The toggle above includes nocturnal visible Suomi NPP VIIRS Day Night Band (0.7 µm) imagery over New England after a strong storm (blogged here), compared with a reference image from 04 October 2017. The primary nighttime light source for the Day Night Band over land on 31 October was cities (since the Moon was below the horizon), thus a comparison between the latest image with one earlier in the month having different lunar illumination (from October 4th) highlights regions that experienced significant power outages due to high winds. Clouds will affect the interpretation of the Day Night Band imagery, and a reference Infrared Window (11.45 µm) image from 31 October at 2:38 AM EST is here. The Day Night Band image with only cloud outlines is here. (VIIRS imagery courtesy of Will Straka, CIMSS).
Politicians, climate activists, and some media outlets have claimed that there is a strong connection between the recent Wine Country fires north of San Francisco and global warming forced by increasing greenhouse gases. Some samples (could provide dozens more):
Climate change had little to do with the initiation and severity of the fire.
The truth is that this was a severe weather event, whose terrible impacts (at least 43 dead and tens of billions of dollars of damage) were greatly magnified by poor societal decisions, inadequate planning, poor management of vegetated areas, ineffective use of forecasts, and inappropriate development.
An Extreme Weather Event
The wildfires that hit Santa Rosa and other communities began shortly after a sudden surge of strong winds in the early evening of Sunday, October 8th. At the Santa Rosa RAWS observing location, winds rapidly increased that evening around 9 PM PDT and reached a peak of 68 mph around 5 AM PDT, after which they dropped rapidly (see graphic).
A map of the maximum gusts that night at higher elevations (see below) shows 108 mph in the mountains NE of Geyserville at 3450 ft, and 79 mph at the nearby (and lower) RAWS site (Hawkeye, 2000 ft), The relatively low (550 ft) Santa Rosa RAWS location had 69 mph, but the Atlas Peak site to the east only reached 34 mph. This will be important.
As I noted in my earlier blog, the regional winds from the NE strengthened as cool air and high pressure built to the northeast (eastern Oregon, NE CA). But something special occurred on top of that: huge wind acceleration over and downstream of the local terrain. To show this, let me show you a vertical cross section from the WRF model forecast for 9 PM Sunday, just as things were really revving up. The path of the cross section is shown by the black line below.
Below is the cross section. You can see the terrain, sustained winds by the colors, and the solid lines are something called potential temperature.
Wow. The low-level winds were from the east and greatly accelerated at and west of the crests...in some places to over 70 knots (81 mph)! Keep in mind this was a 10-hr forecast, so strong winds were expected. Other modeling systems did the same thing (e.g., NOAA HRRR, Desert Research Institute/CANSAC WRF).
(2) Warm temperatures and drought
A number of politicians, media folks, environmental activists, and others have thrown out the argument that droughts and unusually warm temperatures HAD to have contributed to the fires. However, a more careful analysis reveals that this CAN'T be the case in respect to the recent fires.
First, one must ask what was the main vegetation involved in the fires. It was mainly grass, not bushes and trees. Picture after picture demonstrates this, and in many burned locations the trees are still alive and green (see below).
There was more grass than normal going into this summer because of excessive rain, NOT DROUGHT, this last winter. Climate models do not suggest massive increases of rainfall over northern California under global warming. And observed rainfall over the past decades indicate no such trend.
And the dry conditions this summer is absolutely typical for northern California, where rains are generally absent from May to October.
But what about temperatures? Could warm temperatures this summer have contributed to the fires by drying out the vegetation more than normal. The answer is no...and let me tell you why. It is true that this summer was warmer than normal in California, but average summer conditions are plenty warm to do all the drying needed.
The U.S. Forest Service considers grasses 1-h fuels, meaning the dry/warm conditions can sufficient remove the moisture in hours, allowing them to burn. And bushes are generally 10-hr fuels. This was the end of the summer. There was plenty of time to dry out all the vegetation and a few degrees of warming had no impact--the excessive warmth was immaterial. A normal summer would have done the drying job fine.
