Figure 1: Air mass product example. Warmer air is displayed in green and red where the green regions have higher moisture content than the red regions. Mid-latitude air has a bluish color and areas or dark red show areas of subsidence and high ozone and PV.
1) Product Information:
- Who is developing and distributing this product?
This product is being developed by The Cooperative Institute for Research in the Atmosphere (CIRA) in Fort Collins, Colorado, together with the NOAA/NESDIS/STAR RAMM Branch.
- Who is receiving this product, and how?
The Red-Blue-Green (RGB) Air Mass Product is being disseminated to the NOAA’s Hydrometeorlogical Prediction Center (HPC) and other National Centers via a Local Data Manager (LDM). This is a collaborative effort with NASA’s Short-term Prediction Research and Transition (SPoRT) group who convents the product generated at CIRA to a N-AWIPS image format. Furthermore, imagery and RGB products are being archived for the duration of the Proving Ground Demonstration period and can be supplied to for post-season applications.
- What is the product size?
Original images are created every hour by remapping GOES-East and GOES-West sounder sectors into a common projection. The eclipse periods of GOES-West are accounted for by using the last available image.
2) Product Description:
- Purpose of this product:
The purpose of the product is to provide the HPC forecasters with an additional decision aid for their forecasting tasks. The product strongly highlights differences between dry, tropical and mid-latitude air masses.
- Why is this a GOES-R Proving Ground Product?
The RGB air mass product demonstrates the kind of imagery that will be possible in the GOES-R era. The product is currently based on the GOES-Sounder data, simulating the future features the GOES-R Advanced Baseline Imager (ABI) sensor, albeit at much lower resolution (9 km for the sounder vs. 2km for ABI). ABI will be able to produce both a higher spatial resolution (2 km), higher temporal resolution (5 min), and higher spectral resolution than the current GOES satellites do.
- How is this product created now?
The RGB air mass product is generated from MSG channels 12 (WV6.51), 10 (WV7.43), 9 (IR9.71), and 8 (IR11.03). The raw imagery is ingested from CIRA’s local GOES servers and generated using Man computer Interactive Data Access System (MCIDAS) and the following recipe developed by European Organization for the Exploitation of Meteorological Satellites (EUMETSAT).
|Red||WV6.2 - WV7.3||-25 ... 0 K||1|
|Green||IR9.7 - IR10.8||-40 ... +5K||1|
|Blue||WV6.2||+243 ... +208 K||1|
The channel differences are scaled over the ranges provided above and the individual color composites are created in satellite projection. These components are then remapped into a 5 km Lambert Conformal projection. These remapped components are then combined to create a composite RGB. Images shown on the web page have 24-bit, and the images produced for N-AWIPS are approximately 7-bit depth resolutions.
3) Product Examples and Interpretation
The air mass product is an RGB composite based upon data from infrared and water vapor channels from Meteosat Second Generation (MSG) and applied here to the GOES sounder data. Originally designed and tuned to monitor the evolution of extra-tropical cyclones, in particular rapid cyclogenesis, jet streaks and PV (potential vorticity) anomalies by scientists at (EUMETSAT), it is also useful for tropical/subtropical applications. The product highlights differences between dry, tropical and cold air masses, as can be seen in the example below. This is accomplished by differencing the two water vapor channels (i.e., at 6.51 µ and at 7.41 µ) as depicted in the red colors, where red is associated with dryer air mass conditions locally, by Ozone differences by differencing at 9.71 µ and at 11.03 µ, where green indicates low Ozone & typically thus tropical air masses, and by using 6.51 µ to indicate gross air mass temperature differences.
Figure 2: Air mass product example. Warmer air is displayed in green and red where the green regions have higher moisture content than the red regions. Mid-latitude air has a bluish color and areas or dark red show areas of subsidence and high ozone and PV.
There are two situations to consider cloud-free and cloudy areas. In the cloud free regions, the air mass product helps discriminate tropical air masses (i.e., moist and lower ozone) that are predominantly green, from subtropical air masses (i.e., dryer) that are depicted greenish red, and mid-latitude air masses, typically having more blue colors. In the mid-latitude setting the maroon colored regions are characterized by dry and higher ozone. These high-ozone areas are often associated with regions of tropopause folding and high potential vorticity. For mid-latitude applications the product can be used for tracking short-waves and synoptic scale airmass differences. For tropical applications it should be helpful in determining and tracking the origin of air parcels as they interact with tropical systems, and improved identification of shallow upper level features (cold lows and jets streaks). It should be noted that this product can have large diurnal fluctuations over the warm air masses. When the land surface temperatures are very warm the difference between the 11.03 micron and 9.71 become very large. In these cases the blacker the region the higher the upper-level relative humidity.
In cloudy regions, deep and high clouds show up as white and mid-level clouds show up as a beige color. For more information on the interpretation of this product see (Kirkman, cited 2010). An annotated example is provided below.
Kirkman, J., cited 2010: Applications of Meteosat Second Generation (Meteosat-8), AIRMASS. [available on-line at http://oiswww.eumetsat.org/IPPS/html/bin/guides/msg_rgb_airmass.ppt]
Google Earth loops of GOES-E imagery over the CONUS are available at http://rammb.cira.colostate.edu/products/google_earth/
4) Advantages and Limitations
The RGB air mass product provides a simple decision aid tool to HPC forecasters by visually discriminating tropical air masses from subtropical air masses. For tropical applications it should be helpful in determining and tracking the origin of air parcels as they interact with tropical systems, and improved identification of shallow upper level features (cold lows and jets streaks). The current product is limited to the GOES Sounder sectors.
This product is affected by surface diurnal temperature changes and viewing angle. At steep viewing angles there is limb darkening of the water vapor (6.51, 7.43) and window (11.03) channels and a warming of the ozone channel (9.71).