A Look at Why Death Valley is the Hottest, Driest, and Lowest Place in US

Death Valley National Park is famous for being the hottest, driest, and lowest place in the United States. The interesting thing about all these extremes, as I learned during a recent visit, is how they interconnect.

Situated in eastern California near the Nevada border, the park’s topography is known as basin and range. This is where the earth’s crust is rifting apart, creating mountains in some areas and deep basins in others. Death Valley is a long, narrow basin that reaches a depth of 282 feet below sea level. It is also in the rain shadow of four different mountain ranges to the west – the Coastal Range, the Sierra Nevada, the Argus Range, and the Panamint Range.

As storms move inland from the Pacific, they must rise up and over each range. In doing so, they cool and their water vapor condenses into rain or snow that falls on the western side of these mountains. By the time a storm system reaches Death Valley, it has lost most of its moisture. The average annual rainfall in the park, according to NOAA, is just 2.36 inches.

These dry conditions, along with the valley’s below-sea-level elevation, help to produce the park’s famous heat. With cloud free skies and sparse vegetation, a maximum amount of sunlight can reach the ground. The rocks and parched soil absorb the heat and radiate it into the air. The warm air rises but becomes trapped by the steep valley walls. After cooling slightly, it is recycled back toward the valley floor where it is heated even further by atmospheric compression. During the summer months, this process generates hot winds and sizzling temperatures. The average high temperature in the park ranges from 67°F in January to 116°F in July. The hottest temperature ever recorded was 134°F on July 10, 1913 – a world record.

Looking ahead, as the climate changes, the southwestern region of the US is expected to become even hotter and drier. It seems like only a matter of time before Death Valley breaks its own heat record.

At 282 feet below sea level, Basin in Death Valley National Park is the lowest point in the US. Credit: Melissa Fleming

Climate Change is Changing Glacier National Park

Glacier National Park (GNP) in western Montana is on the verge of losing its namesake features to climate change. Given this fact, I made a point to visit the park this summer to see what remains of its famous glaciers before they completely melt away.

According to the National Park Service, the area that is now GNP was home to 150 glaciers at the end of the Little Ice Age in 1850. Today, because of rising global temperatures, only 25 remain and most are mere vestiges of what they once were. Looking ahead, if the current rate of melting continues, all of the park’s glaciers are expected to disappear by 2030, if not sooner.

Glaciers are dynamic entities that respond to changes in temperature and precipitation. They advance when more snow accumulates in the winter than melts in the summer. When this process is reversed, they retreat. Sadly, the new norm in GNP includes warmer summers and a decreasing snowpack.

The USGS, which monitors the park’s glaciers, reports that the mean annual temperature in GNP has increased 1.33°C (2.4°F) since 1900. That is nearly twice the global average. The park also now sees 16 fewer days each year with below-freezing temperatures. These warmer conditions mean that more precipitation is falling as rain rather than snow.

Beyond aesthetic changes to the landscape, the shrinking glaciers and reduced snow pack mean less melt water for the region and therefore warmer and drier summers. This, in turn, affects soil moisture and the proliferation of wildfires. It also has serious ramifications on the availability of fresh water for drinking and irrigation.

In arid regions, like the American West, people depend on mountain run-off from melting glaciers and winter snow packs for the majority of their fresh water. In western Montana, according to the NPS, snowmelt accounts for 60-80% of the annual freshwater supply. As temperatures rise and the stores of this precious resource dwindle, competition for it is expected to increase.

But, glaciers are not the only things changing in GNP. As the atmosphere heats up and the ice retreats, the park’s various ecosystems are also being reshaped. Sub-alpine trees are moving upslope replacing alpine meadows, for example. This changing distribution of vegetation affects the type of wildlife the park can support. While some animals can adapt and move upslope with their habitat, others, like the pika – a small furry relative of the rabbit who lives at high elevations and cannot survive temperatures above 75°F – already live at the end of their range and have no place to go.

The NPS has no plans to change the name of Glacier National Park.

"Repeat Photography", a USGS project, documents the changes to GNP's glaciers over the years. Credit: USGS/NPS

Images of Sperry Glacier from “Repeat Photography”, a USGS project, that documents the changes to GNP’s glaciers over the years. Credit: USGS/NPS

Giant Sequoias Challenged by Climate Change

Many things in nature are adapted to certain climate conditions. That said, some are choosier than others. Giant Sequoia trees, the largest living organisms on the planet, need a “Goldilocks” type of environment to grow and reproduce. Visiting Sequoia National Park recently, I had the opportunity to learn more about the climate requirements of these amazing trees.

