Cloud and Aerosol Research

Aerosols and clouds are being investigated using a variety of remote and in situ measurements combined with theory.   This work is leading to a broader understanding of atmospheric particles from the troposphere through the mesosphere,  and boasts some exciting new discoveries.  

Particles under investigation include Stratospheric Sulfate Aerosols:  These particles consist of H2SO 4-H2O mixtures and are always present at stratospheric altitudes around the globe. Cirrus:   These clouds consist of ice particles and occur globally throughout the year within the upper troposphere. Polar Stratospheric Clouds (PSCs):   These clouds consist of either ice or nitric acid condensates and occur within the stratosphere during winter at polar latitudes in both hemispheres. Polar Mesospheric Clouds (PMCs):   These clouds consist of ice particles and occur near the mesopause (83 km) during polar summer in both hemispheres. Tropical Nitric Acid Clouds (TNCs): These clouds consist of nitric acid condensates and occur at tropical latitudes throughout the year at altitudes from the upper troposphere to the lower stratosphere. Cosmic Smoke and Dust: Meteoroids are constantly entering the Earth's atmosphere, and are vaporized in the lower thermosphere/upper mesosphere due to heating during atmospheric entry.  The resulting cosmic "smoke" particles accumulate near 85 km altitude globally.

Recent Investigations

• HALOE observations have demonstrated for the first time,  that nitric acid clouds exist near the tropical tropopause   [Hervig and McHugh, Geophys. Res. Letters, 29(7) , 10.1029/2001GL014271, 2002]

• Analysis of stratospheric aerosol measurements from SAGE II,  HALOE,  and in situ optical particle counters  [Hervig and Deshler, J. Geophys., Res., 107(D3), 10.1029/2001JD000703, 2002; abstract ]
   
• Infrared measurements from HALOE have provided the first physical evidence that water ice is the primary component of polar mesospheric clouds (PMCs)   [Hervig et al., Geophys. Res. Letters, 28, 971-974, 2001]

• Measurements of polar stratospheric clouds (PSCs) from AVHRR   [Hervig et al., J. Geophys. Res., 106, 10,363-10375, 2001]

• Exploring the detection of cosmic dust in the Earth's upper atmosphere

• A climatology of stratospheric aerosol size distributions from HALOE measurements

• An unusual low latitude display of stratospheric clouds over England,  observed by HALOE    [Hervig, Geophys. Res. Letters, 26, 1137-1140,  1999].

Relevant Links

   AVHRR