World wide weather
Global atmospheric measurements can help strengthen regional weather forecasts.
In early September of last year, residents of Northern California awoke to dark and orange skies. But this was no ordinary sunrise. Even as the morning progressed, the day remained eerily dim as smoke from nearby wildfires blotted out the sun. Now it appears that the chain of events leading to the fires and apocalyptic skies may have stretched halfway around the world.
Scientists recently identified a link between the devastating 2020 wildfires on the West Coast of the United States and typhoons on the other side of the Pacific Ocean. They found that a barrage of three storms over the Korean peninsula created an “atmospheric wave train” that ultimately amplified weather patterns that drove infernos through Oregon, Washington, and California.
“The implication is that the effect of weather extremes that are known to be exasperated by climate warming are not always limited to the region in which those extremes occur,” the researchers wrote.
As this example shows, our atmosphere is a connected fluid. Changes in conditions in one location ripple around the planet, propelling weather systems over continents and seas. The systems also travel vertically through the atmosphere. Conditions in the stratosphere—from about 8 to 50 kilometers above the Earth’s surface—eventually turn into the events we experience on the ground.
The clearest examples of weather systems transforming over long distances are the storms that gather above oceans and crash onto land. But even small pockets of air change the world’s weather as they travel and collide, like the proverbial butterfly flapping its wings.
For this reason, accurately forecasting in one location requires measuring conditions around the world.
“For any forecast more than a day and a half, you need a global observing system. And to improve one-to-three week forecasts, you need to observe the stratosphere,” said Dr. Alexander MacDonald, a Spire Global advisor with over 40 years of experience at NOAA.
To understand why worldwide observations will improve predictions, it helps to examine how meteorologists produce forecasts. The first step to creating a weather forecast is measuring atmospheric conditions with sensors attached to buoys, balloons, planes, and satellites. These devices record temperature, humidity, pressure, wind speed, and other essential variables. However, even with hundreds of thousands of sensors on Earth, 90% of the world lacks highly detailed and dense measurements above the surface, Dr. MacDonald said.
To fill in the gaps, meteorologists use the available measurements to estimate conditions in unobserved areas. They start by plotting an imaginary grid covering the planet’s surface and extending it through the atmosphere. Usually, the squares are about 12 kilometers wide and a few hundred meters tall. The meteorologists enter data for the grid points where they have measurements and then extrapolate for the rest. The result is an estimation of the atmosphere’s current conditions, which the industry calls an initialization.
Next, meteorologists feed the initialization into computer models programmed with the numerous physics equations that govern how our atmosphere evolves. The models crunch the numbers and simulate how conditions will develop over hours, days, and weeks. The results are the forecasts we see.
“One of the most effective ways to enhance forecasts is to improve and expand weather observations, especially in areas that are currently under-observed.”
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This entire process involves assimilating observations from multiple sources, tracking dozens of variables over millions of points, and running scores of complex equations on supercomputers.
“As a computational problem, global weather prediction is comparable to the simulation of the human brain and of the evolution of the early Universe, and it is performed every day at major operational centers across the world,” wrote three leading scientists in an article for Nature.
With so much complexity, small errors in the initial grid can balloon into significant miscalculations in final forecasts. To cut down on initial estimations and reduce forecasting errors, meteorologists need widespread, consistent, and reliable measurements.
Meteorologists can then use global observations to check and optimize the very models the data helps produce. By comparing the real-world measurements to their predictions, the scientists can calculate how well their models function for various locations and time frames. They can then correct errors and combine systems to produce the best possible predictions.
“One of the most effective ways to enhance forecasts is to improve and expand weather observations, especially in areas that are currently under-observed,” said Fabio Mano, a product manager at Spire Weather.
The true impact of including measurements from remote areas into weather predictions appears in severe weather tracking. For example, the thunderstorms that grew into Hurricane Sandy left Africa’s west coast on October 11, 2012. About eleven days later, the disturbance had morphed into a tropical storm cutting a deadly path through the Caribbean. As Sandy pushed north, it looked like it would blow out to sea, but observations over the mid-Atlantic alerted meteorologists that the catastrophe would continue. The system made a sudden left hook and barreled straight into New Jersey, landing eighteen days after leaving Africa. In the end, the storm claimed 286 lives and caused about $70 billion in damages. Devastating as Sandy was, the measurements and forecasts at sea helped prevent its consequences from being worse.
Making weather measurements in the under-observed areas of the world has been historically challenging. It is impossible to place millions of buoys across oceans. Nor can we release one balloon for every 12 square kilometers of the planet. But nanosatellites making radio occultation measurements can help overcome observation challenges.
Radio occultation measurements capture precise temperature, pressure, and humidity readings for vertical bands of the atmosphere, creating a detailed profile of conditions that extend from the Earth’s surface into the stratosphere. Nanosatellites can scan the planet, including areas beyond a terrestrial station’s range. Combining the measurement and the satellite produces a 3D map of conditions throughout our atmosphere—the answer to improved forecasting. This data-verse is already in production.
Spire’s fleet of more than 100+ satellites collects more than 10,000 radio occultation measurements a day. The European Centre for Medium-Range Weather Forecasts started using Spire’s data last year and found radio occultation measurements among the top five reducers of errors in predictions. Another leading meteorological organization, the United Kingdom’s Met Office, also reported a notable improvement in forecasting by incorporating Spire’s data.
“Spire is a pioneer in making dense observations around the world and in measuring the upper parts of the atmosphere that are important for longer-term prediction,” said Dr. MacDonald.
Satellites and radio occultation help forecasters study and predict global weather. These observations are a boon for everyone. Advanced forecasts not only alert us to deadly storms, but they also support sustainable agriculture, identify fuel-efficient transportation routes, and optimize renewable energy production. These are the exact programs we need to protect our world.
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