ALBERT

Description: Stratospheric aerosol and ozone profiles obtained simoultaneosly from the lidar station at the university of L'Aquila during the first 6 months following the eruption of Mount Pinatubo are compared with corresponding nearby Stratosperic Aerosol and Gas Experiment (SAGE) II profiles. The agreement between the two data stes is found to be reasonably good. The temporal change of aerosol profiles obtained by both technique showed the intrusion and growth of Pinatubo aerosols. In addition, ozone concntration profiles derivide from an empirical time-series model based on SAGE II ozone data obtained bifore the Pinatubo eruption are compared with measured profiles. Good agreement is shown in the 1991 profiles, but ozone concentration measured in January 1992 were reduced relative ti time-series model estimates. Possible reasons for the diffrences between measured and model-based ozone profiles are discussed.

Description: NASA ING

Description: Published

Description: 1881-1884

Description: 1.8. Osservazioni di geofisica ambientale

Description: JCR Journal

Description: open

Description: The long-term evolution of upper stratospheric ozone has been recorded by lidars and microwave radiometers within the ground-based Network for the Detection of Stratospheric Change (NDSC), and by the space-borne Solar Backscatter Ultra-Violet instruments (SBUV), Stratospheric Aerosol and Gas Experiment (SAGE), and Halogen Occultation Experiment (HALOE). Climatological mean differences between these instruments are typically smaller than 5% between 25 and 50 km. Ozone anomaly time series from all instruments, averaged from 35 to 45 km altitude, track each other very well and typically agree within 3 to 5%. SBUV seems to have a slight positive drift against the other instruments. The corresponding 1979 to 1999 period from a transient simulation by the fully coupled MAECHAM4-CHEM chemistry climate model reproduces many features of the observed anomalies. However, in the upper stratosphere the model shows too low ozone values and too negative ozone trends, probably due to an underestimation of methane and a consequent overestimation of ClO. The combination of all observational data sets provides a very consistent picture, with a long-term stability of 2% or better. Upper stratospheric ozone shows three main features: (1) a decline by 10 to 15% since 1980, due to chemical destruction by chlorine; (2) two to three year fluctuations by 5 to 10%, due to the Quasi-Biennial Oscillation (QBO); (3) an 11-year oscillation by about 5%, due to the 11-year solar cycle. The 1979 to 1997 ozone trends are larger at the southern mid-latitude station Lauder (45 S), reaching 8%/decade, compared to only about 6%/decade at Table Mountain (35 N), Haute Provence/Bordeaux ( 45 N), and Hohenpeissenberg/Bern( 47 N). At Lauder, Hawaii (20 N), Table Mountain, and Haute Provence, ozone residuals after subtraction of QBO- and solar cycle effects have levelled off in recent years, or are even increasing. Assuming a turning point in January 1997, the change of trend is largest at southern mid-latitude Lauder, +11%/decade, compared to +7%/decade at northern mid-latitudes. This points to a beginning recovery of upper stratospheric ozone. However, chlorine levels are still very high and ozone will remain vulnerable. At this point the most northerly mid-latitude station, Hohenpeissenberg/Bern differs from the other stations, and shows much less clear evidence for a beginning recovery, with a change of trend in 1997 by only +3%/decade. In fact, record low upper stratospheric ozone values were observed at Hohenpeissenberg/Bern, and to a lesser degree at Table Mountain and Haute Provence, in the winters 2003/2004 and 2004/2005.

Description: Published

Description: D10308

Description: open

Description: This paper presents extensive {bias determination} analyses of ozone observations from the Atmospheric Chemistry Experiment (ACE) satellite instruments: the ACE Fourier Transform Spectrometer (ACE-FTS) and the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) instrument. Here we compare the latest ozone data products from ACE-FTS and ACE-MAESTRO with coincident observations from nearly 20 satellite-borne, airborne, balloon-borne and ground-based instruments, by analysing volume mixing ratio profiles and partial column densities. The ACE-FTS version 2.2 Ozone Update product reports more ozone than most correlative measurements from the upper troposphere to the lower mesosphere. At altitude levels from 16 to 44 km, the average values of the mean relative differences are nearly all within +1 to +8%. At higher altitudes (4560 km), the ACE-FTS ozone amounts are significantly larger than those of the comparison instruments, with mean relative differences of up to +40% (about +20% on average). For the ACE-MAESTRO version 1.2 ozone data product, mean relative differences are within ±10% (average values within ±6%) between 18 and 40 km for both the sunrise and sunset measurements. At higher altitudes (~3555 km), systematic biases of opposite sign are found between the ACE-MAESTRO sunrise and sunset observations. While ozone amounts derived from the ACE-MAESTRO sunrise occultation data are often smaller than the coincident observations (with mean relative differences down to −10%), the sunset occultation profiles for ACE-MAESTRO show results that are qualitatively similar to ACE-FTS, indicating a large positive bias (mean relative differences within +10 to +30%) in the 4555 km altitude range. In contrast, there is no significant systematic difference in bias found for the ACE-FTS sunrise and sunset measurements.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 1983

