Observational evidence for interhemispheric hydroxyl-radical parity.

The hydroxyl radical (OH) is a key oxidant involved in the removal of air pollutants and greenhouse gases from the atmosphere. The ratio of Northern Hemispheric to Southern Hemispheric (NH/SH) OH concentration is important for our understanding of emission estimates of atmospheric species such as nitrogen oxides and methane. It remains poorly constrained, however, with a range of estimates from 0.85 to 1.4 (refs 4, 7-10). Here we determine the NH/SH ratio of OH with the help of methyl chloroform data (a proxy for OH concentrations) and an atmospheric transport model that accurately describes interhemispheric transport and modelled emissions. We find that for the years 2004-2011 the model predicts an annual mean NH-SH gradient of methyl chloroform that is a tight linear function of the modelled NH/SH ratio in annual mean OH. We estimate a NH/SH OH ratio of 0.97 ± 0.12 during this time period by optimizing global total emissions and mean OH abundance to fit methyl chloroform data from two surface-measurement networks and aircraft campaigns. Our findings suggest that top-down emission estimates of reactive species such as nitrogen oxides in key emitting countries in the NH that are based on a NH/SH OH ratio larger than 1 may be overestimated.

Evaluation of UT/LS hygrometer accuracy by intercomparison during the NASA MACPEX mission.

Acquiring accurate measurements of water vapor at the low mixing ratios (< 10 ppm) encountered in the upper troposphere and lower stratosphere (UT/LS) has proven to be a significant analytical challenge evidenced by persistent disagreements between high-precision hygrometers. These disagreements have caused uncertainties in the description of the physical processes controlling dehydration of air in the tropical tropopause layer and entry of water into the stratosphere and have hindered validation of satellite water vapor retrievals. A 2011 airborne intercomparison of a large group of in situ hygrometers onboard the NASA WB-57F high-altitude research aircraft and balloons has provided an excellent opportunity to evaluate progress in the scientific community toward improved measurement agreement. In this work we intercompare the measurements from the Midlatitude Airborne Cirrus Properties Experiment (MACPEX) and discuss the quality of agreement. Differences between values reported by the instruments were reduced in comparison to some prior campaigns but were nonnegligible and on the order of 20% (0.8 ppm). Our analysis suggests that unrecognized errors in the quantification of instrumental background for some or all of the hygrometers are a likely cause. Until these errors are understood, differences at this level will continue to somewhat limit our understanding of cirrus microphysical processes and dehydration in the tropical tropopause layer.

The relationship of self-esteem to the health-related behaviors of the patients of a primary care clinic.

To clarify the relationship of self-esteem and health-related behaviors of primary care clinic patients, 500 family practice residency patients were invited to complete self-esteem and health-risk appraisal instruments. Of the final subject pool (N = 469), 154 responded to the single-mailing solicitation, thereby yielding a 32.8% response rate. Correlational analysis found self-esteem to be associated with predicted longevity, life satisfaction, social ties, overall health, personal loss, seatbelt use, age, physical activity, smoking, exposure to violence, and substance use. Multiple regression analysis of male subjects' data found self-esteem most closely related to the frequency of exposure to danger, self-perceptions of health, and tobacco use. Similar analysis of the women's data most closely associated self-esteem to perceived social support, self-perception of health, diastolic blood pressure, and seatbelt use. The data clearly link individuals' self-esteem to predicted longevity. Those with greater self-regard were predicted to live longer, while those with poorer self-esteem achieved shorter predicted longevity. Contributing factors may have included greater emphasis on self-care.