Comparisons of downwelling radiation to model predictions based on groundbased measurements during FIRE 1991

Surface radiation measurements and simultaneous ground-based measurements of the atmosphere during the FIRE'91 cirrus field experiment provided an opportunity to identify crucial measurements and parameterization deficiencies in current cloud-radiation models. Comparisons between measured and calculated broadband surface fluxes with only a small data subset already reveal these needs: accurate humidity and aerosol vertical profiles for clear cases, accurate vertical extinction profiles and dimensions for clouds, and understanding of the (solar) scattering properties of cirrus

Information content of ozone retrieval algorithms

The algorithms are characterized that were used for production processing by the major suppliers of ozone data to show quantitatively: how the retrieved profile is related to the actual profile (This characterizes the altitude range and vertical resolution of the data); the nature of systematic errors in the retrieved profiles, including their vertical structure and relation to uncertain instrumental parameters; how trends in the real ozone are reflected in trends in the retrieved ozone profile; and how trends in other quantities (both instrumental and atmospheric) might appear as trends in the ozone profile. No serious deficiencies were found in the algorithms used in generating the major available ozone data sets. As the measurements are all indirect in someway, and the retrieved profiles have different characteristics, data from different instruments are not directly comparable

Trends in aerosol abundances and distributions

The properties of aerosols that reside in the upper atmosphere are described. Special emphasis is given to the influence these aerosols have on ozone observation systems, mainly through radiative effects, and on ambient ozone concentrations, mainly through chemical effects. It has long been appreciated that stratospheric particles can interfere with the remote sensing of ozone distribution. The mechanism and magnitude of this interference are evaluated. Separate sections deal with the optical properties of upper atmospheric aerosols, long-term trends in stratospheric aerosols, perturbations of the stratospheric aerosol layer by volcanic eruptions, and estimates of the impacts that such particles have on remotely measured ozone concentrations. Another section is devoted to a discussion of the polar stratospheric clouds (PSC's). These unique clouds, recently discovered by satellite observation, are now thought to be intimately connected with the Antarctic ozone hole. Accordingly, interest in PSC's has grown considerably in recent years. This chapter describes what we know about the morphology, physical chemistry, and microphysics of PSC's

A Reassessment of the Effects of Luminal [Ca2+] on Inositol 1,4,5-Trisphosphate-induced Ca2+ Release from Internal Stores

Inositol 1,4,5-trisphosphate (InsP3)-induced Ca2+ release from intracellular stores displays complex kinetic behavior. While it well established that cytosolic [Ca2+] can modulate release by acting on the InsP3 receptor directly, the role of the filling state of internal Ca2+stores in modulating Ca2+ release remains unclear. Here we have reevaluated this topic using a technique that permits rapid and reversible changes in free [Ca2+] in internal stores of living intact cells without altering cytoplasmic [Ca2+], InsP3 receptors, or sarcoendoplasmic reticulum Ca2+ ATPases (SERCAs). N,N,N',N'-Tetrakis(2-pyridylmethyl)ethylene diamine (TPEN), a membrane-permeant, low affinity Ca2+ chelator was used to manipulate [Ca2+] in intracellular stores, while [Ca2+] changes within the store were monitored directly with the low-affinity Ca2+ indicator, mag-fura-2, in intact BHK-21 cells. 200 microM TPEN caused a rapid drop in luminal free [Ca2+] and significantly reduced the extent of the response to stimulation with 100 nm bradykinin, a calcium-mobilizing agonist. The same effect was observed when intact cells were pretreated with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid(acetoxymethyl ester) (BAPTA-AM) to buffer cytoplasmic [Ca2+] changes. Although inhibition of Ca2+ uptake using the SERCA inhibitor tBHQ permitted significantly larger release of Ca2+ from stores, TPEN still attenuated the release in the presence of tBHQ in BAPTA-AM-loaded cells. These results demonstrate that the filling state of stores modulates the magnitude of InsP3-induced Ca2+release by additional mechanism(s) that are independent of regulation by cytoplasmic [Ca2+] or effects on SERCA pumps

