Tag Archives: travel

Temperature Influences Alligators

Posted on by

Temperature affects all living things in some way.  This is especially true of alligators.  While exploring the wetlands of South Carolina last week, I became much more aware of how ambient temperatures drive almost all aspects of their lives.

As cold-blooded reptiles, alligators are ectothermic.  They rely on external sources to regulate their body temperature.  For example, they lay out in the sun to warm up and float in water to cool down.  Temperature also affects an alligator’s ability to eat.  As temperatures decrease, so does its metabolism.  In fact, when temperatures fall below 70°F they stop feeding since they will not be able to digest what they consume.  If temperatures fall even further, into the 50°F range, alligators become inactive or dormant and ride out the colder weather in dens.

Environmental temperature also plays a critical role in determining the gender of baby alligators.  Through a process known as temperature-dependent sex determination (TSD), eggs that incubate at 93°F or higher all become males while temperatures below 86°F produce all females. Temperatures that hover in between create a mixture of both sexes. Scientists do not know exactly why this process developed, but they have found that it tends to produce more females than males.

Gator_SC_A

An alligator basks in the sun along the edge of a swamp in South Carolina.

Image Credit: The Weather Gamut

Floods Nurture Congaree National Park

Posted on by

Floods are often thought of as disasters, especially when people and property are harmed. In nature, however, some ecosystems thrive on periodic flooding. While traveling in South Carolina last week, I had the opportunity to visit one such place – Congaree National Park.

Situated in the floodplain of the meandering Congaree and Wateree Rivers, the park protects the largest expanse of old growth bottomland hardwood trees still standing in the southeastern United States.  It is home to a dazzling array of biodiversity, including a number of champion trees – tress that hold the size record for their species.  These include a bald cypress with a circumference of twenty-seven feet and a loblolly pine standing one hundred seventy feet tall.  These trees would not be able to flourish without the moisture and nutrient–laden sediments that flood waters bring to the forest floor.

This floodplain forest is typically inundated by water several times a year. During my visit, the park was about 90% flooded as a result of recent heavy rainfall on top of an already wet spring.  It was an impressive sight.

The elevated boardwalk trail in Congaree NP disappears into high flood waters.

The elevated boardwalk trail in Congaree NP disappears into high flood waters.

Image Credit: The Weather Gamut

Wettest City in the U.S.

Posted on by

“Rain rain go away, come again another day.”  With rain on fourteen of the last twenty-four days, this old nursery rhyme sums up the feelings of many New Yorkers.  For the residents of Hilo, Hawai’i, however, this sentiment is not an option.

Hilo is the wettest city in the United States.  Situated on the windward coast of the island of Hawai’i, the city is in the path of the moisture laden Trade Winds. Averaging 126 inches of rain annually, Hilo experiences every conceivable type of rainfall, from mist to downpours.  Looking at the calendar’s point of view, some form of precipitation falls there 272 days of the year on average.

As soggy as it may sound, Hilo’s amazing tropical rain forests, waterfalls, and rainbows would not be possible without this significant precipitation.

Above the Clouds on Haleakalā

Posted on by

While traveling among the Hawaiian Islands, I had the opportunity to visit Haleakalā National Park.  Ascending its volcanic slopes, I was struck by its summit region known as “kua mauna”, the land above the clouds.  Its unique view is made possible by an elevated temperature inversion.

In the troposphere, the weather layer of our atmosphere, air temperature usually decreases with height.  An inversion occurs when something causes that situation to reverse and allows air temperature to increase with height.

At Haleakalā , the inversion is caused by a large-scale subsidence in the Trade Winds.  Blowing from centers of high pressure across the Pacific, cool, dense air aloft is warmed by compression as it descends to lower altitudes.  In opposition, solar heating warms air near the surface allowing it to rise and cool, forming clouds.  When these cool clouds meet the warmer air above them, an inversion layer is formed.

The inversion layer acts like a cap for cloud convection.  Therefore, the summit of Haleakalā (10,023 feet), rising above the inversion altitude, stands out like an island in a sea of clouds.

