So, with the moon now passing into the waning crescent phase, the Day-Night Band imagery is less operationally useful, at least for the detection of fog and other lower level cloud types. That is, at least until the moon is back into the waxing gibbous phase. Nevertheless, when cirrus clouds aren’t present, the Nighttime Microphysics RGB has proven to be a very valuable tool for the detection of fog and other low-level clouds. Just this morning a forecaster at the Huntsville, AL WFO was able to use the imagery not only for the detection of fog, but also to aid in the issuance of a special weather statement about the fog. The image below valid at ~724 UTC (0224 am CDT) 17 Oct shows the fog (whitish-aqua colors) lying across the valley areas of NE Alabama and adjacent areas of southern Tennessee and NW Georgia.
MODIS Nighttime Microphysics RGB 724 UTC 17 October 2014
Around the time of this image, the visibility in the foggy locations had decreased to ~1/4 – 1/2 SM or less. Notice the fog in the DeKalb Valley is fainter than the fog in areas to the north and west. Not only is the DeKalb Valley more narrow, but the fog was likely more shallow. This feature of the imagery can also help to guide forecasters in assessing the longevity of the fog once sunrise breaks. Over time, forecasters can develop a sense of pattern recognition with the varying degrees of color shading and tailor forecasts to better match the time of dissipation. In this case, the fog in the DeKalb Valley began to dissipate significantly by about 1430 UTC, while the deeper and more expansive fog to the north and west lasted about an hour longer.
Read Full Post »
I wanted to follow up with this sooner, but I’ve been rather busy preparing for the NWA conference. Yep, I tend to be one of those “last-minute” people. Anyway, just last week I posted an example showcasing the advantage of the VIIRS Day-Night Band Radiance RGB in detecting fog through cirrus clouds. The next day, SPoRT collaborator Doug Schneider (Morristown WFO), followed up with another great example that I wanted to share. I’m just going to take an excerpt from an email he sent to the Morristown staff…
“I know I’ve been sending out quite a few emails lately about NASA SPoRT products, so please bear with me, but I thought this was a great example of how they can add value.
I’ve mentioned the MODIS/VIIRS Fog product before, but sometimes there are better products available for identifying fog, especially when thin cirrus are present. In the MODISVIIRS Fog product image that is attached, you can see that it is difficult to see the extent of fog. There’s clearly some in the Sequatchie Valley, but there is also some in the NE TN/SW VA area that can’t be easily seen.
The attached MODIS/VIIRS Nighttime Microphysics product also shows fog in the southern areas where it is clear (fog is light blue colors), but cirrus obscures NE sections.
The VIIRS Day/Night Band Radiance RGB product does the best job showing the extent of fog. Fog is clearly identified in the valleys of SW VA and NE TN, despite the presence of cirrus. The extent of fog is also more easily seen in the central and southern valley areas.
The attached menu image shows where you can find the Day/Night Band Radiance RGB product under the Satellite -> NASA SPoRT -> Polar Imager -> MODIS/VIIRS -> SR East menus.
Remember that these products are from a polar-orbiting satellite, and may only be available once a night, usually between 07z and 10z.”
I’ve included the images he referenced below, and circled the specific area of fog in NE Tennessee / SW Virginia that he was mentioning.
Suomi-NPP VIIRS Day-Night Band Radiance RGB, 0724 UTC 10 Oct 2014. Circled area shows valley fog not detectable in subsequent GOES or VIIRS NT Microphysics images.
Suomi-NPP VIIRS 11-3.9 um image, 0724 UTC 10 Oct 2014. Notice that high cirrus clouds (blue colors) obscure the fog below.
Suomi-NPP VIIRS Nighttime Microphysics RGB, 0724 UTC 10 Oct 2014. Fog can be seen in other areas to the south/southwest, but not beneath the cold, cirrus clouds (under the yellow circle) since this RGB recipe contains multi-spectral IR components.
This is exactly the kind of inter-office sharing SPoRT is looking for from our close partners. We greatly thank Doug and the Morristown office for their collaborative efforts!
Read Full Post »
From September 20 through September 23, 2014, the Ocean Prediction Center (OPC) was monitoring the development of the season’s first hurricane-force extratropical storm in the East Pacific. Models were suggesting a marginal hurricane-force wind event would unfold well west of the Pacific Northwest, near 140W longitude, north of 40N latitude. OPC is routinely using satellite data to monitor and forecast these strong ocean storms. On this particular event, OPC forecaster James Kells collaborated with Michael Rowland and David Kosier on if and when to pull the trigger on the hurricane-force warning.
GOES-15 6.5 um water vapor animation showing the evolution of the hurricane-force low.
The above animation shows the evolution of the hurricane-force low, with an eye-like feature evident near the end of the loop. By 1200 UTC on the 23rd, it was forecast to develop hurricane force winds (64 knots or greater) just west of Oregon near 140W. During the production of the 1200 UTC OPC Surface Analysis, there was question of whether or not the winds had reached hurricane force intensity. The ASCAT pass from ~0600 UTC showed a large area of 50-55 knot winds in the strong cold advection south of the low center, and the GFS model indicated that the system was still developing. The GFS 0-30m boundary layer winds also indicated a very small area with hurricane force intensity.
