The phrase "annual average level" is correct and usable in written English.
It can be used when discussing statistical data or measurements that are calculated on a yearly basis.
Example: "The annual average level of rainfall in this region has increased over the past decade."
Alternatives: "yearly mean value" or "annual mean level".
When the measurements started in 1959 the annual average level was 315 parts per million, and it has gone up every year since.
Monitoring studies have shown that visibility at Arches and Canyonlands national park is harmed by human-caused haze 83% of the time, relative to the annual average level of natural haze, due in part to pollution from the Hunter and Huntington plants.
Revenue from international sales by OPEC, which accounts for about a third of world oil production, surged nearly 25percentt in 2003 -- to $247 billion from $199 billion the previous year -- as oil prices climbed to their highest annual average level in two decades, according to Cambridge Energy Research Associates.
The maximum allowable annual average level of trihalomethane and haloacetic acids is 80 and 60μg/L, respectively.
Air pollution hit new highs in March, nearly five times the annual average level recorded in London and nearly six times that of Los Angeles.
To measure the influence of environmental conditions, we take the annual average level of particulate matter pollution (PM10) 3 recorded at over 400 measuring stations distributed across Germany and published by the Federal Environment Agency (Umweltbundesamt).
But the analysts caution that the growth in demand is unlikely to return to the annual average levels seen in 2003-7, of 1.6 million barrels a day.
This followed a presentation in June by King's College London air researcher David Carslaw which questioned whether the hourly and annual average levels of nitrogen dioxide (NO2) pollution – mainly caused by diesel traffic – were the highest in the world.
For example, the study shows that in 1999, the latest year with comprehensive data, New York City, Los Angeles, Atlanta, Chicago, and several other cities had annual average levels of the 2.5-micron particles that would -- if seen for three years in a row -- violate the proposed rule.
The proposal calls for total Pacific bluefin catches to be kept below the 2002 to 2004 annual average levels and for catches of fish weighing fewer than 30 kilograms—juveniles too young to spawn to be reduced to 50% of those levels.
Using a computer model that fused air pollution and atmospheric chemistry data, they estimated what annual average levels of ozone (a key smog ingredient) and fine particulates smaller than 2.5 microns (PM2.5) were in 2010 within 100-km-by-100-km grid squares across the world.