View from the summit of Haleakalā, Maui, Hawai'i

Photo Credt: MF at The Weather Gamut

Diversity of Climate Zones on Hawai’i

Posted on by

The island of Hawai’i is a place of tremendous climate diversity. From tropical to sub-arctic, the Big Island has it all.

Hawai’i has eleven of the thirteen climatic zones defined in the Koppen Climate Classification System.  Developed by Wladimir Koppen in 1884, this climate system is based on average values of temperature and precipitation as well as the distribution of native vegetation. Hawai’i only lacks the extremes of cold winters and summer heat waves.

The primary reason for this wide range of climates is topography.  Two huge volcanic mountains, Mauna Kea (13,796 feet) and Mauna Loa (13,679 feet), dominate the landscape of Hawai’i. Since air temperature decreases 3.6°F per one thousand feet, it can be in the 80’s at the beach and below freezing in the summit regions on any given day.  Mauna Kea, the White Mountain, even supports a seasonal snow-pack.

These mountains also create orographic rainfall and affect the overall distribution of precipitation on the island.  When warm, moist air is forced up along the windward slopes, it condenses into clouds that produce rain. This precipitation supports the island’s lush rainforests and cascading waterfalls. The leeward side of the mountains, where the air descends, is sunnier and more arid.

The vast assortment of climate zones on Hawai’i is remarkable for an island roughly the size of Connecticut.  In many ways, Hawai’i is an island of all seasons.

Koppen System of Climate Classification

Posted on by

Climate, the long term statistical average of weather conditions, helps describe the character of a region.

Technically, every place on Earth has its own climate. To deal with such tremendous variety, scientists set up categories.  They organize locations with similar characteristics into groups. The ancient Greeks were among the first to attempt climate classification.  They divided the world into three zones: torrid, temperate, and frigid.  Today, the most widely used scheme is the Koppen Climate Classification System.

Wladimir Koppen (1846-1940) was a German climatologist working at the turn of the 20th century.  He developed a climate system based on monthly and annual averages of temperature and precipitation. Koppen also believed that a region’s vegetation was its best expression of climate. So, the natural distribution of native plants heavily influenced his zonal boundaries.

The Koppen system recognizes five principle climate groups, each with various sub-categories.  They are:

  • Tropical: Tropical Rainforest, Tropical Monsoon, Tropical Savanna
  • Dry: Semi-arid, Arid
  • Temperate: Mediterranean, Humid Sub-tropical, Marine West Coast
  • Continental: Warm Summer, Cool Winter, Sub-arctic
  • Polar: Tundra, Ice Sheets

Over the years, people have expanded this system to better suit their needs.  While the number of sub-categories differ, most are based on Koppen’s original idea.

U.V. Index in Hawai’i

Posted on by

Since returning from Hawai’i, everyone has been asking me, “Why aren’t you more tan?”  My response is, “SPF 70 and a hat.”  The UV index in Hawai’i ranges from high to extreme, so sun protection is necessary to avoid serious sunburn and other long-term skin problems.

The UV index is a scale that measures the intensity of the sun’s ultraviolet radiation reaching the Earth’s surface. Readings vary from place to place as local factors affect the amount of UV light that reaches the ground. These include, the thickness of the ozone layer, latitude, season, elevation, and cloud cover. Developed in the early 1990’s by the NWS and EPA to warn the public about the risk of overexposure to the sun, it is calculated on a daily basis for every city in the U.S.

Hawai’i is located in the tropics at approximately 20°N latitude.  As a result, the sun sits higher in the sky as compared to the mainland.  When the sun’s rays are more directly overhead, they filter through less of the atmosphere and are therefore more intense when they reach the ground. Consequently, the UV index in Hawai’i is higher than any other location in the U.S.  It averages around 7 in the winter and 11+ in the summer.

