Nitric acid particles in cold thick ice clouds observed at global scale: Link with lightning, temperature, and upper tropospheric water vapor (original) (raw)
Related papers
Nitric Acid Trihydrate (NAT) in Polar Stratospheric Clouds
Science, 2000
A comprehensive investigation of polar stratospheric clouds was performed on 25 January 2000 with instruments onboard a balloon gondola flown from Kiruna, Sweden. Cloud layers were repeatedly encountered at altitudes between 20 and 24 kilometers over a wide range of atmospheric temperatures (185 t o 197 kelvin). Particle composition analysis showed that a large fraction of the cloud layers was composed of nitric acid trihydrate (NAT) particles, containing water and nitric acid at a molar ratio of 3 : l ;this confirmed that these longsought solid crystals exist well above ice formation temperatures. The presence of NAT particles enhances the potential for chlorine activation with subsequent ozone destruction in polar regions, particularly in early and late winter.
Atmospheric Chemistry and Physics, 2005
A PSC was detected on 6 February 2003 in the Arctic stratosphere by in-situ measurements onboard the high-altitude research aircraft Geophysica. Low number densities (∼10 −4 cm −3 ) of small nitric acid (HNO 3 ) containing particles (d<6 µm) were observed at altitudes between 18 and 20 km. Provided the temperatures remain below the NAT equilibrium temperature T NAT , these NAT particles have the potential to grow further and to remove HNO 3 from the stratosphere, thereby enhancing polar ozone loss. Interestingly, the NAT particles formed in less than a day at temperatures just slightly below T NAT (T >T NAT −3.1 K). This unique measurement of PSC formation at extremely low NAT saturation ratios (S NAT 10) constrains current NAT nucleation theories. We suggest, that the NAT particles have formed heterogeneously, but for certain not on ice. Conversely, meteoritic particles may be favorable candidates for triggering NAT nucleation at the observed low number densities.
Geophysical Research Letters, 2006
1] Uptake of nitric acid (HNO 3 ) in Arctic cirrus ice crystals was observed on 11 February 2003 by in-situ instruments onboard the M55 Geophysica aircraft. The cirrus cloud with a mean ice water content of 5.4 mg m À3 covered northern Scandinavia for several hours and extended up to the thermal tropopause at 12.3 km. Within the cirrus region, on average 9% of the total HNO 3 measured as reactive nitrogen (NO y ) is present in ice particles, increasing to 19% at temperatures below 205 K. In contrast to previous studies, we discuss the HNO 3 uptake in ice in terms of HNO 3 /H 2 O molar ratios in ice crystals. The HNO 3 content of the ice increases with increasing gas phase HNO 3 concentrations and decreasing temperatures. Enhanced uptake of HNO 3 in ice and heterogeneous chemistry on cold cirrus clouds may disturb the upper tropospheric ozone budget. Citation: Voigt, C.
Condensed-phase nitric acid in a tropical subvisible cirrus cloud
Geophysical Research Letters, 2007
1] In situ observations in a tropical subvisible cirrus cloud during the Costa Rica Aura Validation Experiment on 2 February 2006 show the presence of condensed-phase nitric acid. The cloud was observed near the tropopause at altitudes of 16.3 -17.7 km in an extremely cold (183 -191 K) and dry (<5 ppm H 2 O) air mass. Relative humidities with respect to ice ranged from 150-250% throughout most of the cloud. Optical particle measurements indicate the presence of ice crystals as large as 90 mm in diameter. Condensed HNO 3 /H 2 O molar ratios observed in the cloud particles were 1 -2 orders of magnitude greater than ratios observed previously in cirrus clouds at similar HNO 3 partial pressures. Nitric acid trihydrate saturation ratios were 10 or greater during much of the cloud encounter, indicating that HNO 3 may be present in the cloud particles as a stable condensate and not simply physically adsorbed on or trapped in the particles. Citation: Popp, P. J., et al. Condensed-phase nitric acid in a tropical subvisible cirrus cloud,
In-situ observations and modeling of small nitric acid-containing ice crystals
Atmospheric Chemistry and Physics, 2007
Measurements in nascent ice forming regions are very rare and help understand cirrus cloud formation and the interactions of trace gases with ice crystals. A tenuous cirrus cloud has been probed with in-situ and remote sensing instruments onboard the high altitude research aircraft Geophysica M55 in the tropical upper troposphere. Besides microphysical and optical particle properties, water (H 2 O) and reactive nitrogen species (NO y ) have been measured. In slightly ice supersaturated air between 14.2 and 14.9 km altitude, an unusually low ice water content of 0.031 mg m −3 and small ice crystals with mean radii of 5 µm have been detected. A high nitric acid to water molar ratio (HNO 3 /H 2 O) of 5.4×10 −5 has been observed in the ice crystals, about an order of magnitude higher compared to previous observations in cirrus at temperatures near 202 K. A model describing the trapping of HNO 3 in growing ice particles shows that a high HNO 3 content in ice crystals is expected during early growth stages, mainly originating from uptake in aerosol particles prior to freezing. Water vapor deposition on ice crystals and trapping of additional HNO 3 reduces the molar ratio to values close to the ratio of HNO 3 /H 2 O in the gas phase while the cloud ages.
