Using NUCAPS soundings in and around fire locations

September 7th, 2020 |

GOES-16 Visible (0.64 µm) hourly imagery, 1811-2311 UTC on 6 September 2020 (click to enlarge)

GOES-16 Visible imagery, above, during the late afternoon on 6 September, shows an invigoration of the Cameron Peak fire in Larimer County, Colorado, with visible evidence of a pyrocumulus development.  Are there tools a forecaster can use to anticipate such extraordinary afternoon fire growth?

NOAA-20 overflew Colorado shortly after (NOAA-20 orbits can be viewed at this website) 2000 UTC on 6 September (see NUCAPS Sounding availability points below;  note that the date of these plots — 1951 UTC — corresponds to the time of  the first NUCAPS swath is available in AWIPS from this NOAA-20 pass;  for this ascending pass, that swath is near 40 S latitude!)

NUCAPS Sounding Points from the 2000 UTC overpass on 6 September 2020 (Click too enlage)

What do the NUCAPS Sounding surrounding Larimer County Colorado look like?  The animation below steps through the profiles surrounding the fire.  Consider using the LCL and EL information (and other information) in these profiles when diagnosing the likelihood of convection developing in response to an intense fire.  On this day, NUCAPS showed steep mid-tropospheric lapse rates that help support pyrocumulonimbus.

Select NUCAPS Soundings and thermodynamic variables (from AWIPS, locations as indicated) on 6 September 2020 (Click to enlarge)

NUCAPS diagnoses of stable air near Tropical Storm Marco

August 22nd, 2020 |

GOES-16 ABI Band 13 Clean Window Infrared Imagery (10.3  µm) and NOAA-20 derived Gridded NUCAPS 850-500 mb lapse rates, 0656 UTC on 22 August 2020 (Click to enlarge)

Tropical Storm Marco over the northwest Caribbean Sea, shown above in a toggle of GOES-16 ABI Clean window imagery (10.3 µm) and a NUCAPS diagnosis of 850-500mb lapse rates, is over very warm waters and in a region of favorably low diagnosed vertical wind shear. (Wind shear is from this website, (direct link to shear); the product is described here)  An inhibiting feature in strengthening, as noted in the National Hurricane Center discussion, is stable air.

NOAA-20 overflew Marco shortly before 0700 UTC on 22 August, and NUCAPS soundings derived from CrIS and ATMS data on NOAA-20 showed the stable mid-tropospheric air surrounding the storm. The 850-500 mb lapse rates were around 5.5 C/km. (Gridded NUCAPS data can also be viewed here) Individual soundings over western Cuba and just off the northwest tip of the Yucatan peninsula also show the relatively stable air. (Click here to see the Lapse Rate Analysis overlain with NUCAPS Sounding Availability points from the AWIPS display)

Marco’s future path is forecast to move over very warm waters that are shown in the ACSPO analysis of SSTs, below, from Suomi-NPP VIIRS data.  Consult the National Hurricane Center for the latest on this storm that will likely affect the Texas/Louisiana Gulf Coasts.

Suomi-NPP ACSPO analysis of Sea Surface Temperatures, 0730 UTC on 22 August 2020 (Click to enlarge)

Using CSPP QuickLooks and Direct Broadcast data to view gridded NUCAPS fields

August 7th, 2020 |

NOAA-20 852-mb Temperatures, ca. 1750 UTC on 7 August 2020.  Inset:  Global Map of where the data sit (Click to enlarge)

A previous blog post (link) detailed how to access NOAA CLASS to create Gridded NUCAPS (NOAA-Unique Combined Atmospheric Processing System) imagery from those data.  (You can also view some gridded NUCAPS fields here;  click here to see the 850-mb field of Temperature from that site, it is very similar to the imagery above).   This post details how to use the CSPP QuickLooks software package to create imagery at different levels.  These QuickLook fields give good information quickly and at many different levels for Direct Broadcast data.

Download the Sounder QuickLook software for Linux from the CIMSS website here.  Documentation is also available at the download website.  The files to download are shown in this graphic. The package is self-contained and requires only unzipping and un-tarring.

After downloading, define the $CSPP_SOUNDER_QL_HOME variable as the directory where the package sits on your unix platform.  Then, set up the environment with the command:  source $CSPP_SOUNDER_QL_HOME/cspp_sounder_ql_env.sh.

This software package works on NUCAPS EDR (Environmental Data Records) files created at Direct Broadcast sites by CSPP (that are also available after some time from CLASS), and those files can be found at websites such as this one: ftp://ftp.ssec.wisc.edu/pub/eosdb/ — underneath this are directories for NOAA-20 (‘j01’) and Suomi-NPP (‘npp’). For example, NOAA-20 data from 7 August 2020 from the ~1747 UTC overpass is at ftp://ftp.ssec.wisc.edu/pub/eosdb/j01/crisfsr/2020_08_07_220_1747/ (This website is not preserved forever but will go away after about a week. The directory includes an edr subdirectory that contains the files needed; a typical filename looks like this:  NUCAPS-EDR_v2r0_j01_s202008071752319_e202008071753017_c202008071830250.nc; it is the EDR for NOAA-20 and it contains data on 7 August 2020 from 1752 through 1753 UTC. The directory will include up to about 18 of these EDRs (the number depends on how long the satellite is within view of the Direct Broadcast antenna at CIMSS).

How do you create the QuickLooks?