Needing conditions that are not too hot and not too cold, as well as not too wet and not too dry, Giant Sequoias grow naturally in only one place on Earth. That unique place is a narrow band about 70-miles long on the western slopes of California’s Sierra Nevada Mountains known as the Sequoia Belt. According to the National Park Service (NPS), these trees only grow at elevations between 5,000 and 7,500 feet. Temperatures above 7,500 feet are usually too cold and conditions below 5,000 feet are too dry. Within this limited range, about 75 groves reveal where conditions for the massive trees are just right.

These ideal conditions are produced by a combination of weather and topography. When moisture-laden air from the Pacific runs into the Sierras, it rises and cools. On average, it cools about 3.6°F for every 1000 feet it rises. Since cooler air holds less moisture than warm air, the moisture is dropped as rain and snow over the mountains with precipitation amounts generally increasing with elevation. While California is in the midst of a multi-year drought, the NPS says the area around Giant Forest (elevation 6400 feet) usually gets an average of 44 inches of precipitation a year. It also typically sees only one day a year with temperatures below 10°F.

Compared to other sites within a five mile radius, the average conditions in Giant Forest are perfect for the giant sequoias. Upslope, Emerald Lake (elevation 9200 feet) gets 59 inches in average annual precipitation and sees around ten days a year with temperatures below 10°F. Downslope, Ash Mountain (elevation 1700 feet), only sees about 26 inches of precipitation a year and the temperature reportedly never falls below 10°F.

Given the narrow natural range in which these giant trees are able to thrive, they face serious challenges from climate change. As temperatures increase, more precipitation is coming down in the form of rain instead of snow. This reduces the snowpack and the subsequent spring and summer melt water available to the trees during the region’s dry season. While the resilient mature sequoias – some are over 3000 years old – are not in immediate danger, researchers say these big trees were not made to withstand decades of drought. The younger trees – seedlings and saplings – on the other hand, face a more difficult struggle for survival. The drier conditions make it harder for them to develop robust root systems and also leave them more susceptible to wildfires, which are projected to increase.

Given the impressive age of some of these trees, they must have endured natural climate fluctuations in the past. This time, however, the human caused change is happening very quickly and is forecast to produce conditions unfamiliar to even these ancient giants. According to the US National Climate Assessment, the southwest – which includes California – is normally the hottest and driest part of the country, but climate change is making it even more so. The report shows that 2001 through 2010 was the region’s warmest decade on record with temperatures almost 2°F above historic averages. Looking ahead, it projects continued increases in average annual temperature and a decrease in precipitation. In the meantime, scientists continue to monitor and research the giant sequoias to better understand how they will react to our changing climate and to offer informed recommendations to evolving conservation strategies.

Below is a short video by The Redwoods and Climate Change Initiative (RCCI) on the impact of extended drought on Giant Sequoias. Oh, and in case you were wondering, Giant Sequoias (sequoiadendron giganteum) and Coastal Redwoods (sequoia sempervirens) are closely related, but are two different species.

Air Quality Concerns in Sequoia National Park

Situated high is California’s Sierra Nevada Mountains, Sequoia National Park protects the only place on Earth where giant sequoias – the world’s largest trees by volume – grow naturally. Air pollution, however, does not recognize the boundaries set up by the National Park Service (NPS). While hiking there recently, I learned more about the air quality issues facing this national natural treasure.

According to a recent report by the National Parks Conservation Association, Sequoia National Park received an “F” for air quality. While other parks in the NPS system also have air quality concerns, Sequoia NP was rated the worst in the nation. In 2014, its Ash Mountain monitoring station recorded 56 days where the level of ozone was above federal health standards.

In most parts of the country, air quality issues are often connected to emissions from coal-fired power plants, but in California there are a few other factors at play. While the region’s notorious wildfires do create some air quality problems, the NPS says the vast majority of the pollution in the park comes from human activities outside its borders. With a prevailing westerly wind in the region during the summer months, emissions from large-scale industrial and agricultural activities as well as massive amounts of vehicle exhaust are swept eastward from San Francisco and across the San Joaquin Valley. Trapped by the topography of the valley, the polluted air is heated and forced to rise up to the elevation of the park. Pollutants found in the air include nitrogen oxides, ground level ozone, fine particulate matter, and traces of pesticides.

