Tuesday, July 31, 2018

Differences Between Winter and Summer Air Pollution Episodes

There are dramatic differences in air pollution episodes over the Salt Lake Valley between winter and summer.

During winter, when the sun angle is low, we frequently lack sufficient surface heating to warm the atmosphere and develop a deep layer in which turbulence can mix the near-surface air with the atmosphere aloft.  The layer in which that turbulence occurs, which is known as the boundary layer (or mixed layer), can be very shallow.  As a result, emissions from our urban area are trapped in the valley, leading to elevated particular matter concentrations.

An example is the inversion event of late December 2016.  As can be seen in the photo below, taken on the afternoon of 30 December, smog is confined primarily to the valley and the visibility improves dramatically with altitude.  Typically in these instances, one can find clean air simply by going to the mountains.

A sounding taken that afternoon at the Salt Lake Airport is very typical of of wintertime pollution events and features a very shallow boundary layer that extends from the surface to about 850 mb, which equates to about 300 meters (1000 feet) of depth, roughly consistent with the depth of smog above.  At the top of the boundary layer is a strong inversion in which the temperature increases very dramatically with height nearly 15ºC from about 850 to 800 mb (about 500 meters).

That inversion essentially puts a lid on the valley atmosphere.  In the winter, we have met the enemy and it is us.  We can't really blame our pollution problems on anybody else.

In the summer, the situation is much different.  The sun angle is high and there is strong heating of the surface and lower atmosphere, which leads to a deep boundary layer and turbulent mixing.  In contrast to winter, when the pollution is confined to near the valley floor, it can be much deeper.  For example, the photo below from Snowbird's Hidden Peak cam was taken yesterday.  Smoke and pollution extend to and above mountaintop levels and the Oquirrh Mountains to the west are obscured.

Source: Snowbird
The sounding taken at the Salt Lake airport yesterday afternoon is very typical of summer in northern Utah.  Very near the surface to about 850 mb, temperature decreases very rapidly with height, more than 1˚C per 100 meters.  Such a layer is called superadiabatic and the air density in such a layer actually increases with height rather than decreases.  Basically, the near-surface atmosphere is being heated so intensely that the turbulence can't mix the atmosphere fast enough to keep that layer at a constant density. 

From about 850 mb to 750 mb, the temperature decreases at about 1˚C per 100 meters.  Such a layer is known as dry adiabatic and the air density in such a layer is constant with height.  Turbulence has little trouble mixing through such an atmosphere and this is why we see smoke, haze, and pollution through such a deep layer.

There is a very weak stable layer at about 750 mb that might cap the turbulence, however I suspect at times strong thermals penetrated to greater heights than that.  The paragliders will know.

So, unlike wintertime pollution episodes, during the summer, we have mixing through deep layer.

Another difference is the pollution sources.  Long-range transport plays a role in the summer.  Yesterday afternoon's MODIS image shows several major fires over the western U.S.  Smoke and trace gases from those fires are being transported into our area.  There is probably no single fire that is producing our smoke.  Some of it is long-range transport from California, Oregon, and possibly Idaho, and some might be coming from the Goose Creek Fire along the Utah-Nevada border.  There are some smaller fires in the vicinity that might serve as local sources in some areas.

Source: NASA
The smoke and trace gases then combine with local emissions over the Salt Lake Valley.  Much of the PM2.5 is probably due to long range transport, with some local production.  In the absence of the smoke, PM2.5 values would probably be "good" during this period.  On the other hand, ozone can be elevated even without the smoke, and sometimes the trace gases in the smoke interact with local emissions to elevate ozone further.

Over the last five days, PM2.5 at Hawthorne elementary has been on the boundary between good and moderate levels.  This is somewhat higher than we would expect this time of year in the absence of smoke.  Ozone shows a stronger diurnal cycle, poking up into moderate values on some afternoons, occasionally approaching the cusp of unhealthy for sensitive groups.

In a situation like this, the mountains do not necessarily provide a reprieve from the pollution.  It is even possible in the afternoon that ozone is higher than in the valley (this reflects transport and air chemistry that I don't have time to get into today).  In patterns like this, I typically exercise in the morning when ozone concentrations are typically lower.  

