The term monsoon is tricky, scientifically speaking, yet an evocative one full of real and imagined rain-fed delights and potential calamities. Here in southern Arizona, we associate it with our summer rainy season, a time of great anticipation and proverbial boom or bust cycles. What other northern parts of the globe have weather patterns similar to our monsoon and how does our resulting flora and fauna compare to theirs?
Here in Arizona, we experience the North American Southwest, or (my preference) Arizona Monsoon. NOAA defines a monsoon as ” the seasonal reversal in atmospheric low-level circulations, particularly the surface winds and associated precipitation, resulting in a pattern of wet summers and dry winters.”
Driven each June by consistent soaring, searing temperatures, moisture is drawn into our region from the Sea of Cortez and the eastern Pacific Ocean. The extreme heat along with high atmospheric pressures over the Four Corners region are both seminal in enacting our monsoon.
Monsoonal patterns start earlier as one travels south into Mexico until May, not July, marks the onset of heavy rains deep into our neighboring country. We are towards the northern end of the North American Monsoon and hence must bide our desiccated time until, and if, the rains inch their way to our latitudes.The official start of the monsoon in southern Arizona is often touted as June 21st, which marks the Summer Solstice, though people in the know regard the 4th of July as a more consistent landmark.
Once the rains come, watch out! We are treated to/menaced by tremendous rain accompanied by equally extreme lightning, sometimes hail, and often squalling winds. Summer monsoons are infamously fickle and frequently highly localized events. It’s raining in one hand and not the other. Once you’ve lived here long enough you soon realize that the topic of conversation in summer is who got rain, where, when, and how much. Any other topics seem banal, given our unquenchable lust for rain in the Southwest.
When enough rain has infiltrated the soil, it triggers an ecological avalanche of biodiversity, transforming June’s dead-looking moonscapes into miniature versions of Costa Rica.
Elsewhere in the northern hemisphere, India famously is frequently deluged by its larger monsoon system, termed the South Asian Monsoon. The precipitation of that monsoon can at times make ours seem like a meager sprinkler hose. This is owing to two key factors. First, the source of the moisture is larger than ours. The Sea of Cortez (our main source) is dwarfed by the Indian Ocean. They have a bigger hose than we do. Second, the Himalayas serve as a barrier to their monsoons spreading further north, effectively trapping it over Southeast Asia. As we share the same hemisphere, both the North American and Southeast Asian Monsoons generally begin at the official onset of summer until its official curtain call, the Autumn Equinox in late September.
Here in the Sky Islands, the monsoon is a critical player in supporting our world class levels of biodiversity. Sonoran toads, elf butterflies, American black bear, varied buntings, a few wandering jaguars, and a formidable array of other fauna and flora owe their lives to the monsoon. Without it, we would rely on our much more fickle winter rains and in essence become an even drier version of California.
In India and other parts of Southeast Asia their monsoons also enable spectacular creatures and a multiplicity of plants. India’s Great Himalayan National Park lies at nearly the identical latitude as the town of Patagonia – both at near 31.5 degrees latitude North. Himalayan brown bear – Ursus arctos, and hence the same species as our exterminated (circa 1935) Mexican grizzly bear – roams the park. So does a relative of our Bighorn Sheep, the blue sheep. Its snow leopards are in the same genus, Panthera, as our Jaguar. Pines and spruces grow in the subalpine zones of the park, mimicking, at least prior to the large fires of the last 20 years, the high elevation forests of our Pinaleno and Chiricahua Mountains.
Parts of the Arabian Peninsula also get a summer monsoon – courtesy of India’s leftovers – the khareef. I once marveled at the verdant transformation of the mountains in Oman in a Youtube video on the Arabian Leopard, a critically endangered subspecies of the cat with the largest range of any. As with our jaguar, conservationists strive to protect and secure the ecological future of this rare feline, including educating people who own livestock about their inherent value. Worlds apart, same struggle.
I listened to a classical piece of music while writing this article, “Scheherazade” by Rimsky-Korsakov. In it, the namesake heroine keeps the murderous sultan at bay by artfully weaving stories each night to keep him spellbound, otherwise he will kill her. The music is ominous at times, like a threatening monsoon storm, and calm at others, as with our dry, inter-monsoonal days.
Like the music, we must keep hoping to stay alive for one more day, one more year, one more decade, perhaps, when it comes to precipitation, our aquifers, our water supply, our agriculture. I won’t even venture into the realm of centuries. Let’s just hope the monsoon delivers.
Vincent Pinto and his wife, Claudia, run RAVENS-WAY WILD JOURNEYS LLC, their Nature Adventure & Conservation organization devoted to protecting and promoting the unique biodiversity of the Sky Islands region. RWWJ offers a wide variety of private, custom-made courses, birding & biodiversity tours. Visit: www.ravensnatureschool.org