What’s the weirdest weather?

Episode Summary

Executive Summary: This episode of CrowdScience from the BBC World Service explores various weather-related questions from listeners, with experts Professor Liz Bentley (Royal Meteorological Society) and Dr. Anthony Ray (World Meteorological Organisation). Topics include how weather forecasting works using observations, numerical models, and supercomputers; the size and behavior of raindrops; the perception of worse weather on weekends; differences in morning vs afternoon sunshine; how latitude affects seasons; and whether wildfire smoke can influence weather. The show concludes with a discussion on cloud seeding as a potential weather modification technique.

Main Topics: Weather Forecasting Process (Priority: 5/5): The three-step process involves collecting over 200 million daily observations globally, running numerical models on supercomputers (petascale machines), and having human forecasters interpret the data. Raindrop Size Determinants (Priority: 4/5): Raindrop size varies due to updrafts in convective systems (like thunderstorms), where drops can freeze into hail or aggregate into larger drops. The shape is more kidney-like than tear-shaped, typically around 1 mm across. Weekend Weather Perception vs Reality (Priority: 3/5): Though it's partly perception, a 110-year study in Manchester found Tuesday wettest, followed by Sunday. Weekend rain probability has increased 10% over 30 years, with unclear links to pollution. Morning vs Afternoon Sunshine (Priority: 3/5): The distinction is between sunlight (daylight hours) and sunshine (solar radiation reaching ground depending on cloud cover). Weather patterns like fair-weather clouds or morning mist determine which part of the day is sunnier. Seasons Around the World (Priority: 4/5): Mid-latitudes have four seasons, while equatorial regions may have none. Indigenous Australian knowledge includes up to 11 seasons based on ecological cues. Changing climate is extending wildfire and growing seasons. Wildfire Smoke Effects on Weather (Priority: 4/5): Wildfire particles can act as cloud condensation nuclei and be transported far (e.g., from West Coast to Colorado). The burned landscape changes albedo, potentially making surfaces colder locally. It's difficult to attribute specific weather events to fires. Weather Modification: Cloud Seeding (Priority: 3/5): Cloud seeding uses chemicals like silver iodide or salt to enhance rain. It has limited success (e.g., 2008 Beijing Olympics) but risks negative consequences elsewhere.

Key Arguments: Weather forecasting relies on huge data volumes (200M+ daily observations) and powerful supercomputers (petascale, moving to exascale), but human interpretation remains essential. Raindrop size is primarily determined by updraft strength in thunderstorms, leading to larger drops in convective systems; shape differs from common depictions. The perception that weekends are rainier is partly psychological but supported by some data (10% increase in weekend rain probability over 30 years); pollution linkage is inconclusive. Morning vs afternoon sunshine depends on specific weather patterns (e.g., fair-weather clouds vs morning fog), not a fixed rule. Seasons vary by latitude and culture; climate change is altering season length and increasing wildfire/extreme weather risks. Wildfire smoke can affect weather via cloud nucleation and albedo changes, but isolating single-fire impacts is scientifically challenging. Cloud seeding can produce rain locally (as in Beijing Olympics), but ethical and environmental concerns arise about unintended consequences.

Data Points: Daily weather observations: 200 million - Collected globally every day from land, satellite, and weather balloon observations. Supercomputer scale: Petascale (moving to exascale) - Global numerical weather prediction centers operate some of the world's largest supercomputers. Global forecasting centers: 12-13 - Number of global centers running large-scale numerical weather prediction models. Raindrop model resolution: 1 kilometer - Forecast models now operate at finer scale, improving accuracy. Weekend rain probability increase: 10% - Over the last 30 years in Manchester, UK, based on a 110-year study. Pollution level comparison: Higher than Delhi and Beijing - During major California wildfires in 2018, air pollution exceeded typically polluted cities. Particle lifetime in atmosphere: About 2 weeks - Wildfire smoke particles stay aloft roughly two weeks before falling out. Temperature drop example: >20 degrees Celsius in minutes - Melbourne weather variability with cold front passage.

Pivotal Quotes: "In simple terms, weather is what we get in the short term here and now, so it might be today or the next few days, and climate is what we get over longer periods of time. So, typically, we'd look over maybe two or three decades to kind of see what the climate looks like. And a good analogy of this is your wardrobe." — Professor Liz Bentley: Explaining the fundamental difference between weather and climate to listeners. "The particles that get emitted from the fires can impact cloud formation, for example. The particles become little condensation nuclei for water to condense on and become clouds." — Dr. Rebecca Buchholtz: Describing how wildfire smoke can affect local and distant weather through cloud nucleation. "I think any sort of weather modification, you really have to take heed that if you're going to try and change the atmosphere to do something, it'll probably have some negative consequence somewhere else." — Professor Liz Bentley: Warning about unintended consequences of cloud seeding and weather modification efforts.

Implications: This episode emphasizes the growing complexity and data intensity of weather forecasting as climate change increases extreme events. It highlights the need for global cooperation in weather monitoring and the potential ethical dilemmas of weather modification. For listeners, it provides practical insights into why weather feels worse on weekends and how individual choices (like solar panel installation) can benefit from sunlight data.