instead– INT=lat lon option specifies lat/lon line spacing

• Examples: MAP H 1 DOM=YES MAP LALO 5 INT=5 5

McIDAS Commands—Cleanup

• EG m n erases graphics (map overlays, etc.) in frames m through n.– ERASE G m n does the same thing.

• EG I m n erases the image (but NOT the graphics) in frames m through n.– ERASE I m n does the same thing.

• ERASE F m n erases everything from frames m through n.

McIDAS Commands—Loops

• It is possible to load a series of images into consecutive frames and then loop through them.

• Manual loop: use <ALT-A> to advance the display by one frame; use <ALT-B> to go back by one frame. You can also just type A or B and hit <Enter>.

• Toggle <ALT-L> to turn looping through the frames on and off, or just type L and hit <Enter>.

• To set boundaries on the frames through which <ALT-L> will loop, use LB m n, where m is the first frame and n is the last.

• Type F and hit <Enter> to see your current frame configuration.

McIDAS Commands—IMGPROBE

• IMGPROBE will cause McIDAS to return information about any grid point which you right-click on using the mouse and cursor. Use <ALT-Q> to turn it off.

• You can also use <ALT-D> to get a similar display for the point beneath the cursor.

McIDAS Commands—IMGREMAP• Remaps the image into a different map projection

• IMGREMAP sdataset ddataset [keywords] – sdataset and ddataset are the source and destination

datasets, as before

• Selected keywords:– LAT=clat clon (center lat/lon of area to remap)– PRO=DEST (same projection as ddataset if there’s something

already in there)– PRO=LAMB slat1 slat2 slon (Lambert conformal projection

with standard latitudes slat1 and slat2 and standard longitude slon

– PRO=MERC (Mercator projection)– PRO=PS slat slon (Polar stereographic projection)– RES= resolution in km– SIZ=line ele (size of destination image)

McIDAS Commands—GRDCOPY

• Copies grid data–analogous to IMGCOPY• GRDCOPY sdataset ddataset [keywords]

– sdataset = source dataset group and position– sdataset = destination dataset group and position

• Typically one copies into the local data directory, where sdataset is given as LOC/GRID.# (or just LG.#), where # is a number up to 9999.

• These files can be also be viewed outside of McIDAS in the mcidas/data directory.

• Try IMGCOPY MOD/GFS LG.# NUM=250

McIDAS Commands—GRDCOPY

• Important GRDCOPY keywords:– LEV=lev, which can be either SFC or a pressure

surface (e.g., 850[MB]) or a height surface (e.g., 5000[M]).

– PAR=par, which are the model parameters, including T (temperature), Z (height), RH (relative humidity), PWAT (precipitable water)

– NUM=num, which is the number of grids meeting the criteria which are to be copied (default is 1—the first grid only)

– FHO=fho, which is the forecast lead time in hours– FTI=ft, which is the forecast time in hours– GRI=gri, which is the grid number (from GRDLIST)

McIDAS Commands—GRDLIST

• Lists the properties of the image• GRDLIST dataset [keywords]

– dataset is the same as before

• Keywords are largely the same as GRDCOPY

McIDAS Commands—GRDDISP

• Plots grid data• GRDDISP dataset frame [keywords]

– dataset and frame are same as previously

• Keywords are the same as for GRDLIST, plus:– LAT=lat1 lat2 for the latitude range– LON=lon1 lon2 for the longitude range– COL=graphics color– OUT=CON (contour plot) or OUT=PLOT (plots the

numbers, but they’re usually hard to read unless it’s a small area)

McIDAS Commands—GRDIMG• Converts a portion of a GRID file to an AREA file• GRDIMG sdataset ddataset [keywords]

– sdataset and ddataset are same as previously

• Keywords are the same as for GRDLIST, but you will only copy the FIRST grid that meets the specifications given. So be sure to use GRDLIST (which gives only the first grid meeting those specifications) to be sure that you get what you want!

• Try converting your local GRID file to an AREA file and then displaying it using IMGDISP. Overlay the GRID file on top of the AREA file to see if you did it correctly.