Western Heat

An atmospheric ridge, stretching from the valleys of California to the Wasatch Front, will allow heat to stream northward today.  Many areas will experience afternoon highs above 100 degrees F, breaking records for the date.

Since most areas affected by the heat lie in desert areas, this event is easy to ignore.  But the early date and the extreme conditions are just another sign that climate change is altering the seasonal transitions that we have long come to anticipate.

Fortunately, the extreme heat will be short-lived as a Pacific front come ashore with its rain and cooler air.  Then again, a long, hot summer surely lies ahead. 

Hilary Churns toward the Southwest

Having formed in the warm Pacific waters off Mexico, Hurricane Hilary rapidly intensified into a Category 4 storm and is churning to the NNW.  Expected to weaken in cooler waters off the Baja Peninsula, the storm may still retain Tropical Storm status when it enters Southern California; if so, it will be the first to do so in 84 years.

While high winds may cause damage, the primary concern with Hilary is widespread flooding.  Directing a steady flow of tropical moisture across much of the Desert Southwest and Great Basin, the storm will likely drop up to 10 inches of rain in mountainous areas; while 2-3 inches is forecast for most of the region, that is a year's worth of precipitation for many desert locations.

Like so many "natural disasters" over the past few years, this unusual weather event reflects our warming climate.  Warmer ocean waters and higher sea levels will produce havoc across the globe, primarily for coastal regions but, at times, far inland. 

Climate Change and the Monsoon

For those who care to check the news, climate change is already having major impacts on our planet.  Rising oceans and warming seas threaten coastal communities, fuel major hurricanes and feed strong thunderstorms with tropical moisture,  producing catastrophic floods.  Prolonged drought and intense heat have set forests ablaze across the globe and have greatly diminished the mountain snowpack, especially across the American West.

Of interest, the Southwest Monsoon began early this year and has been especially potent, dumping torrential rain across naturally dry country; this leads to flash floods, especially in burn scar areas.  One wonders if this pattern will continue (or even be enhanced) as the climate warms; if so, the Desert Southwest could gradually become a landscape of semiarid ecosystems.

Indeed, we do not yet fully understand the varied ramifications of climate change.  No doubt, human civilization will be severely tested in many ways.  It is time that we take it seriously and reject those politicians and corporate leaders who do not. 

Joshua Trees

Returning to Colorado, we drove east on Interstate 15 across Southern California and Southern Nevada.  Just short of the California-Nevada border, the highway climbed across a ridge and, near an elevation of 4000 feet, Joshua trees appeared in abundance.

Also known as the yucca palm, the Joshua Tree is native to the Mojave Desert of the Desert Southwest.  It is relatively fast growing and may reach 50 feet in height; flowering occurs in late winter or early spring (if weather conditions permit) and these hardy plants disperse by seed or suckering.  The yucca moth is the primary pollinator.

For some of us, the term Joshua Tree will always be associated with U2's best album (in my humble opinion), but, for most, it will bring to mind the distinctive, top-heavy denizen of the otherwise bleak Mojave landscape. 

Westward from Flagstaff

Leading westward from Flagstaff, Arizona, Interstate 40 passes through a scenic landscape of meadows and ponderosa pine forests.  Beyond Williams, the highway leaves this lofty terrain and descends into a broad swath of open parklands and low ridges; covered by juniper shrubs; this attractive ecosystem generally ranges in elevation from 3000 to 4000 feet.

Nearing Kingman, the highway drops further into the bleak landscape of the Mojave Desert, bordered by high but treeless ranges.  Three hours later, during which we crossed the Colorado River south of Needles, California, we finally escaped the Mojave west of Barstow; we then followed Interstate 15 westward to Cajon Pass and descended into the Los Angeles basin.

One cannot fully appreciate the dimensions and severity of a desert without driving across it; even today, with our modern, air-conditioned vehicles, it is a tiring experience.  We can only begin to imagine the challenges endured by those who used horses and wagons to make the journey. 

An Island of Greenery

Heading to California for my son's wedding, we left Denver early yesterday morning, driving south on Interstate 25.  Once we crossed Raton Pass, on the Colorado-New Mexico border, trees and other greenery was limited to the stream and river channels.

