Gypsy moth defoliation in parts of New England

June 26th, 2016

Props to the Boston/Taunton National Weather Service forecast office for sending out the following on Twitter:

Terra MODIS true-color images from 25 May and 26 June 2016 [click to enlarge

Terra MODIS true-color images from 25 May and 26 June 2016 [click to enlarge]

Taking a closer look at 250-meter resolution Terra MODIS true-color (Bands 1/4/3) Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above), the loss of “green-ness” due to defoliation of large areas of trees is quite evident — most notably in western Rhode Island, but also across the border into extreme southern Massachusetts and in parts of eastern Connecticut. This defoliation was caused by an infestation of gypsy moth caterpillars (media report 1 | media report 2).

The corresponding Terra MODIS false-color (Bands 7/2/1) RGB images (below) also help to highlight the areas of tree defoliation, as indicated by a decrease in bright green hues.

Terra MODIS false-color images from 25 May and 26 June 2016 [click to enlarge]

Terra MODIS false-color images from 25 May and 26 June 2016 [click to enlarge]

On 25 June, the highly-concentrated area of tree defoliation across northwestern Rhode Island exhibited a low Normalized Difference Vegetation Index (NDVI) of 0.4 to 0.6, compared to other areas in the southern and eastern part of the state where NDVI values were in the 0.7 to 0.8 range (below).

Aqua MODIS Normalized Difference Vegetation Index (NDVI) product [click to enlarge]

Aqua MODIS Normalized Difference Vegetation Index (NDVI) product [click to enlarge]

Much of the affected region was experiencing Abnormally Dry to Moderate Drought conditions, and had only received  between 25-75% of normal precipitation during the preceding 30/60/90-day periods — this created ideal conditions for the hatching of gypsy moth caterpillar eggs. If these dry conditions persist, it will limit the ability of the deciduous trees to recover and begin producing leaves again during the remainder of the summer season.

First full day of Summer: snow in the Brooks Range of Alaska

June 22nd, 2016

GOES-15 Water Vapor (6.5 µm) images [click to play animation]

GOES-15 Water Vapor (6.5 µm) images [click to play animation]

GOES-15 (GOES-West) Water Vapor (6.5 µm) images (above) showed the southeastward migration of an upper-level low across the North Slope and the eastern Brooks Range of Alaska during the 21 June – 22 June 2016 period. A potential vorticity (PV) anomaly was associated with this disturbance, which brought the dynamic tropopause — taken to be the pressure of the PV 1.5 surface — downward to below the 600 hPa pressure level over northern Alaska. Several inches of snow were forecast to fall in higher elevations of the eastern portion of the Brooks Range.

With the very large satellite viewing angle (or “zenith angle”) associated with GOES-15 imagery over Alaska  — which turns out to be 73.8 degrees for Fairbanks — the altitude of the peak of the Imager 6.5 µm water vapor weighting function (below) was shifted to higher altitudes (in this case, calculated using rawinsonde data from 12 UTC on 22 June, near the 300 hPa pressure level).

GOES-15 Imager water vapor (Band 3, 6.5 µm) weighting function [click to enlarge]

GOES-15 Imager water vapor (Band 3, 6.5 µm) weighting function [click to enlarge]

The ABI instrument on GOES-R will have 3 water vapor bands, roughly comparable to the 3 water vapor bands on the GOES-15 Sounder — the weighting functions for those 3 GOES-15 Sounder water vapor bands (calculated using the same Fairbanks rawinsonde data) are shown below. Assuming a similar spatial resolution as the Imager, the GOES-15 Sounder bands 11 (7.0 µm, green) and 12 (7.4 µm, red) would have allowed better sampling and visualization of the lower-altitude portion of this particular storm system. The 3 ABI water vapor bands are nearly identical to those on the Himawari-8 AHI instrument; an example of AHI water vapor imagery over part of Alaska can be seen here.

GOES-15 Sounder water vapor weighting function plots [click to enlarge]

GOES-15 Sounder water vapor weighting function plots [click to enlarge]

As the system departed and the clouds began to dissipate on 22 June, GOES-13 Visible (0.63 µm) images (below) did indeed show evidence of bright white snow-covered terrain on the northern slopes and highest elevations of the Brooks Range.

GOES-15 Visible (0.63 µm) images [click to play animation]

GOES-15 Visible (0.63 µm) images [click to play animation]

A sequence of 1-km resolution POES AVHRR Visible (0.86 µm) images (below) showed a view of the storm during the 21-22 June period, along with the resultant snow cover on 22 June. However, the snow quickly began to melt as the surface air temperature rebounded into the 50’s and 60’s F at some locations.

