Warmest day of the year

Warmest day of the year

From NOAA’s National Centers for Environmental Information:

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“During the summer months, many areas in the United States approach their highest temperatures for the year. To give you a better idea of the warmest time of year for your area, NCEI has created these “Warmest Day of the Year” maps for thecontiguous United States, Alaska, Hawaii, and Puerto Rico. The maps are derived from the 1981–2010 U.S. Climate Normals, NCEI’s 30-year averages of climatological variables including the average high temperature for every day. From these values scientists can identify which day of the year, on average, has the highest maximum temperature, referred to here as the “warmest day.”

Although the amount of solar radiation reaching Earth peaks at the summer solstice on June 21 in the Northern Hemisphere, temperatures for most of the United States tend to keep increasing into July. The temperature increase after the solstice occurs because the rate of heat input from the sun during the day continues to be greater than the cooling at night for several weeks, until temperatures start to descend in late July and early August.

But, this isn’t the case everywhere! The “Warmest Day of the Year” maps show just how variable the climate of the United States can be. For instance, the June values in New Mexico and Arizona reflect the North American Monsoon, a period of increased rainfall affecting the U.S. Southwest. Because these areas tend to be cloudier and wetter from July through September, the temperature is highest on average in June. Similarly, the persistence of the marine layer along the Pacific Coast leads to cool temperatures in early summer with the warmest days on average later in the season.”

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Vane mount for Kestrel weather meter

Kestrel vane mount

Kestrel Portable Vane Mount. Kestrel photo.

Many wildland fire crews carry some sort of pocketable weather monitoring device, ranging from a sling psychrometer to an electronic weather meter which can cost up to many hundreds of dollars.

After seeing a Tweet by Southeast England Wildfire Group about a wind direction vane mount for a Kestrel weather meter, we checked it out and it’s a real thing. It is designed to be tripod-mountable and can hold any Kestrel weather meter. The idea is that the mount will rotate so that the back of the meter always faces into the wind, enabling accurate wind speed readings. This could be useful if you’re going to be in the same place for a long time, your meter can log the data which you intend to upload onto a computer, or if your meter has Bluetooth capability.

It has received mixed reviews on Amazon, and is priced at $41.18 to $63.06 from various sellers, some without Prime free 2-day shipping. At one point it came with a small tripod (which was criticized by reviewers), but appears now to come without it.

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Record rainfall pauses fire season in southern California

Precipitation last 24 hrs SoCal

Precipitation for the 24-hour period ending at 8 a.m. PT, July 20, 2015 in southern California. (Click to enlarge.)

The remnants of Hurricane Dolores passed over southern California Sunday setting precipitation records across the area, putting a sudden pause on the wildfire season. All-time rainfall records were set in Los Angeles, San Diego and more than a dozen other cities.

A bridge on Interstate 10 between Palm Springs and the Arizona border washed out and nearby highways that could have served as detours were closed.

Bridge washed out on I-10

A truck sits precariously at a bridge washout on Interstate 10 east of Palm Springs. The driver had moderate injuries. Photo from CAL FIRE/Riverside County Fire Department.

Here are some of the highest precipitation amounts at weather stations in and near National Forests for the 24-hour period that ended at 8 a.m. PT, July 20, 2015:

  • Warm Springs near Castaic, 3.0″
  • Pinyon, San Jacinto Mountains, 2.9″
  • Cameron, east of San Diego, 1.03″
  • Rock Camp, near Lake Arrowhead, 2.8″
  • Mormon Rock, near the recent North Fire, 1.15″

Below is an excerpt from an article at The Weather Channel:

…San Diego broke its all-time July rainfall record Saturday when 1.03 inches fell. That broke not only the July single-day record of 0.83 inches set July 25, 1902, but also the record for an entire July’s rainfall, which was 0.92 inches July 1-31, 1902.

It’s also more rain than San Diego saw in all of January this year; on average, January is the second-wettest month and July the second-driest, with January averaging 66 times more rainfall than July. The only other time July has out-dampened January in San Diego was 1976, when July had 0.02 inch to January’s trace.

San Diego added to its total Sunday with another 0.66 inch of rain as of 11 p.m. The month-to-date total of 1.70 inches, which fell in less than 36 hours, is more rainfall than San Diego had seen in the previous 101 Julys combined; a total of 1.68 inches fell during July from 1914 through 2014 in San Diego.

Los Angeles has also broken its July rainfall records. Downtown Los Angeles picked up 0.36 inch Saturday, which broke the July full-month record of 0.24 inch from July 1-31, 1886. Los Angeles International Airport saw 0.32 inch of rain, tying the record for all of July set in 1992.

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Researchers determine that fire seasons are becoming longer

Fire Season Length

We keep hearing that wildfire seasons are becoming longer. One way to verify this for a particular location is by analyzing times of the year that fires occur and the acres burned by date. But researchers have provided more information for the longer fire season discussion by studying weather across planet Earth. They used the data for a 34-year period, from 1979 to 2013, to calculate the U.S. Burning Index, the Canadian Fire Weather Index, and the Australian (or McArthur) Forest Fire Danger Index. They normalized the daily fire danger indices to a common scale and resampled to a common resolution.

What the researchers found was that fire seasons have lengthened across 29.6 million km2 (25.3%) of the Earth’s vegetated surface, resulting in an 18.7% increase in global mean fire season length. They also show a doubling (108.1% increase) of global burnable area affected by long fire seasons.