Of these pollutants, ground level ozone, which forms when nitrogen oxides react with heat and U.V. light, poses the most serious threat to human health. It is known to cause a variety of repository problems and is often the reason given for air quality alerts.  It is also harmful to plants and trees – the organisms that are supposed to be protected by the park.

While ozone does not seem to be impacting mature sequoias, the NPS says experiments have shown that it is stunting the growth of sequoia seedlings. That said, other trees in the park, such as Ponderosa and Jeffrey Pines are feeling its full effect. Damaging their stomata – tiny pores on their needles that usually absorb carbon dioxide -the pollutant reduces a tree’s ability to perform photosynthesis and therefore its ability to produce and store food.  As a result, they are weakened and more susceptible to disease and insects. The telltale sign of ozone damage is the yellowing and thinning of a conifer’s needles.

Air pollution is also responsible for the smog that obscures views in the park. On a clear day, according the NPS, the view from Beetle Rock – which is about 6,200 feet above sea level – extends for more than 100 miles. In summer, when the smog is worst, that view is often significantly reduced.

The good news is that air quality issues in the park – like much of the rest of the country – have improved in recent years as a result of measures associated with the Clean Air Act. The bad news is that it still remains a serious problem. Seeing that our actions can make a difference, we can continue to reduce air pollution by conserving energy and reducing emissions – a similar strategy to reducing the impacts of climate change.

View from the edge of Giant Forest. Credit: NPS

A view looking southwest from the edge of Giant Forest in Sequoia National Park. Credit: NPS

Pyrocumulus Cloud Forms Over Wildfire in Kings Canyon National Park

Fueled by drought, wildfires have been blazing across the American West all summer.   Sixteen are currently burning in California alone. While hiking in Kings Canyon National Park in the state’s rugged Sierra Nevada Mountains recently, I crossed paths with the “Rough Fire” and saw it produce a billowing pyrocumulus cloud.

Pyrocumulus clouds form when intense heat at the surface – usually from a wildfire or volcanic eruption – causes air to rise rapidly. As it travels upward, water vapor in the air condenses into droplets and forms a cloud. Filled with ash and smoke, the swelling cloud generally appears more grey than white.

Ignited by lightning over three weeks ago, the Rough Fire continues to spread and has even caused parts of Kings Canyon National Park to close. According to the NPS, smoke from the massive fire has also impacted the air quality in and around the park. To date, the fire has charred close to 50,000 acres and is only 17% contained.

Pyrocumulus cloud rising over California's Rough Fire in Sierra National Forest and Kings Canyon National Park. August 2015. Credit: The Weather Gamut.

Pyrocumulus cloud rising over California’s Rough Fire in Sierra National Forest and Kings Canyon National Park, August 2015. Credit: The Weather Gamut.

Climate Change in Saguaro National Park

The saguaro – the classic symbol of the American southwest – is the largest cactus species in the United States and only grows in the Sonoran Desert. Straddling the city of Tucson, AZ, Saguaro National Park protects over 90,000 acres of its namesake cactus. While visiting there recently, I learned how this unique environment is being impacted by climate change.

The Southwest is the hottest and driest part of this country and climate change is making it even more so.  According to the US National Climate Assessment, 2001 through 2010 was the region’s warmest decade on record with temperatures almost 2°F above historic averages. Looking ahead, the report projects continued increases in average annual temperature and a decrease in precipitation, especially in the southernmost part of the region. In a National Park Service (NPS) report on arid lands, the agency says it has already observed a widespread winter and spring warming trend and a lengthening of the frost-free season in the Sonoran Desert.

These warmer conditions are causing a variety of environmental changes in Saguaro National Park. While fewer cacti are dying from severe freeze events, evaporation rates are increasing, making an already parched area even drier. “Arid ecosystems,” the NPS says, “are particularly sensitive to climate change and climate variability because organisms in these regions live near their physiological limits for water and temperature stress.” Even slight changes in the environment can dramatically alter the distribution and abundance of many desert species. On average, the region currently receives less than 12 inches of rain per year.

The phenology, or the timing of natural events, is also being thrown out of sync as the climate changes. The vital rains of the region’s monsoon season traditionally begin in early July, but are projected to arrive later and later in the coming years. This can be a problem for the saguaros, because they have evolved to produce fruit in the beginning of July. While adapted for the dry desert environment, the cacti still depend on adequate rain during the summer growing season for both their own survival and the establishment of seedlings.

