The weather: why predicting the conditions to come is much more complicated than it seems

In Spanish we use ‘climate‘ to discuss current conditions and the days ahead, as well as broader, long-term weather patterns and characteristics. However, there is a difference between meteorology, which studies the weather and atmospheric phenomena of the moment, for days or weeks, and climatology, which studies long-term atmospheric trends and variations (years, centuries or millennia) and geological eras. .

Both are geographic or Earth sciences, and climatology in particular is more closely tied to geophysics, which studies the physical behavior of the planet’s atmosphere, oceans, and structures. Climate change triggered by an accelerated warming of the atmosphere has highlighted the importance of these sciences, the climate impact in the economy and welfare, and has complicated weather forecasts.

For a long time it has been said that the weather forecast in Lima and spas is not complicated: one degree less or more than the day before, sun in summer, cloudy and drizzle in winter, except on National Holidays. In the mountains, dry season and rainy season; in the jungle, rainy season, and season of more rain.

Things get complicated when trying to go into details, or when there is some unusual factor that alters traditional patterns, such as the El Niño phenomenon. This is because the climate in reality it is, even in countries like ours with relative meteorological stability, extremely complex due to the number of factors that affect it.

“Meteorology is similar to medicine, in that it is a mixture of science and art with individual talent.”

Determinants and variables

Everything is governed first and foremost by the Sun, which spreads its energy by raising the temperature of water, land and air. This is something we understand intuitively; the temperature changes and glare generated by solar energy are what we call, at first glance, the current climate, from the Lima haze to hurricanes.

There are other ‘macro’ factors that affect and broadly define the parameters and patterns of the climate of a place For example, its position on the continent, its height above sea level, and its distance from the equator.

In the case of Peru, the coast is a thin strip between an ocean and a mountain range, which carries currents of water and wind in a counterclockwise direction, because it is in the southern hemisphere. The planet’s rotation creates large eddy currents in the oceans and atmosphere. This is a result of constant rotation and is called the Coriolis effect (discovered in 1836 by the Frenchman Gaspard-Gustave Coriolis). The same effect very slightly deflects a bullet or arrow to the left in the southern hemisphere, or to the right in the north.

These great currents—the Humboldt and the South Pacific Anticyclone—collide with the shoreline and with the Andes Mountains, respectively. This creates somewhat stable conditions, with seasonal variations.

“The coast is a thin strip between an ocean and a mountain range, which carries currents of water and wind against the clock.”

Solar heating affects humidity, pressure and wind intensity; in the winter it generates low clouds and mists that turn the coastal hills green; in the summer, clouds more loaded with humidity at higher altitudes, which collide with the mountains and produce intense rains in the mountains.

Then there are the global variations caused by variables that until today are not fully understood, such as the El Niño phenomenon, which warms the sea waters by altering the currents of water and wind. Solar and geological activity, such as underwater volcanic eruptions, contribute to cyclical or occasional changes, bringing rain to the desert and drought to normally rainy areas.

We also have local variations and microclimates. These are weather conditions affected by specific differences such as water from an adjacent lake, hill, or forest that can block wind or trap moisture. Large cities, with their greater absorption and generation of heat, in many cases heat the air that surrounds them creating heat islands, affecting precipitation, wind and certainly air quality.

science and art

Although it is clear how to describe the weather of the moment –temperature, amount of rain, wind speed and atmospheric pressure– forecasting conditions to come is where things get drastically complicated. With knowledge of the conditions of a place and how various variables affect it, climate projections or models can be produced. However, the more distant in time, the predictions will be less and less accurate, since there are too many variables.

Weather forecasting is based on measurements of the various variables – air and water temperature, wind speed and currents, humidity and air pressure – in as many places as possible. This data is used to create maps and mathematical models, using formulas to describe how they can interact and affect each other.

The amount of information and the complexity of the models today requires the use of supercomputers, although the knowledge and experience of meteorologists is what allows the data and results to be interpreted. Meteorology is similar to medicine, in that it is a mixture of science and art with individual talent; In both, the stages to follow are: observation, information analysis, diagnosis and prognosis or climate model (occasionally more than one, which reveals the diversity of possible results).

Present and future climate

On a next page we will deal in more detail with weather analysis, and how it uses a variety of instruments on land, sea and in the air – wind vanes, barometers, thermometers, buoys, balloons and even satellites.

For now, it is worth mentioning, however briefly, the growing importance of meteorological services. As global warming affects determinants that were considered relatively stable, local knowledge, data recording and interpretation will become increasingly important and inseparable from infrastructure development, production and economic prosperity.