Advanced Scatterometers A and B overlaid on GOES-15 Infrared imagery showing storm force winds at ~0600 UTC on 09/23/14.
The 1130 UTC MODIS RGB Air Mass product was timelier, and it showed an area of downward momentum south of the low with the deep purple shading. The corresponding water vapor image was less clear with upper level moisture obscuring the downward motion just beneath it. In addition, there were no surface reports south of the low center as there were no buoys moored nor drifting in that vicinity. Furthermore, most ships were aware of the danger and navigated away from the region neglecting the possibility of a surface report in the area of question.
Aqua MODIS RGB Air Mass image from 1130 UTC on 09/23/14.
A cross-section of the 1200 UTC 09/23/14 GFS model potential temperature and dew point temperature was taken through the low center in order to analyze the depth of the stratospheric intrusion, and also to gauge the magnitude of the downward momentum. It showed a deep stratospheric intrusion to roughly 500 hPa, and it corroborated the strong downward momentum indicated by the imagery. The RGB Air Mass image showed the intensity of the downward momentum through the red/purple coloring and gave a good indication of the stronger winds aloft mixing down toward the surface. The imagery increased confidence with classifying the system as a hurricane force low.
The 1200 UTC 09/23/14 GFS vertical cross-section of potential temperature and dewpoint showing the downward transport of drier air associated with the tropopause fold.
The 1200 UTC 09/23/14 OPC surface analysis.
~ Guest blogger, James Kells (OPC)
Read Full Post »
A unique weather event is unfolding this week as Hurricane Odile, now a tropical storm, is impacting Baja California Sur, bringing heavy rain and high winds to the region and causing tourists to evacuate resorts. The National Hurricane Center reports that Odile ties Olivia (1967) as the strongest hurricane to make landfall in the satellite era in Baja California Sur**. NASA SPoRT provides specialized satellite products to National Weather Service Forecast Offices as well as National Centers such as the National Hurricane Center to aid forecasting high impact events such as Hurricane Odile.
Below is an example of Passive Microwave RGB imagery created from the NASA Global Precipitation Measurement (GPM) mission as part of The Core Observatory satellite launched on 27 February 2014. The images are in N-AWIPS (National Centers for Environmental Prediction Advanced Weather Interactive Processing System) format and are an example of products available to forecasters at the National Hurricane Center. Forecasters use the 89 GHz RGB product to look for areas of strong convection which show up as deep red as seen in Fig. 1 which captures Hurricane Odile a few hours before landfall.
Figure 1. GMI 89 GHz RGB 0121 UTC 15 September 2014. Areas of deep convection appear red and can be seen surrounding the eye and within the rainbands of Hurricane Odile in this image a few hours before landfall.
The 37 GHz can additionally be used to distinguish areas of deep cloudiness (light blue) from more active convection (pink) as well as open water (green) or land (cyan). Note the areas of pink or active convective in Fig. 2 surrounding the eye and within the rainbands.
Figure 2. GMI 37 GHz RGB 0121 UTC 15 September 2014. Areas of active convection appear pink and can be seen surrounding the eye and within the rainbands of Hurricane Odile in this image a few hours before landfall.
Figure 3 and 4 show similar observations from the legacy NASA Tropical Rainfall Measurement Mission (TRMM) as Hurricane Odile made landfall near Cabo San Lucas around 445 UTC 15 September. TRMM is expected to run out of fuel by February 2016 and will no longer be available to collect valuable observations. We are well prepared for a replacement with GPM in orbit and already collecting observations.
Figure 3. TRMM 89 GHz RGB 0307 UTC 15 September 2014. Areas of deep convection appear red and can be seen surrounding the eye and within the rainbands of Hurricane Odile in this image a little over one hour before landfall.
Figure 4. TRMM 37 GHz RGB 0307 UTC 15 September 2014. Areas of active convection appear pink and can be seen surrounding the eye and within the rainbands of Hurricane Odile in this image a little over one hour before landfall.
Additionally the Visible Infrared Imaging Radiometer Suite (VIIRS) Day-Night Band Radiance imagery from the next generation NASA Suomi National Polar-orbiting Partnership (NPP) satellite shows an impressive picture of Hurricane Odile approximately one day before landfall (Fig. 5). Note the city lights that can be seen through the clouds in Fig. 5 as well as lightning within the area of convection in the rainband. This imagery can be used to support disaster response and help emergency managers identify the areas where conditions have caused power outages. Local knowledge of city light patterns can allow users to identify where the most significant power outages are and determine where to begin relief efforts.
Figure 5. VIIRS Day-Night Band Radiance 0904 UTC 14 September 2014. City lights and lightning observed approximately one day before Hurricane Odile made landfall.
As the community transitions from legacy instruments such at TRMM and MODIS, NASA SPoRT will continue to develop unique products from Next-Generation missions such as GPM and Suomi NPP to aid National Weather Service Forecast Offices and National Centers in forecasting high impact events such as Hurricane Odile.
