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Kevin Fuell:

Here is an excellent satellite imagery interpretation by Paul Nutter of the Great Falls WFO regarding the Nighttime Microphysics RGB. As Paul demonstrates with his ability to describe this image and support its value based on current imagery, training and continued experience can lead to efficient use of RGB-type imagery.

Originally posted on TFX-shoptalk:

A strong early season cold front pushed through Montana from Alberta on 9 September 2014. The front produced several layers of cloud cover that appeared richly on the Nighttime Microphysics RGB imagery. This provides an excellent case for a study of capabilities we expect to have available on the GOES-R platform.

WPC Daily Weather Map valid 12 UTC 9 Sept 2014

WPC Daily Weather Map valid 12 UTC 9 Sept 2014

SPoRT VIIRS Night-time Microphysics RGB valid 0844 UTC 09-Sep-2014.

SPoRT VIIRS Night-time Microphysics RGB valid 0844 UTC 09-Sep-2014.

Table 1. Wavelength Band or band difference contributions to the RGB triplets and their physical interpretation used within the Nighttime Microphysics RGB composite imagery.

Color Band / Band Diff. Physically Relates to: Little contribution to composite indicates: Large contribution to composite indicates:
Red 12.0 – 10.8 Optical Depth Thin clouds Thick clouds
Green 10.8 – 3.9 Particle Phase and Size Ice particles;
Surface (i.e. cloud free)
Water clouds with
small particles
Blue 10.8 Temperature of surface Cold surface Warm surface

Violet colored…

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Kevin Fuell:

Here is a posted application of the VIIRS Day-Night Band by the NWS Forecast Office in Great Falls. It was posted on their local blog.

Originally posted on TFX-shoptalk:

Clear skies and a bright moon in the early morning hours on September 12th 2014 allowed for good view of the extent of recent snowfall on the VIIRS Day-Night Band Reflectance imagery. At 1km resolution it’s about as detailed as a GOES visible image during daylight.

-Bob

VIIRS_DNB_ref_201409120930z_state_snow


Image1: Note Calgary’s location (bright city lights) on the eastern flank of the snowfield. east of the Canadian Rockies.

Viirs_snow_tfx

Image 2: Closer look at the TFX CWA

VIIRS_snow_RMF

Image3: Good detail of the extend of snowfall along the Rocky Mtn Front.

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The previous blog post made by the NWS forecast office at Raleigh, NC (WFO RAH) illustrated the decrease in LIS total column relative soil moisture over North Carolina (NC) associated with the recent lack of rainfall through 1 September.  Despite receiving some nominal precipitation up to 0.50″ during the previous week, portions of eastern NC experienced the greatest amount of soil drying compared to central NC where practically no rain fell. 

This response in the Noah land surface model within the real-time SPoRT-LIS is related to the disparate soil composition across NC as seen in Figure 1.  The soils consist of mostly sand or sandy loam composition across eastern NC compared to silty loam in central NC.  The movement of water in lower porosity, sandy soils is dominated by capillary action (upward movement of water against gravity) and thus readily release its water at higher soil moisture values.  Meanwhile, higher porosity soils (i.e., clay/silt with numerous smaller pores) retain water for longer time periods and tend to dry out more slowly at higher values of soil moisture (google “water retention curve” for more details).  Thus, despite the modest rainfall over the sandy soils of eastern NC, the soil actually dried out faster than over central NC where less rainfall was observed. 

soilType_nc

Figure 1. Soil texture classifications used in the SPoRT-LIS runs of the Noah land surface model, centered over North Carolina.

 

 

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NASA SPoRT has developed a real-time configuration of the NASA Land Information System (LIS) that runs over much of the central and eastern United States at 3-km grid spacing.  The LIS produces several products, including a suite of soil moisture products that can be used to help assess drought and flooding potential.  WFO Raleigh is pleased to be participating (along with WFOs Houston and Huntsville) in an assessment of these products from August through October.

Central North Carolina has been in a short-term relative dry spell of late, with much of the area having seen little to no rainfall in the last week (Fig. 1). One ramification of this lack of rainfall is the soil drying evident in the 1-week difference in column relative soil moisture imagery (Fig. 2), which shows marked drying over all of Central NC in the last week. Interestingly, in coastal sections of NC that actually have seen some rainfall in the last week, the soil drying has been even more pronounced. Reasons for this are unclear, but it may have to do with the soil type over Eastern NC.

7dayrainfall.ending12z20140901

Fig. 1. Seven-day rainfall over North Carolina, for the period ending at 8 am EDT 1 September 2014.

1weekdiffinsoilmstr.ending00z20140901

Fig. 2. One-week difference in column relative soil moisture (%) over North Carolina, for the period ending at 8 pm EDT 31 August 2014.

