Airplanes collect important weather data everyday around the world.

The data is directly uploaded into weather models and those weather models are what meteorologists use to make a forecast.

As more and more flights are grounded the amount of weather data is drastically decreasing and directly affecting the accuracy of weather models around the world.

One of the weather models that has been impacted is the European model (ECMWF). This model is known by forecasters as being the most accurate numerical weather model in the world.

Dr. Florence Rabier, Director General at ECMWF says "the data collected by aircraft is the second most important source of weather data compared to satellite data."

AMDAR (Aircraft Meteorological Data Relay) on average collects 700,000 weather observations each day.

That number as has drastically decreased by close to 80 percent in parts of the world.

The ECMWF estimates that this loss of data could result in the European computer model suffering as much as a 15 percent decline in accuracy.

Some meteorological organizations around the world are attempting to curb this issues by launching weather balloons more frequently and other remote sensing techniques.

Both the quantity and quality of weather observations and forecasts, as well as atmospheric and climate monitoring are at stake, according to the World Meteorological Organization (WMO) in Geneva.

“We are concerned about the impact on the ability of our Members to deliver their basic weather and climate services”, said Lars Peter Riishojgaard, Director of WMO’s Earth System Branch. “And you may think, why would we care about this, we have bigger things to worry about right now…But even in this situation, there could be situations where all of a sudden you could be critically reliant on weather forecasting if a hurricane, tornado, or some other adverse weather situation breaks out.”

In a statement, WMO Secretary-General Petteri Taalas urged Governments to support their national early warning and weather observing capacities despite the “severe challenges” caused by the COVID-19 crisis.

He explained that the devastating impacts of climate change haven’t stopped since the new coronavirus emerged in December, and neither have the “growing” number of weather-related disasters.

Without reliable weather data, the COVID-19 pandemic “poses an additional challenge and may exacerbate multi-hazard risks at a single-country level”, the WMO chief maintained.

Automated monitoring systems vulnerable

Many parts of the global weather monitoring system are automated, such as satellites and land-based observation points.

But other parts of the network have experienced a “dramatic” impact over the last few weeks – such as high-altitude readings - thanks to a sharp decrease in air traffic levels.

Before the COVID-19 era, commercial airlines took around 700,000 daily readings of air temperature, wind speed and wind direction.

This data and much more is fed into WMO’s Global Observing System, which supports weather and climate services and products provided by the 193 WMO Members.

In Europe, where air traffic readings are down by 85 to 90 per cent according to WMO, countries affiliated with 31 national weather services are already discussing how to boost the short-term capabilities of other parts of their observing networks, to mitigate this loss of aircraft-sourced data.

The impact has been less severe in the US, where commercial airline traffic data is down by 60 per cent, WMO said.

“At the present time, the adverse impact of the loss of observations on the quality of weather forecast products is still expected to be relatively modest”, said Mr. Riishojgaard. “However, as the decrease in availability of aircraft weather observations continues and expands, we may expect a gradual decrease in reliability of the forecasts.”

Data dip in developing countries

The situation is also concerning in many developing countries, where data is retrieved manually by weather observers, before being shared with international forecasting databases

“WMO has seen a significant decrease in the availability of this type of manual observations taken every few hours and reported to national centres over the last two weeks,” Mr. Riishojgaard said. “WMO will continue to monitor the situation, and the organization is working with its Members to mitigate the impact as much as possible.”

WMO chief Mr. Taalas added: “National Meteorological and Hydrological Services continue to perform their essential 24/7 functions despite the severe challenges posed by the coronavirus pandemic.”

“We salute their dedication to protecting lives and property but we are mindful of the increasing constraints on capacity and resources.”