Description: Brook trout (Salvelinus fontinalis) raised from eggs under two photoperiod and two feeding regimes were tested for physiological changes preparatory for transition from freshwater to seawater. Size, age, growth rate, photoperiod, and diel rhythms were examined for possible influences on plasma osmolarity, [Na+], [Cl-], [K+], [Mg2+], thyroxine concentration, hematocrit, and gill Na+,K+-ATPase activity of brook trout in freshwater. Significant diel cycles were found in plasma osmolarity, (Na+] and thyroxine concentration. Significant size and/or age related changes occurred for plasma osmolarity, [Na+], [K+] and hematocrit, but could explain little of their total variation (0.02 〈 r2 〈0.18). A sexually dimorphic response to photoperiod was observed in hematocrit for both mature and immature fish, with hematocrit of mature females declining in autumn and hematocrit of immature males increasing in autumn. Gill Na+,K+-ATPase activity did not respond to photoperiod or feeding treatment and showed no change with size or age. Plasma thyroxine levels responded to feeding and photoperiod treatment. There was a significant correlation between the percent mean difference in plasma thyroxine and the mean difference in growth rate between high and low feed fish (r2 = 0.51), suggesting a relationship between thyroxine and growth. In 11 experiments over 1.5 yrs, brook trout were gradually exposed to 32 ppt seawater for 20 d to investigate the ontogeny of salinity tolerance. A single experiment examined daily changes in plasma osmolarity, [Na+], [Cl-], [K+], [Mg2+], thyroxine, hematocrit and gill Na+,K+-ATPase during adaptation to 10 ppt, 20 ppt and 32 ppt. Size was the primary determinant of seawater survival (r2 = 0.77); the effect of size on seawater survival slowed after fish reached a fork length of 14 cm. The effect of age on seawater. survival (r2 = 0.65) was through its covariance with size. Photoperiod affected seawater survival only through its influence on the timing of male maturation, which decreased salinity tolerance. Hypoosmoregulation of plasma osmolarity, [Na+], [Cl-], [K+], [Mg2+] and hematocrit increased linearly with size over the entire range of sizes (6-32 cm). Gill Na+,K+-ATPase activity after 20 d in seawater decreased with increasing size of brook trout, possibly reflecting decreased demand for active ion transport in larger fish. Plasma thyroxine concentrations generally declined in seawater, but no definitive role of this hormone in seawater adaptation was found. Size dependent survival and osmoregulatory ability of brook trout is compared to other salmonids and a conceptual model is developed. Decreased salinity tolerance and hypoosmoregulatory ability was found in mature male brook trout and was not found in females or immature males. Lowered salinity tolerance of adult males becomes acute during autumn photoperiod when normal spawning occurs. Plasma [Cl-], [Mg2+], osmolarity and hematocrit are significantly higher in mature males after transfer to seawater, relative to mature females. It is postulated that reduced adult male hypoosmoregulatory ability explains skewed sex ratios in anadromous populations, limits the extent of anadromy, and was a significant phase in the evolution of extended salmonid migration. Anadromous brook trout of Riviere a la Truite, Quebec, were examined for physiological changes associated with salmonid smoltification, and compared to non-anadromous brook trout of the Matamek River. There were no significant differences in plasma thyroxine concentration, gill Na+,K+-ATPase activity, hematocrit or osmoregulatory ability of anadromous and non-anadromous brook trout. Moisture content was significantly different between fish from the two river systems, but had the same pattern of declining moisture content as summer progressed. Silver coloration of brook trout in Riviere a la Truite was significantly associated with larger fish and higher gill Na+,K+-ATPase activity, but not with changes in plasma thyroxine, moisture content, hematocrit or condition factor. Silver coloration was absent in Matamek River brook trout. Brook trout at high salinity estuarine sites had significantly greater gill Na+,K+-ATPase activity and hypoosmoregulatory ability than brook trout at low salinity sites. Atlantic salmon (Salmo salar) in high salinity estuarine sites had significantly higher plasma thyroxine and gill Na+,K+-ATPase activity than brook trout. The results indicate that smoltification is relatively undeveloped in brook trout and that estuarine residence is important in salinity adaptation and eventual seaward migration.

Description: I gratefully acknowledge the financial support of the W.H.O.I. education office, the Tai Ping foundation and the U.S. Department of Commerce Sea Grant Program.