Why India’s Weather Service Still Depends on Classic Balloons in the Age of Satellites

When you picture weather forecasting today, it’s easy to imagine dazzling satellites looping around the globe, Doppler radars sweeping the skies, and computer models churning out numbers faster than a calculator. Yet, on the ground in Kerala, the Indian Meteorological Department (IMD) still packs a handful of bright‑orange balloons with a thin, flexible tube called a radiosonde and sends them drifting upward. It’s a practice that feels almost nostalgic, but it’s far from obsolete.

Those balloons rise—sometimes beyond 30 km—collecting temperature, humidity, wind speed and direction at every meter. The data they feed back in real time is raw, unfiltered, and crucial for understanding the atmosphere’s vertical structure. “A satellite gives us a picture from above, but it can’t tell you what the wind is doing at 5 km or 12 km,” says senior IMD scientist Dr. Anil Kumar. “That’s where the balloon’s direct measurements become irreplaceable, especially for short‑range forecasts and severe weather warnings.”

Modern tools have certainly broadened the horizon. High‑resolution radar now spots thunderstorms in their infancy, while satellite‑derived wind vectors provide a bird’s‑eye view of large‑scale patterns. Still, each technology has its blind spots. Radar struggles with range limitations over oceans, and satellites, for all their coverage, can miss micro‑scale variations that influence local rain showers. The radiosonde, though simple, fills those gaps with precision.

In Kerala, IMD operates a network of launch sites—Thiruvananthapuram, Kochi, Kozhikode and others—where balloons ascend twice a day, rain or shine. The process is surprisingly meticulous: technicians check the balloon’s elasticity, calibrate the radiosonde’s sensors, and then release it just as sunrise paints the horizon. The ascent is tracked via GPS, and the data streams instantly to regional centers, where forecasters blend it with satellite imagery and model outputs.

There’s talk of newer, unmanned platforms—high‑altitude drones and weather‑sensing balloons that can stay aloft for weeks. IMD is experimenting with those, but the classic weather balloon remains the workhorse, mainly because it’s cost‑effective, reliable, and backed by decades of operational experience. As Dr. Kumar puts it, “We’re not shunning technology; we’re complementing it. The balloon gives us the baseline, the truth, that we can trust when we calibrate everything else.”