NUCAPS Sounding Availability

May 16th, 2019 |

NUCAPS soundings from NOAA-20 at 0653 UTC on 16 May 2019, 34.4 N, 75.8 W (Click to enlarge)

The Cross-Track Infrared Sounder (CrIS) on Suomi NPP suffered an anomaly back in late March and the mid-wave portion of the detectors are not functioning as designed; the wavelengths affected include those sensitive to water vapor. Because of this data outage, NUCAPS soundings are not being produced from Suomi NPP. Suomi NPP was the sole data source for NUCAPS in National Weather Service offices over the contiguous United States.

As shown above, NUCAPS soundings are being produced by NOAA-20, which, like Suomi NPP, carries both the CrIS and the Advanced Technology Microwave Sounder (ATMS). NOAA-20 NUCAPS soundings are scheduled to replace the Suomi NPP NUCAPS soundings in National Weather Service Forecast Offices in late May 2019. NOAA-20 is in the same orbit as Suomi NPP, but offset by half an orbit; overpasses are offset by about 45 minutes, so the NUCAPS data should show up in forecast offices at about the same time of day. (Compare these Suomi NPP orbits over North America to these from NOAA-20; Orbital tracks for most polar orbiters are here.) Time latency for NOAA-20 soundings is improved over Suomi-NPP however; there will be less wait needed for the soundings.

NUCAPS soundings are also produced from Metop-A and Metop-B, satellites that carry the Infrared Atmospheric Sounding Interferometer (IASI) and the Advanced Microwave Sounding Unit (AMSU) and Microwave Humidity Sensor(MHS) instruments.

NUCAPS soundings from NOAA-20, Metop-A and Metop-B are available at this site. That site includes a map (shown here) To access the soundings, move the map to your desired location, and click on the small box in the upper left of the map (under the +/- that cause the map to zoom in and out).  After clicking the box, use a left click and mouse drag on the map to define a region where sounding points will appear. (Alternatively, click the ‘Thumbnail Viewer’ box above the map; as you mouse over the points, a sounding will appear in the window.) The points are color-coordinated based on how old the latest sounding is. Zoom in, and choose your point.  Three profiles are displayed: The initial regression profile (labeled MW+IR Regr), the microwave-only profile (labeled MW phys) and the final physical retrieval profile (labeled MW+IR phys).  The resultant sounding you see will be the latest, but 10 soundings near that point over the past several days can be accessed as well.

NUCAPS soundings from Suomi NPP are not gone for good, however.  The CrIS has redundant electronics, and ‘A’ side — that has partially failed — and a ‘B’ side that has not been tested since before launch (Suomi NPP was launched on 28 October 2011!  Here is one of its first images).  The ‘B’ side electronics can be activated, and if they work, NUCAPS algorithms would have to be recalibrated for an essentially new data source.  This would take several months.  Alternatively, NUCAPS for Suomi NPP could be reformulated to account for the missing data with the ‘A’ side electrontics, something that also would take several months.  A decision on the path to take is forthcoming.

NUCAPS Profiles across a Saharan Air Layer (SAL) Outbreak

March 12th, 2019 |

Split Window Difference imagery over the Atlantic Basin, 1800 UTC 11 March through 1800 UTC 12 March 2019 (Click to animate)

A Saharan Air Layer (SAL) outbreak is occurring over the eastern Atlantic Ocean on 11-12 March 2019. The animation above shows the Split-Window Difference (10.3 µm – 12.3 µm) (link, from this website) color-enhanced to accentuate in red/pink/white the regions where Saharan Dust has been lofted into the atmosphere. This outbreak has been developing — this animation (courtesy Arunas Kuciauskas, NRL in Monterey) from 0400 UTC on 8 March to 1400 UTC on 11 March of the DEBRA product (now the Dynamic Enhanced Background Reduction Algorithm, from this website) shows the dust originating west of a departing cyclone over northwest Africa).

NUCAPS Profiles sampled a region of the SAL on Tuesday 12 March, and those are shown below. (This has been discussed previously on this blog, here)  The swath of points is shown on top of a GOES-16 Red/Green/Blue image composite designed to highlight dust in pink. Sounding locations shown are denoted by the orange dot, and Precipitable Water associated with the sounding is indicated.  The accentuated mid-level drying associated with the SAL air, inferred by the pink in the RGB, is readily apparent.