Another serious climate change challenge for the Sonoran Desert is the spread of non-native plant species. Buffelgrass, a native of Africa, was introduced to Arizona in the 1940’s for cattle forage. Thriving in the heat, this invasive species is crowding out the native plants (including the cacti), changing the look of the landscape, and increasing the risk of wildfires.

The Sonoran Desert did not evolve with fire as an ecological factor. Lush with vegetation by desert standards, the region usually had large gaps between groups of plants. This helped keep any wildfires small. Now, as the buffelgrass fills in those open spaces, fires can burn hotter and spread much more easily. Adding insult to injury, the buffelgrass grows back after a fire has killed the native plants.

The changing environment is also problematic for the animals that depend on the saguaros for food and shelter. These include a wide array of species, ranging from woodpeckers to coyotes.

Scientists are continuing to monitor and research how additional changes in temperature and precipitation will affect this beautiful and unique place.

Saguaro National Park, Arizona.  Photo Credit: The Weather Gamut

Saguaro National Park, Arizona.  Photo Credit: The Weather Gamut

Climate Change at Rocky Mountain National Park

Rocky Mountain National Park (RMNP) protects 415 square miles of spectacular mountain environments in northern Colorado. It is home to a diversity of ecosystems – alpine, subalpine, and montane – that are each uniquely adapted to the climate zone of their elevation. This is why, as I learned during a recent visit,  climate change is a serious issue for the park.

According to the National Park Service, the average annual temperature in RMNP has increased 3.4°F over the past century. A report from a weather station inside the park (Grand Lake), shows that the number of frost-free days has increased from an average of 65 in the mid-20th century to an average of 100 in this past decade.

temperature_graph_1

In the 20th century, the area including Rocky Mountain National Park experienced a warming trend. The five-year rolling average (thick red line) allows the viewer to look beyond annual variability to focus on long-term trends. (Analysis of PRISM data, original source Daly 2008). Credit: NPS

This warming trend, says the NPS, has caused a number of environmental changes in RMNP. The winter snowpack is melting approximately 2 to 3 weeks earlier, resulting in less water being available for people, plants, and animals during the summer. There has been an explosive increase in the number of mountain pine beetles surviving the now warmer winter months, allowing them to devour more trees. The phenology, or the timing of natural events, can also be thrown out of sync when warm spring weather arrives earlier than normal. Wildflowers that bloom before the arrival of butterflies, for example, can leave the insects with a reduced food source. This puts a kink in how the larger food chain fits together.

In the park’s alpine tundra region, the American Pika is at particular risk. According to scientists, this small furry relative of the rabbit can only live at high elevations in cool, rocky environments. They say it cannot survive in temperatures above 75°F for more than a few hours.  While other species adapted to lower elevations can move upslope as average temperatures rise, the pika has nowhere to go.

American Pika on the rocky terrain of RMNP's alpine tundra region.  Image Credit: The Weather Gamut.

The American Pika, a native of RMNP, is sensitive to even small changes in climate.  Image Credit: The Weather Gamut.

Another impact of climate change is the spreading of non-native plant species that can thrive in the now warmer environment of RMNP. While Cheatgrass, a native of Eurasia, is found throughout the western US, it used to be limited to lower elevations.  Now, it is found as high as 9,500 feet in parts of RMNP. In addition to crowding out native plants and changing the look of the landscape, this invasive species is highly flammable. Its presence increases the danger of wildfires – something the West certainly does not need.

While these are just a few examples of the observed and expected impacts climate change is and will have on RMNP, scientists are continuing to research how additional increases in temperature will affect this national treasure.

Why Air Temperature Decreases with Height

While visiting Colorado recently, I had the opportunity to explore Rocky Mountain National Park, and it was largely a vertical experience. Within its borders are 72 named peaks that reach above 12,000 feet in elevation. Traveling from the Beaver Meadow Visitor Center – elevation 7,840 feet – to the Alpine Visitor Center – elevation 11,796 feet – the drop in temperature was anything but subtle.

The reason for air being cooler at higher elevations is twofold. First, the sun’s rays heat the Earth’s surface, which in turn, radiates that warmth into the atmosphere. As you climb in altitude, there is less surface area of land available to heat the air. Second, as air rises, it expands and cools. This is because air density and pressure aloft are lower than at the surface.