The landscape was especially dry after we passed Santa Fe and descended to Albuquerque.  There we switched to Interstate 40 and headed west, undulating through scrub grasslands broken by rock outcrops and low mesas; only the bulk of the Mt. Taylor massif, north of Grants, towered above the arid terrain.  Crossing into Arizona, streams were limited to shallow washes and the Little Colorado River, which cut a deep channel through the high desert landscape.  Then, fifty miles from Flagstaff, a cluster of mountains appeared on the western horizon, our first glimpse of the volcanic San Francisco peaks.

Within a few miles of the city, piñon pine woodlands spread along the highway and, once in Flagstaff (elevation 6909 feet), taller ponderosa pines adorned the meadows and suburbs.  Indeed, sitting along the southern edge of the highlands, the city is a welcome island of greenery in the Desert Southwest; we stopped to enjoy a meal, walk through the historic district in a cool, light mist and spend the night.

From Drought to Flood

The annual Southwestern Monsoon has developed over the past week or so, bringing much needed rain to the parched landscape of the Sonoran and Chihuahuan Deserts, the Colorado Plateau and the Great Basin. While brief, heavy rain is typical of this weather pattern, regional flooding is especially severe this year.

Of course, climate change is fueling both the extreme drought and the destructive floods; the severe heat in the Pacific Northwest, torrential rains in the Southeast and catastrophic flooding in Germany also reflect the natural consequences of a warming climate.  As wildfires rage across the Western U.S., the monsoon moisture will be welcomed but heavy rain over short periods of time may unleash mudslides and flash floods, especially within and near the burn scars.

Some effects of the monsoon are expected to reach the Colorado Front Range over the next few days, well ahead of schedule; August is generally the period of monsoon rains in this region, often extending into early September.  Since we have enjoyed a wet spring and summer (to this point), we may also experience flooding in the foothill canyons and along tributaries of the South Platte River.

Steinbeck in the Desert

As I near the end of Travels with Charley (see posts on February 25 & 27), John Steinbeck finally diverts his mind from the people, cities and roads that he encounters on his cross-country trip and turns to ecology while enjoying a cold beer in the Mojave Desert.  Ironically, this diversion begins as he spots two coyotes in the distance; inclined to shoot the "varmints," he then decides to leave dog food for them (neither appropriate from a naturalist's point of view).

Nevertheless, he devotes most of that section to describing the plants and animals that reside in the harsh environment and how they adapt to the intense heat and lack of water.  Going beyond the facts of desert biology, Steinbeck surmises that these hardy species will likely be the last to succumb to our gradual destruction of the planet and the first to rebound from our careless stewardship.  Prescient words in 1960!

All in all, it turned out to be an enjoyable journey with this renowned author who would die at 66 within six years of his road trip.  We would all do well to follow his example and explore the fabulous diversity of America while we can.  I highly recommend the book.

Rain, Snow & Wildfire

Over the next few days, light to moderate rain will fall across the Sonoran and Chihuahuan Deserts of the American Southwest, bringing some relief to the ongoing drought in those areas.  Across the higher terrain of Northern Arizona and New Mexico, the precipitation will fall as snow.

The benefactors for this scenario are a deep atmospheric trough across the Western U.S. and a "cutoff low" (i.e. not associated with a front) off the coast of Northwest Mexico.  This low, spinning counterclockwise over the Pacific will sweep in moisture from both the ocean and the Gulf of California.  Farther east, the southern edge of the trough will angle to the northeast, igniting showers and thunderstorms across Texas and the Gulf Coast States.

Meanwhile, high pressure over the Great Basin, interacting with the cutoff low, will send strong Santa Ana winds through the canyons of Southern California, increasing the risk for wildfires.  In effect, the same atmospheric conditions may produce beneficial and destructive results in two adjacent geographic areas. 

A Tardy Southwest Monsoon

Monsoon thunderstorms generally begin to develop across the Desert Southwest by mid July, spreading northward over the following month.  In desert areas, the storms bring welcome rain but often cause flash flooding and haboobs (dust storms).