GOES-16 Dust RGB at 1530 UTC on 12 March 2019 superimposed with NUCAPS sounding locations. Inset: NUCAPS Sounding in the location indicated by the orange dot. Total Precipitable Water for the sounding as indicated (Click to enlarge)

============= Update 13 March 2019 ==============

DEBRA dust product from MSG Seviri data, hourly from 0000 UTC on 11 March to 1500 UTC 12 March 2019 (Click to enlarge)

The animation above and the one below are courtesy Arunas Kuciauskas from the Naval Research Lab in Monterey CA. The Dynamic Enhanced Background Reduction Algorithm (DEBRA) dust product animation, above, is a product developed at both NRL and the Cooperate Institute for Research in the Atmosphere (CIRA) by Steve Miller. DEBRA was derived from the MSG SEVIRI dataset. The background is gray-scaled to enhance the yellow-shaded lofted dust. Brighter yellow shades suggest greater confidence that a pixel is dusty.

The animation below shows output from the ICAP model;  this is an Aerosol optical depth (AOD) prediction model that was initialized with data from 0000 UTC 11 March 2019; it provides 6-hourly forecasts of AOD (colored contours) through 0000 UTC on 16 March 2019.   This ICAP Multi Model Ensemble (ICAP MME) is a consensus style 550 nm aerosol optical thickness (AOT) forecast ensemble from the following systems: ECMWF MACC, JMA MASINGAR, NASA GSFC/GMAO, FNMOC/NRL NAAPS, NOAA NGAC,  Barcelona Supercomputing Centre NMMB/BSC-CTM and UK Met office unified model.

Aerosol Optical Depth predictions from the ICAP MME, 0000 UTC 11 March through 0000 UTC 16 March 2019 (Click to enlarge)

Suomi NPP overflew the leading edge of the SAL in the eastern Atlantic around 1500 UTC on 13 March 2019. The animation below shows the NUCAPS points superimposed on the GOES-16 Baseline Total Precipitable Water Product (very dry air is indicated) and on the Dust RGB that highlights the SAL in Red. Additionally, 6 NUCAPS Soundings are shown. They captured the very dry air associated with the SAL.  Total Precipitable Water estimates from the GOES Baseline Product and from the NUCAPS sounding are indicated.  The GOES moisture estimates are heavily constrained by GFS model data as the Advanced Baseline Imager (ABI) has only 3 infrared bands (at 6.19 µm, 6.95 µm and 7.34 µm, Bands 8, 9 and 10) that are sensitive to water vapor.  In contrast, the Cross-track Infrared Sounder (CrIS) on Suomi NPP has many more bands that are sensitive to Water Vapor.  More than 60 are used in the NUCAPS retrieval.

NUCAPS Sounding Points at 1520 UTC on 13 March 2019, along with Baseline Total Precipitable Water and the Dust RGB at 1515 UTC 13 March 2019. NUCAPS soundings at the points indicated are shown. Total Precipitable Water from GOES and from NUCAPS are indicated as well (Click to enlarge)

NUCAPS Soundings and GOES-16 Derived Stability Index Lifted Index Comparison

March 6th, 2019 |

GOES-16 ABI Band 2 (0.64 µm) and Clear-Sky Lifted Index at 1730 UTC on 6 March 2019 (Click to enlarge)

The toggle above compares a CONUS Sector visible image (0.64 µm) over the Caribbean (at 1732 UTC) with a 1730 UTC Full Disk Legacy Atmospheric Profile (LAP) Derived Stability Lifted Index field.  (A “Veggie” Band 03 0.86 µm image, here, means that coastlines need not be drawn in because of the outstanding land/sea contrast at the wavelength).  The LAP Derived Stability Lifted Index shows modestly stable air southwest of the island of Jamaica;  the blue enhancement suggests positive lifted indices (stable air) vs. the yellow regions north and south where values range from -1 to -2.  Visible imagery over the stable region does show fewer clouds than to the north and south.  Does that help you believe the small variations in stability?

