Water Vapor, Clouds, and Saturation in the Tropical Tropopause Layer.

The goal of this investigation is to understand the mechanism behind the observed high relative humidity with respect to ice (RHi) in the tropical region between ~14 km (150 hPa) and the tropopause, often referred to as the tropical tropopause layer (TTL). As shown by satellite, aircraft and balloon observations, high (>80%) RHi regions are widespread within the TTL. Regions with the highest RHi are co-located with extensive cirrus. During boreal winter, the TTL RHi is highest over the Tropical Western Pacific (TWP) with a weaker maximum over South America and Africa. In the winter, TTL temperatures are coldest and upward motion is the greatest in the TWP. It is this upward motion, driving humid air into the colder upper troposphere that produces the persistent high RHi and cirrus formation. Back trajectory calculations show that comparable adiabatic and diabatic processes contribute to this upward motion. We construct a bulk model of TWP TTL water vapor transport that includes cloud nucleation and ice microphysics that quantifies how upward motion drives the persistent high RHi in the TTL region. We find that atmospheric waves triggering cloud formation regulate the RHi, and that convection dehydrates the TTL. Our forward domain-filling trajectory (FDF) model is used to more precisely simulate the TTL spatial and vertical distribution of RHi. The observed RHi distribution is reproduced by the model and we show that convection increases RHi below the base of the TTL with little impact on the RHi in the TTL region.

The Role of Sulfur Dioxide in Stratospheric Aerosol Formation Evaluated Using In-Situ Measurements in the Tropical Lower Stratosphere.

Stratospheric aerosols (SAs) are a variable component of the Earth's albedo that may be intentionally enhanced in the future to offset greenhouse gases (geoengineering). The role of tropospheric-sourced sulfur dioxide (SO2) in maintaining background SAs has been debated for decades without in-situ measurements of SO2 at the tropical tropopause to inform this issue. Here we clarify the role of SO2 in maintaining SAs by using new in-situ SO2 measurements to evaluate climate models and satellite retrievals. We then use the observed tropical tropopause SO2 mixing ratios to estimate the global flux of SO2 across the tropical tropopause. These analyses show that the tropopause background SO2 is about 5 times smaller than reported by the average satellite observations that have been used recently to test atmospheric models. This shifts the view of SO2 as a dominant source of SAs to a near-negligible one, possibly revealing a significant gap in the SA budget.

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.

Note: Compact, two-dimension translatable slit aperture.

A compact, light-weight, two-dimension translatable slit aperture is described. The slit dimensions are scalable, allowing for wide application. With all metal construction, the device would be suitable for high temperature degassing and vacuum compatible. Alternatively, the main structure may be printed using a 3D printer for rapid prototyping and/or lighter weight. The precision of the slit movement is 0.014 mm.

Introduction to special section on three-generation studies.

Interest in lifespan research and cross-generational associations in parenting practices and child behaviors has grown rapidly in recent years. The four papers presented in this journal test three key intergenerational research questions regarding intergenerational continuities for externalizing behaviors, using different 3-generational samples.

The importance of timing: the varying impact of childhood and adolescent maltreatment on multiple problem outcomes.

A substantial body of literature suggests that childhood maltreatment is related to negative outcomes during adolescence, including delinquency, drug use, teenage pregnancy, and school failure. There has been relatively little research examining the impact that variation in the developmental stage during which the maltreatment occurs has on these relationships, however. In this paper, we reassess the impact of maltreatment on a number of adverse outcomes when developmentally specific measures of maltreatment-maltreatment that occurs only in childhood, only in adolescence, or in both childhood and adolescence-are considered. Data are drawn from the Rochester Youth Development Study, a broad-based longitudinal study of adolescent development. The analysis examines how maltreatment affects delinquency, drug use, alcohol-related problems, depressive symptoms, teen pregnancy. school dropout, and internalizing and externalizing problems during adolescence. We also examine whether the type of maltreatment experienced at various developmental stages influences the outcomes. Overall, our results suggest that adolescent and persistent maltreatment have stronger and more consistent negative consequences during adolescence than does maltreatment experienced only in childhood.

Longitudinal study of delinquency, drug use, sexual activity, and pregnancy among children and youth in three cities.

Using data from a collaborative program of research, this paper examines the prevalence of delinquency, alcohol and drug use, sexual intercourse, and pregnancy among youth in three urban settings. The findings indicate that a substantial portion of adolescents are involved in these behaviors. There are indications that for many youth the initiation of delinquency and drug use is occurring before the teenage years. There are also indications that all of these behaviors are often co-occurring, suggesting that comprehensive intervention programs may be required. Importantly, the high rate of sexual activity and pregnancy, combined with alcohol and drug use, suggests that greater attention to this combination of behaviors is needed.