Differential mortality and wealth accumulation

The issue of asset accumulation and decumulation is central to the life cycle theory of consumer behavior and to many policy questions. One of the main implications of the life cycle model is that assets are decumulated in the last part of life. Most empirical studies in this area use cross-sectional data of estimate mean or median wealth-age profiles. The use of cross-sections to estimate the age profile of assets is full of pitfalls. For example, if wealth and mortality are related, in that poorer individuals die younger, one overestimates the last part of the wealth-age profile when using cross-sectional data because means (or other measures of location) are taken over a population which becomes 'richer' as it ages. This paper examines the effect of differential mortality on cross-sectional estimates of wealth-age profiles. Our approach is to quantify the dependence of mortality rates on wealth and use these estimates to 'correct' wealth-age profiles for sample selection due to differential mortality. We estimate mortality rates as a function of wealth and age for a sample of married couples drawn from the Survey of Income and Program Participation (SIPP). Our results show that accounting for differential mortality produces wealth profiles with significantly more dissaving among the elderly

Differential Mortality and Wealth Accumulation

The issue of asset accumulation and decumulation is central to the life cycle theory of consumer behavior and to many policy questions. One of the main implications of the life cycle model is that assets are decumulated in the last part of life. Most empirical studies in this area use cross-sectional data of estimate mean or median wealth-age profiles. The use of cross-sections to estimate the age profile of assets is full of pitfalls. For example, if wealth and mortality are related, in that poorer individuals die younger, one overestimates the last part of the wealth-age profile when using cross-sectional data because means (or other measures of location) are taken over a population which becomes 'richer' as it ages. This paper examines the effect of differential mortality on cross-sectional estimates of wealth-age profiles. Our approach is to quantify the dependence of mortality rates on wealth and use these estimates to 'correct' wealth-age profiles for sample selection due to differential mortality. We estimate mortality rates as a function of wealth and age for a sample of married couples drawn from the Survey of Income and Program Participation (SIPP). Our results show that accounting for differential mortality produces wealth profiles with significantly more dissaving among the elderly.

Profiles of Problematic Soils and Spatial Distribution: Implication on Foundation Construction in Parts of Kosofe Lagos, Southwestern Nigeria.

Geotechnical data were complemented with geophysical investigation and employed to delineate problematic soils in parts of Kosofe Lagos, Southwestern Nigeria. The study area was chosen because of known issues regarding cracks in buildings and differential settlement of infrastructures founded on soils in the area. The aim is to generate profiles and maps of the spatial distribution of the subsurface soils to aid in foundation planning. Forty eight borehole logs and nine Vertical Electrical Soundings were compiled to delineate the different subsurface lithology which include peat, clay and sand. The results showed that the peat layer has maximum thickness of about 18.25 m but absent in some boreholes. This is underlain by clay unit with thickness ranging between 2.50-28.50 m. Sand unit constitute the third layer delineated with maximum thickness of 14 m. There is a general thickening of peat soils in the northern parts, especially around the streams in the area, which is instructive on the role of stream in the formation of the peat. The clay on the other hand is thickest around the northeastern and southeastern parts. The soil profiles generated reveal that the area is underlain by thick peat and clay having significant lateral, vertical variation and rapidly changing lithological facie over short distances. The extensive occurrence of these poor engineering soils calls for adequate engineering precaution in designs of building foundation

Latent Heat Flux Profiles from Collocated Airborne Water Vapor and Wind Lidars during IHOP_2002

Latent heat flux profiles in the convective boundary layer (CBL) are obtained for the first time with the combination of the DLR water vapor differential absorption lidar (DIAL) and the NOAA high resolution Doppler wind lidar (HRDL). Both instruments were integrated nadir viewing on board the DLR “Falcon” research aircraft during the International H2O Project (IHOP_2002) over the U.S. Southern Great Plains. Flux profiles from 300 – 2500 m AGL are computed from high spatial resolution (150 m horizontal and vertical) two-dimensional water vapor and vertical velocity lidar cross sections using the eddy covariance technique. All cospectra show significant contributions to the flux between 1 and 10 km wavelength, with peaks between 2 and 6 km, originating from large eddies. The main flux uncertainty is due to low sampling (55 % rmse at mid-CBL), while instrument noise (15 %) and systematic errors (7 %) play a minor role. The combination of a water vapor and a wind lidar on an aircraft appears as an attractive new tool that allows measuring latent heat flux profiles from a single over-flight of the investigated area

Latent Heat Fluxes over Complex Terrain from Airborne Water Vapour and Wind Lidars

