Evaluating WRF-GC v2.0 predictions of boundary layer height and vertical ozone profile during the 2021 TRACER-AQ campaign in Houston, Texas

The TRacking Aerosol Convection ExpeRiment – Air Quality (TRACER-AQ) campaign probed Houston air quality with a comprehensive suite of ground-based and airborne remote sensing measurements during the intensive operating period in September 2021. Two post-frontal high-ozone episodes (6–11 and 23–26 September) were recorded during the aforementioned period. In this study, we evaluated the simulation of the planetary boundary layer (PBL) height and the vertical ozone profile by a high-resolution (1.33 km) 3-D photochemical model, the Weather Research and Forecasting (WRF)-driven GEOS-Chem (WRF-GC). We evaluated the PBL heights with a ceilometer at the coastal site La Porte and the airborne High Spectral Resolution Lidar 2 (HSRL-2) flying over urban Houston and adjacent waters. Compared with the ceilometer at La Porte, the model captures the diurnal variations in the PBL heights with a very strong temporal correlation (R&gt;0.7) and ±20 % biases. Compared with the airborne HSRL-2, the model exhibits a moderate to strong spatial correlation (R=0.26–0.68), with ±20 % biases during the noon and afternoon hours during ozone episodes. For land–water differences in PBL heights, the water has shallower PBL heights compared to land. The model predicts larger land–water differences than the observations because the model consistently underestimates the PBL heights over land compared to water. We evaluated vertical ozone distributions by comparing the model against vertical measurements from the TROPospheric OZone lidar (TROPOZ), the HSRL-2, and ozonesondes, as well as surface measurements at La Porte from a model 49i ozone analyzer and one Continuous Ambient Monitoring Station (CAMS). The model underestimates free-tropospheric ozone (2–3 km aloft) by 9 %–22 % but overestimates near-ground ozone (&lt;50 m aloft) by 6 %-39 % during the two ozone episodes. Boundary layer ozone (0.5–1 km aloft) is underestimated by 1 %–11 % during 8–11 September but overestimated by 0 %–7 % during 23–26 September. Based on these evaluations, we identified two model limitations, namely the single-layer PBL representation and the free-tropospheric ozone underestimation. These limitations have implications for the predictivity of ozone's vertical mixing and distribution in other models.</p

Geomembrane-geotextile interface shear properties as determined by inclined board and direct shear box tests

Geomembrane-geotextile interface shear strength parameters were measured using inclined board (tilting table), standard size (60 mm x 60 mm) and large-scale (300 mm x 300 mm) direct shear box tests. Smooth and rough HDPE, PVC geomembranes and nonwoven needle-punched geotextiles were used in the experiments. Inclined board tests were conducted under a normal stress range of about 5-50 kPa on variable size interface areas. In direct shear tests the applied normal stresses were about 25-300 kPa and 110-400 kPa in the small and large size tests, respectively, The interface friction angle and adhesion intercept values obtained by fitting a straight line through the plots of interface shear strength versus the normal stress were compared for different tests. It has been found that inclined board test results produce envelopes with relatively small adhesion values for both smooth and rough HDPE geomembrane-geotextile interfaces. The size of the interface does not appear to be a significant factor. For smooth geomembranes direct shear and inclined board tests give comparable interface friction angle and adhesion values. For rough geomembranes, however, the direct sheer adhesion values are markedly higher and friction angle values are a few degrees higher when compared to the inclined board test results

AN EXPERIMENTAL-STUDY OF THE PERFORMANCE OF GEOSYNTHETIC BAND DRAINS

The performance of two basic types of geosynthetic band-shaped/strip drains - a composite drain (core surrounded by a geotextile filter) and a monolithic drain (without a geotextile filter) - has been compared by means of radial consolidation tests. Tests were repeated employing the monolithic drain wrapped in the same filter fabric as the composite drain, a cylindrical porous stone and a sand drain. Two fine-grained soils of varying plasticity and gradation were used, initially at a water content equal to their respective liquid limits. The results were evaluated to compare the rate and amount of consolidation in each case and to assess the possible effect of clogging on the performance of geosynthetic drains. It was observed that the composite drain performed better than the monolithic drain, especially in the case of finer soil. Wrapping the monolithic drain with the geotextile filter significantly increased its performance

Characteristics of menopause in three socioeconomic urban groups in Karachi, Pakistan

To determine age, symptoms and treatment choices in Pakistani women with spontaneous menopause, three groups in Karachi were interviewed using a structured questionnaire. The groups consisted of 250 poor slum dwellers, 250 middle class clinic attenders and 150 wives of retired military officers. Interviews were carried out in 1989 and 1990 by members of a team from the Aga Khan University consisting of a gynaecologist, a community health physician and two senior medical students. All interviewees had natural menopause at least 12 months previously. The results showed a mean age of 47 years for menopause in all groups. One in five women were symptomatic in the poorest group but one in two were in the other groups. Treatment was sought by 6% in the poor group, 26% of the middle class group and 38% of the most privileged group. Age at menopause was 4 years earlier than in most reports and fewer women had menopausal symptoms. These urban women may not represent the situation across the country but, as life expectancy in Pakistan is rising (now 56.4 years for women), menopausal problems may increase