Monday, July 30, 2018

Normal Is Gone Forever

"The old records belong to a world that no longer exists"
- Dr. Marty Hoerling, Research Meteorologist
NOAA Earth Systems Research Laboratory

It has been a remarkable summer across the Northern Hemisphere, with high-temperature records being set at locations in North America, Asia, Europe, and North Africa.  Now that we are well into the fire season, a pall of smoke generated by large wildfires hangs over much of the western United States, as evident in yesterday afternoon's GOES-16 satellite image.  

Source: CIRA
Will we ever return to normal?


Although the climate, especially on regional scales, has always exhibited variability, we are now accelerating into a future in which the planet will be warming at a rate not seen since the emergence of human civilization. 

Further, while this warming may occur in fits and starts rather than at a steady rate, the idea that what we are currently experiencing is "just a cycle" is pure fantasy.  We will also not settle around a "new normal" for at least the next few decades, and even that assumes we get our greenhouse gas emissions under control quickly.  

The reality is that we have poked the climate bear with a hot poker and it is not going to calm down anytime soon.  If we curtail greenhouse gas emissions dramatically, perhaps we can get this thing under control in the latter half of the 21st century, but right now, that's looking unlikely.  

So, it is time that we all get used to a world of remarkable change, that we give up on the idea of a stationary climate, and we rise to meet the challenge posed by rapid change.  

If you want an example, look no farther than the western U.S. wildfires.  Yes, the lack of precipitation this past winter probably wasn't due to global warming and wildland management, development patterns, and climate variability have contributed to the mess we're in, but the fingerprints of climate change are in the ashes.  Global warming is shifting the weather in ways that we are seeing longer fire seasons, increased fuel aridity, increased acreage burned, and more extreme fire behavior (see, for example, Abatzoglou and Williams 2016).  

And here's a sobering thought.  The train has just left the station.  The fire season of the future is longer, hotter, and drier.  If you think 2018 is bad, fast forward to a drought period around 2048 or 2078.

Normal is gone forever.  The sooner we accept that and build a weather and climate resilient society for the future, the better.  

Friday, July 27, 2018

The Catastrophic Carr Fire

Thermal anomalies (red) and smoke from the Carr Fire as seen from Aqua/MODIS 26 July 2018
A catostrophic situation is unfolding in northern California where the Carr Fire is threatening communities in and around Redding.

The latest incident information from Cal Fire indicates that as of 9:17 AM this morning (27 July), the Carr Fire has burned 44, 450 acres, destroyed 65 structures, and damaged 55 structures.  Only 3% contained, the fire is currently threatening almost 5,000 structures, with numerous evacuations and road closures.  News reports indicate that the fire has now claimed the lives of two firefighters.

News footage of the fire is simply unbelievable.  Below are a couple of perspectives on rotating updrafts associated with the fire.

The rotation was clearly evident in Doppler velocity imagery from the Beal Air Force Base, posted by U of U mountain meteorology alum Neil Lareau.  In this image, red indicates flow away from the radar, which is to the south, and blue flow towards the radar.  In this case, the radar is sensing ash, not precipitation. 
Redding is a hot place in summer, but the situation right now is inferno like.  The average high for yesterday and today is 100ºF at the Redding airport a bit southeast of the fire.  Yesterday it hit 113˚F, a new record for the day, with a relative humidity that dropped below 10%.

Winds have not been as insane as they were during the Tubbs Fire that affected Santa Rosa, but looking at stations around the area, I can find locations with wind gusts to 20 mph yesterday afternoon.

Forecast highs for Today through Monday are 110˚F, 110˚F, 109˚F, and 107˚F. 

Thursday, July 26, 2018

Smoke in Salt Lake, Misery in California

This morning dawned with smoky skies and a fairly orange sun that wasn't well captured by my cell phone camera while looking up City Creek Canyon from the Bonneville Shoreline Trail. 

Although the perspective is a bit oblique, I love looking at the beautiful GOES-16 imagery from CIRA.  Smoke covers a large portion of central and northern California, northern Nevada, southern Oregon, and southern Idaho.  There's some that has snuck into northern Utah as well. 

GOES-16 imagery from CIRA at 1507 UTC 26 July 2018
The purple air network shows moderate or worse air quality across much of that area (sadly with few observations in Nevada). 

