Cloud effects on evaporation at a sub-tropical site

Water usage impacts the management of our water resources. It is believed that accurate information on the hydrological cycle disseminated to the public, will considerably alter consumer usage behaviour. Evapotranspiration is one of the most variable and sensitive of the hydrological components and it is imperative that we fully understand what environmental factors directly or indirectly affect evapotranspiration. The objective of this study was to confirm the indirect affect of clouds on evaporation by examining how clouds affect variables used by the Penman-Monteith equation. As expected, during the day or night it was found that clouds had a negative correlation with solar radiation and temperature, and a positive correlation with humidity all at the earth's surface. There was no significant relationship between wind speed and clouds except during the night. Correlation coefficients, with respect to cloud, for temperature and humidity varied only slightly from day to night, but interestingly wind speed showed a significant change from 0.077 to 0.264. These findings may suggest that there are some occasions when 'water-wise' activities, for example watering the garden at night to decrease potential evaporation, may not be as beneficial as previously thought

Comparison of biologically damaging spectral solar ultraviolet radiation at a southern hemisphere sub-tropical site

The first data set of a complete year of biologically damaging spectral UV at a sub-tropical latitude in the SH has been presented. The new data provides a baseline data set against which comparisons can be made in the future to establish if there have been any long term trends in the biologically damaging UV. The general shape of the variation of the daily biologically damaging exposures through the year depends on the relative response of the various action spectra at the different wavelengths. The ratio of the daily erythemal to actinic exposures drops by approximately 20 to 25% from winter to summer. The ratio of the erythemal to DNA exposures drops by approximately 50% over the same period. In contrast, the ratio of the erythemal to plant damage exposures is higher in summer compared to winter. This is due to the changes in the relative proportion of UVA to UVB wavebands and relative responses of the different action spectra. The relative changes for the different action spectra show that the erythemal action spectrum cannot be used as a proxy for other biologically damaging responses

Comparisons of corrected daily-integrated erythermal UVR data from the U.S. EPA/UGA network of Brewer spectroradiometers with model and TOMS-inferred data

A network of 21 Brewer spectroradiometers, owned by the U.S. Environmental Protection Agency (U.S. EPA) and operated by the University of Georgia (UGA), is measuring ultraviolet (UV) spectral irradiances throughout the United States. Corrections to the raw data for 4 of the 21 Brewers have now been implemented. These corrections include (1) the stray light rejection, (2) the cosine errors associated with the full sky diffuser, (3) the temperature dependence of the response of the instruments, and (4) the temporal variation in the instrument response due to changes in the optical characteristics of the instruments. While for many sites the total corrections amount to less than 10%, for certain sites they are much larger, in some cases amounting to more than 25%. It is estimated that application of these corrections brings the uncertainty of the absolute irradiance of individual spectral scans to approximately 6% for all known major sources of error for all solar zenith angles. A comparison is presented of corrected daily integrated erythemal UV doses on clear days to both model and Total Ozone Mapping Spectrometer (TOMS) UV values. The TOMS retrievals show a positive bias with respect to the measured values that falls in the range of 12.5–1.4% with an average value of 5% for the four sites studied

Optical properties of poly (2,6-dimethyl-1,4-phenylene oxide) film and its potential for a long-term solar ultraviolet dosimeter

The optical properties of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) film have been characterized in order to develop an alternative method for UV dosimetry with a focus on long-term human exposure measurements. The dynamic range of PPO film was found to extend to 2 MJ m(-2) of broadband UV exposure independently of film thickness, providing an exposure range of roughly four summer days at subtropical latitudes. The sensitivity of the film to UV exposure was positively related to film thickness in the 20-40 microm range. Films of 40 microm thickness proved to be the most suitable for long-term human UV exposure measurements. The temperature independence of the response of 40 microm PPO film was established from 1.5 degrees C to 50 degrees C within a dosimeter response uncertainty of 6.5%. Dose-rate independence was also demonstrated within 8% of the mean dosimeter response. The spectral response approximates the CIE erythemal action spectrum between 300 and 340 nm, with a peak response at 305 nm. A large deviation from this action spectrum was observed at shorter wavelengths. Investigation of the angular response in both the azimuth and altitude planes showed a cosine error of less than 6.2% between 0 degrees and 40 degrees, and did not exceed 13.3% at any angle greater than 40 degrees. These results indicate that PPO film satisfies the requirements for use as a UV dosimeter, and may be employed in long-term human exposure measurements

Optical Properties of Poly(2,6-Dimethyl 1,4 Phenylene Oxide) and it's potential for a long term dosimeter

