Some ozone soundings performed inside the Antarctic ozone hole exhibit localized ozone increases within thin layers in the lower stratosphere. These structures, called laminae, are explained by poleward filaments emerging from the vortex edge and transporting relatively rich ozone air into levels above the geographical site where the soundings have been launched. It is shown that the interior of the Antarctic vortex is not completely isolated with respect to the poleward air mixing. The filament development follows after inward breaking occurs near the vortex edge in a region where isentropes are locally uplifted. It is shown that the circulation associated with such uplift may produce the poleward breaking. The role of that circulation is supported by simple barotropic simulations where a poleward filament development in a realistic circular undisturbed vortex is reproduced.

Vertical displacements induced by the quasi-stationary wave with wavenumber 1 (QSW1) in the Southern Hemisphere stratosphere during spring are studied. The displacement exhibits two amplitude maxima located in the upper and lower stratosphere with a phase change of 180 degrees between the two regions. Ozone mixing ratio and temperature wave signatures are explained by the wave-induced displacement in the presence of mean vertical gradients. The QSW1 induces radiative diabatic forcing in the upper stratosphere that results in a cross-isentropic ozone transport. Correlation between vertical displacement at different levels and total ozone indicates that total ozone is directly connected to the displacement in the lower stratosphere. The displacement extends to tropopause and results in a correlation between total ozone and the tropopause height, but with smaller values. Relative deviation between reconstructed potential vorticity by using a high-resolution model and PV from observations indicates the existence of a preferred region for wave breaking and high-low latitude air exchange, in close connection with the upward displacement and the local background flow induced by the QSW1.

Surface radiation measurements were made at Gosan, Jeju, Republic of Korea during the ACE-Asia field campaign aimed at assessing the impact of aerosols, specifically the "Asian yellow dust", throughout the region. Downwelling total direct, and diffuse radiative fluxes were measured in the total solar spectrum as well as near-infrared and visible portions of the spectrum. Aerosol optical depth measurements at 500 nm were also made using a scanning shadowband radiometer. Surface radiative forcing values were determined during clear-sky conditions made from March 25 to May 4, 2001. The diurnal forcing efficiency, determined by taking the slope of the best fit line through the flux versus optical depth plot, was found to be -73.0 +/- 9.6, -35.8 +/- 5.5, and -42.2 +/- 4.8 W/m2/tau for the total solar, near-infrared, and visible spectral regions. We also introduce a new radiative forcing parameter, the fractional forcing efficiency, defined to express the radiative forcing relative to the total energy incident at the top of the atmosphere. The fractional diurnal forcing efficiency at Gosan during ACE-Asia was -18.0 +/- 2.3, -16.2 +/- 2.4, and -26.7 +/- 3.3 %/tau for the same bandpasses, indicating that a larger percentage of the flux at visible wavelengths is radiatively forced compared to the total and near-infrared portions of the solar spectrum.

The observed correlation between global low cloud amount and the flux of high energy cosmic rays supports the idea that ionization plays a crucial role in tropospheric cloud formation. This idea is explored quantitatively with a simple model linking the concentration of cloud condensation nuclei to the varying ionization rate due to cosmic rays. Among the predictions of the model is a variation in global cloud optical thickness, or opacity, with cosmic ray rate. Using the International Satellite Cloud Climatology Project (ISCCP) database (1983-99), a search was conducted for variations in the yearly mean visible cloud opacity and visible cloud amount due to cosmic rays. After separating out temporal variations in the data due to the Mount Pinatubo eruption and El Nino-Southern Oscillation, systematic variations in opacity and cloud amount due to cosmic rays were identified. It was found that the fractional amplitude of the opacity variations due to cosmic rays increases with cloud altitude, becoming approximately zero or negative (inverse correlation) for low clouds. Conversely, the fractional changes in visible cloud amount due to cosmic rays are only positively correlated for low clouds and become negative or zero for the higher clouds. The opacity trends suggest behavior contrary to the current predictions of ion-mediated nucleation (IMN) models, but more accurate temporal modeling of the ISCCP data is needed before definitive conclusions can be drawn.

As a follow-on to the Atmospheric Radiation Measurement (ARM) Enhanced Shortwave Experiment (ARESE) I, which provided atmospheric shortwave measurements from collocated aircraft, ARESE II performed similar measurements with a single aircraft flying at an altitude of 7 km over an instrumented surface site. ARESE I and ARESE II absorptance measurements are found to agree with each other and, when converted to top of the atmosphere (TOA) instantaneous column absorption, are also consistent with GOES 8 and Scanner for Radiation Budget (ScaRaB) satellite observations. Measurements are compared to calculations performed with five different radiative transfer models. It is found that the calculated absorption differs systematically from the observations in cloudy conditions, with models underpredicting the absorption. In particular, all the models tested here underpredict the measured instantaneous cloudy column absorption by amounts ranging from 17 to 61 W/m2, depending on the models and cases studied. The various models, using identical input, differ among themselves; for example, for the same cloudy case, absorptance estimates range from 0.22 to 0.27 for the atmospheric column from the surface to the TOA. It is also found that model-calculated absorptances appear not as well correlated to cloud optical depth variations as the measured absorptances appear to be. Measured and calculated clear-sky absorptances agree well within the uncertainties. Cloudy-sky absorptances in the visible spectral region (300 to 700 nm) reach values of as much as 0.02 during ARESE II while the equivalent measurements for ARESE I range around 0.06. This visible absorptance may be related to aerosols and their day-to-day and seasonal variability.