GOES-18 images shown in this blog post are preliminary and non-operational

GOES-18 Mid-level Water Vapor (6.9 µm) images during the 18 July – 19 July 2022 period (above) showed a series of impulses rotating within the broader circulation of an anomalously-deep low pressure system that meandered over the Bering Strait region. Anomalously-cold air associated with this deep low helped to produce brief periods of unusual July snow at some locations across the Seward Peninsula and northwestern Alaska.

In GOES-18 Air Mass RGB images created using Geo2Grid (below), brighter shades of red highlighted the core of this broad low pressure system, where high-altitude ozone levels were elevated (due to an unusually low tropopause).

In fact, at 12 UTC on 19 July the low 500 hPa geopotential height value of 5269.3 meters from the Nome, Alaska rawinsonde report (above) established a new July record for that site. The 12 UTC sounding also suggested that the tropopause was located at an unusually low pressure level of 483 hPa — such a low tropopause height was supported by NOAA-20 Gridded NUCAPS data from the SPoRT site (below).

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GOES-16 (GOES-East) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed that a large wildfire burning in far western Manitoba produced a series of 3 brief pyrocumulonimbus (pyroCb) clouds late in the day on 19 July 2022. The coldest pyroCb cloud-top infrared brightness temperature was -52.1ºC at 0230 UTC.

GOES-18 images shown in this blog post are preliminary and non-operational

In the corresponding imagery from GOES-18, the coldest pyroCb cloud-top infrared brightness temperature was -53.3ºC at 0230 UTC.

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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.

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.

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The animation above shows ACSPO estimates of Lake Surface Temperature (LST) over Lake Michigan from 3 different VIIRS overpasses: NPP at 0703 and 0844, and NOAA-20 at 0753 UTC (despite the AWIPS label!) early on 18 July 2022; VIIRS data were downloaded at the CIMSS Direct Broadcast antennae, and ACSPO SST fields were created using CSPP software; AWIPS-ready tiles are available via an LDM feed from CIMSS. Orange to red enhancement values show lake surface temperature at/above 20^oC/68^oF (the color bar limits are 41^oF/77^oF). Two NOAA buoys are also present within Lake Michigan, and both show lake temperatures of 69^oF; satellite values show far greater variability within the lake than can be deduced from just two buoy-based observations.

GOES-R data are used to create lake-surface (and sea-surface) temperatures. The toggle below over Green Bay and central Lake Michigan shows the superior spatial resolution of the VIIRS instrument. Over the open lake, GOES-R SSTs run about 1/2^oF warmer than SSTs from VIIRS.

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Similar imagery (also using Direct Broadcast data and created using CSPP software) was available slightly later off the coast of Oregon, as shown below. Three consecutive passes of VIIRS, at about 45-minute intervals, allow for changes in the surface temperature fields to be monitored with high spatial and temporal resolution.

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ACSPO SST (and individual channel, and true/false color) imagery is routinely available at the CIMSS direct broadcast site at this link for NOAA-20 and this link for NPP. You can also find True Color imagery over the Great Lakes, such as the image below from NOAA-20, posted for your viewing pleasure.

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