Source: PurpleAir, 9:35 AM MDT 26 July 2018
Those of us in northern Utah shouldn't complain.  The misery index in California is off the scale.  In addition to smoke and associated poor air quality, high temperatures in the Central Valley are expected to be anywhere from 106 to 112˚F. 


Wednesday, July 25, 2018

Threats from Ensign Peak Fire Continue

Yesterday afternoon, a grass fire quickly burned 100 acres above Victory Lane just north of the Utah State Capitol, threatening homes in the area. 

Source: Rich Bowmer | The Associated Press | The Salt Lake Tribune
Smoke from the fire sent a chill up my spine as it emerged from Capitol Hill, illustrating that this was a very serious situation. 

Kudos to the Salt Lake City Fire Department, which responded quickly and got the situation under control.  According to the Salt Lake Tribune, only one home was damaged.  Three firefighters were, however, hospitalized, two for heat exhaustion and smoke inhalation and one for a leg injury.  We wish them speedy and complete recoveries. 

The origin of the fire remains unknown, but was almost surely human caused.  The threat of a similar fire remains, with caution, vigilance, and taking steps to protect your home the keys to reducing risk.  Below are recommendations of the National Fire Protection Association. 
Some neighbors in the Avenues hired goats to consume grasses on the slopes below their homes a couple of weeks ago, and I thought that was looking like a really good investment yesterday.  

Although the Ensign Peak Fire is contained, the area is denuded of vegetation and will be prone to erosion and potentially debris flows during precipitation events.  Threats from wildfires continue even after the last ember is extinguished. 

Tuesday, July 24, 2018

A Beastly July Ridge Dominating Southwest Weather

Take a gander at the GFS 10-day forecast below, especially the top frame, which illustrates the evolution of the winds on the dynamic tropopause (jet-stream level).  Note the slow westward movement, or retrogression, of a very strong upper-level ridge across the southwest US and northern Mexico during the period. 

The intensity of this ridge over the southwest US and northern Mexico is quite unusual for this time of year.  For example, the NAEFS mean 500-mb height forecast for 1800 UTC today shows values that are outside climatological values for the 1979-2009 period.  In other words, we are dealing with unusually strong ridging at those latitudes for July.

Source: NWS
In general, people associate high pressure with fair weather, but the #1 weather-related killer nationally is heat and a strong ridge this time of year over the southwest makes for extreme heat.   As can be seen in the NWS forecast below, excessive heat warnings extend across much of southern Arizona and California, and up the lower Colorado River Valley to portions of Nevada and southern Utah. 

Source: NWS
I'll provide the NWS infographic below as an example of forecasts for today's max temperatures, which include everything from 123˚F in Thermal to 96˚F in Los Angeles. 

Source: NWS
With the ridge moving so slowly, this is going to be a multiday event.  Riverside, for example, is currently 102˚F (1:15 PM PDT), with a high expected to be near 110˚F today, tomorrow, and Thursday.  Riverside is inland enough that it is typically warmer than Los Angeles, but still, the average high this time of year is about 94˚F, comparable to the average for Salt Lake City.  

Source: NWS
We should all feel fortunate that we're on the periphery of this ridge and only running in the mid 90s here in Salt Lake.  

Monday, July 23, 2018

Temperature Oddities as We Enter "Hump Week"

The climatologically hottest week of the year begins today.

There is a 7-day stretch from 23-29 July during which each day the average temperature is 80˚F at the Salt Lake City airport, the warmest of the year.

Call it hump week.  After this, we are on the downward slope to winter!

It's worth a look back at the summer so far.  We've done this once or twice already, but let's dig a little deeper. 

The period from 1 June - 22 July ranks as the 4th warmest on record based on average temperature.  Technically, we are tied for 4th with 2007.

Source: NOAA Regional Climate Centers
Curiously, this warmth has been achieved with only one day with a maximum temperature of 100˚F or greater (102˚F on 6 July).  Indeed, for average maximum temperature, the period only rates as the 15th on record with 90.6˚F, nearly 3˚F behind 1961 (93.5˚F).

Source: NOAA Regional Climate Centers
However, for minimum temperature the period is the 4th warmest on record behind only, drumroll please, the three previous years (2017, 2016, and 2015).  

