Climate Monitoring and Diagnostics Laboratory

About: Climate Monitoring and Diagnostics Laboratory is a based out in . It is known for research contribution in the topics: Aerosol & Stratosphere. The organization has 107 authors who have published 263 publications receiving 26434 citations.

Electron microscope studies of Mt. Pinatubo aerosol layers over Laramie, Wyoming during summer 1991

Abstract: Stratospheric aerosol layers resulting from the June 1991 eruptions of Mt. Pinatubo were first observed over Laramie, Wyoming in July 1991. Atmospheric particles were collected from these layers during three balloon flights in July and August using cascade impactors. Analytical electron microscope analysis of the aerosol deposits indicated that a large majority (> 99%) of the fine particles in all three samples were collected as submicrometer aqueous H2SO4 droplets, which changed to (NH4)2SO4 particles over time. Other particles observed in the aerosol were larger, and consisted of supermicrometer sulfate particles and composite sulfate/crustal particles which ranged up to ∼10 μm in size. Peak aerosol concentrations for r > 0.15 μm diameter particles (determined by optical particle counters) in the layers were higher for the July flights than for the August sounding. This was reflected in the electron microscope results, which showed that the July impactor samples had particulate loadings on the fine particle stages which were 20–30% higher than those from the corresponding substrate from the August sample. A detailed analysis of the fine sulfate aerosol was performed to assess whether the sulfate particles contained small condensation nuclei. Nearly all analyzed sulfate particles showed no evidence of a solid or dissolved nucleus particle, which suggests that the volcanic H2SO4 aerosol formed through homogeneous nucleation processes. These data support heated-inlet optical particle counter data from the balloon flights which suggest that 95–98% of the volcanic particles were aqueous H2SO4.

A multiple-scale simulation of variations in atmospheric carbon dioxide using a coupled biosphere-atmospheric model

Abstract: [1] Variations of atmospheric CO2 at regional scales are becoming increasingly important in understanding regional carbon budgets, yet the processes that drive them remain relatively unexplored. A simulation was conducted to test a coupled biosphere-atmospheric model (SiB2-RAMS), by comparing with measurements made at the WLEF-TV tower in Wisconsin, and to investigate some of the mechanisms leading to CO2 variability, both on local and regional scales. The simulation was run for a 5-day period from 26 to 30 July 1997. Multiple nested grids were employed, which enabled mesoscale features to be simulated and which resolved small-scale features in the vicinity of the WLEF tower. In many respects the model was successful at simulating observed meteorological variables and CO2 fluxes and concentrations. The two most significant deficiencies were that excessive nighttime cooling occurred on two of the nights and that late afternoon uptake of CO2 was larger than observed. Results of the simulation suggest that in addition to biological processes causing variations in CO2 concentrations at the WLEF site other factors, such as small nearby lakes, turbulence induced by vertical wind shear, boundary layer thermals, and clouds, also had significant impacts. These factors add to the difficulty of interpreting CO2 measurements. Regional-scale patterns of CO2 variability caused by meteorological processes were also identified. Katabatic winds had a significant effect by causing respired CO2 to pool in valleys and along the shores of the Great Lakes during the night. Furthermore, a large diurnal cycle of CO2 concentration occurred over the lakes, which appeared to be mainly due to the combined action of katabatic winds, ambient winds, and the lake breeze circulation. These results suggest that meteorological processes associated with the complex terrain in this region leads to substantial CO2 advection. Therefore meteorological as well as biological processes are likely to be important causes of regional-scale CO2 variability in the Great Lakes region. A sensitivity test conducted to examine the differences between using a turbulent kinetic energy based subgrid-scale scheme versus a deformation-type subgrid-scale scheme showed advantages and disadvantages to both approaches. Our results suggest that continuous records of CO2 variability measured over heterogeneous continental regions must be interpreted with caution because of the impact of mesoscale circulations on the concentration time series.

Carbon isotope discrimination of arctic and boreal biomes inferred from remote atmospheric measurements and a biosphere-atmosphere model

Abstract: Estimating discrimination against ^(13)C during photosynthesis at landscape, regional, and biome scales is difficult because of large-scale variability in plant stress, vegetation composition, and photosynthetic pathway. Here we present estimates of ^(13)C discrimination for northern biomes based on a biosphere-atmosphere model and on National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostics Laboratory and Institute of Arctic and Alpine Research remote flask measurements. With our inversion approach, we solved for three ecophysiological parameters of the northern biosphere (^(13)C discrimination, a net primary production light use efficiency, and a temperature sensitivity of heterotrophic respiration (a Q10 factor)) that provided a best fit between modeled and observed δ^(13)C and CO_2. In our analysis we attempted to explicitly correct for fossil fuel emissions, remote C4 ecosystem fluxes, ocean exchange, and isotopic disequilibria of terrestrial heterotrophic respiration caused by the Suess effect. We obtained a photosynthetic discrimination for arctic and boreal biomes between 19.0 and 19.6‰. Our inversion analysis suggests that Q10 and light use efficiency values that minimize the cost function covary. The optimal light use efficiency was 0.47 gC MJ^(−1) photosynthetically active radiation, and the optimal Q10 value was 1.52. Fossil fuel and ocean exchange contributed proportionally more to month-to-month changes in the atmospheric growth rate of δ^(13)C and CO_2 during winter months, suggesting that remote atmospheric observations during the summer may yield more precise estimates of the isotopic composition of the biosphere.

Transport of Carbon Dioxide in the Presence of Storm Systems over a Northern Wisconsin Forest

Abstract: Mixing ratios of CO2 often change abruptly in the presence of inclement weather and low pressure systems. Water vapor mixing ratio, temperature, wind speed, and wind direction data are used to infer that the abrupt changes in CO2 mixing ratios at a site in northern Wisconsin are due to tropospheric mixing, horizontal transport, or a combination of both processes. Four different scenarios are examined: the passage of a summer cold front, a summer convective storm, an early spring frontal passage, and a late autumn low pressure system. Each event caused CO2 mixing ratios to change rapidly when compared to biological processes. In one summer convective event, vertical mixing caused CO 2 mixing ratios to rise more than 22 ppm in just 90 s. Synoptic-scale transport was also evident in the presence of storm systems and frontal boundaries. In the cases examined, synoptic-scale transport changed CO2 mixing ratios as much as 15 ppm in a 1-h time period. The events selected here represent extremes in the rate of change of boundary layer CO2 mixing ratios, excluding the commonly observed venting of a shallow, stable boundary layer. The rapid changes in CO 2 mixing ratios that were observed imply that large mixing ratio gradients must exist, often over rather small spatial scales, in the troposphere over North America. These rapid changes may be utilized in inverse modeling techniques aimed at identifying sources and sinks of CO2 on regional to continental scales.

Determining surface solar absorption from broadband satellite measurements for clear skies - Comparison with surface measurements

Abstract: Using data from collocated satellite pixel measurements obtained during the Earth Radiation Budget Experiement and near-surface measurements carried out at the Boulder Atmospheric Observatory Tower, the shortwave (SW) surface radiation from broadband satellite measurements for clear-sky conditions was compared with surface measurements. Results demonstrate that the surface-SW absorption is a more meaningful quantity for climate studies than is surface insolation. It is also shown that a direct evaluation of the surface-SW absorption can be more accurately obtained from satellite measurements than can be surface insolation. An algorithm is presented for transferring satellite SW measurements to surface-SW absorption.