GOES-16 Legacy Atmospheric Profile Derived Lifted Index at 1730 UTC along with NUCAPS Sounding Locations, ~1730 UTC on 6 March 2019 (Click to enlarge)

Suomi NPP Overflew the region shortly before 1800 UTC, and NUCAPS soundings that are produced using data from the CrIS (Cross-Track Infared Sounder) and ATMS (Advanced Technology Microwave Sounder) on Suomi NPP are available at the points shown above. Points indicated in green show where both the Infrared and Microwave retrievals successfully completed, and the animation below shows NUCAPS Soundings (at 18.66ºN, 18.20ºN, 17.74ºN, 17.28ºN, 16.82ºN and 16.36ºN) that bisect the region diagnosed as stable by the LAP Lifted Index.  Note that the NUCAPS sounding with the smallest MU Parcel CAPE, at 17.28ºN, is in the middle of the GOES-16-diagnosed stable region.

NUCAPS Soundings over the Caribbean, location as indicated by the large Purple dot. Most Unstable Parcel CAPE is noted (and also available in the nSharp readout)

Using NUCAPS Soundings near Tropical Cyclones

February 25th, 2019 |

Himawari-8 Advanced Himawari Imagery (AHI) “Clean Window” Band 13 (10.41 µm) at 0330 UTC on 25 February 2019 (Click to enlarge)

Tropical systems over the western Pacific are in a region where surface observations are few and far between.  Imagers on geostationary satellites, such as the Advanced Himawari Imagery (AHI) on Himawari-8, shown above, capably track such systems, but sounders do a much better job diagnosing the atmosphere through and towards which storms are moving.  Data from the Cross-track Infrared Sounder (CrIS) on Suomi NPP (and NOAA-20) is combined with microwave sounder from ATMS (the Advanced Technology Microwave Sounder) also on Suomi NPP (and NOAA-20) to produce NUCAPS (NOAA-Unique Combined Atmospheric Profiling System) Soundings.  These vertical profiles (independent of numerical model simulations) can provide information that is difficult to find elsewhere.  The AHI Clean Window image above is overlain with a swath of NUCAPS Sounding points, and seven (noted on the image as 1-7) are shown below. In the image, NUCAPS profile points coded green denote successful infrared and microwave retrievals; yellow denotes an infrared retrieval that failed, but a microwave retrieval was successful; red denotes failure in both infrared and microwave retrievals — typically meaning that they both failed to converge. Infrared retrievals are most likely to fail in regions of thick clouds, microwave retrievals are most likely to fail in regions of heavy precipitation.

MIMIC Total Precipitable Water, 1500 UTC 24 February – 1400 UTC 25 February 2019 (Click to enlage)

Microwave data alone can also be used to diagnose precipitable water, and an estimate from the MIMIC Total Precipitable Water website for the 24 hours ending at 1400 UTC on 25 February 2019 is shown above.  There is considerable dry air in advance of Wutip, and dry air is also wrapping around the south and east of the storm.

Profile 2 for example, was taken over Guam at 0329 UTC on 25 February 2019 and is shown below. Total Precipitable Water at this time was 1.32″, fairly low for a tropical region. The animation of the Guam radiosondes from 0000 UTC on 24 February to 1200 UTC on 25 February is shown beneath the NUCAPS profile.  Total Precipitable Water values over Guam as determined by the radiosonde exceeded 2.3″ on 24 February before dropping to 1.86″ at 00 UTC on the 25th, and 1.37″ on 1200 UTC on 25 February.  The NUCAPS plot over Guam gives an extra observation point — at 0330 UTC, in between ‘normal’ synoptic times — to confirm the arrival of dry air.

NSharp readout of NUCAPS profile over Guam (point 2) at 0329 UTC on 25 February 2019 (Click to enlarge)

PGUM Rawinsondes, 0000 and 1200 UTC on 24 and 25 February 2019 (Click to enlarge)

NUCAPS suggests that the dry air south of Wutip is exceptionally dry indeed. The NUCAPS plot from Point 7, above, shown below, shows a total Precipitable water in the deep tropics of only 0.5″!

NSharp readout of NUCAPS profile at 5.7 N, 140.1 E (point 7) at 0329 UTC on 25 February 2019 (Click to enlarge)

You can also view other NUCAPS profiles by clicking on the number: 1, 3, 4, 5, 6. Point 4, to the north of Wutip, shows more moisture than the other points. Equilibrium Levels for each of the points north of Wutip are near the tropopause.

Horizontal fields derived from NUCAPS values (for example, Dewpoint temperature at 700 mb) will be available in AWIPS later this year. Himawari imagery in this post courtesy of the Japan Meteorological Agency (JMA).