Source: NOAA Regional Climate Centers
We also had a 13 day run from 5-17 July during which the temperature did not drop below 70˚F.  That represents the 2nd longest streak on record (tied with periods during July 2007 and 2013), but lies short of the 22 day run we experienced last year.  


In case you are wondering, the warmest day of the year exhibits significant geographic variability.  The earliest is in extreme western Texas, New Mexico, and Arizona where temperatures peak in June or early July and temperatures later in the summer are damped by the monsoon.  Northern Utah and the greater northwestern U.S. with the exception of coastal areas, sees an average warmest day of the year in late June or early August.  Locations along the Pacific Coast have a much later maximum, some in September, since it is very difficult to get warm, offshore flow at those locales in June and July.  

If you wish to extend your misery, consider a trip to the Gulf Coast of Texas and Louisiana where the average warmest day of the year is in mid to late August and you can double down the heat with brutal humidity.  

Tuesday, July 17, 2018

Blast from the Past

The past few decades have been quite exciting for meteorologists as our field, like many others, has been transformed by massive technological change. 

Today I took some time to go through my personal archives from graduate school and finally pitch some stuff that's been collecting dust for years.  It was a good reminder of just how far we've come in the past 25 to 30 years. 

As an undergrad in the late 1980s, the Internet wasn't really yet a thing.  I don't recall using it and I certainly didn't have an e-mail account.  We did not look at weather observations, satellite imagery, radar imagery, or model forecasts online.  That information came via DIFAX charts and you were happy to get what you got.  If you wanted to forecast the weather, you had to go somewhere that had these charts, such as a University "map room", so named because the maps were simply hung on the wall. 

Through the 1990s, DIFAX remained a thing and I spent a lot of time in graduate school in the map room trying to figure out the ski weather in the Cascades.  Here's an analysis from 06Z 20 January 1993, a day that will live in infamy in Seattle.  Note the tightly wound cyclone just offshore, which would continue to deepen, eventually generating damaging winds across the Puget Sound.

A portion of my dissertation examined the fine-scale structure of that storm and why it was so damaging, but I have two strong memories about that day.  The first is that one of my fellow graduate students surfed the Puget Sound.  The second is that we tried to go night skiing after the big blow and it was pretty much a disaster trying to get up to the ski area.  I have no recollection of whether or not the skiing was any good, but it probably wasn't.  It sowed heavily in advance of the cyclone, but as it moved through, marine air flooded into the Cascades and likely created even mankier conditions.  Yet another reason to live in Utah. 

When I started at the University of Washington in the summer of 1989, the first job I was assigned involved plotting cross sections.  This involved plotting profiles of wind and temperature by hand from alphanumeric upper-air sounding data, something that nobody has done in ages.  There was no computer program that could do this at the time.  Below is an example, with a manual analysis of temperature (solid lines) and wind speed into/out of the cross section dashed). 

My oh my how things have changed and for the better.   Eventually the bots will probably take over, but for now, this really is a great time to be a meteorologist.  I don't long for the old days, although I would take my 25-year-old body again in a heart beat. 

Monday, July 16, 2018

Upper-Level Flow Forecast over the Western U.S.

This morning's 500-mb upper air pattern features an upper-level ridge, or anticyclone, centered off the southern California coast.  The anticyclone is zonally elongated, which means stretched in an east-west direction.  The flow at this level roughly parallels the 500-mb height contours, with lower heights on the left, which yields easterly flow to the south of the anticylcone over Mexico and the subtropical eastern Pacific Ocean, and westerly flow to the north over Canada and the Pacific Northwest. 

Such a pattern is not unusual in July, although in this case, the anticyclone is centered west of its climatological mean position over southern New Mexico and the easterlies to the south are a bit stronger than average. 

There are two important smaller-scale features at this level.  The first is a trough in the westerlies over the Pacific Northwest, indicated by a brown dashed line.  The second is a trough in the easterlies over northern Mexico, also indicated by a brown dashed line.  Meteorologists typically call such features short-wave troughs, although troughs in the easterlies are often called easterly waves

The ability to predict the movement and evolution of both the large-scale cyclones and anticyclones, as well as short-wave features, is critical for weather prediction.  During the monsoon, these features play an important role in moisture transport, convective initiation, and precipitation coverage and intensity. 

