StratoClim EU project: ricercatore ISAC-CNR tra gli autori di una pubblicazione su Nature Geoscience
The Nature Geoscience journal has recently published an article (see link below) which deonstrate the presence of ammonium nitrate particles in the upper troposphere and allowed to trace the source of ammonia at the origin of the formation of particles.
A CNR-ISAC researcher, Dr. Francesco Cairo was among the international group of scientists that took part to the esxperimental research.
Abstract of the published work: The Asian monsoon is one of the largest and most energetic meteorological systems on earth, and the monsoon rains are essential to feed more than a billion people in Asia. It also affects meteorological phenomena on the entire northern hemisphere. The Monsoon also functions as a huge lift, pumping large amounts of air and pollutants from the surface to altitudes above 16 km. From those altitudes, the air can rise freely in the stratosphere, the stable layer that overhangs the lower part of the atmosphere and contains the protective ozone layer of the Earth. Once in the stratosphere, monsoon air spreads globally and persists for years.
Satellite images showed the presence of a large aerosol cloud - small droplets or dust particles - directly above the monsoon, which extends from the Arabian peninsula to the east coast of China. The formation processes and properties of this aerosol cloud are one of the unknowns that hinder our ability to make climate forecasts both on the region and globally; in general, aerosols can heat or cool the earth's surface, depending on their composition and the way in which they interact with the cloud formation processes. The increase in ammonia emissions in Asia is expected to increase radiative cooling, forming ammonium nitrate particles in the lower troposphere. There is, however, a serious gap in knowledge about ammonia and ammonia particles in the upper part of the troposphere and their possible effects on the formation of high-altitude clouds.
An international team of scientists led by the Alfred Wegener Institute has sought to bridge this knowledge gap. The EU StratoClim project involved scientists from 37 research institutes from 11 European countries, including the ISAC which was entrusted, among other things, with the task of contributing to achieving the first scientific mission aimed at characterizing the upper troposphere , above the monsoon system, using a high-altitude research aircraft that flew from Nepal in July-August 2017. For the first time measurements of the composition of the air reaching the stratosphere above the monsoon, influencing the composition of the atmosphere on a global level, have been carried out.
These measurements, complemented by satellite observations, simulations of atmospheric trajectories and laboratory experiments, demonstrated the presence of ammonium nitrate particles in the upper troposphere and allowed to trace the source of ammonia at the origin of the formation of particles. Furthermore it has been observed that during the Asian monsoon period, the solid particles of ammonium nitrate are surprisingly ubiquitous in the upper part of the troposphere from the eastern Mediterranean to the western Pacific. This aerosol layer of ammonium nitrate and organic compounds is fed by convection, which transports large amounts of ammonia from surface sources to the top of the troposphere. Impurities of ammonium sulphate allow the crystallization of ammonium nitrate even in conditions of high relative humidity that prevail in the upper part of the troposphere. The solid particles of ammonium nitrate in the upper part of the troposphere play a role so far neglected in the formation of ice clouds and radiative forcing.
Direct link to the Nature article: