Monthly Averages of GOES-17 Band 13 Brightness Temperatures for 2021

August 23rd, 2022 |

Access to SSEC’s Data Center allows for some serious “data crunching” with the full record of GOES-17 ABI data. In Figure 1 below, GOES-17 Band 13 Full Disk brightness temperatures have been averaged for each month in 2021. These fields of averaged brightness temperature are useful for assisting forecasters in knowing what can be expected from satellite retrievals on monthly timescales, especially in remote Pacific regions where forecasters are heavily reliant on satellite data.

Figure 1. An animation of monthly mean GOES-17 Band 13 Full Disk brightness temperatures for 2021. [Click to open in new tab.]

2021 was a typical La Nina year, which is associated with dry weather in the Southwest United States. A strong surface heat signal can be seen in that region from April – September.

May – October experiences cooler temperatures in the East Pacific near Mexico and Central America. This may be associated with the 2021 Pacific Hurricane season.

Figure 2 is the same animation for tropical latitudes only. In all months, the ITCZ band is visible. It can be recognized as a band of cooler brightness temperatures (green-teal color) that sits slightly north of the equator. If you look closely, the ITCZ seems to undergo a slight northward migration as the year progresses. This northward shift is more noticeable in the transitions from April to May and from September to October.

Figure 2. An animation of tropical monthly mean GOES-17 Band 13 brightness temperatures for 2021. [Click to open in new tab.]

Aerosols blowing from Mount St. Helens

August 3rd, 2022 |

GOES-17 captured ash blowing off Mount St. Helens in Washington State, which erupted over forty years ago. The blowing debris can be seen from the GOES-17 ABI in this true color animation from 13:00 UTC to 16:50 UTC on 8-3-2022.

Testing an interpolation technique for building a continuous GOES-17 data series

July 19th, 2022 |

In a previous post, we explored a data interpolation technique that involved running sections of missing GOES-17 Band 13 data through a shape-preserving piecewise cubic spline method in order to fill the data gaps for brightness temperature (BT). (That method was nicknamed ‘pchip’ interpolation.) In this post, we introduce a more advanced type of interpolation for data filling known as interpolation by Principal Component Analysis, or PCA interpolation. One benefit of PCA interpolation is that data does not need to be smoothed to create a believable interpolation. It is, however, more computationally intense and the interpolation requires more time.

To test PCA interpolation, artificial gaps are created in portions of the complete GOES-17 time series data and compared for accuracy. The longest real gap in the GOES-17 time series is approximately 31 hours. Twenty artificial gaps of 31 hours are created in the time series and run through PCA interpolation. Examples are shown below.

Example 1 of PCA-filled data (red) compared to the original true data (blue) for 31 hours of data on May 22, 2020. The red line is an interpolation or ‘educated guess’ of the blue line values, using Principal Component Analysis.
Example 2 of PCA-filled data (red) compared to the original true data (blue) for 31 hours of data on July 8, 2020. The red line is an interpolation or ‘educated guess’ of the blue line values, using Principal Component Analysis.

Clearly from the examples above, the PCA interpolation does not replicate the original data. Comparing the trends by eye, the PCA interpolation does not seem to mimic the original data well. However, the difference between the true BT and the interpolated BT is computed and has a mean of 1.2032 Kelvin, which is fairly low. 51.4% of all tested retrievals yielded a difference of less than 10 Kelvin. That is, for more than half of the tested retrievals, the filled interpolation is within 10 Kelvin of the original value.

A distribution of the differences between interpolated BT and true BT for the retrievals tested.

The Electra Fire in California

July 5th, 2022 |

The Electra Fire near Jackson, California began on the afternoon of 2022-07-04 and can be observed with GOES-West (GOES-17) satellite imagery on RealEarth. The fire produced pyrocumulonimbus clouds, or pyroCb, which are storm clouds that start due to fire conditions.

As of 2022-07-05 at 15:00 UTC, the Electra Fire is 0% contained and has affected 3,034 acres.

Five-minute imagery video of GOES-17 Band 2 (visible) overlayed with Band 7 (infrared) showing the Electra Fire in northern California from 2022-07-04 22:30UTC to 2022-07-05 3:30UTC. The Band 7 “enhanced fire” signature can be seen beginning at 23:00UTC. This animation can be recreated using RealEarth.
A quick loop of GOES-17 true color imagery over the area, from 2022-07-04 22:20UTC to 2022-07-05 3:50UTC. The Electra Fire event is indicated by a red arrow. This animation was made using CSPP geo2grid.