**see archived National Hurricane Center forecast discussion at http://www.nhc.noaa.gov/archive/2014/ep15/ep152014.discus.021.shtml?
Read Full Post »
It is said that a picture says a thousand words…well in this case let’s just say 434 words, as are contained in this post. Anyway, I’d like to point out six features in this morning’s Nighttime Microphysics RGB. The image below (MODIS Nighttime Microphysics RGB) showed several features of varying degrees of operational relevance.
MODIS Nighttime Microphysics RGB with annotations valid 0755 UTC 16 July 2014
A myriad of cloud features can be observed, including fog in the valleys of central Appalachia, deep convective clouds along the Florida coast, patches of thin and thick cirrus over north-central Alabama, and low stratus clouds in Missouri…to name just a few. Sure, this isn’t an exhaustive list of the potential cloud features to observe, but showcases the ability to contrast effectively between different cloud types. Of perhaps significant interest is the ability to see the contrasting airmasses displayed across the Southeast region. Notice the pinkish colors north and west of the yellow curved line that stretches from central Louisiana to southern Virginia. This represents a lower relative contribution of blue color, or lesser longwave radiation at the 10.8 µm wavelength, which is indicative of cooler temperatures. To the south and east of this line, much more blue is apparent, which is thus indicative of warmer temperatures. Surface observations valid at about the same time have been overlaid with the RGB image to provide temperature data context. Air and dew point temperatures are around 10 degrees F cooler behind the line/front, but notice that the northerly wind shift is still on the south/east side of the line at such locations as Montgomery, AL and Columbus, GA. At those locations, dew point temperatures were still 70 and 71 F, respectively, with air temperatures at 72 F. So, the gradient in temperatures still lingered behind the surface front and is well depicted in the RGB imagery. This type of information can be valuable to forecasters, as temperature, moisture, and wind characteristics are often complex in the vicinity of surface fronts. Thus, while wind shifts may be observed initially, as in this case, the imagery shows the location of the temperature gradient much better.
The importance of this type of imagery is that it offers a much more effective assessment of meteorological phenomena than existing GOES imagery. The only problem currently is the limitation of available imagery to forecasters, since these are from polar-orbiting platforms (Terra, Aqua, Suomi NPP), and thus provide just a few snapshots per night over a given location. Nevertheless, the imagery form the VIIRS and MODIS instruments offer added value to existing GOES imagery and serve as valuable teaching and preparatory aids for future GOES-R and JPSS missions.
Read Full Post »
I didn’t have a chance to make this post last week when the imagery were more time-relevant. Nevertheless, I wanted to point out another example of the usefulness of MODIS and VIIRS imagery over current GOES imagery and show the usefulness of exciting products and imagery to come! First, let’s take a look at the color-enhanced GOES-IR image below from the morning (0715 UTC) of June 20th.
Image 1. Color-enhanced GOES-IR (11 µm) image valid 0715 UTC 20 June 2014
I’ve placed the yellow circles in the image for a reason, which you’ll see below. Further down, I’m going to show areas of fog displayed in the MODIS and VIIRS imagery, and granted, this is not the standard GOES channel difference (11-3.9 µm) typically used for making fog assessments. However, this post is meant to show current (MODIS / VIIRS) and future capabilities (GOES-R / JPSS) that will make fog detection and cloud differentiation much more easy for the operational forecaster. So, in the image above, fog is nearly unidentifiable as it was in the 11-3.9 µm channel difference image that morning (not shown). Mainly high cirrus clouds can be observed scattered across the region. Now, let’s take a look at the MODIS “fog” product, or channel difference (11-3.9 um) product valid at about the same time (Image 2).
Image 2. Color-enhanced MODIS 11-3.9 µm image valid 0718 UTC 20 June 2014
Notice that in the same areas we can now begin to see low clouds (indicated by yellow colors) scattered around the valleys of the southern Appalachian region. While the GOES-East imager is capable of detecting larger scale fog often in the valleys in the eastern circle, fog in the valleys in the western circle present challenges for the current GOES-East instrument, and is often not shown very well (even in the standard 11-3.9 µm channel difference). Next, let’s take a look at a VIIRS Nighttime Microphysics RGB valid at about the same time.
Image 3. VIIRS Nighttime Microphysics RGB valid 0723 UTC 20 June 2014
In the RGB imagery it is much easier to detect the extent of the fog, making the operational forecast process much more effective. Notice also that it is possible to see the fog through the higher clouds around the TN/GA/NC border region. Not only does the resolution of the VIIRS and MODIS instruments allow for superior fog detection, but the RGBs in particular offer tremendous operational advantages. As a user of RGBs for about 2 years now, I am convinced that this type of imagery has a relevant and needed place in future operational forecasting. Of course, it will take time for forecasters to become accustomed and adjust to the new imagery, but it will happen.
Read Full Post »
Posted in GOES-R Proving Ground, MODIS, RGB, Uncategorized, tagged Air Mass, bias, bias correction, limb, limb correction, MODIS, RGB on May 15, 2014 |
Leave a Comment »
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)
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, 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
Read Full Post »