This year, persistent high pressure over the Desert Southwest has produced relentless sunshine and oppressive heat; it has also shut off the monsoon flow.  By mid summer, high pressure over the Southern Plains usually combines with low pressure over the Baja region to sweep in moisture from the Gulf of Mexico and the Sea of Cortez, igniting the storms.  There is some evidence this week that the high pressure dome over the Southwest is finally shifting eastward, allowing the humid monsoon winds to enter the Sonoran and Chihuahuan Deserts.

While the Southwest Monsoon generally reaches the Colorado Front Range during the second half of August, we have been receiving regular, late-day thunderstorms throughout July.  These storms, in part, have resulted from the persistent high pressure over the Desert Southwest, which has shunted Pacific moisture to the north of the Four Corners region.  Stagnant weather patterns often benefit one geographic area at the expense of another.

Grasshoppers Invade Las Vegas

Reminiscent of a story from Scripture, hordes of grasshoppers have invaded Sin City this week.  But unlike assumptions offered in the Bible, we have a modern scientific explanation for this scourge.

As explained by an entomologist on the Weather Channel this evening, the wet winter and early spring across the Desert Southwest produced an abundance of food for this year's grasshopper population, resulting in large swarms that may cause some agricultural damage in the region.  Furthermore, the species that has invaded Las Vegas, Nevada, is attracted to light and there are few places on this planet more thoroughly illuminated than the Vegas Strip.

So, it appears that the residents of and visitors to this Entertainment Mecca are being inconvenienced more for the city's light pollution than for certain behaviors that are encouraged there.  I'm sure some evangelical ministers may disagree.

Heat, Life & Survival

Wandering outside this morning, it was easy to see the toll that our hot, dry summer has taken on the foliage of our Littleton farm.  While heat and water are essential to life, the balance of these factors is crucial and this season has not been kind to the plants.

Life first evolved in warm, shallow seas and near hot smokers along mid oceanic ridges.  Even today, the vast majority of species are found in the Tropics, where moisture is abundant, placing a check on the air temperature.  In desert regions and semiarid landscapes, the low humidity results in dense air which can reach much higher (and often deadly) temperatures; of course, animals and plants that inhabit deserts have adapted to their environment in a variety of anatomic, physiologic and behavioral ways.  While birds and mammals can generate their own internal heat, the low temperatures in polar regions have also required physical and physiologic adaptations for wild residents (fat insulation, thick fur and dense plumage, to name a few).  We humans, having evolved in the Tropics, were able to colonize hot and cold landscapes due to our large brains; the use of clothing, wells, tents and air conditioning come to mind.

Humans and wildlife now face global warming, a product of fossil fuel consumption, which threatens the survival of many species.  Melting polar ice sheets and mountain glaciers are already stressing regional inhabitants and flooding coastal ecosystems (at all latitudes) as sea levels rise.  In concert, warming ocean waters are killing coral reefs, spawning deadly algal blooms and reducing the supply of plankton, vital to marine food chains.  It is imperative that we humans use our large brains once again to mitigate climate change and protect Earth's ecosystems.  

Haboob Season

The annual Southwestern Monsoon is beginning to intensify as high pressure over the Southern Plains and low pressure over the Baja region combine to sweep moisture into the Desert Southwest; some of this precipitation arrives from the Pacific Ocean and Sea of Cortez but even more is swept across Mexico from the Gulf of Mexico.

The heat and moisture ignite thunderstorms which often drop torrential rain on the parched landscape, leading to flash floods in the canyons and arroyos.  Cold downdrafts within these storms are forced outward when they strike the ground, producing gust fronts that race across the adjacent desert, picking up sand and dry soil to create massive dust storms, known as haboobs.

Often hundreds (if not thousands) of feet high and moving at 60 mph or more, these storms blind drivers, coat buildings and cars with debris and, of course, severely impact air quality.  The Southwest Monsoon, with its thunderstorms and haboobs, peaks in July and early August in Arizona and New Mexico; by mid August, its nourishing rains generally reach the Colorado Front Range and will be especially welcome after this hot, dry summer. 

Four Valleys in New Mexico

Yesterday morning, I left Roswell (in the Pecos River Valley) and drove west on Highway 380.  Climbing toward the Sacramento Mountains, I left the desert and soon reached grass-covered hills, passing Capitan Peak (10,083 feet) to my north.  The highway then entered steep-wall canyons before offering a spectacular view of Sierra Blanca (11,973 feet), the crest of the Sacramento Range.