The loop below shows the GFS forecast for the next 5 days, ending at 1200 UTC (0600 MDT) Saturday 21 July.  Note how the short-wave features "pinwheel" around the anticyclone.  This is a defining characteristic of upper-level waves.  Short-wave features move faster than long-wave features.  The short-wave trough in the northerlies moves over the upper-midwest and amplifies, forming a stronger upper-level trough over the Great Lakes region.  Similarly, the easterly wave moves over the eastern Pacific and amplifies, closing off west of California.  Meanwhile, the anticyclone shifts slowly eastward, ending the loop centered over New Mexico and west Texas. 

The image below is for the end of the loop [i.e., 1200 UTC (0600 MDT) Saturday 21 July] to highlight those key features.  In addition, the position of the anticyclone and easterly wave opens up the potential for the transport of moisture later this week and weekend.  For example, such a pattern is one where the Sierra Nevada could see some thunderstorm activity. 

All of this is based on one model forecast produced by the Global Forecast System (GFS).  Typically the details of the forecast are sensitive to how all these features interact, and this is why meteorologists consult ensembles and multiple modeling systems to try and get a handle on the full range of possibilities. 

Sunday, July 15, 2018

Even Meteorologists Get Burned by the Weather

After an aborted attempt to ski Kings Peak in May (see Uinta Misadventures), my son and I decided we needed to go back this summer and make the summit.  I have lived in Utah for 23 years and incredibly haven't done Kings Peak, so we left Friday afternoon to try and bag it Saturday (yesterday). 

The hike in on Friday evening was as enjoyable as a long slog can be.  The meadows were pretty and the trail dry and fast.  We realized quickly what a folly it had been to try and ski Kings in May with patchy, unsupportable snow on AT gear.  Good golly, what a long approach for what would have been a minimal amount of turns!

Friday night I awoke at 2 AM or so and peered out at wonderfully clear skies.  Sunrise Saturday morning was beautiful. 

However, just visible in the pond reflection are some clouds that were floating about and gave me a little heartburn.  I was mainly concerned about afternoon thunderstorms.  I had anticipated a slight threat of those happening as often occurs in the Uintas, and this was also reflected in the National Weather Service Forecast for the western Uintas issued Friday afternoon. 

We left our campsite around 7:30 am, and already the partly cloud skies were starting to fill. 

Nearing the summit at 9:30 am, it was clear things were going south with showers in many areas, including looking west. 

A bit later, at the summit, it was clear that the 30% chance would "verify" and that things were falling apart sooner than anticipated, although thankfully we hadn't heard thunder or seen lightning.

As we took a summit photo, it was just starting to sprinkle. 

And, looking west, it was clear that things were going to change.

We began our descent.  When we reached the summit, we were the only ones on top and we hadn't passed anyone descending.  On the descent, the line of climbers was long.  We had fortunately brought some layers and rain gear, but others were in true Alpine style with shorts, thin T-shirts, and minimal gear if any.  A few were in sandals.  Kings Peak is a long ways from home when the weather goes south.  We were glad to have brought up some warmer clothes.

Indeed, the rain came in on the descent, and we had steady develop as we descended below Gunsight Pass. 

Fortunately, we got a break before reaching camp.  My son wanted to head all the way out so he could watch the World Cup Final this morning, so we spread stuff out to dry and I caught I quick nap.  We broke camp and began the long slog out, with rain starting again shortly thereafter. 

Really, it didn't rain all that much, but it was enough that portions of the trail turned into a quagmire.  At this point, we kept our heads down and the legs churning. 

All of this is a reminder that Meteorologists get burned by the weather too and that a 30% chance of showers doesn't mean a 0% chance of showers.  On the other hand, I the early development of showers that morning was a surprise.  I consider this a penalty for not paying proper sacrifice to the Gods of Kings Peak.   Clearly that area is cursed for me.  At least we summited and enjoyed a decent view. 

Friday, July 13, 2018

Large Climate Vulnerability at the Proposed Nordic Valley Ski Resort

Nordic Valley is a small ski area near Eden in the Odgen Valley east of the northern Wasatch Mountains.  It has a base elevation of 5400 feet, the lowest in Utah, and a vertical drop of 1000 feet.

