It is raining! We, desert dwellers, greet any rain with relief and joy, but there is something special about the monsoon that follows our dry hot season to cool and rejuvenate a scorched, parched and dusty landscape. The monsoon puts the power of nature on full display with its thunder and lightning shows, and musical pitter patter of gentle rain that sometimes crescendos to roars of downpour. But my favorite thing about the monsoon is the unmistakable scent of rain and that feeling of euphoria as a storm approaches.
That smell and feeling, according to recent studies by University of Arizona scientists, are the result of oils and organic compounds released by desert plants after a rain. The scientists report that the Sonoran Desert is rich in plant species that emit hundreds of fragrant volatile oils. These compounds evolved to protect plants from damaging solar radiation, heat waves, drought stress and predators. Many desert plants produce more of the oils during the harshest, dry, hot parts of summer, and the oils remain on the leaves until the start of the monsoon. With humidity and the winds that precede the onset of rain, the oils are released even before the rain falls. Their accumulation in the atmosphere immediately above desert vegetation is what contributes to that surge of anticipation you feel right before the first raindrop of a monsoon storm, and to the smell of the rain when it does fall. Several of the fragrant oils are also thought to improve sleep, heighten mental clarity and reduce depression or anxiety. Although these effects are not well understood, they are thought to occur through the impact of the fragrances on the brain’s olfactory system.
Olfaction - the sense of smell - is handled directly by the olfactory bulb, a structure in the front of the brain that then sends information about what you have smelled to other brain regions. From the olfactory bulb, signals take a direct and rapid route to the limbic system, including the amygdala and hippocampus - regions related to emotion and memory. So, often, a smell is not just a smell – it is a vivid memory ingrained in our minds and associated with a particular feeling. For example, think of how the scent of your mother’s perfume or the aroma of your favorite childhood food triggers a flood of memories and emotions.
Like other smells, the smell of rain likely also triggers certain memories and feelings that we have stored as positive. I recall my own experience as a kid waiting for the storms and then running outside with cousins and friends to play barefoot in the deluge of summer rains. Anthropologists suggest that humans may have inherited our affection for the scent of rain from ancestors who relied on rainy weather for their survival, as rain brought abundance of plants and animals to eat. In that case, the smell of rain may be triggering a cultural memory related to evolutionary history.
Now, if it were only a matter of smell, some ‘rain-scented’ candles and lotions might suffice. But, like all complex human experiences, there is also the anticipation, context and spectacle of the monsoon that adds to the earthy rain smell blowing in on the wind, and satisfies some deep craving. So, you’ll just have to wait for the storms to approach, have a seat on the porch, take a whiff of those fragrant oils on the breeze and find your own rain soaked bliss!
Post by: Nadia Fike
Read More: 1. Castellanos KM, et al. Does exposure to ambient odors influence the emotional content of memories? Am J Psychol. 2010;123(3):269. doi:10.5406/amerjpsyc.123.3.0269 2. Nabhan G, et al. Health Benefits of the Diverse Volatile Oils in Native Plants of Ancient Ironwood-Giant Cactus Forests of the Sonoran Desert: Adaptation to Climate Change? Int. J. Environ. Res. Public Health 2022, 19(6), 3250; https://doi.org/10.3390/ijerph19063250