Take a look at the 10-hr fuel moisture for Santa Rosa for the past five years...no real trend. The moisture goes up in the winter and down in the summer, with no obvious trend on the low side.
Why Blaming Climate Change for the Fires is a Bad Idea
Blaming global warming is a convenient excuse not to deal with the real problems that produced these fires:
- Large number of homes and structures have been built in the Santa Rosa/Napa region over the past 50 years, with population going up by roughly five times. Many were built in bad locations in the forest/urban interface or actually in the forests. Major housing developments were built in regions that had experienced catastrophic wildfires relatively recently.
- Fire has been suppressed in the surrounding vegetated hills, results in the build up of dangerous fuel loads (dry vegetation). A catastrophe ready to happen.
- The electrical system was vulnerable to winds, resulting in the ignition of fires. Furthermore, there have been several suggestions that PG&E has not properly maintained its powerline right of ways.
- Inadequate use of state-of-the-science weather prediction results in a lack of timely warning of a catastrophic situation.
- Lack of robust building codes for a fire-endangered region.
It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so. Mark Twain
GOES-16 Mid-level Water Vapor (6.9 µm) images with hourly surface weather symbols plotted in red (above) showed the large-scale evolution of a storm system that deepened rapidly as it moved across the Northeast US during the 29 October – 30 October 2017 period (surface analyses). This storm produced widespread high winds and heavy rain (WPC storm summary | NWS Boston PNS | NWS Caribou PNS). Record low sea level pressures for the month of October were set in New York at Albany (977.7 hPa) and Fort Drum (977.5 hPa), and in Massachusetts at Nantucket (982.6 hPa) — a map of the minimum sea level pressures from the New York State Mesonet can be seen here.
Closer views of the Northeast US using images from the GOES-16 Upper-level Water Vapor (6.2 µm), Mid-level Water Vapor (6.9 µm) and Low-level Water Vapor (7.3 µm) bands are shown below, with hourly surface wind gusts (knots) plotted in red. The high winds caused extensive damage to trees and power lines, leading to power outages in some areas — and also contributed to coastal storm surge.One interesting aspect of this rapidly-deepening storm was the absorption/merging of the northward-moving remnants of Tropical Storm Philippe (storm track), which was shown by the CIMSS 850 hPa relative vorticity product (below). Additional details of this event can be found on the Satellite Liaison Blog.
The ABI “Cirrus” (1.37 µm) band is centered in a strong water vapor absorption spectral region — therefore it does not routinely sense the lower troposphere, where there is usually substantial amounts of water vapor. Hence, its main application is the detection of higher-altitude cirrus cloud features.
However, in areas of the atmosphere characterized by low amounts of total precipitable water, the Cirrus band can sense clouds (and other features, such as blowing dust) in the lower troposphere. Such was the case on 29 October 2017, when a ribbon of dry air resided over the northern Gulf of Mexico in the wake of a strong cold frontal passage; low-level stratocumulus clouds were very apparent on GOES-16 Cirrus band images (above). Also of note: cloud features associated with Tropical Storm Philippe could be seen east of Florida.
The three GOES-16 Water Vapor bands (Upper-level 6.2 µm, Mid-level 6.9 µm and Lower-level 7.3 µm) highlighted the pocket of dry air that was moving across the northern Gulf of Mexico on that day (below).The MODIS instrument on Terra and Aqua has a 1.37 µm Cirrus band as well; 1619 UTC Terra images (below) also revealed the stratocumulus clouds (especially those over the northeastern Gulf, where the driest air resided). Conversely, note how the low cloud features of Philippe were not seen on the Cirrus image, since abundant moisture within the tropical air mass east of Florida attenuated 1.37 µm wavelength radiation originating from the lower atmosphere.
In addition, the VIIRS instrument — on Suomi NPP, and the upcoming JPSS series — has a 1.37 µm Cirrus band.Hourly images of the MIMIC Total Precipitable Water product (below) showed the ribbon of very dry air (TPW values less than 10 mm or 0.4 inch) sinking southward over the northern Gulf of Mexico. This TPW product uses microwave data from POES, Metop and Suomi NPP satellites (description).