Atmospheric Chemistry and Physics, 2008
The detection of nitric acid trihydrate (NAT, HNO 3 ×3H 2 O) particles in the tropical transition layer (TTL) harmonizes our understanding of polar stratospheric cloud formation. Large reactive nitrogen (NO y ) containing particles were observed on 8 August 2006 by instruments onboard the high altitude research aircraft M55-Geophysica near and below the tropical tropopause. The particles, most likely NAT, have diameters less than 6 µm and concentrations below 10 −4 cm −3 . The NAT particle layer was repeatedly detected at altitudes between 15.1 and 17.5 km over extended areas of 9.5 to 17.2 • N and 1.5 • W to 2.7 • E above the African continent. Satellite observations suggest that the NAT particles could have nucleated on ice fed by convective activity. Once nucleated, the NAT particles can slowly grow within the TTL for days, while being transported over long distances. Their in-situ detection combined with global model simulations of the NAT supersaturation near the tropical tropopause indicate the potential for a tropical tropopause NAT particle belt.
Evidence That Nitric Acid Increases Relative Humidity in Low-Temperature Cirrus Clouds
Science, 2004
Our results demonstrate that the viscosity of aqueous fluids increases only slowly with increasing silicate content. The viscosity of a fluid with 20 wt % (12 mol %) silicate at 800°C, for example, is equal to that of pure water at room temperature (1.0 ϫ 10 -3 Pa s), and that of a fluid with 50 wt % (35 mol %) silicate at the same condition is comparable to olive oil at room temperature (0.8 ϫ 10 -1 Pa s). The low viscosity of such silicate-rich fluids, together with their favorable wetting properties compared with silica-poor fluids , allows them to migrate out of the subducting slab even at low volume fractions and to infiltrate the overlying mantle wedge along channels or grain boundaries. High contents of dissolved silicate could be a prerequisite for the mobilization of subduction-related aqueous fluids, because silicate-poor fluids remain trapped in the slab as a result of their high wetting angles (23). Therefore, it may be no coincidence that volcanic fronts occur only at positions where complete miscibility between aqueous fluids and silicate melts is possible [ϳ70 to 150 km above the subducting plate (24, 25)]. Our results also suggest that the fast ascent rates of subduction-derived material observed in certain arc lavas (26 ) do not necessarily indicate transport by means of a near-endmember aqueous fluid, but could be accomplished by liquids with high silica contents. The possibility of material transport by silica-rich hydrous fluids should therefore be considered in any quantitative model of element recycling in subduction zone environments. . 20. The entire data set of the system albite-H 2 O is represented by the formula log ϭ -4.2 ϩ ͭ m aͩ c solids (wt %) 100 ͪ 3 ϩ m bͫ 1 -ͩ c solids (wt %) 100 ͪ 3 ͬͮ ϫ ͩ 10,000 T -2 ͫ 1 -e -cwater(wt %) 15 ͬͪ where m a ϭ 1.68 -0.42[c water (wt %)] 0.29 , m b ϭ 0.008 c solids (wt %), and e is the base of the natural logarithm.
Balloon observations of nitric acid aerosol formation in the Arctic stratosphere: II. Aerosol
Geophysical Research Letters, 1990
Balloonborne aerosol measurements over the size range r=0.01 to 10 mum on 31 January 1990 are used to determine the HNO3 vapor mass deposited in Arctic nitric acid trihydrate (NAY) clouds in the 21-24 km region. The clouds consisted mainly of small (r~0.2 mum) particles and appeared to have been formed during recent cooling because the r>=0.15 mum aerosol concentration