The owners, however, have recently announced major expansion plans (see this Salt Lake Tribune article published this morning and this Ogden Standard-Examiner article published on June 25th) that include the installation multiple lifts including a 4.3 mile long gondola from North Ogden and expansion onto 2800 acres of national forest.  The map below is from the Nordic Valley expansion plan web site (https://nordicvalleyproject.com), which unfortunately is oriented so that north is toward the bottom.  The summit elevation would be around 8100 feet, a tad higher than the base of Snowbird and a tad lower than the base of Alta.

Source: https://nordicvalleyproject.com/
There are a host of concerns about the proposed project highlighted in the articles linked above, but let's talk about this from a weather and climate perspective.  This would be a remarkably low elevation ski area for Utah, with a base on the Eden side near the current 5400 feet and, if the map above is to be believed, 4725 feet on the North Ogden side.

In the climate of the late 20th and early 21st century, the area around Eden has been quite snowy for its elevation.  As I like to say, pound for pound it is the snowiest place in Utah.  Just to the north of Nordic Valley, the Ben Lomond Trail Snotel Site at 5971 feet has a maximum median snowpack water equivalent of 19.1 inches in late March.  Observing sites don't exist elsewhere in the Wasatch at that elevation, but I suspect there's nowhere in the range at around 6000 feet that compares to that.  Higher, at the Ben Lomond Peak site at 7688 feet, the maximum median snowpack water equivalent is 37.2 inches in early April.  This is higher than the 24.1 inches at Thaynes Canyon (9247 feet at Park City Mountain Resort) and just a bit lower than the 42.9 inches at Snowbird (9615 feet).  

However, the low elevation makes Nordic Valley the most vulnerable ski area in Utah to climate change.  The graph below illustrates estimates of the fraction of precipitation that currently falls as snow that would instead fall as rain at Wasatch and Oquirrh Mountain SNOTEL sites for every degree Celsius of warming.  By far, the highest sensitivity is the Ben Lomond Trail site, with a 20% reduction for 1˚C of warming, 40% for 2˚C, 55% for 3˚C, and 70% for 4˚C.  Ben Lomond Peak's sensitivity is lower due to it's higher elevation, but it is still larger than at Thaynes Canyon or the Snowbird SNOTEL due to it's lower elevation.  Snowpack sensitivity, not examined here, would probably be higher.  
Source: Jones (2010)

The bottom line is that the new Nordic Valley, even with expansion to the Wasatch Crest at 8100 feet, will still be the must vulnerable Wasatch Mountain ski resort to future climate change.  It is at an elevation where the fraction of wintertime precipitation that falls as snow will be decreasing the fastest and at which vulnerability to wintertime thaws and sublimation losses will be the highest.  

On the other hand, the owners don't seem to be too concerned.  In an interview with the Ogden Standard Examiner, James Colman, the resort manager said,
"There’s been climate change for millennia. There’s no question the Earth goes through cycles, there is climate change, in general the Earth has been heating up. It’s not something I worry about a whole lot myself. We do the best we can to deal with it, to improve our snowmaking, to improve the way we manage the mountain.  
"I just think there are bigger things I have to deal with, personally, that I can have more control over than the climate. I don’t think it’s conclusive, personally, that climate change is human caused. My home in Durango, 10,000 years ago, was under 2,000 feet of ice."

Thursday, July 12, 2018

Thinking of Kikkan Randall and Others Affected by Breast Cancer

Olympic gold medalist Kikkan Randall announced yesterday that she was recently diagnosed with breast cancer. 

Randall is a 5-time Olympian and 13-time World Cup race winner in cross country skiing.  She and Jessie Diggins provided one of the great moments during the 2018 Pyeongchang Winter Olympics when they won the women's team sprint and earned the first Olympic gold medals for a U.S. cross-country skiers. 

Jessie Diggins and Kikkan Randall (right).  Photo: Sarah Brunson/U.S. Ski & Snowboard.
Randall's diagnosis hits home for me as my wife is a two-time breast cancer survivor.  According to the Anchorage Daily News, Randall found two pea-sized lumps in her breast on Mother's Day and will begin chemotherapy this week.  Like many younger women affected by the disease, she is a mother, with a 2-year-old son. 