Typically the evolution of the boundary layer is conceptualized as shown below. During the morning, sunlight heats the Earth's surface, resulting in a transfer of heat into the atmosphere. This erodes the shallow stable layer that typically forms overnight from radiational cooling. The boundary layer then continues to grow, eventually reaching maximum depth later in the day (the time varies depending on conditions). Within the boundary layer, turbulence driven by wind shear and surface heating results in considerable mixing. Concentrations of gasses like water vapor and carbon dioxide are often nearly constant with height in the boundary layer. Hence, the "mixed layer" label in the schematic. Often there is a stable layer or inversion at the top of the mixed layer.
In quiescent weather conditions, this pattern repeats itself daily: 1. The sun rises; 2. The nocturnal stable boundary layer is "burned off"; 3. The boundary layer grows rapidly into the residual layer and constituents (including pollutants) are mixed through its depth; 4. The sun sets and the nocturnal boundary layer forms and strengthens, leaving a residual layer aloft.
Evidence of these processes was very apparent on my ride above Ensign Peak this morning. At the time, the top of the pollution layer was perhaps 1 km above the valley floor. There was a very clear discontinuity in the pollution at that level. It was early enough that I suspect that discontinuity did not mark the top of today's boundary layer, but instead the top of the residual layer, which was loaded with pollutants from emissions from yesterday.
I've added by eye yesterday's sounding (red=temperature, green=dewpoint) from the airport. In this case, the temperature or dewpoint decrease if the line slopes to the left and increase if it slopes to the right. The top of the residual layer was very near the elevation of an inversion in yesterday's sounding, as one might expect. Below that inversion, the atmosphere yesterday afternoon was relatively well mixed. For example, temperature decreased rapidly with height at a rate of about 10ºC per kilometer, which is consistent the density being constant with height. Dewpoint decreased with height at a rate close to that expected if the concentration of water vapor is constant with height. However, the decrease with height near the surface was more rapid than one might expect if the atmosphere is well mixed. This isn't unusual as the turbulence typically can't mix the atmosphere fast enough right near the ground to make the water vapor concentration constant with height if there is evaporation or transpiration occurring.
Expect views like this most days this week due to the presence of high pressure. Note that the sharp top of the residual layer is most apparent in the morning and evening if you are at an elevation somewhat above the valley floor and you face somewhat toward the sun (but perhaps not right at it). This is an optical effect related to how pollution scatters sunlight.
I'm pleased to announce that we will be exhibiting the Doppler on Wheels mobile radar (pictured below) at the Natural History Museum of Utah this coming Saturday, November 4, from 10–5 PM. Bring yourself, the family, and friends. The exhibit is also one of their Behind the Scenes days when they open the place up for a public viewing of their collections. Come and geek out!
With high pressure dominating across the region during the pre-dawn nighttime hours (surface analyses), strong radiational cooling (minimum temperatures) aided in the formation of widespread valley fog across New England on 28 October 2017. Post-sunrise GOES-16 “Red” Visible (0.64 µm) images revealed the areal extent of the valley fog; however, fog dissipation was fairly rapid during the morning hours as surface heating from abundant sunlight promoted sufficient boundary layer mixing.
During the preceding nighttime hours, development of widespread valley fog could be seen on Suomi NPP VIIRS Infrared Brightness Temperature Difference (11.45 µm – 3.74 µm) images (below) — although surface fog features were obscured at times by patchy cirrus clouds aloft (black enhancement). This example demonstrates that because of the wide (3000 km) scan swath of the VIIRS instrument, in many cases the same region might be sampled by 2 consecutive overpasses. VIIRS will also be part of the instrument payload on the upcoming JPSS series of polar-orbiting satellites.
Below the inversion, the air has become saturated, with lots of fog. The view from the Seattle SpaceNeedle panocam shows a dramatic, and very beautiful, scene:
But the surface view from North Seattle is one of fairly dense fog.
