The top panel shows the forecast for the Common Air Quality Index (CAQI) used in Europe since 2006. It is a number on a scale from 1 to 100, where a low value (green colors) means good air quality and a high value (red colors) means bad air quality. CAQI colour-coding is used in all air pollution forecast panels of the meteogram to indicate the level of pollution. For the pollen forecast there are no official guidelines for color-coding, as pollen are not part of the Air Quality Index forecast. The Air Quality index is defined separately near roads (“roadside” index) or away from roads ("background" index). meteoblue uses the background index, because weather models can not reproduce small-scale differences along the roads. Therefore, measurements along roads will show higher values than forecast here.
The second panel shows the forecast of particles (PM and desert dust) for San Francisco. Atmospheric particulate matter (PM) are microscopic solid or liquid matter suspended in the air. Sources of particulate matter can be natural or anthropogenic. Of greatest concern to public health are the particles small enough to be inhaled into the deepest parts of the lung. These particles are less than 10 microns in diameter (approximately 1/7th the thickness of the a human hair) and are defined as PM10. They are a mixture of materials that can include smoke, soot, dust, salt, acids, and metals. Particulate matter also forms when gases emitted from motor vehicles and industry undergo chemical reactions in the atmosphere. PM10 is visible by eye as the haze that we think of as smog. PM10 are among the most harmful of all air pollutants.
- PM10 can increase the number and severity of asthma attacks
- PM10 causes or aggravate bronchitis and other lung diseases
- PM10 reduces the body's ability to fight infections
PM10 includes fine particulate matter defined as PM2.5, which are fine particles with a diameter of 2.5 μm or less. The biggest impact of particulate air pollution on public health is understood to be from long-term exposure to PM2.5:
- PM2.5 increases the age-specific mortality risk, particularly from cardiovascular causes.
Desert Dust consists of particles smaller than 62 μm originating in deserts. Often, the dust particles are small, leading to high concentrations of PM10 and PM2.5 and all related health impacts.
Forecasts of concentrations of air pollution gases are presented in the third panel. Ozone (O₃) pollution in the lower troposphere is caused mainly in urban areas. Ozone can:
- Make it more difficult to breathe deeply and vigorously
- Cause shortness of breath, and pain when taking a deep breath
- Cause coughing and sore or scratchy throat
- Inflame and damage the breathing airways
- Aggravate lung diseases such as asthma, emphysema, and chronic bronchitis
- Increase the frequency of asthma attacks
- Make the lungs more susceptible to infection
- Continue to damage the lungs even when the symptoms have disappeared
- Cause chronic obstructive pulmonary disease (COPD)
Sulfur dioxide (SO₂) is a gas, which is invisible and has a nasty, sharp smell. It reacts easily with other substances to form harmful compounds, such as sulfuric acid, sulfurous acid and sulfate particles.
- Short-term exposures to SO₂ can harm the human respiratory system and make breathing difficult.
- SO₂ and other sulfur oxides can contribute to acid rain, which can harm sensitive ecosystems.
- Children, the elderly, and those who suffer from asthma are particularly sensitive to effects of SO₂.
Nitrogen dioxide (NO₂) is a reddish-brown gas that has a characteristic sharp, biting odor and is a prominent air pollutant. The major source of nitrogen dioxide is the burning of fossil fuels: coal, oil and gas. Most of the nitrogen dioxide in cities comes from motor vehicle exhaust. Nitrogen dioxide is an important air pollutant because it contributes to the formation of ozone, which can have significant impacts on human health.
- NO₂ inflames the lining of the lungs, and it can reduce immunity to lung infections
- NO₂ causes problems such as wheezing, coughing, colds, flu and bronchitis
For Europe, the air pollution meteogram has a fourth panel, showing the pollen forecast for San Francisco.
Birch pollen is one of the most common airborne allergens during springtime, or later in the year in higher latitudes. As the trees bloom, they release tiny grains of pollen that are scattered by the wind. A single birch tree can produce up to five million pollen grains. Pollen is dispersed by air currents and can be transported over large distances. We thus show the pollen forecast overlayed with the 10 m wind speed.
Grass pollen are the primary trigger of pollen allergies during the summer months. They cause some of the most severe and difficult-to-treat symptoms. In humid climates, the grass pollen season lasts several months. In drier climates the grass pollen season is significantly shorter, as are the birch and olive pollen season.
Precipitation can clean the air from pollen, but if it is associated with thunderstorms, the strong winds initially increase the pollen concentration.
Neither the European Commission nor ECMWF nor meteoblue is responsible for any use that may be made of the forecast information presented here. Predictions are issued from an atmospheric model with 12 km resolution. Outputs may not be correlated enough with real concentrations. Please consult your local air quality agency, especially in the case of a pollution peak or a pollution alert.