Tropospheric profiles of water vapour and wind were measured with a differential absorption lidar (DIAL) and a heterodyne detection Doppler wind lidar collo-cated onboard the DLR Falcon research aircraft in the past two years. The DIAL is a newly developed four-wavelength system operating on three water vapour absorption lines of different strengths, one offline wavelength at 935 nm (each 50 Hz, 40 mJ), and 532 and 1064 nm for aerosol profiling. It is designed as an airborne demonstrator for a possible future space-borne water vapour lidar mission. It operated success-fully during the Convective and Orographically-induced Precipitation Study (COPS) in July 2007 over the Black Forest Mountains in southern Germany, and during the Norwegian THORPEX-IPY field experiment in March 2008 over the European North Sea. For the study of summertime convection initiation over complex terrain and the development of Polar Lows in the North Sea both campaigns included latent heat flux missions where both airborne lidars were pointed nadir-viewing. Using eddy-correlation of the remotely-sensed wind and water vapour fluctuations, a repre-sentative flux profile can be obtained from a single over-flight of the area under investigation. The lidars’ spatial resolution is ~200 m which resolves the domi-nant circulation and flux patterns in a convective boundary layer. This novel instrumentation allows ob-taining profiles of the latent heat flux beneath the air-craft from one single over-flight of any area of interest

Axial and Radial Investigation of Hydrodynamics in a Bubble Column;Influence of Fluids Flow Rates and Sparger Type

A detailed investigation of local hydrodynamics in a pilot plant bubble column has been performed using various techniques, exploring both axial and radial variations of the gas hold-up, bubble average diameter and frequency, surface area. A wide range of operating conditions has been explored up to large gas and liquid flow rates, with two sparger types. Two main complementary techniques were used: a quasi local measurement of gas hold-up via series of differential pressure sensors to get the axial variation and a double optic probe giving radial variations of gad hold-up, bubble average size and frequency and surface area. According to axial evolutions, three zones, where radial evolutions have been detailed,have been separated: at the bottom the gas injection zone, the large central region or column bulk and the disengagement zone at the column top. It was found that significant axial and radial variations of the two phase flow characteristics do exist even in the so called homogeneous regime. The normalized profiles of bubble frequency appear sparger and gas velocity independent contrary to bubble diameter, gas hold-up and interfacial area normalized profiles. In any case bubbles are larger in the sparger zone than elsewhere. The main result of this work is the very strong effect of liquid flow on bubble column hydrodynamics at low gas flow rate. First the flow regime map observed in batch mode is dramatically modified with a drastic reduction of the homogeneous regime region, up to a complete heterogeneous regime in the working conditions (uG> 0.02 m/s). On the contrary, liquid flow has limited effects at very high gas flow rates. A large data bank is provided to be used for example in detailed comparison with CFD calculations

Cumulus cloud venting of mixed layer ozone

Observations are presented which substantiate the hypothesis that significant vertical exchange of ozone and aerosols occurs between the mixed layer and the free troposphere during cumulus cloud convective activity. The experiments utilized the airborne Ultra-Violet Differential Absorption Lidar (UV-DIAL) system. This system provides simultaneous range resolved ozone concentration and aerosol backscatter profiles with high spatial resolution. Evening transects were obtained in the downwind area where the air mass had been advected. Space-height analyses for the evening flight show the cloud debris as patterns of ozone typically in excess of the ambient free tropospheric background. This ozone excess was approximately the value of the concentration difference between the mixed layer and free troposphere determined from independent vertical soundings made by another aircraft in the afternoon

Physical effects of vegetation on wind-blown sand in the coastal environments of Florida

One and two-dimensional, second order turbulence plant canopy flow models were developed for the purpose of estimating the effect of coastal vegetation on wind blown sand transport. The computer program that solves the governing differential equations uses measured leaf area density profiles and drag coefficients for crop plants similar in shape and size to the more common coastal vegetation in Florida. (Document has 57 pages.

Ice storm effects on the canopy structure of a northern hardwood forest after 8 years

Ice storms can cause severe damage to forest canopies, resulting in differential mortality among tree species and size classes and leading to long-lasting changes in the vertical structure and composition of the forest. An intense ice storm in 1998 damaged large areas of the northern hardwood forest, including much of the Hubbard Brook Experimental Forest, New Hampshire (USA). Following up on detailed poststorm assessments, we measured changes in the vertical structure of the forest canopy 8 years poststorm. We focused on how the presence of disease-induced advance regeneration of American beech (Fagus grandifolia Ehrh.) has affected canopy structure in the recovering forest. We measured foliage-height profiles using a point-quadrat approach and a pole-mounted leaf area index (LAI) sensor. Although the total LAIs of damaged and undamaged areas were similar, areas damaged in 1998 showed an increased proportion of total leaf area between 6 and 10 m above the ground. The foliage at this height is largely (54%) beech. To the extent that this heavily beech-dominated understory layer suppresses regeneration of other species, these findings suggest that rare disturbances of mature northern hardwood forests affected by beech bark disease will increase the importance of damage-prone and economically marginal beech