There is a 1 in 8 chance of a woman in the United States developing breast cancer during her life time.  However, there are also 3.1 million breast cancer survivors in the United States and many reasons to be optimistic.  Increasing survival rates in recent years are believed to be due to catching breast cancer earlier and improved treatments.  Forty percent of breast cancers are discovered by women who find a lump, as was the case for Kikkan, highlighting the importance of performing self exams and taking action to see a doctor if anything unusual is detected. 

I am thinking of Kikkan and everyone who is affected by breast cancer today.  Be vigilant, perform self exams and screenings as recommended by medical professionals, and keep the faith. 

Wednesday, July 11, 2018

Salt Lake's July "Human Misery Index" Is Climbing

Human comfort is strongly influenced by a number of factors including temperature, humidity, cloud cover, and wind.  For the purposes of this post, I am going to focus on one that I consider to be especially relevant to human comfort in the Salt Lake Valley, the minimum temperature.

In particular, I am going to declare 70ºF as a critical threshold in comfort, with minimum temperatures below that value generally yielding reasonable comfort, whereas minimum temperatures above that level generally yielding uncomfortable sleeping conditions.  Going a step further, I'll define the human misery index in Salt Lake City as being equal to the number of days with a minimum temperature at or above 70ºF. 

Looking at historical data for the Salt Lake City Area stretching back to 1874, we see a rapid change in the July human misery index beginning around Y2K.  In particular, around that time a clear upward trend began and we have had five Julys since 2007 with 15 or more days with a minimum at or above 70ºF, something that never happened previously. 

Source: NOAA Regional Climate Centers
So, if you think that nighttime comfort around here ain't what it used to be, you are right.

This trends has a variety of implications for everything from human and environmental health to electricity demand. Cooling degree days in July, for example, show a gradual increase for the periods prior to 2000, but since then, we've been experiencing a new normal, with the average number of days clearly higher and several years with values near or above 600.  

Source: NOAA Regional Climate Centers
Thus, in addition to growth and increased use of air conditioners, a hotter valley climate is also contributing to increased electricity usage.  

Development and associated urban heat island effects, global warming, and recent circulation patterns are possible contributors to these recent trends, although I am unaware of a study that has attempted to quantify the contributions of each of these effects.  I suspect it is likely that that both the urban heat island and global warming are contributing significantly to the upward trends.  It is possible that instrumentation moves and local conditions around the airport might also be contributing.  

Personally, I'm starting to find all of this quite depressing.  Mother Nature might perturb the jet stream some summer to give us an unusually cool July, but it is difficult to imagine the long-term trend not being towards an even hotter future.  By the end of the century, Salt Lake could be the new St. George.  Good luck with that.   

Note on Comments:

I usually try to keep up with comments, but for some reason, blogger is no longer sending me an e-mail when you comment.  As a result, I've been missing your comments.  Please keep commenting.  I'm hoping to get this fixed and to be better about responding.  

Sunday, July 8, 2018

Observations from Mt. Baldy and Hidden Peak

Beating the heat, I did a quick climb of Mt. Baldy and Hidden Peak this morning, giving my knees a break with a descent via the Snowbird Tram.  Some observations.

I was on the summit of Mt. Baldy at about 9:45 am.  The view to the east was a scene from the Great Smokies and a good example of how smoke can become trapped in valley cold pools that develop overnight. 

We've been fortunate in the Salt Lake Valley to have not been in the smoke plume except for a brief period late Thursday night and Friday. 

For snow lovers, I found the patch below at about 9400 feet in an area where contributions of artificial snow to the snowpack would probably be small to non-existent. 

I'm guessing it is the lowest remaining snow in the Wasatch.  Prove me wrong...

Finally, a little comparison of the snowpack on this date (8 July), compared photos I've taken in July the previous two years.  The situation this yea is pretty grim.  Just a few patches to be had on the north side of Twin Peaks and in the usual spots in Upper Hogum. 

Last summer was preceded by a much better snow season and it shows.  The photo below was taken 22 July 2017 when you could almost send it down the Pipeline couloir and coverage in upper Hogum was more extensive. 

If we go back a bit further, to 26 July 2015, one find a situation in which there was virtually no snow except in a few very small pockets. 

Will we get to nearly snow free by the end of the month and will we have a snow-free Wasatch before the start of the next snow accumulation season?  Time will tell.