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.

Trajectory model sensitivity to differences in input data and vertical transport method

Abstract: [1] In this study, trajectory model sensitivity to the input meteorological data and vertical transport method is quantified. ERA-40 and NCEP/NCAR reanalysis data sets are used to compare isentropic and kinematic 3-D tropospheric trajectories. Expanding on previous trajectory sensitivity studies, we accumulate deviation statistics for an entire year and for three geographically diverse sites. The horizontal trajectory deviations are summarized as a percentage of average distance traveled. These results allow ranking from least to greatest among the five causes of trajectory uncertainty investigated here: minor differences in computational methodology, 3–4%; time interpolation, 9–25%; vertical transport method, 18–34%; meteorological input data, 30–40%; and combined two-way differences in vertical transport method and meteorological input data, 39–47%. Although the deviations are somewhat dependent on starting location because of the influence of meteorology, at all three sites, 3-D trajectories attained higher elevations and wind speeds than isentropic trajectories. In addition, deviation statistics for 3-D trajectories exceeded those for isentropic trajectories. The reasons for this derive from uncertainties in the supplied vertical wind fields and the higher wind speeds in 3-D trajectories on the one hand and the vertical constraints imposed by the isentropic assumption on the other.

Observation and possible causes of new ozone depletion in Antarctica in 1991

Abstract: Local ozone reductions approaching 50% in magnitude were observed during the Antarctic spring in the 11–13 and 25–30 km altitude regions over South Pole and McMurdo Stations in 1991. These reductions, at altitudes where depletion has not been observed previously, resulted in a late September total ozone column 10–15% lower than previous years. The added depletion in the lower stratosphere was observed to coincide with penetration into the polar vortex of highly enhanced concentrations of aerosol particles from volcanic activity in 1991.

Toward regional‐scale modeling using the two‐way nested global model TM5: Characterization of transport using SF6

Abstract: [1] We present an evaluation of transport of sulfur hexafluoride (SF6) in the two-way nested chemistry-transport model “Tracer Model 5” (TM5). Modeled SF6 values for January 2000 to November 2003 are compared with NOAA CMDL observations. This includes new high-frequency SF6 observations, frequent vertical profiles, and weekly flask data from more than 60 sites around the globe. This constitutes the most extensive set of SF6 observations used in transport model evaluation to date. We find that TM5 captures temporal variability on all timescales well, including the relatively large SF6 signals on synoptic scales (2–5 days). The model overestimates the meridional gradient of SF6 by 19%, similar to previously used transport models. Vertical profiles are reproduced to within the standard error of the observations, and do not reveal large biases. An important area for future improvements is the mixing of the planetary boundary layer which is currently too slow, leading to modeled SF6 mixing ratios that are too large over the continents. Increasing the horizontal resolution over North America from 6×4°, to 3×2°, to even 1×1° (lon×lat) does not affect the simulated global scale SF6 distribution and potentially minimizes representation errors for continental sites. These results are highly relevant for future CO2 flux estimates with TM5, which will be briefly discussed.

Early lidar observations of the June 1991 Pinatubo eruption plume at Mauna Loa Observatory, Hawaii

Abstract: The June 1991 eruption of the Philippine volcano Pinatubo introduced a massive plume of volcanic ash and other aerosol material into a stratosphere containing only near-background concentrations of aerosol material. At Mauna Loa Observatory, Hawaii, the Pinatubo plume was first observed by lidar on 1 July 1991. During July and August the observable effects from this plume increased in intensity in terms of aerosol optical properties, plume height, and broad band solar radiation. Preliminary data analysis shows that the plume over Hawaii arrived in three generalized pulses or waves on approximately 3 July, 24 July, and 9 August. There was a decrease of about 13% in a broad band atmospheric transmission factor over Hawaii between June 1991 and Pinatubo affected conditions on 31 August 1991. At the end of August 1991, the Pinatubo plume over Hawaii exhibited characteristics similar in magnitude to what was observed at Mauna Loa after the El Chichon eruption in 1982. However, the early Pinatubo maximum plume heights were lower than were observed in the early months of the El Chichon plume dispersion. The Pinatubo plume was continuing to increase in magnitude and height at MLO at the end of August.

Column closure studies of lower tropospheric aerosol and water vapor during ACE-Asia using airborne Sun photometer and airborne in situ and ship-based lidar measurements

Abstract: We assess the consistency (closure) between solar beam attenuation by aerosols and water vapor measured by airborne sunphotometry and derived from airborne in-situ, and ship-based lidar measurements during the April 2001 Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia). The airborne data presented here were obtained aboard the Twin Otter aircraft. Comparing aerosol extinction o(550 nm) from four different techniques shows good agreement for the vertical distribution of aerosol layers. However, the level of agreement in absolute magnitude of the derived aerosol extinction varied among the aerosol layers sampled. The sigma(550 nm) computed from airborne in-situ size distribution and composition measurements shows good agreement with airborne sunphotometry in the marine boundary layer but is considerably lower in layers dominated by dust if the particles are assumed to be spherical. The sigma(550 nm) from airborne in-situ scattering and absorption measurements are about approx. 13% lower than those obtained from airborne sunphotometry during 14 vertical profiles. Combining lidar and the airborne sunphotometer measurements reveals the prevalence of dust layers at altitudes up to 10 km with layer aerosol optical depth (from 3.5 to 10 km altitude) of approx. 0.1 to 0.2 (500 nm) and extinction-to-backscatter ratios of 59-71 sr (523 nm). The airborne sunphotometer aboard the Twin Otter reveals a relatively dry atmosphere during ACE- Asia with all water vapor columns less than 1.5 cm and water vapor densities w less than 12 g/cu m. Comparing layer water vapor amounts and w from the airborne sunphotometer to the same quantities measured with aircraft in-situ sensors leads to a high correlation (r(sup 3)=0.96) but the sunphotometer tends to underestimate w by 7%.