National Meteorological and Hydrological Services (NMHS) operate a number of in-situ observing systems in order to feed in-situ data into Numerical Weather Prediction systems. The data produced by what we call the European Composite Observing System (EUCOS) is also used for situational awareness of forecasters (e.g. warning/advisory production, aviation) and climate applications.
EUMETNET’s Observation Programme coordinates EUCOS across all domains that span from research to operations. It also includes a comprehensive performance monitoring tool for the ground-based, shipborne or aircraft-based observing systems operated by the NMHS that form its membership.
The hardest hit by the COVID-19 situation are clearly aircraft-based observations. We have seen a severe drop (-78%) of what are known as AMDAR reports in which reliable and high-quality wind and temperature in-situ data from the atmosphere are produced. When well distributed spatially, AMDARs represent a significant contribution to numerical model performance. The number of AMDAR reports has plunged in proportion to the drop in the number of aircraft that are still flying.
Fig. 1 AMDAR data stats through May 4th 2020.
The COVID-19 situation has also created other shortcomings and increased the risk of other types of data gaps should the situation last. Although most ground-based weather stations or moored buoys are automatic, maintaining them requires engineering e.g. people that can travel on-site regularly and working calibration labs.
Drifting buoys have an average lifespan of 18 months but require people and ships to deploy them regularly. Some older generation ship-borne measuring systems require shipmates to operate them. If less of these ships are plying, less data is produced in the Atlantic and the data sparse Arctic.
Moreover, a lot of the data provided by in-situ systems requires several stages of quality control. If some can be automated, a lot requires manual intervention from staff that may not be able to telework with the same capacities as usual.
EUMETNET Members are coordinating efforts to mitigate some of these risks.
Responding to the reduction in aircraft data, EUMETNET is coordinating an enhanced programme of radiosonde launches across Europe. Many NMHS have agreed to increase the number of radio-soundings they make each day which has been widely appreciated by global NWP centres. Radiosondes provide very high-quality observations of temperature, wind and humidity as they ascend from the ground to an altitude that can exceed 35km (~115,000 feet). Although relatively few in number compared to the huge quantities of data obtained from meteorological satellites, they are highly complementary and continue to be one of the most valuable sources of weather data.
Another response thread consists of accelerating the expansion to a wider geographical area of a novel system initially funded by the EU’s SESAR programme. The system derives Air Traffic Management aircraft transponder data in order to calculate wind and temperature through ‘big data’ algorithms and bias corrections. Although few aircraft are flying, the volume of processed data is 2 orders of magnitude higher than the traditional AMDAR sensor data.
The sharing of such resources and implementing solutions is at the core of the cooperative spirit that must prevail when facing hard times.