Chart Source: EPA

Ancient Climate of the Tall Grass Prairie

Posted on by

While traveling in the Mid-West not too long ago, I enjoyed a visit to the Tall Grass Prairie National Preserve in the Flint Hills region of Kansas. When you hike through its beautiful open landscape, the limestone beneath the grass stands out as evidence of past climate change.

Climate can shape the geology of a region in many ways.  In this case, the freezing and thawing of glaciers affected the existence of an ocean that covered much of present-day Kansas and Oklahoma.  Today’s vast “sea of grass” was once the bed of the Permian Sea. According to scientists, this shallow sea rose and fell numerous times during the Permian Period of the Paleozoic Era, about 251-299 million years ago.

This ancient sea sustained an array of aquatic-life, including fish and plants.  Just like today, these marine organisms took calcium carbonate out of the water to form their shells and skeletons.  After they died, these prehistoric sea creatures fell to the ocean floor where their stored calcium carbonate accumulated to form limestone over time.

These layers of sedimentary rock and the fossils they contain give us a much different view of America’s heartland than we are used to today.

Open landscape at the Tall Grass Prairie National Preserve, Kansas.

Limestone at Tall Grass Prairie National Preserve, Kansas.

Photo Credit: MF at The Weather Gamut

Redwoods and Climate Change

Posted on by

Last week, while traveling in northern California, I had the opportunity to visit Redwood National and State Parks.  The trees there, coastal redwoods, are among the oldest and tallest on Earth.  Often called “living fossils”, they are currently facing the challenges of climate change.

Redwoods have an ancient heritage dating back more than 100 million years to the days of the dinosaurs. These giant trees once covered much of the northern hemisphere. Today, however, they are limited to a few distinct regions like the foggy coast of northern California.

These trees depend on coastal fog for water, especially during the dry summer season and in times of drought. Redwoods have countless tiny, closely spaced leaves that act like a comb to capture the moisture of the fog.   The condensed moisture then falls to the forest floor, watering the root system. Fog also helps to reduce transpiration, or the loss of water through leaf surfaces.

Fog along the northern California coastline is generated when cool, moist Pacific air interacts with warmer inland air. As ocean temperatures rise as a result of climate change, less fog is being created here.  In a recent study, scientists found that over the past one-hundred years coastal fog production has decreased by 33% in the region.

Given the species primeval lineage, coastal redwoods must have endured climate changes in the past.  This time, however, the change is happening very quickly and no one knows for sure how the tress will respond.   Scientists from the Redwoods and Climate Change Initiative have been studying core-samples from fallen trees to see how redwoods dealt with previous climate variations.  They have also been placing sensors on trees to measure temperature, humidity, rainfall, fog, and wind.  This data will, hopefully, help them discern the impacts of global warming on the unique redwood eco-system.

Redwoods in fog

Photo Credit: fortbragg.com

San Francisco’s Microclimates

Posted on by

San Francisco, a city known for its fog, is actually a composite of microclimates. Last week, I was visiting the Bay Area and was reminded of its unique climate situation.

The area, in general, has a Mediterranean climate with mild, wet winters and dry summers. It is rare for the city to get warmer than 70°F in summer or cooler than 45°F in winter. Situated on a peninsula along the California coastline, San Francisco is kept mild by the Pacific Ocean’s chilly currents and local coastal upwelling.

Famous for its hills, the city’s complex topography is another major influence on its climate. The Golden Gate, a break in the mountainous Coast Range, funnels Pacific air into the Bay Area. The hills and basins of the peninsula then capture and divert the circulating marine air in intricate ways, forming a variety of  microclimates. As a result, weather conditions can vary widely across short distances, such as 10°F between neighborhoods.  In San Francisco, the forty hills that form the center of the city create a general weather divide. The western side of the city usually bears the brunt of the incoming Pacific air, with cool temperatures, strong winds, and fog.  The more sheltered eastern side generally sees more sun and warmer temperatures.

On a larger regional scale, temperature differences have an even wider scope.  For example, the average high temperature in July in the city is 68°F, while temperatures can reach 100°F in the Sacramento Valley, just 50 miles inland.