Diurnal variability

Further, the above day-to-day variabilities can be compared with the observed diurnal variability of around 15 D.U., or 20%, in total ozone to argue that tropospheric ozone variations are of sufficient magnitude to potentially be able to account for a diurnal variation in total ozone. 

Coffey, M.T., W.G. Mankin and A Golden (1981) Simultaneous spectroscopic determination of the latitudinal, seasonal, and diurnal variability of NiO, NO, NO] and HNOi- Journal Geophysical Research 86 7331-7341. 

Kevseroglu, K., Crak, C. and Ozyazc, C. (2003) A study on ontogenetic and diurnal variability of laurel (Laurus nobilis L.) leaves. Turkish journal of Field Crops 8(1), 29-32. 

Peak flow measurement of peak expiratory flow rate (PEFR) on waking, before bed, before and after bronchodilator medication is useful to assess the extent of airflow limitation and the characteristic of the disease in terms of reversibility. There is some evidence of diurnal variability. PEFR is also useful in assessing the disease progression longer term and the response to therapy. Patients are advised to keep an asthma diary and record regularly the peak flows to ascertain their diurnal pattern. 

The analysis of the diurnal cycle at the urban Vaerlose station (55.77°N, 12.33°E) located in central Copenhagen showed that the diurnal variability of the wind direction was modelled in all runs with practically no differences between the control and modified runs. A similar situation was observed for the suburban Jegersborg station (55.77°N, 12.53°E) and the Kastrup station (55.62°N, 12.65°E) located not far from the seashore (so that urban effects were minimised during the studied day due to eastern winds). 

Fig. 1 shows the diurnal changes in 3-h averaged concentrations of 1-NP and 2-NTP and in 1-h averaged concentration of CO during May 12-14. The diurnal variation of the concentration of 1-NP was similar to that of CO, while the concentration of 2-NTP showed slightly different pattern in the diurnal variability. 

The most frequently used method to measure lung function objectively at and away from work is performance of serial peak expiratory flow rates (PEFR) over periods of 2 to 3 weeks (Bernstein, DI, 1993). The subject measures and records his/her PEFR every 1 to 2 hours while at work and at home and at the same times documents symptoms and medication usage. A diurnal variability of greater than 20 per cent at work with subsequent improvement or normalization at home is considered an abnormal response consistent with OA. Ideally, PEFRs should be monitored for 2 weeks at work and during a 1 to 2 week period away from work. One of the shortcomings of these measurements is that patients can falsify or inaccurately record their readings (Bernstein, DI, 1993). 

Galasyn, J. F.. Tschudy, K. L., and Huebert, B. J., Seasonal and diurnal variability of nitric acid vapor and ionic aerosol species in the remote free troposphere at Mauna Loa, Hawaii. J. Geophys. Res. 92, 3105 (1987). 

Dissolved CO exhibits diurnal variability in the surface ocean in response to its photolytic source, although this is also indicative of a strong sink term. The decline in the surface mixed-layer CO concentration in the dark results from a combination of CO oxidation, vertical mixing, and air-sea exchange. As the equilibration time between atmosphere and oceanic surface mixed layer is on the order of a month, this suggests that the former two processes dominate. Superimposed upon the diurnal cycle of CO in the surface ocean are spatial and seasonal gradients that result from the interaction of photoproduction and the sink processes. Below the euphotic zone CO is uniformly low throughout the intermediate water column. 

Spencer, R.G.M., Pellerin, B.A., Bergamaschi, B.A., Downing, B.D., Kraus, T.E.C., Smart, D.R., Dahlgren, R.A., and Hemes, PJ. (2007a). Diurnal variability in riverine dissolved organic matter composition determined by in sim optical measurement in the San Joaquin River (California, USA). Hydrol. Process., 21, 3181-3189. 

The amount of solar radiation that reaches any point on the ground is extremely variable. As it passes through the atmosphere, 25 to 50 percent of the incident energy is lost due to reflection, scattering nr absorption. Even on a cloud-free day about 30 percent is lost, and only 70 percent of 1,367 W/nf, or 960 W/m, is available at the earth s surface. One must also take into account the earth s rotation and the resultant day-night (diurnal) cycle. If the sun shines 50 percent of the time (twelve hours per day, every day) on a one square meter surface, that surface receives no more than (960 W/m ) X (12 hours/day) X (365 days/year) =... 

Cycles established as statistically real are the familiar annual and diurnal radiation/temperature cycles, a quasibiennial (about every 2 years) fluctuation in various climatic elements, and the interannual variability of June rainfall in northern India. The first merely means that winters are cooler than summers and nights are cooler than days. Examples of the second cycle include Midwestern rainfall, a lengthy temperature record from central England, and winds over the western Paciflc and eastern Indian Ocean. According to Campbell et al (19), the third cycle may be a response to the monthly solar-lunar tide and its influence on the monsoon circulation. 

Some physiological variables influence the measurement of fibrinolytic activators and inhibitors. For instance, both t-PA and plasminogen activator inhibitor 1 (PAI-1) levels in plasma are subject to diurnal variation in a 12-hour period. Even in samples taken at the same time of day the coefficient of variation (CV) of measured PAI levels range from 8 to 143% To account for this diurnal variation, blood samples spaced over several time intervals during a 24-hour period should be collected. Consumption of alcohol induces the PAI level in plasma. The half-life of t-PA is 360 seconds. However, in the presence of trauma or inflammation, when the PAI-1 level is expected to be elevated 10-fold, the half-life of t-PA is reduced to 36 seconds (114). 

HPLC has been further employed for the mesurement of the spatial and temporal variabilities of phytoplankton community structure [287], for the investigation of the seasonal change of algal pigments [288], for the study of the seasonal and interannual change of phytoplankton communities [289] and for the assessment of the tidal and diurnal periodicities of pigment profiles [290],... 

At sea level, Pj is approximately 1 atm, but exhibits some temporal and spatial variability. For example, the annual mean pressure in the northern hemisphere is 0.969 atm and in the southern hemisphere is 0.974 atm, with monthly averages varying by as much as 0.0001 atm, i.e., about 1 mbar (1 atm = 1013.25 mbar). These fluctuations are caused by spatial and temporal variations in atmospheric temperature and water vapor content associated with weather, and seasonal and longer-term climate shifts. Pj is also affected by diurnal atmospheric tides, and it decreases with increasing altitude above sea level. Some gases, such CO2 and O2, exhibit seasonal variability that is caused in part by seasonal variability in plant and animal activity (see Figures 25.4 and 6.7). 

Second, in bi- and termolecular reactions, tl/2 and r depend on the concentration of other reactants this is particularly important when interpreting atmospheric lifetimes. For example, as discussed earlier, reaction with the OH radical is a major fate of most organics during daylight in both the clean and polluted troposphere. However, the actual concentrations of OH at various geographical locations and under a variety of conditions are highly variable for example, its concentration varies diurnally since it is produced primarily by photochemical processes. Finally, the concentration of OH varies with altitude as well, so the lifetime will depend on where in the troposphere the reaction occurs. 

---