Calibration of radiation codes in climate models: Comparison of calculations with observations from the SPECtral Radiation Experiment (SPECTRE)

The primary goal of SPECTRE is to: close the loopholes by which longwave radiation models have eluded incisive comparisons with measurements. Likewise, the experimental approach was quite simple in concept, namely: accurately measure the zenith infrared radiance at high spectral resolution while simultaneously profiling the radiatively important atmospheric properties with conventional and remote sensing devices. The field phase of SPECTRE was carried out as part of FIRE Cirrus II, and detailed spectra of the down welling radiance were obtained by several interferometers simultaneous to the measurement of the optical properties of the atmosphere. We are now well along in the process of analyzing the data and calibrating radiation codes so that they may be used more effectively in climate related studies. The calibration is being done with models ranging from the most detailed (line-by-line) to the broad-band parameterizations used in climate models. This paper summarizes our progress in the calibration for clear-sky conditions. When this stage is completed, we will move on to the calibration for cirrus conditions

Optimal measurement of surface shortwave irradiance using current instrumentation -- the ARM experience

Shortwave (solar) measurements of surface irradiance for clear sky conditions disagree with a number of different models. Betts used the European Center for Medium-range Forecasts (ECMWF) shortwave model to calculate surface irradiance that were 5-10 percent higher than measurements. Wild used a different formulation of the ECMWF shortwave model, but found that the model overpredicted clear-sky shortwave and average of 3 percent. Ding and Wang used data from the Atmospheric Radiation Measurement (ARM) program and found that the GENESIS GCM shortwave model, likewise, overpredicted clear-sky irradiance by about 4 percent. To help resolve the measurement dilemma, reference instruments were deployed in April 1996 at the Southern Great Plains ARM site central facility very near the shortwave measurements. The rest of the paper describes the experiment undertaken to ascertain total horizontal shortwave irradiance at the surface, including a separation of the direct normal and diffuse horizontal components. Results and a discussion of same concludes the paper

On the correspondence between surface UV observations and TOMS determinations of surface UV: a potential method for quality evaluating world surface UV observations

A comparison of erythemally weighted surface UV irradiance observations with similar NASA TOMS surface UV determinations is described. Comparisons are made for two observation periods: the Robertson-Berger (R-B) meter period from 1974 to the late 1980s and the current period from 1996 to the present when more sophisticated UVB-1 instruments were used. The more primitive R-B meter observations that comprised the fi rst U.S. UV network are seen to drift downward with respect to those of the TOMS. While the UVB-1 observations did not appear to drift, a substantial bias is noted to exist between the TOMS and the UVB-1 stations collecting observations; the TOMS estimations tend to be higher. A portion of the bias may be attributed to errors in calibration, total ozone, and cosine response of the surface instrumentation. Unaccounted aerosol effects, although not considered to be large in the TOMS estimations, present another source of error. Comparisons are fi rst done for all sky conditions and then for clear sky conditions. The biases typically agree for all sky conditions within the uncertainties of the surface instruments' calibrations, liberally defi ned as ± 5%, implying that the TOMS cloud correction scheme performs reasonably well. Snow cover severely impacts the TOMS observations, giving considerably higher estimations. The biases for clear sky conditions ranged from 15% to 19% with no obvious drifts between the satellite and surface observations. The variation in the biases among stations is within the calibration uncertainties of the instruments, but the absolute bias is unexpectedly large. The standard deviations of the clear sky comparisons among all stations are steady at 4.8% ± 0.7%. A plot of the TOMS/UVB-1 ratio versus TOMS cloud refl ectivity observations is noisy, but qualitatively suggestive of a possible slight increase (~ 5% or greater) over the range of clear to overcast skies. The results from these comparisons is believed to be relevant to a WMO goal of uniformly assuring the quality of UV observations made by networks in many countries. The results for clear sky comparisons suggest that a satellite observing system such as TOMS, which provides global coverage daily, might partially serve as a fi rst-order check to quality assure UV observations being made by networks worldwide. Future research should concentrate on determining the causes of the large differences seen between the UVB-1 and TOMS and the range of uncertainties, using a larger array of stations