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NDACC News and Highlights
2011 NDACC News and Highlights
2011 NDACC News and Highlights
December 2010 - September 2011:
This section highlights significant items of interest within NDACC, with updates at least annually following the NDACC Steering Committee meeting.
An international Symposium celebrating 20 years of global atmospheric research enhanced by NDACC/ NDSC observations will be held the November 7-10, 2011 in Saint Paul, Reunion Island, France. The symposium is being organized by the Observatoire de Physique de l'Atmosphere de la Reunion. Attendees will be given the opportunity to visit the Maido Observatory which is scheduled to begin operations in early 2012. A Symposium web site will be available in March 2011 for registration, abstract submission, and booking. The abstract deadline is June 10, 2011. Second Announcement.
The Baseline Surface Radiation Network (BSRN) provides near-continuous, long-term, in situ-observed, Earth-surface, broadband irradiances (solar and thermal infrared) and certain related parameters from a network of more than 50 globally diverse sites. The observed data are collected, processed and reviewed by the individual sites' scientists and subsequently provided to network's central data archive and dissemination center, the World Radiation Monitoring Center (WRMC), located at the Alfred Wagner Institute in Bremerhaven, Germany (AWI).
BSRN closely links to NDACC in that atmospheric composition is a primary determinant of the non-geometric variability of the surface-received irradiances observed by BSRN. BSRN encourages but does not require nearby simultaneous observations of aerosol optical depth, water vapor and ozone at its sites. Some sites overlap between the two networks but most do not.
The BSRN was conceived and implemented in the late 1980s by the World Climate Research Program (WCRP, sponsored by WMO, ICSU, and IOC)with the collected data intended to be utilized for climate research applications, in particular; satellite product validation, climate model comparisons, and establishment of regional radiation climatologies, all in support of Earth radiation budget studies. In the mid 1990s, BSRN was included under the WCRP program called The Global Energy and Water Experiment (GEWEX). By the late 1990s, BSRN was designated as a contributing network the the WMO Global Atmospheric Watch (GAW) program and in the early 2000s was designated as the Global Baseline Surface Radiation Network of the Global Climate Observing System (GCOS).
Irradiance data collected and provided by the BSRN derive from instrumentation and operating practices that fulfill specifications developed by BSRN intended to provide the highest possible quality data from remote, continuously-operated field sites. Each participating site has a designated Site Scientist who is responsible for the operation of the site and the quality of the final data product submitted to the central archive at AWI.
To fulfill its institutional obligations to respond to the broader climate/scientific community, BSRN reports and answers annually to the GEWEX Radiation Panel, currently chaired by Prof. Christian Kummerow, and the GCOS/Atmospheric Observations Panel for Climate (AOPC) chaired by Dr. Adrian Simmons. The overall international management of the BSRN is provided by Dr. Ellsworth Dutton as part of his responsibilities within NOAA. The AWI BSRN Archive (also called the World Radiation Monitoring Center) is under the direction of Dr. Gert Koenig-Langlo. All data are interactively available for any scientist who accepted the data release guidelines see: http://www.bsrn.awi.de/en/data/data_retrieval_via_pangaea/ .
BSRN sites are typically sponsored by the host country's national government or in some cases other public or private institutions. The sites' participation in BSRN is generally considered part of the countries' contribution and obligation to the UN and other international sponsoring organizations.
The primary reference for the BSRN is:
Ohmura, A., E. G. Dutton, B. Forgan and 12 co-authors, 1998: Baseline Surface Radiation Network (BSRN)/WCRP): New precision radiometry for climate research. Bull. Amer. Meteoro. Soc. 79, 2115- 2136.
NDACC welcomes new UV data from the United States National Science Foundation's network of UV spectrometers operated by Biospherical Instruments Inc. The spectral UV data set from this network is one of the longest and most extensive in existence, and covers geographical areas where ozone changes have been most pronounced. Data summaries through November 2009 have been archived for most sites in the NDACC database. See http://UV.biospherical.com for other archivals. In our view it is crucial to maintain this network to monitor future changes in spectral UV irradiance. The following contribution was provided by Dr Germar Bernhard of Biospherical Instruments. For further information, including examples of data products available, see the NDACC Spectral UV Working Group page.
Thierry Leblanc, NASA Jet Propulsion Laboratory, California Institute of Technology, Wrightwood, CA 92397; USA
The MOHAVE-2009 campaign took place on October 11-27, 2009 at the Jet Propulsion Laboratory (JPL) Table Mountain Facility in California (TMF, 34.4N, 117.7W). This third MOHAVE campaign involved more instruments and datasets than the two previous ones held in 2006 and 2007. The main objectives of the campaign were 1) to compare and validate the water vapor measurements (profile and total column) from several instruments including, two types of frost-point hygrometers, two types of radiosondes, four Raman lidars, two microwave radiometers, two Fourier-Transform spectrometers, and two GPS receivers; 2) to cover water vapor measurements from the ground to the mesopause without gaps; 3) to study upper tropospheric humidity variability at timescales varying from a few minutes to several days. Nine of the participating instruments are currently affiliated with NDACC.
Comparisons of the balloon-borne measurements showed small, but non negligible differences in the derivation of water vapor mixing ratio profiles by the frost-point hygrometers depending on the radiosonde pressure and temperature information used. The typical 0.5 K and 0.5 hPa differences observed between the Vaisala RS92 and Intermet-1 radiosondes measurements resulted in the mean frost-point-derived mixing ratio difference shown in Fig. 1 (from the 12 most stable CFH flights of the campaign).
Figure 1: Effect of the differing pressure reading of the
Vaisala RS92 and Intermet PTU radiosondes on the derivation of
water vapor mixing ratio by the Cryogenic Frost-Point Hygrometer;
The 12 most stable balloon flights of MOHAVE-2009 were used.
Over 270 hours of water vapor nighttime measurements from three of the four Raman lidars were compared to that from the radiosondes and Frost-Point hygrometer sondes. As shown in Fig. 2, excellent agreement between the JPL lidar and the CFH was found throughout the measurement range, with only a 3% (0.2 ppmv) mean wet bias for the lidar with respect to CFH in the upper troposphere and lower stratosphere (UTLS). The two other operating water vapor lidars provided satisfactory results in the lower troposphere, but suffered from contamination by fluorescence, preventing their use in the UTLS (wet bias ranging from 5 to 50% between 10 km and 15 km).
Figure 2: Campaign-mean and standard deviations of water
vapor measured by lidar and CFH; a time coindicence and lidar
integration time of 1 hour is used in the troposphere (below 14
km); a time coindidence of 6 hours and full-night lidar
integration is used above 14 km.
Comparisons were also made in the stratosphere and mesosphere between the WVMS radiometer, Aura-MLS, and the MIAWARA-C radiometer. A typical example of the measured profiles and their uncertainties is given in Fig. 3. Between 40 and 65 km, general agreement within 10% is found between all instruments. Below 40 km, MIAWARA-C was wetter than MLS, while throughout the stratosphere WVMS was generally drier than MLS. These discrepancies are currently under investigation. The numerous results from MOHAVE-2009 have shown the critical importance of such multi-techniques comparison campaigns. On one hand, they remind us that the measurements of water vapor in the UTLS remains a contemporary challenge. On the other hand, they provide new confidence in the future simultaneous detection by lidar of long-term variability of water vapor and ozone in the UTLS.
Figure 3: One example of simultaneous and co-located water
vapor measurements, and their reported uncertainties during
MOHAVE-2009. The microwave measurements use 6-hour integration.