GOES Imager Product Details
TRANSITIONED PRODUCT DETAILS
Fog Depth
The fog depth product is generated by NOAA NESDIS and distributed by SPoRT to its NWS partners. The fog depth product combines image data from two GOES IR channels to create a product to detect fog and low stratus clouds at night. The product is obtained by subtracting the shortwave IR window channel (3.9 µm) temperatures from the longwave IR window channel (10.7 µm) temperatures. The image displayed here and distributed to the NWS partners has been enhanced by SPoRT to provide an estimation of fog depth based on the temperature difference between the two channels. In the image, the turquoise shading denotes clouds of various depths. The green, blue, red, and yellow pixels indicate the presence of fog with depth between 100 and 500 m. Additional information can be found at the NOAA NESDIS Operational Products Development Branch site.
TRANSITIONED PRODUCT DETAILS
Low Cloud Base
The low cloud base is another product generated by NOAA NESDIS and distributed by SPoRT to its NWS partners. The low cloud base product combines image data from twoGOES IR channels to create a product to detect regions where aviators will encounter Instrument Flight Rule (IFR) ceilings vs. non-IFR ceilings. The product is obtained by subtracting the shortwave IR window channel (3.9 µm) temperatures from the longwave IR window channel (10.7 µm) temperatures. The image displayed here and distributed to the NWS partners has been enhanced by SPoRT to differentiate low cloud bases from other cloud areas. In the image, the turquoise shading denotes upper-level cirrus clouds. The green pixels indicate higher based clouds (above IFR level of 1000 ft.), and the red pixels indicate the presence of low-based clouds (below IFR level of 1000 ft.).
TRANSITIONED PRODUCT DETAILS
Icing Product
The third product generated by NOAA NESDIS and distributed by SPoRT to its NWS partners is an icing product. The icing product combines four spectral channels during the day (3 spectral channels at night) to detect regions of supercooled water clouds that could result in aircraft icing. The image displayed here and distributed to the NWS partners has been enhanced by SPoRT to differentiate regions where icing might occur from areas that are just cloudy. In the image, the light blue pixels denote areas where supercooled water is present denoting areas where icing is likely. Additional information can be found at the NOAA NESDIS Operational Products Development Branch site.
TRANSITIONED PRODUCT DETAILS
Icing and Cloud Top Height
The icing and cloud height product is generated by NOAA NESDIS and distributed by SPoRT to its NWS partners. The icing product combines four spectral channels during the day (3 spectral channels at night) to detect regions of supercooled water clouds that could result in aircraft icing. The image displayed here and distributed to the NWS partners has been enhanced by SPoRT to differentiate regions where icing might occur from areas that are just cloudy. In the image, the white pixels denote clouds without supercooled droplets (or clouds with unknown icing height). The orange pixels denote clouds at or below 6,000 ft. that might cause icing, yellow pixels denote clouds between 6,000 and 12,000 feet that might cause icing, turquoise pixels denote clouds between 12,000 and 18,000 feet that might cause icing, and light blue pixels denote clouds above 18,000 feet that might cause icing. Additional information can be found at the NOAA NESDIS Operational Products Development Branch site.
RESEARCH PRODUCT DETAILS
Surface Albedo
Surface albedo is the ratio of the radiation reflected by the surface to the incoming solar radiation, and an image of it describes the variation of the amount of solar radiation absorbed by the surface over a region. Surface albedo is derived from the visible channel's measurements of reflectance. Albedo is determined using the clear-sky composite image.
RESEARCH PRODUCT DETAILS
Surface Insolation
Surface insolation is the amount of solar radiation reaching the surface, and an image of it describes the variation of direct and indirect (scattered) solar radiation reaching the ground, and is assimilated into regional forecast models to improve the surface energy balance. Surface insolation is derived from the visible channel's measurements of reflectance. The insolation is calculated as the sum of solar radiation incident on the surface from both direct and indirect sources and also includes the effect of attenuation by clouds.
RESEARCH PRODUCT DETAILS
Cloud Top Pressure
Cloud top pressure images describe the spatial variation of height and type of clouds over a region and are useful for nowcasting and forecast-model data assimilation. The presence or lack of clouds over a region is very important for modeling and diagnostic studies. When a cloud is present in a satellite image, it's height (or cloud top pressure) is an important additional parameter. Cloud top pressure is derived using a method that correlates the cloud top temperature in an infrared window channel to a thermodynamic profile from the MM5 forecast model. The cloud top pressure product incorporates the GHCC operational cloud mask, produced using a technique that relies upon a 11 - 3.7 µm difference image to enhance surface versus cloud contrast to delineate cloudy pixels from clear.
RESEARCH PRODUCT DETAILS
20-Day Clear Sky Composite
The 20-day clear-sky visible composite is the minimum visible channel radiance value for each pixel from the past 20 days, and is an intermediate product that provides an estimate of the minimum in surface reflectivity for each pixel, assuming no pixel is cloud covered for all 20 days. It is used to produce the surface albedo and insolation products.
RESEARCH PRODUCT DETAILS
Cloud Albedo
Cloud albedo is a representation of the reflectance of a cloud with higher values indicating clouds that allow less solar radiation to hit the surface. The albedo is a percentage (from 0-100%) and is primarily dependent on the drop size, liquid water and ice content, and cloud thickness. Clouds that are low and thick (such as stratus or cumulus) tend to reflect more radiation resulting in higher albedo; whereas, high and thin clouds (such as cirrus) tend to transmit more radition resulting in lower albedo.
RESEARCH PRODUCT DETAILS
Cloud Mask
Jedlovec and Laws (2001) and Jedlovec and Laws (2003) describe the methodology for the GOES Sounder cloud mask. In summary, the cloud mask method applies two spatial tests and one threshold test on a 11 - 3.7 µm difference image. An additional test implemented since the writing of the paper is a temperature threshold test. This fourth test compares the temperature from the 11 µm channel to a 20-day clear-sky composite of 11 µm temperatures, and labels the pixel as cloudy if the difference is greater than the threshold. This additional test is intended to produce improvements mainly during the nighttime hours.
RESEARCH PRODUCT DETAILS
SPoRT Spectral Difference
Generated in the same way as the Fog Depth product, the SPoRT Spectral Difference product provides a different view of fog and low cloud locations. The product is at a slightly higher spatial resolution and can also be used to determine the location of low-level clouds.
