Tag Archives: Earth Observation

ESA: understanding of snow

Estimating the amount of seasonal snow is important for understanding the water cycle and Earth’s climate system, but establishing a clear and coherent picture of change has proven difficult. New research from ESA’s Climate Change Initiative has helped to produce the first reliable estimate of snow mass change and has helped to identify different continental trends.

Warming surface temperatures are known to have driven substantial reductions in the extent and duration of northern hemisphere snow cover. Equally important, but much less well understood is snow mass – the amount of water held in the snow pack – and how it has changed over time.

Millions of people rely on snow meltwaters for power, irrigation and drinking water. More accurate snow mass information would not only help to assess the availability of freshwater resources and identify flood risk, but also enable the better assessment of the role seasonal snow plays in the climate system.

In a new paper, published in Nature, researchers from the Finnish Meteorological Institute (FMI) and the Environment and Climate Change Canada, working as part of ESA’s Climate Change Initiative, have reliably estimated the amount of annual snow mass and changes in snow cover in the northern hemisphere between 1980 and 2018. Their research shows that snow mass has remained the same in Eurasia and has decreased in North America, but the extent of snow cover has decreased in both regions.

The combined 39-year snow mass climate data record is based on passive microwave satellite observations combined with ground-based snow depth measurements. This allowed the team to narrow the annual maximum snow mass for the northern hemisphere to 3062 gigatonnes between 1980-2018, with the peak snow mass occurring in March, while previous estimates ranged from 2500-4200 gigatonnes.

The team used this method, which corrects any anomalies in the data, and compared them to estimates from the Global Snow Monitoring for Climate Research, also known as GlobSnow, with three independent estimates of snow mass.

Jouni Pulliainen, the paper’s lead author and Research Professor at FMI, says, “The method can be used to combine different observations and it provides more accurate information about the amount of snow than ever before. The previous considerable uncertainty of 33% in the amount of snow has decreased to 7.4%.”

The research team found little reduction in northern hemisphere snow mass over the four decades of satellite observations when looking at the annual maximum amount of snow at the turn of February-March.

However, the more reliable estimates enabled the team to identify different continental trends. For example, snow mass decreased by 46 gigatonnes per decade across North America. This was not reflected in Eurasia, but high regional variability was observed.

Jouni continues, “In the past, estimates of global and regional snowfall trends have only been indicative. The results show that the amount of rainfall has increased in the northern regions, especially in the northern parts of Asia.”

In northern areas, where rainfall generally turns to snow in winter, the snow mass has remained the same or even increased. In the southern parts, where in winter rainfall comes down as water rather than snow, both the extent of the snow cover and the snow mass have decreased.

Snow mass data have the potential to help scientists analyse and improve the reliability of models used to predict future change, however, previous attempts to estimate the amount of snow mass in northern latitudes are so varied that it is not possible to judge if changes have occurred with sufficient confidence.

Floods in Italy by Sentinel-1

Torrential downpours have battered many parts of Italy this month, with extreme flooding wreaking havoc across northern Italy. The province of Alessandria is said to be one of the worst-affected areas according to Italian media, with around 200 people evacuated and 600 said to be left stranded.

This multi-temporal image uses two separate images captured by the Copernicus Sentinel-1 missiom on 13 November and 25 November. The flooded areas can be seen depicted in red, the Po River in black, and urban areas in white.

Copernicus Sentinel-1 radar ability to ‘see’ through clouds and rain, and in darkness, makes it particularly useful for monitoring floods. It can even easily differentiate water bodies, highlighting the difference between the Po River in black, and the extent of the flooding in red.
Around 500 people were evacuated further north in the Aosta Valley, where many roads were closed in fear of potential avalanches. Part of a viaduct serving the A6 motorway near Savona, in the northern region of Liguria, was washed away by a mudslide – leaving a 30 m gap in the road.

Images acquired before and after flooding offer immediate information on the extent of inundation and support assessments of property and environmental damage.

Earlier this month, the Copernicus Emergency Mapping Service was activated
to help respond to the floods in northeast Italy, where Venice saw record-breaking water levels and the worst flooding in 50 years.

#LPS19: ESA ‘Big Bang’ in Milan

The European Space Agency’s 2019 Living Planet Symposium has opened its working sessions today in Milan (Italy) Convention Centre MiCo. This symposium focuses on Earth Observation contribution to science and society, and spreading knowledge on disruptive technologies and actors, changing the traditional Earth Observation landscape, which also reveals new challenges and opens opportunities for public and private sector interactions.

Josef ASCHBACKER, (@AschbacherJosef ‏) Director of observation programs @ESA, shares his views with Europe Diplomatic Magazine on further integration of Earth observation data into European and global politics, shaping the new types of green economies, and lifestyle respectful of nature and planet. ASCHBACKER is profoundly convinced that ESA data on climate change and the other issues should be at heart of the upcoming political cycle of the EU.

The event, which is held every three years, will take place on 13–17 May 2019 in Milan, Italy. The Symposium is organised with the support of the Italian Space Agency.

This symposium focuses on how Earth Observation contributes to science and society, and how disruptive technologies and actors are changing the traditional Earth Observation landscape, which is also creating new opportunities for public and private sector interactions.