At the Indian Divide, I left the Pecos River watershed and dropped into the Tularosa Basin, famous for White Sands National Monument and the massive Carrizozo basalt flow (5000 years old).  Highway 380 crosses the latter and several pull-offs are provided for close observation of this interesting volcanic landscape.  After climbing the Oscura Mountains, the road then drops into the Jornada del Muerto (Day of Death) which I hastened to cross.  A long, slow climb from there took me to the east wall of the Rio Grande Rift, lined with fault-block ranges, laccoliths and volcanic domes.

After descending to the valley floor and crossing the Rio Grande River, I took the opportunity to visit Bosque del Apache NWR, a renowned birding site, 8 miles south of San Antonio, New Mexico.  There I saw large flocks of snow geese, a fabulous diversity of waterfowl, bald eagles and, yes indeed, thousands of sandhill cranes! (See the last few posts).

Bitter Lake National Wildlife Refuge

Named for its large alkaline lake, Bitter Lake National Wildlife Refuge, in the Pecos River Valley, was established in 1937 to protect a vital desert oasis for migratory birds and resident wildlife.  As the Pleistocene gave way to the Holocene, some 10,000 years ago, the climate gradually warmed and flow through the Pecos River has gradually declined.  Fed by artesian springs from the Roswell Aquifer, the lakes, ponds and wetlands of the refuge have been managed by the use of levees and canals to ensure a range of salinity that provides diverse natural habitat.

Renowned for its large variety of dragonflies, Bitter Lake NWR also provides vital breeding habitat for least terns and snowy plovers.  A wide variety of shorebirds stop here to rest and feed during their spring and summer migrations while wintering sandhill cranes, geese (including Ross's geese), ducks, coot, bitterns and wading birds utilize the preserve from mid autumn to early spring.  Among other birds that breed here are greater roadrunners, northern harriers, American avocets, ladder-backed woodpeckers, Chihuahuan ravens, scaled quail, loggerhead shrikes, black phoebes, vermillion flycatchers and rock wrens.  Mammalian residents include six species of bat, kangaroo rats, porcupines, nutria, kit fox, black-footed ferrets, ringtails, bobcats and pronghorn, among others.

The refuge is best reached via Pine Lodge Road near the north edge of Roswell, New Mexico.  Drive east for 7 miles to the entrance and proceed to the Visitor Center (open Monday-Saturday, 8-4) for an overview of the landscape and its wildlife.  An auto tour loop, 6.5 miles long, is open everyday from dawn to dusk. 

Drought & Global Warming

Following the heavy precipitation in California and the Southeast this winter, the National Weather Service announced that, for the first time since 2011, there are no areas of extreme drought in the United States.  No doubt, many climate change deniers will use this information to bolster their argument that global warming is a politically motivated delusion.

Of course, we have plenty of scientific evidence to support both the occurrence of global warming and the fact that human activity is a major factor in its development.  Average annual temperatures have been rising across the globe, polar ice sheets are melting and sea levels are rising.  How climate change will alter regional drought, however, is not yet clear.

While desert regions that lie within the rain shadow of mountain ranges will likely remain arid, those that formed due to the effects of ocean currents may experience a dramatic change as a warming climate alters weather patterns near the poles.  It is certainly possible that some semiarid regions will become wetter while humid areas of the Temperature Zone (including farmlands of the American Midwest) will experience more droughts.  We already know that fisheries are being altered and tropical reefs are being threatened by rising sea temperatures and similar effects will surely become evident in terrestrial ecosystems.  We can either ignore the potential impacts of climate change or do what we can to minimize man-induced global warming; unfortunately, the new Administration in Washington appears to favor a wait-and-see approach.

Visitor from the Desert Southwest

On my usual birding walk at South Platte Park this morning, sightings were unremarkable except for a large number of yellow warblers and the presence of an ash-throated flycatcher.  The latter bird, rare along the Colorado Front Range, is a summer resident of the Desert Southwest, from western Colorado to California and from the northern Great Basin to Mexico.