 

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MODIS Air Mass RGB Imagery with limb correction applied to the water vapor and ozone channels.  1859 UTC, 13 May 2014

MODIS Air Mass RGB Imagery with limb correction applied to the water vapor and ozone channels. 1859 UTC, 13 May 2014

The Air Mass RGB imagery product via MODIS has often appeared to lack “green” coloring near the edge of the swath and there have been noticeable differences between the channels from Aqua and Terra used within the RGB.  Forecasters from the Great Falls, MT and Albuquerque, NM WFOs applying this experimental data noted these issues.  The above image is a limb and bias corrected version of the Air Mass RGB.  The water vapor and ozone channels tend to “cool” near the swath edge as they pass through more atmosphere and the differences in satellite instrument quality result in physical characteristics between the images having different coloring.  SPoRT has worked to develop a non-linear function to correct much of the limb cooling as well as a bias correction, both through comparison of the MODIS instruments to the EUMETSAT SEVIRI instrument.  Annotations to the image attempt to classify the various features indicated by the resulting composite color during a MODIS pass from 1859 UTC on 13 May 2014 when a cold air mass was moving into the upper Midwest.  Simple interpretation guides can be found via SPoRT’s Training page or EUMETSAT. For comparison, additional plots of GOES Water Vapor,  and NAM 500mb Temperature, Humidity, and Height 0-hour analysis and 6-hour forecasts are provided below for reference. There is also a single image of the Hybrid GEO/LEO Water Vapor / Air Mass RGB product that loops GOES Water Vapor imagery and inserts the MODIS Air Mass RGB swath as it is available because the RGB is largely made up of water vapor channels.  Both the Hybrid and single-swath MODIS files are available in netCDF format for use in AWIPS I or II as well as KML format.

This new limb/bias corrected Air Mass RGB product is credited in large part to graduate student work being done at the University of Alabama Huntsville in conjunction with NASA/SPoRT. Primary contributors are:
Nicolas Elmer (UAH graduate student)
Dr. Emily Berndt (NASA/SPoRT Post-Doctoral Scientist)
Dr. Gary Jedlovec (NASA/SPoRT PI)

Additional contributors include:
Frank LaFontaine (Raytheon, Data processing and analysis)
Kevin McGrath (Jacobs, Product code development and real-time processing)
Matthew Smith (UAH, Data processing and product code development)
Dr. Andrew Molthan (NASA/SPoRT, RGB code development and research science)

g13.2014133.1845_US_wv

GOES Water Vapor Imagery at 1845 UTC, for 13 May 2014

 

 

 

 

NAM 500mb, 0-hour forecast valid 1200 UTC, 12 May 2014 of Temperature, Humidity, and Height via

NAM 500mb, 0-hour forecast valid 1200 UTC, 13 May 2014 of Temperature, Humidity, and Height via NCAR RAL website

NAM 500mb, 0-hour forecast valid 1200 UTC, 13 May 2014 of Temperature, Humidity, and Height via NCAR RAL website

N

NAM 500mb, 6-hour forecast valid 1800 UTC, 13 May 2014 of Temperature, Humidity, and Height via NCAR RAL website

NAM 500mb, 6-hour forecast valid 1800 UTC, 13 May 2014 of Temperature, Humidity, and Height via NCAR RAL website

CAR RAL website

Example: SPoRT Hybrid GEO/LEO Water Vapor and Air Mass RGBimagery

Example: SPoRT Hybrid GEO/LEO Water Vapor and Air Mass RGBimagery

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Despite the hours of darkness becoming rare over Alaska as the northern hemisphere approaches its summer solstice, the RGB Night-Time Microphysics product still has some utility in Alaska south of the Arctic Circle right around midnight. Just before midnight Alaska Time on May 6, 2014 (0743 UTC, May 7) an RGB NT Micro image derived from the SNPP VIIRS instrument depicted a deck of moderately low marine stratus clouds over the northeastern Bering Sea, as outlined in the black box in Figure 1.

Image

Figure 1: RGB NT Micro product derived from VIIRS data, 1143pm Alaska Daylight Time May 6, 2014. Area of interest noted in the black box.

A closer view of this area is shown in Figure 2, along with the ceiling and visibility data from surface observing sites. In this scenario, ceilings, rather than visibility, are the problematic weather element, with the exception of Nome where the imagery shows a localized area of higher conditions. It can be challenging to discern ceilings and visibilities from satellite imagery, and in this respect the RGB NT Micro product has an advantage over conventional satellite imagery. Per the Quick Guide available at http://weather.msfc.nasa.gov/sport/training/rgb_ntmicro/RGB%20Night-time%20Microphysics%20Reference%20Guide%20AK%20by%20SPoRT.pdf and as demonstrated in the Alaskan training module http://weather.msfc.nasa.gov/sport/training/aviationForecasting_Alaska/launcher.html a tan to light green appearance indicates low clouds, but not necessarily fog, in colder climate regions such as Alaska. Surface observations on Saint Lawrence Island and in the Yukon Delta area indicate MVFR ceilings of between one and three thousand feet, but no reduction to visibility due to fog.

Image

Figure2 : the same RGB NT Micro product as in Figure 1, zoomed into the northeastern Bering Sea. Ceiling and visibility data from surface observation sites are also shown in green.

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On April 28, 2014 a tornado outbreak occurred across the Southeast, with the states of Mississippi, Alabama and Tennessee being hit the hardest. Several EF-3 and EF-4 tornadoes occurred across these states. As skies cleared over the area from west to eas, the International Space Station (ISS) orbit tracked across the city of Louisville, MS on Sunday May 4. This town was hard hit by an EF-4 tornado.  True color imagery from the ISS SERVIR Environmental Research and Visualization System (ISERV) captured the track of this tornado in its entirely.

 

The above ISERV image shows the tornado track on the southeastern portion of the town with the EF Scale Damage Indicators overlaid on top.

The above ISERV image shows the tornado track on the southeastern portion of the town with the EF Scale Damage Indicators overlaid on top.

 

SPoRT uploaded all the ISERV images to an online viewer where one can explore for more detail. That viewer can be found here.

For a comparison between pre-storm Landsat imagery and post-storm ISERV imagery, see the SERVIR team link and story here.

 

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