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.

New evidence for the stratospheric dehydration mechanism in the equatorial Pacific

Abstract: Water vapor profile measurements obtained in the western and central Pacific during the Central Equatorial Pacific Experiment (CEPEX) show a strong connection between the water vapor content near the tropopause and areas of deep convection. We show that air ascending within deep convective towers can be dried to mixing ratios below 1 part per million by volume (ppmv), which is much lower than the average mixing ratio observed in the stratosphere. A sharp increase of water vapor mixing ratio above the tropopause is an indication of the evaporation of ice particles at the top of deep convective cells. A mixed layer of up to around 1 km thickness above the tropopause in the regions of deep convection is indicated by the vertical profiles of ozone, water vapor, and potential temperature. Furthermore, a local maximum was observed at 20 km, which is an indication for the seasonal cycle of the tropopause temperature.

A Design for Unattended Monitoring of Carbon Dioxide on a Very Tall Tower

Abstract: Unattended measurements of carbon dioxide (CO2) mixing ratio at three altitudes up to 496 m above the surface on a television transmitter tower in the southeastern United States have been made for a period of 4 yr. This report describes the design of the automatic tower measuring system in detail. A nondispersive infrared (NDIR) analyzer is used to measure the CO2 concentration continuously. Real-time control and data collection uses a PC 486 running under the multitasking operating system QNX. The CO2 data show strong diurnal and seasonal variations, and large vertical gradients. A comparison of this study’s continental tower data with data from “background” sites should provide a strong constraint for regional and global models of terrestrial CO2 fluxes.

Observational evidence for the role of denitrification in Arctic stratospheric ozone loss

Abstract: Severe and extensive denitrification, chlorine activation, and photochemical ozone loss were observed throughout the lower stratosphere in the 1999–2000 Arctic vortex. A large number of air parcels sampled between late February and mid-March, 2000, were photochemically intercomparable for chemical O3 loss rates. In these air parcels, the temporal evolution of the correlations of O3 with the NOy remaining after denitrification provides strong evidence for the role of NOy in moderating O3 destruction. In 71%-denitrified air parcels, a chemical O3 destruction rate of 63 ppbv/day was calculated, while in 43%-denitrified air parcels the destruction rate was only 43 ppbv/day. These observational results show that representative denitrification models will be required for accurate prediction of future Arctic O3 changes.

An Extended Comparison between LOWTRAN7 Computed and Observed Broadband Thermal Irradiances: Global Extreme and Intermediate Surface Conditions

Abstract: Differences between observed and LOWTRAN7-computed downward longwave irradiances were examined at each of four globally diverse locations for an entire year at each site. The final results are restricted to times determined to be completely or nearly cloud-free. The irradiances from 367 such times range from 60 to 435 W m−2, and results indicate that the modeled irradiances and those measured directly using a pyrgeometer agree to within 5 W m−2 at individual sites and to within lm than 0.2 W m−2 when averaged over all four sites, neglecting any site-specific biases. The standard deviations and standard errors associated with these results are roughly 10 and 1 W m−2, respectively. An unbiased estimate of the agreement between the model and observations results in a mean difference of 0.62 W m−2 with standard deviation of 5 W m−2 but an even larger 95% confidence interval because of the small sample size. The comparison variance can be logically ascribed to a number of different sources, including ...

Calibrating Broadband UV Instruments: Ozone and Solar Zenith Angle Dependence

Abstract: A UV spectroradiometer was installed at Mauna Loa Observatory (MLO), Hawaii, in July 1995. This instrument has been employed to characterize several broadband UV instruments of a type commonly used to estimate erythemal irradiance at many sites around the globe. One year of clear-sky data from MLO has been analyzed for solar zenith angles (SZAs) of 5°–85°, in steps of 5°, and for total ozone values in the range 220–310 DU measured with a Dobson spectrophotometer. Because the spectral responses of various broadband instruments can be quite different, and particularly because the erythemal response defined for human skin is significantly different than that of many broadband instruments, the calibration of a broadband instrument reporting in erythemal units is strongly dependent on total ozone and SZA. When a broadband instrument is placed in the field it is necessary to know the calibration as a function of ozone and SZA to determine accurate erythemal irradiance. However, the manufacturers of bro...