The exact rate at which the temperature decreases with height – the environmental lapse rate – varies with location and daily conditions. On average, however, for every 1000 feet gained in elevation, the temperature drops by about 3.6°F.

Image Credit:British Geographer

Image Credit: The British Geographer

Opposing Winds Help Shape Great Sand Dunes National Park

When you think of the Rocky Mountains, sand dunes are probably not the first thing that come to mind. While driving across southern Colorado earlier this month, however, giant white sand dunes glimmered in the distance. No, it was not a mirage; it was Great Sand Dunes National Park and Preserve.

Sprawling across the arid San Luis Valley between the San Jose Mountains to the west and the Sangre de Cristos to the east, the dunes cover 30 square miles and rise as high as 750 feet. They are the tallest dunes in North America and were formed, and continually maintained, by a complex interaction of geology and weather.

Over the millennia, according to the National Park Service, rocks from the surrounding mountains eroded and their sandy sediments were transported by stream to the valley floodplain. Prevailing southwesterly winds then carried the sand grains toward a low curve in the Sangre de Cristo Mountains, where they accumulated in a natural pocket.  On occasion, when the wind direction reverses during storms, the sand is pushed back toward the west. This process causes the dunes to grow vertically.

Two mountain streams, the Medano and Sand Creeks, also border the dunes. They capture sand grains from the eastern side of the dunes and carry them back to the valley floor.  This effectively recycles the sand and re-exposes it to the winds.

While the forces of wind and water are continually reshaping the massive dunes, they essentially remain in the same position.

Sand dunes nestled against the foothills of the Sangre de Cristo Mountains, Great Sand Dunes National Park, CO.  Image Credit The Weather Gamut.

Massive sand dunes nestled against the foothills of the Sangre de Cristo Mountains, Great Sand Dunes National Park, CO.  Image Credit: The Weather Gamut.

Air Quality Concerns in Great Smoky Mountains National Park

Straddling the border of North Carolina and Tennessee, Great Smoky Mountains National Park protects 800 square miles of the southern Appalachian Mountains. It is the largest federally protected upland landmass east of the Mississippi River.  Air pollution, however, does not recognize these human-drawn borders. While traveling in the Smokies recently, I learned more about the air quality issues facing this country’s most visited national park.

According to the NPS, most of the air pollution impacting the park originates outside its boundaries. Emissions of sulfur dioxide and nitrogen oxides from power plants, factories, and vehicles are the main sources. Carried by wind to the southern Appalachians, the height of the mountains and the prevailing weather patterns of the region tend to trap the pollution in and around the park.

Originally named for its naturally occurring smoke-like blue haze, the park in recent years has been shrouded by unnatural white smog. Produced by tiny sulfate particles – released into the air by the burning of fossil fuels – the smog scatters light and reduces visibility. It has degraded views from the park’s scenic mountain overlooks and dulled its signature blue haze. Since 1948, according the NPS, human-made pollution has decreased average visibility in the region by 40% in winter and 80% in summer.

Ground level ozone, formed when nitrogen oxides react with heat and U.V. light, is known to have negative impacts on human health.  In the Smokies, it is also injuring trees and plants. Damaging leaves, it reduces photosynthesis and limits a plant’s ability to produce and store food.  As a result, they are more susceptible to disease, insects, and extreme weather events.

Acid rain is another problem for the park that is rooted in air pollution. It develops when sulfur dioxide and nitrogen oxides react with water and oxygen in the atmosphere to form solutions of sulfuric acid and nitric acid. This type of precipitation alters the chemistry of forest soils and streams. It jeopardizes the health of entire ecosystems, as a large array of species – from fish to trees – cannot adapt to the more acidic conditions. The average pH of rainfall in the Smokies, according to the NPS, is 4.5. That is 5–10 times more acidic than the pH range of normal rainfall.

While air quality issues in the park – like much of the rest of the country – have improved in recent years, it still remains a serious problem. Addressing the matter, the NPS says: “The Park Service is working with state regulatory agencies, the Environmental Protection Agency, and industrial and utility interests to develop a comprehensive plan to prevent future damage through such measures as offset programs, the use of improved technology, and determination of emission caps and government standards for various pollutants. To remedy air pollution problems at the park, additional reductions of nitrogen oxides and sulfur dioxide are necessary.”