Transport of radon-222 and methyl iodide by deep convection in the GFDL Global Atmospheric Model AM2

Transport of radon-222 and methyl iodide by deep convection is analyzed in the Geophysical Fluid Dynamics Laboratory (GFDL) Atmospheric Model 2 (AM2) using two parameterizations for deep convection. One of these parameterizations represents deep convection as an ensemble of entraining plumes; the other represents deep convection as an ensemble of entraining plumes with associated mesoscale updrafts and downdrafts. Although precipitation patterns are generally similar in AM2 with both parameterizations, the deep convective mass fluxes are more than three times larger in the middle- to upper troposphere for the parameterization consisting only of entraining plumes, but do not extend across the tropopause, unlike the parameterization including mesoscale circulations. The differences in mass fluxes result mainly from a different partitioning between convective and stratiform precipitation; the parameterization including mesoscale circulations detrains considerably more water vapor in the middle troposphere and is associated with more stratiform rain. The distributions of both radon-222 and methyl iodide reflect the different mass fluxes. Relative to observations (limited by infrequent spatial and temporal sampling), AM2 tends to simulate lower concentrations of radon-222 and methyl iodide in the planetary boundary layer, producing a negative model bias through much of the troposphere, with both cumulus parameterizations. The shapes of the observed profiles suggest that the larger deep convective mass fluxes and associated transport in the parameterization lacking a mesoscale component are less realistic

Ascorbic acid supplementation does not lower plasma lipoprotein(a) concentrations

Abstract Elevated plasma concentrations of lipoprotein(a) (Lp[a]) are associated with premature coronary heart disease (CHD). Lp(a) is a lipoprotein particle consisting of low-density lipoprotein (LDL) with apolipoprotein (apo) (a) attached to the apo B-100 component of LDL. It has been hypothesized that ascorbic acid supplementation may reduce plasma levels of Lp(a). The purpose of this study was to determine whether ascorbic acid supplementation at a dose of 1 g/day would lower plasma concentrations of Lp(a) when studied in a randomized, placebo-controlled, blinded fashion. One hundred and one healthy men and women ranging in age from 20 to 69 years were studied for 8 months. Lp(a) values at baseline for the placebo group (n= 52) and the ascorbic acid supplemented group (n= 49) were 0.026 and 0.033 g/l, respectively. The 8-month concentrations were 0.027 g/l (placebo) and 0.038 g/l (supplemented group). None of these values were significantly different from each other. In addition, no difference in plasma Lp(a) concentration was seen between the placebo and supplemented groups when only subjects with an initial Lp(a) value of ]0.050 g/l were analyzed. Our data indicate that plasma Lp(a) concentrations are not significantly affected by ascorbic acid supplementation in healthy human subjects

Evaluating the Diurnal Cycle of Upper-Tropospheric Ice Clouds in Climate Models Using SMILES Observations

International audienceUpper-tropospheric ice cloud measurements from the Superconducting Submillimeter Limb Emission Sounder (SMILES) on the International Space Station (ISS) are used to study the diurnal cycle of upper-tropospheric ice cloud in the tropics and midlatitudes (40°S–40°N) and to quantitatively evaluate ice cloud diurnal variability simulated by 10 climate models. Over land, the SMILES-observed diurnal cycle has a maximum around 1800 local solar time (LST), while the model-simulated diurnal cycles have phases differing from the observed cycle by −4 to 12 h. Over ocean, the observations show much smaller diurnal cycle amplitudes than over land with a peak at 1200 LST, while the modeled diurnal cycle phases are widely distributed throughout the 24-h period. Most models show smaller diurnal cycle amplitudes over ocean than over land, which is in agreement with the observations. However, there is a large spread of modeled diurnal cycle amplitudes ranging from 20% to more than 300% of the observed over both land and ocean. Empirical orthogonal function (EOF) analysis on the observed and model-simulated variations of ice clouds finds that the first EOF modes over land from both observation and model simulations explain more than 70% of the ice cloud diurnal variations and they have similar spatial and temporal patterns. Over ocean, the first EOF from observation explains 26.4% of the variance, while the first EOF from most models explains more than 70%. The modeled spatial and temporal patterns of the leading EOFs over ocean show large differences from observations, indicating that the physical mechanisms governing the diurnal cycle of oceanic ice clouds are more complicated and not well simulated by the current climate models