  1. Move the EDR files to your machine, and that’s easily done with wget ftp://ftp.ssec.wisc.edu/pub/eosdb/j01/crisfsr/2020_08_07_220_1747/edr/NUCAPS-EDR*.  Of course, the yyyy_mm_dd_jdy_hhmm value (2020_08_07_220_1747 above) changes with each satellite overpass!
  2. Create a list of the files in that directory, i.e., files=$CSPP_SOUNDER_QL_HOME/data/NUCAPS-EDR*
  3. Invoke the shell script from $CSPP_SOUNDER_QL_HOME/scripts/ql_level2_image.sh "$files" NUCAPS --dset temp --pressure 850.   This will create an image, shown above, that is a temperature mapping at the closest pressure level to 850 mb in the NUCAPS retrieval. (Pressure levels in the Radiative Transfer Model that is used by NUCAPS are listed here;  in the map label above, note that values are truncated, not rounded).  You can also map dewpoint temperature (dwpt), relative humidity (relh) and mixing ratio (wmix). By default, temperature scaling matches the bounds of the image, but you can specify the bounds if needed, using --plotMin=250.0 --plotMax=300.0, for example.  The time of the image is the time of the first scan line — for this ascending pass, it’s the southernmost line.  In this QuickLook image, the airmass difference between the relatively cool air over Ohio/Indiana and the warmer air to the south is apparent.

You can also create a QuickLook SkewT/logP plots for each scan. This produces one SkewT per ScanLine, at the mid-point along the scanline that contains 30 separate profiles.   The sounding below was produced by this command:

./ql_level2_skewt.sh ./data/NUCAPS-EDR_v2r0_j01_s202008071755119_e202008071755417_c202008071831450.nc NUCAPS

NOAA-20 NUCAPS Sounding from 1755 UTC on 7 August 2020 at 41.93º N, 75.81º W (Click to enlarge)

The SkewT has characteristics that suggest the presence of clouds.  What did this particular sounding look like in AWIPS?  That’s shown below.  In AWIPS, the sounding also terminated at about 550 mb, and the temperature and dewpoint lines above that level match the Quick Look sounding shown above.

NSharp AWIPS presentation of NOAA-20 NUCAPS Sounding at 41.93 N, 75.81 W at ~17UTC on 7 August 2020 (Click to enlarge)

NUCAPS Sounding Availability points from this NOAA-20 pass are shown below. The sounding point — in yellow — that is circled in blue is the one shown above. The sounding just to the east of that point — a green point that gives useful information down into the boundary layer — is shown here. Quick Looks choose the mid-point sounding along the line, and sometimes, as in this case, the retrieval that produced the profile did not converge.

NOAA-20 NUCAPS Sounding Availability Points from AWIPS, 1732 UTC on 7 August 2020 (Click to enlarge). The sounding shown above is from the point circled in blue.  This is in the middle of the 30 sounding points along the horizontal line of available profiles.

Dry Air in the southwest Atlantic Ocean

July 29th, 2020 |

Saharan Air Layer (SAL) analysis at 1500 UTC on 29 July 2020 (Click to enlarge)

An analysis of the Saharan Air Layer, above (from this website), shows dry conditions stretching from Africa to the southwestern Atlantic, wrapping around the clouds associated with a strong tropical disturbance that is forecast to move northwestward over the Lesser and Greater Antilles in the next couple days.  (Both the dry air and the presence of high terrain in the Antilles will likely affect the development and structure of this storm).

The Saharan Air Layer is accompanied by an Elevated Mixed Layer (EML) that was apparent in the 0000 UTC Upper-Air sounding from San Juan (TJSJ), as shown below (from this site).  (At 0000 UTC, Puerto Rico was entrenched within the SAL air as shown in this analysis).  Note the steep lapse rate from 800 to 550 mb and the strong east winds in the layer.  By 1200 UTC, moist air moving in from the east had altered the EML.

Skew-T of temperature and pressure, 0000 UTC on 29 July 2020, at station 78526 (TJSJ, San Juan, Puerto Rico) (Click to enlarge)

NOAA-20 overflew this region just after 0600 UTC (orbits, from this website), and its thermodynamic profiles also gave evidence of the EML.  NUCAPS profiles in the region were produced by infrared/microwave retrievals that converged to a solution, as shown in the map below.  (The region of the tropical disturbance, over the Leeward Islands, shows red sounding dots where rain is likely falling).

NOAA-20 NUCAPS sounding locations in/around Puerto Rico at ~0550 UTC on 29 July 2020 (Click to enlarge)

Two soundings from this overpass are shown below, along 65º W at ~21º N and ~20º N, also show evidence of an Elevated Mixed Layer in the same region of the atmosphere.  (It is more apparent at 21.15º N/64.73º W)

NUCAPS Profiles from ~0600 UTC 29 July 2020 at 21.15 N, 65 W (left) and at 19.75 N, 65 W (right) (click to enlarge)

Gridded NUCAPS fields are available in AWIPS, but they are also available outside of AWIPS at this site from NASA SPoRT.  850-500 mb and 700-500 mb Lapse rates, shown below, show a region of steep lapse rates as you might expect from an EML to the north of Puerto Rico (yellow in the color enhancement applied).

850-500 mb Lapse Rates (left) and 700-500 mb Lapse Rates (right) from the ~0600 UTC NOAA-20 overpass (Click to enlarge)

Gridded NUCAPS fields also confirm the dry air associated with the SAL air that contains the EML.  Total Precipitable water is around 30 mm, and 850-mb relative humidity is under 40% in the region where the EML is indicated by lapse rates.

Total Precipitable Water (left) and 850-mb Relative Humidity (right) derived from the NOAA-20 NUCAPS data from the ~0600 UTC overpass on 29 July 2020 (click to enlarge)

For the latest information on Potential Tropical Cyclone #9 (should this system be named, the next name in the Atlantic alphabet is Isaías), refer to the National Hurricane Center website.