How strong is the inversion? Let me tell you...and be prepared to be impressed.
Here are the temperatures above north Seattle from the regional profiler, a sophisticated device that can measure temperature aloft by tracking sound waves (the speed of sound depends on temperature). Temperatures are in C and range from 10C (50F) to about 22C (72F), 700 meters above the surface. Most of the change is in the lower 300 meters (about 1000 ft)
But there is more. A big high pressure area is associated with sinking air aloft, but less sinking near the surface (air can't pass through the surface). Sinking causes air to be compressed (pressure increases towards the ground) and compressing air warms it up (think about how warm your bike pump is after use).
So with more sinking aloft than at the surface, the high is preferentially warming aloft compared to the surface---this helps build the inversion.
And if you like subtleties there is more. At the surface, the highest pressures of the region are east of the Cascades, causing some easterly flow aloft.
To show this, here are the winds and temperatures above Sea Tac Airport for the past day (time increases to the left, height is in pressure, 850=5000ft). The wind barbs show easterly flow (from the east), which descends over the western slopes of the Cascades producing MORE compressional warming aloft.
Good for the inversion. In fact, look at the temperatures on the chart...there is a big increase from the surface to roughly 930 hPa pressure (about 800 meters above sea level.)
The fog will burn out in a few hours and warmer air should mix down to the surface, giving a fine day in the 60s.
But if you can't wait to warm up, put on your hiking shoes and head up a local foothill. You will start with a jacket and end up in a tee shirt...guaranteed.
The article summarizes the findings of a survey of 5700 doctoral students worldwide. Perhaps not surprisingly, the responses "uncovered a strong, perhaps crucial, connection between a well-matched PhD adviser and the student's success." In my experience, it is often the adviser–student relationship that determines student success, rather than the graduate program. If you are a student, chose your adviser carefully. Make your choice of adviser a higher priority than your choice of program if you are in a fortunate position to have such a choice before entering graduate school. If you are an adviser, recognize that student success equates to your success. One size doesn't fit all. Recognize that students have varied abilities and goals and adapt your mentoring accordingly.
One of the more important topics covered was student anxiety and success. I was surprised to read that anxiety and depression are prevalent in graduate student life. More than a quarter of the respondents listed mental health as an area of concern and 45% had sought help for anxiety or depression caused by their doctoral studies. Of these students, only 35% felt they had helpful resources at their institution and 20% said they didn't feel supported.
I am now more than 20 years out of graduate school. I remember anxious times in graduate school, but I've largely forgotten those issues and tend to remember the good times. Thus, seeing those numbers was eye opening for me and an important reminder of the challenges facing our graduate students.
There are may other nuggets in the article that should be helpful for students and faculty. It's well worth the quick read.
The reason? A strong area of high pressure that has built in across the area, and one that will remain in place through the middle of next week.
Let's start with the upper level (500 hPa, about 18,000 ft) map for 5 AM Friday. HUGE ridge over the U.S. West Coast. The problem with having high pressure over us during fall, is that it promotes low clouds and fog...like we had today.
The ridge will stay strong all day Friday and then weaken a bit on Saturday, as a weak disturbance passes to our north (illustrated by the upper level map at 11 AM Saturday).
On Tuesday, the ridge is still strong, but closer to us.
The bottom line is that we have a week of dry weather ahead, with initially warmer than normal temperatures (mid-60s Friday and Saturday), dropping into the upper 50s by early next week. Perfect fall weather.
Have you noticed that the leaf colors have been particularly good this year? What I have read is that warm days and cool nights in late summer and early fall is good for fall color. Taking a look at the temperatures at Sea-Tac for the past 12 weeks (below), we have had a number of warm days, with typically cool nights. Plenty of sun, which supposedly is good for color.
In fact, the surface chart (pressure in solid lines, colors are temperatures), shows very cold air (blue and purple) just to our north.
So put your umbrella and heavy jackets away for the the next 5-6 days, but get them ready. By Friday you will need them, with HIGH temperatures only reaching into the mid-40s!