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.

Trends of ozone in the troposphere

Abstract: Using a set of selected surface ozone (nine stations) and ozone vertical profile measurements (from six stations), we have documented changes in tropospheric ozone at a number of locations. From two stations at high northern hemisphere (NH) latitudes there has been a significant decline in ozone amounts throughout the troposphere since the early 1980s. At midlatitudes of the NH where data are the most abundant, on the other hand, important regional differences prevail. The two stations in the eastern United States show that changes in ozone concentrations since the early 1970s have been relatively small. At the two sites in Europe, however, ozone amounts increased rapidly into the mid-1980s, but have increased less rapidly (or in some places not at all) since then. Increases at the Japanese ozonesonde station have been largest in the lower troposphere, but have slowed in the recent decade. The tropics are sparsely sampled but do not show significant changes. Small increases are suggested at southern hemisphere (SH) midlatitudes by the two surface data records. In Antarctica large declines in the ozone concentration are noted in the South Pole data, and like those at high latitudes of the NH, seem to parallel the large decreases in the stratosphere.

Increasing background ozone during spring on the west coast of North America

Abstract: [1] Using a 15-year record of O3 from Lassen Volcanic National Park, a rural elevated site in northern California, data from two aircraft campaigns conducted in 1984 and 2002 over the eastern North Pacific, and observations spanning 18 years from five U.S. west coast, marine boundary layer sites, we show that O3 in air arriving from the Eastern Pacific in spring has increased by approximately 10 ppbv, i.e. 30% from the mid 1980s to the present. This positive trend in O3 correlates with the increasing trend in global nitrogen oxide emissions, which is especially pronounced in Asia. As spring is the season of strongest transport of Asian emissions to the Pacific, we conclude that the emission trend is the most likely cause of the O3 trend.

A geostatistical approach to surface flux estimation of atmospheric trace gases

Abstract: [1] Inverse modeling methods have been used to estimate surface fluxes of atmospheric trace gases such as CFCs, CH4, and CO2 on the basis of atmospheric mass fraction measurements. A majority of recent studies use a classical Bayesian setup, in which prior flux estimates at regional or grid scales are specified in order to further constrain the flux estimates. This paper, on the other hand, explores the applicability of using a geostatistical approach to the inverse problem, a Bayesian method in which the prior probability density function is based on an assumed form for the spatial and/or temporal correlation of the surface fluxes, and no prior flux estimates are specified. The degree to which surface fluxes at two points are expected to be correlated is defined as a function of the separation distance in space or in time between the two points. Flux estimates obtained in this manner are not subject to some of the limitations associated with traditional Bayesian inversions, such as potential biases created by the choice of prior fluxes and aggregation error resulting from the use of large regions with prescribed flux patterns. In essence, they shed light on the information contained in the measurements themselves. The geostatistical algorithm is tested using CO2 pseudodata at 39 observation locations to recover surface fluxes on a 3.75° latitude by 5.0° longitude grid. Results show that CO2 surface flux variations can be recovered on a significantly smaller scale than that imposed by inversions that group surface fluxes into a small number of large regions.

Measurements of an anomalous global methane increase during 1998

Abstract: Measurements of atmospheric methane from a globally distributed network of air sampling sites indicate that the globally averaged CH4 growth rate increased from an average of 3.9 ppb/yr during 1995-1997 to 12.7 +/- 0.6 ppb in 1998. The global growth rate then decreased to 2.6 +/- 0.6 ppb during 1999, indicating that the large increase in 1998 was an anomaly and not a return to the larger growth rates observed during the late 1970s and early 1980s. The increased growth rate represents an anomalous increase in the imbalance between CH4 sources and sinks equal to approximately 24 Tg CH4 during 1998. Wetlands and boreal biomass burning are sources that may have contributed to the anomaly. During 1998, the globally averaged temperature anomaly was +0.67 C, the largest temperature anomaly in the modern record. A regression model based on temperature and precipitation anomalies was used to calculate emission anomalies of 11.6 Tg CH4 from wetlands north of 30 N and 13 Tg CH4 for tropical wetlands during 1998 compared to average emissions calculated for 1982-1993. In 1999, calculated wetland emission anomalies were negative for high northern latitudes and the tropics, contributing to the low growth rate observed in 1999. Also 1998 was a severe fire year in boreal regions where approximately 1.3x10(exp 5) sq km of forest and peat land burned releasing an estimated 5.7 Tg CH4

When Will the Antarctic Ozone Hole Recover

Abstract: The Antarctic ozone hole develops each year and culminates by early spring (late September - early October). Antarctic ozone values have been monitored since 1979 using satellite observations from the TOMS instrument. The severity of the hole has been assessed from TOMS using the minimum total ozone value from the October monthly mean (depth of the hole) and by calculating the average area coverage during this September-October period. Ozone is mainly destroyed by halogen (chlorine and bromine) catalytic cycles, and these losses are modulated by temperature variations in the collar of the polar lower stratospheric vortex. In this talk, I will show the relationships of halogens and temperature to both the size and depth of the hole. Because atmospheric halogen levels are responding to international agreements that limit or phase out production, the amount of halogens in the stratosphere should decrease over the next few decades. Using projections of halogen levels combined with age-of-air estimates, we find that the ozone hole is recovering at an extremely slow rate and that large ozone holes will regularly recur over the next 2 decades. The ozone hole will begin to show first signs of recovery in about 2023, and the hole will fully recover to pre-1980 levels in approximately 2070. This 2070 recovery is 20 years later than recent projections. I will also discuss current assessments of mid-latitude ozone recovery.