Unlike most flycatchers, ash-throats generally snare their prey from foliage or directly on the ground; large insects, such as beetles and grasshoppers, are favored but they also consume berries and small lizards.  Nests are placed in the cavities of trees, fenceposts or nest boxes and two broods are raised each year.  Wandering widely during migrations, ash-throated flycatchers sometimes turn up on the East Coast; most winter in coastal regions of Mexico and Central America.

This morning's visitor was feeding on a wooded hillside, west of Eaglewatch Lake; on their home summer range, they are best found in pinyon-juniper or mesquite woodlands, along desert streams or in the canyons of desert ranges.  Adapting well to human habitation, ash-throated flycatchers are gradually expanding their territory and may soon be more common along the Front Range.

Crossing the Great Basin

West of Salt Lake City, Interstate 80 passes between the north end of the Oquirrh Range and the Great Salt Lake.  As we drove west, black-necked stilts were feeding in the roadside shallows, cliff swallows swooped about the highway bridges and flocks of California gulls moved across the morning sky.  Throughout western Utah, flat plains, remnants of Lake Bonneville, alternated with stark fault-block ranges, many of which were capped with snow.

In eastern Nevada, the ranges were more numerous and the intervening valleys were both rolling and green, covered by sage grasslands that were grazed by horses, cattle and pronghorn.  Just west of Wells, the highway began to follow the Humboldt River, passing the majestic Ruby Mountains; we would parallel that river all the way to Lovelock, where it enters its terminal sink.  Beyond that point, the greenery of eastern Nevada gave way to desert landscape, characterized by vast lake flats where American avocets patrolled the alkaline pools.  This low desert, lying within the rain shadow of the Sierra Nevada, ended at Fernley where we climbed into the Sierra foothills along the Truckee River.  Passing through Reno, we continued westward and upward on Interstate 80 before turning south to Lake Tahoe.

Backed by the high spine of the Sierra Nevada, this beautiful lake is renowned for both its resorts and its fabulous alpine scenery; after a full day on the road,  it seemed like a great place to spend the night.  Tomorrow we head into the California Cascades.

Ferruginous Hawks

Driving through the Plum Creek Valley (south of Denver) this afternoon, I encountered several ferruginous hawks.  These large buteos, though named for their reddish shoulders, back and feathered legs, are perhaps best identified by their size, their long, pointed wings and by the light coloration of their chest, abdomen and under-wings.

Often hunting from the air, soaring or hovering above potential prey, ferruginous hawks also use perches (poles, trees, rock outcrops) and may stalk prey directly on the ground, staking out the burrows of prairie dogs and ground squirrels.  Their bulky nests are generally placed in solitary trees or on rock ledges in open country; 2-4 eggs are usually produced.

Ferruginous hawks are permanent residents in Colorado and throughout most of the Colorado Plateau and Great Basin, favoring semiarid plains, sage grasslands and open woodlands of pinon pine.  Rabbits, ground squirrels and prairie dogs are their primary prey but they consume a wide variety of small mammals and sometimes kill snakes and game birds.  North of Colorado, ferruginous hawks are primarily summer residents while wintering individuals may be found across the Desert Southwest and southern High Plains.

Southern Heat Dome

For the past few days (and perhaps quite a few more), a dome of high pressure has settled over the Southern Plains and lower Mississippi Valley.  Beneath that atmospheric dome, air is sinking and heating up, producing afternoon highs near or above 100 degrees F; since sinking air retards cloud formation, intense sunshine magnifies the discomfort.

Along the outer rim of the dome, cooler air is sliding beneath and lifting the hot air, igniting thunderstorms.  In concert, clockwise winds at the edge of the dome direct these storms in a broad arc; yesterday, these "riders" were moving from northeastern New Mexico and eastern Colorado across the Central Plains and then southeastward through the Tennessee Valley and down to the Gulf Coast.

While not always as widespread and intense, high pressure domes are common over the Southern Plains in August and play a major role in the development of the Southwestern Monsoon.  As Gulf moisture is drawn westward across Mexico, following the southern edge of the dome, it joins a moisture plume from the Sea of Cortez; the combined humid air masses flow northward along the western rim of the high pressure dome, feeding thunderstorms across the Desert Southwest and into Colorado (see also The Dome of August).