The optical properties of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) film have been characterized in order to develop an alternative method for UV dosimetry with a focus on long-term human exposure measurements. The dynamic range of PPO film was found to extend to 2 MJ m(-2) of broadband UV exposure independently of film thickness, providing an exposure range of roughly four summer days at subtropical latitudes. The sensitivity of the film to UV exposure was positively related to film thickness in the 20-40 microm range. Films of 40 microm thickness proved to be the most suitable for long-term human UV exposure measurements. The temperature independence of the response of 40 microm PPO film was established from 1.5 degrees C to 50 degrees C within a dosimeter response uncertainty of 6.5%. Dose-rate independence was also demonstrated within 8% of the mean dosimeter response. The spectral response approximates the CIE erythemal action spectrum between 300 and 340 nm, with a peak response at 305 nm. A large deviation from this action spectrum was observed at shorter wavelengths. Investigation of the angular response in both the azimuth and altitude planes showed a cosine error of less than 6.2% between 0 degrees and 40 degrees, and did not exceed 13.3% at any angle greater than 40 degrees. These results indicate that PPO film satisfies the requirements for use as a UV dosimeter, and may be employed in long-term human exposure measurements

Comparison of Brewer spectrophotometer ultraviolet data from similar latitudes in the northern and southern hemisphere

This paper presents UV data recorded over 12 months in 2000/2001 at a southern hemisphere (Toowoomba) and similar latitude northern hemisphere (BigBend and Everglades) sites using Brewer spectrophotometers. The peak daily erythemally weighted UV (DUV) at the Toowoomba site was 8.8% and 25% higher compared to that at the BigBend and Everglades sites, respectively. The Everglades site exposures are lower than the BigBend site exposures in summer and spring. This may be due to the higher cloud cover for the Everglades site. The summer DUV values between Toowoomba and BigBend are similar. In spring, the average DUV value is the greatest at BigBend compared to the other two sites. Results indicate that variability between the measurement sites is due to varying cloud and ozone, and possibly due to aerosol and airmass differences of each region. Of these different site-specific local atmospheric conditions, cloud was the main contributor to the differences in UV between the sites

Fusarium graminearum and Fusarium pseudograminearum caused the 2010 head blight epidemics in Australia

Wheat crops in southeast Queensland (Qld) and northern New South Wales (NSW) were infected with fusarium head blight (FHB)-like symptoms during the 201011 wheat growing season. Wheat crops in this region were surveyed at soft dough or early maturity stage to determine the distribution, severity, aetiology and toxigenicity of FHB. FHB was widespread on bread wheat and durum, and Fusarium graminearum and/or F.pseudograminearum were diagnosed from 42 of the 44 sites using species-specific PCR primers directly on spikelets or from monoconidial cultures obtained from spikelets. Stem base browning due to crown rot (CR) was also evident in some samples from both states. The overall FHB and CR severity was higher for NSW than Qld. Deoxynivalenol (DON) concentration of immature grains was more than 1 mg kg-1 in samples from 11 Qld and 14 NSW sites, but only 13 of 498 mature grain samples sourced from the affected areas had more than 1 mg kg-1 DON. DON concentration in straw also exceeded 1 mg kg-1 in eight Qld and all but one NSW sites but this was not linked to DON concentration of immature grains. The proportion of spikelets with positive diagnosis for F.graminearum and/or F.pseudograminearum and weather-related factors influenced DON levels in immature grains. The average monthly rainfall for AugustNovember during crop anthesis and maturation exceeded the long-term monthly average by 10150%. Weather played a critical role in FHB epidemics for Qld sites but this was not apparent for the NSW sites, as weather was generally favourable at all sites

Fusarium graminearum and Fusarium pseudograminearum caused the 2010 head blight epidemics in Australia

Wheat crops in southeast Queensland (Qld) and northern New South Wales (NSW) were infected with fusarium head blight (FHB)-like symptoms during the 2010-11 wheat growing season. Wheat crops in this region were surveyed at soft dough or early maturity stage to determine the distribution, severity, aetiology and toxigenicity of FHB. FHB was widespread on bread wheat and durum, and Fusarium graminearum and/or F. pseudograminearum were diagnosed from 42 of the 44 sites using species-specific PCR primers directly on spikelets or from monoconidial cultures obtained from spikelets. Stem base browning due to crown rot (CR) was also evident in some samples from both states. The overall FHB and CR severity was higher for NSW than Qld. Deoxynivalenol (DON) concentration of immature grains was more than 1mgkg-1 in samples from 11 Qld and 14 NSW sites, but only 13 of 498 mature grain samples sourced from the affected areas had more than 1mgkg-1 DON. DON concentration in straw also exceeded 1mgkg-1 in eight Qld and all but one NSW sites but this was not linked to DON concentration of immature grains. The proportion of spikelets with positive diagnosis for F. graminearum and/or F. pseudograminearum and weather-related factors influenced DON levels in immature grains. The average monthly rainfall for August-November during crop anthesis and maturation exceeded the long-term monthly average by 10-150%. Weather played a critical role in FHB epidemics for Qld sites but this was not apparent for the NSW sites, as weather was generally favourable at all sites