Using the Hydro-Estimator in McIDAS

1. Using the Hydro-Estimator in McIDAS Bob Kuligowski NOAA/NESDIS Center for Satellite Applications and Research (STAR)

2. Outline • Brief McIDAS Background • Hydro-Estimator Basics • Running the Hydro-Estimator • Preparing the data fields • Running the algorithm • Examining the results Appendix: Basic McIDAS Commands

3. 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.

4. 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.kin the mcidas/bindirectory.

5. Outline • Brief McIDAS Background • Hydro-Estimator Basics • Running the Hydro-Estimator • Preparing the data fields • Running the algorithm • Examining the results Appendix: Basic McIDAS Commands

6. 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.

7. Illustration of the IR signal from different rainfall intensities Tb=200 K Tb=212 K Tb=224 K Tb=230 K 250 200 290 T (K)

8. Exceptions to the Rule... Cirrus Tb=205 K Cumulonimbus Tb=200 K Nimbostratus Tb=240 K 200 250 290 T (K)

9. 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

10. Tb < Tb Rain Tb ≥ Tb No Rain Tb < Tb Rain Tb ≥ Tb No Rain 200 250 290 T (K) Illustration of the HE Rain-No Rain Differentiation

11. 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

12. 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)

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

14. GOES T10.7 Eta TEL ORO Eta PW GOES T10.7 Eta TEL N Tadj=T10.7 TEL<270 K? Preliminary EL, ORO, PW Adjustments (T10.7Tpre) Y TELadj=min(TEL+min(T(Z1=10), T10.7))/2, Tmin) N Tpre≤235 K? RR=0 Done Y TEL-min(T(Z1=1.0), T10.7)<10 K? Find Tmin in surrounding 101x101 box Y N r1=250-Tmin; 30≤r1≤50 r2=15 Tadj=0.9*(213 - TELadj Tadj=0.6*(213-TELadj) ORO Compute μ, σ for r1 and r2 Tadj>210? Tadj=max(Tadj-ORO/2,210) Replace Tpre with Tadj Tadj=Tadj-ORO Eta PW Zi=(μ-Tadj)/ σfor r1, r2 Y Y PW>1.5? PW>2.0? DPW=2*(2-PW) N i=1,2 Zi>0? RRi=0 N N Y DPW=2.5*(1-PW) DPW=1.5-PW RRi=[RRc*Z2+RRn*(1.5-Z)2]/[Z2+(1.5-Z)2 Tadj>210? Tadj=max(Tadj+DPW, 210) Y N Y N RR=RR2 RR1>0? RR=SQRT(RR12+RR22) RR’=25.4*(1-DPW/10) Eta RH RH=RH-0.01*SQRT(RR-10) Compute “core” RRc via function fit (RRc@210K=RR’ in/hr; RRc@240K=0.5 in/hr) RR=RR-25*(0.85-RH)-0.35(0.6-RH)-0.5(0.4-RH) (only negative components are used) Compute “non-core” RRn with 12 mm/h cap: RRn=min(RR’*(250-Tadj)/5,RRc/5) Done

15. Outline • Brief McIDAS Background • Hydro-Estimator Basics • Running the Hydro-Estimator • Preparing the data fields • Running the algorithm • Examining the results Appendix: Basic McIDAS Commands

16. 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

17. Sample Hydro-Estimator Run • Necessary Programs (again, a reduced set): • zenitcor.pgm: Corrects for limb cooling at high satellite zenith angles • zenitcor INOUT • parcormercir.pgm: Corrects for parallax • parcormercir IN OUT • rainsplitiso.pgm: Produces rain rate estimates • rainsplitiso GOES OUT PW RH EQL RH ORO DUM

18. 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)

19. 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

20. 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.

21. 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.

22. 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

23. 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)

24. 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).

25. 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.

26. 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…nare the input datasets • ddatasetis 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=dmultiplies all data by a constantd • Try IMGOPER on a file and use IMGPROBE to examine the results. Then try those new files as HE inputs to see what happens!

27. Appendix: Basic McIDAS Commands

28. 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

29. 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

30. 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 justLA.#), 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.

31. McIDAS Commands—IMGCOPY • Important IMGCOPY keywords: • LAT=lat lon, where latand 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=lineele, 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

32. McIDAS Commands—IMGLIST • Lists the properties of the image • IMGLISTdataset 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.

33. McIDAS Commands—IMGDISP • Graphically displays a McIDAS data file • IMGDISP dataset frame [keywords] • datasetis the same format as before • frameis 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 IMGDISPLA.#

34. 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

35. 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 RESTname 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.

36. 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

37. McIDAS Commands—Cleanup • EGmn erases graphics (map overlays, etc.) in frames m through n. • ERASE Gm n does the same thing. • EG Im n erases the image (but NOT the graphics) in frames m through n. • ERASE Im n does the same thing. • ERASE Fm n erases everything from frames m through n.

38. 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 LBm n, where m is the first frame and n is the last. • Type F and hit <Enter> to see your current frame configuration.

39. 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.

40. McIDAS Commands—IMGREMAP • Remaps the image into a different map projection • IMGREMAPsdatasetddataset[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=LAMBslat1 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)

41. 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 justLG.#), 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

42. 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)

43. McIDAS Commands—GRDLIST • Lists the properties of the image • GRDLISTdataset [keywords] • dataset is the same as before • Keywords are largely the same as GRDCOPY

44. McIDAS Commands—GRDDISP • Plots grid data • GRDDISPdataset 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)

45. McIDAS Commands—GRDIMG • Converts a portion of a GRID file to an AREA file • GRDIMGsdataset 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.