There were no significant trends in mean annual total precipitation or total precipitation affected area but they did observe a significant increase in mean annual rain-free days, where the mean number of dry days increased by 1.31 days per decade and the global area affected by anomalously dry years significantly increased by 1.6% per decade.

Global Mean Rain-free Days

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Scientists find that stratospheric intrusions can increase the effects of Santa Ana winds on wildfires

This important research about a little known weather phenomenon that affects wildfires was conducted by government employees working for the National Oceanic and Atmospheric Administration (NOAA) and the University of Colorado at Boulder. However, to get a copy of this taxpayer-funded research, you will have to pay $38 to a private organization, John Wiley & Sons, Inc., a corporation that for the year that ended April 30, 2015 had $1.8 billion in revenue and a net income of $176 million. In that year, 64 percent of their revenue came from journal subscriptions.

While some government and university employees may be able to access this and other research papers, they can only do it because their employer pays tens or hundreds of thousands of dollars in subscription fees to these private companies. The employees can seamlessly read the papers, and don’t always realize that non-employees can’t.

Gowers Weblog has an exhaustive article about this issue in which he lists the exorbitant subscription fees paid by some universities in the United States.

He noted, for example, that the state universities in Arizona pay a total of $2.7 million to just one of these private outfits, Elsevier.

The authors of the paper are Andrew O. Langford (U. of Colo.), R. B. Pierce (NOAA), and P. J. Schultz (NOAA).

The University of Colorado and NOAA have graciously allowed this brief summary of the publicly-funded research to be released — to the public:

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Southern Californians and writers love to blame the hot, dry Santa Ana winds for tense, ugly moods, and the winds have long been associated with destructive wildfires. Now, NOAA researchers have found that on occasion, the winds have an accomplice with respect to fires, at least: Natural atmospheric events known as stratospheric intrusions, which bring extremely dry air from the upper atmosphere down to the surface, adding to the fire danger effects of the Santa Anas, and exacerbating some air pollution episodes.

Springs Fire

Satellite image of the smoke on 2 May 2013, the first day of the Springs Fire northwest of Los Angeles. The photo was taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA’s Terra satellite.

The findings suggest that forecast models with the capacity to predict stratospheric intrusions may provide valuable lead time for agencies to issue air quality alerts and fire weather warnings, or to reallocate fire fighting resources before these extreme events occur.

“The atmosphere could give us an early warning for some wildfires,” said Andrew Langford, a research chemist at NOAA’s Earth System Research Laboratory in Boulder, Colorado, and lead author of the study. Researchers at NOAA’s National Environmental Satellite, Data, and Information Service (NESDIS) and the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder coauthored the work, which was accepted for publication this week in the American Geophysical Union journal Geophysical Research Letters.

The authors took a detailed look at the May 2013 “Springs Fire” that burned 25,000 acres about 50 miles northwest of Los Angeles. The researchers used a NOAA forecast model that incorporates satellite observations of ozone, wind data, and other atmospheric information to detect the occurrence of the intrusions.

The analysis showed that in the early hours before the Springs Fire, a tongue of air characteristic of the stratosphere—extremely dry and very high in ozone from the stratosphere’s ozone layer—reached to the surface in southern California and extended as far south as Baja California.

The researchers found that ground-based monitoring stations near the fire’s origin also confirmed the telltale signs of the intrusion right before the fire broke out: A large drop in relative humidity and a rise in ozone. As the day went on, a combination of factors accelerated the fire: Low humidity, persistent high winds, dry condition of the grasses and other vegetation, clear skies and bright sunlight, and very warm surface temperatures. A few days later, cloudy skies, a drop in temperature, a shift in winds, and widespread rainfall helped extinguish the fire.

The stratospheric intrusion also had another downside during the Springs Fire: it added ozone from the upper atmosphere to the urban and fire-related pollution produced in the lower atmosphere. On the second and third days of the fire, this helped to push levels of ozone—which can harm people’s lungs and damage crops—over the federal ozone limit at 24 monitoring sites across southern California. Monitors as far away as Las Vegas also saw a spike in ozone on the third day of the fire. The observed exceedances of the ozone standard were unusual for the region for that time period, suggesting that the stratospheric intrusions were a contributing factor.

“Stratospheric intrusions are double trouble for Southern California,” said Langford. “We knew that the intrusions can add to surface ozone pollution. Now we know that they also can contribute to the fire danger, particularly during La Niña years when deep intrusions are more frequent, as recently shown by our NOAA colleagues at the Geophysical Fluid Dynamics Laboratory. The good news is that with models and observations, we can get an early warning from the atmosphere in some cases.”

The authors note that stratospheric intrusions have previously been implicated in the explosive development of wildland fires in New Jersey and Michigan, but have not previously been connected to fires in southern California or to the Santa Ana winds. The frequent occurrence of stratospheric intrusions above the west coast during the fall, winter, and spring suggests that similar circumstances may have played a role in other major southern California fires, including the series of destructive fires that burned more than 800,000 acres in October of 2003, and burned nearly a million acres in October of 2007, say the authors.

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(UPDATE July 12, 2015: We contacted one of the authors, Andrew Langford, and he sent us a copy of the paper, which has not been copyedited and typeset yet.)

Information about unrestricted online access (Open Access) to research funded by taxpayers.

Thanks and a tip of the hat go out to Barbara.

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