POES AVHRR Visible (0.86 µm) images [click to play animation]

POES AVHRR Visible (0.86 µm) images [click to play animation]

The increase in fresh snow cover along the northern slopes and the highest elevations of the central and northeastern Brooks Range — most notably from Anaktuvuk Pass to Fort Yukon to Sagwon — was evident in a comparison of Suomi NPP VIIRS true-color Red/Green/Blue (RGB) images from 17 June and 22 June, as viewed using RealEarth (below). The actual time of the satellite overpass on 22 June was 2134 UTC.

Suomi NPP VIIRS true-color RGB images, 17 June and 22 June [click to enlarge]

Suomi NPP VIIRS true-color RGB images, 17 June and 22 June [click to enlarge]

Localized heavy rainfall and flooding in south-central Wisconsin

June 15th, 2016

GOES-13 Infrared Window (10.7 µm) images [click to play animation]

GOES-13 Infrared Window (10.7 µm) images [click to play animation]

GOES-13 Infrared Window (10.7 µm) images (above) showed the development of several rounds of deep convection which moved over parts of southern Wisconsin during the 14 June15 June 2016 period; these storms were responsible for heavy rainfall at some locations (NWS Milwaukee summary). As mentioned in a WPC Mesoscale Precipitation Discussion, some of these storms were focused along the nose of a low-level jet that was helping to push a warm frontal boundary (surface analyses) through the region. Moisture was also abundant south of the warm front, with a total precipitable water value of 55.1 mm (2.17 inches) seen in rawinsonde data from Davenport IA.

Landsat-8 false-color image [click to enlarge]

Landsat-8 false-color image [click to enlarge]

A timely cloud-free overpass of the Landsat-8 satellite on the morning of 15 June provided a 30-meter resolution false-color image as viewed using RealEarth (above), which showed areas of flooding — water appears as darker shades of blue — in the Black Earth area of western Dane County in southern Wisconsin. A before/after comparison of Landsat-8 images processed using an equation to highlight water as blue (below, courtesy of Shane Hubbard, SSEC/CIMSS) revealed the areas of inundation due to the 14-15 June thunderstorms.

Landsat-8 derived water change, 30 May vs 15 June 2016 [click to enlarge]

Landsat-8 derived water change, 30 May vs 15 June 2016 [click to enlarge]

Aerial footage from a drone flight (below) showed vivid images of the flooding along Black Earth Creek.

YouTube video from drone flight near Black Earth, Wisconsin [click to play]

YouTube video from drone flight near Black Earth, Wisconsin [click to play]

Wildfire on the Kamchatka Peninsula of Russia

June 7th, 2016

Himawari-8 Visible (0.64 µm) images [click to play animation]

Himawari-8 Visible (0.64 µm) images [click to play animation]

A large wildfire had been burning for several days from late May into early June 2016 (VIIRS fire detection hot spots) near the west coast of the Kamchatka Peninsula of Russia. On 07 June, Himawari-8 Visible (0.64 µm) images (above) showed smoke from the wildfire which became entrained within the clockwise circulation of a weak area of low pressure (surface analyses) just off the coast over the Sea of Okhotsk. Beneath the smoke aloft, a swirl of low-level stratus cloud associated with this low was also very apparent. Other features of interest seen in the 0.5 km resolution 10-minute imagery include the intermittent formation of standing wave clouds over the high terrain (east of the fire), and small ice floes drifting westward just off the coast of Magadan Oblast (northwest of the fire).

A closer view using Himawari-8 Visible (0.64 µm) and Shortwave Infrared (3.9 µm) images (below) revealed numerous hot spots (dark black to yellow to red pixels) around the periphery of the burn scar of the large fire, along with the brief development of small pyrocumulus clouds over some of the larger, more active fires. Note that the ABI instrument on GOES-R will provide similar imagery at high spatial (0.5 km visible, 2 km infrared) and temporal (5 minute Full Disk coverage) resolutions.

Himawari-8 0.64 µm Visible (top) and 3.9 µm Shortwave Infrared (bottom) images [click to play animation]

Himawari-8 0.64 µm Visible (top) and 3.9 µm Shortwave Infrared (bottom) images [click to play animation]

A Suomi NPP VIIRS true-color Red/Green/Blue (RGB) image viewed using RealEarth (below) provided a high-resolution view of the fire region and the plume of smoke curving around the low pressure feature.

Suomi NPP VIIRS true-color image [click to enlarge]

Suomi NPP VIIRS true-color image [click to enlarge]