Multiwavelength Comparison of Modeled and Measured Remote Tropospheric Aerosol Backscatter Over Pacific Ocean

Aerosol concentrations and size distributions in the middle and upper troposphere over the remote Pacific Ocean were measured with a forward scattering spectrometer probe (FSSP) on the NASA DC-8 aircraft during NASA's Global Backscatter Experiment (GLOBE) in May-June 1990. The FSSP size channels were recalibrated based on refractive index estimates from flight-level aerosol volatility measurements with a collocated laser optical particle counter (LOPC). The recalibrated FSSP size distributions were averaged over 100-s intervals, fitted with lo-normal distributions and used to calculate aerosol backscatter coefficients at selected wavelengths. The FSSP-derived backscatter estimates were averaged over 300-s intervals to reduce large random fluctuations. The smoothed FSSP aerosol backscatter coefficients were then compared with LOPC-derived backscatter values and with backscatter measured at or near flight level from four lidar systems operating at 0.53, 1.06, 9.11, 9.25, and 10.59 micrometers. Agreement between FSSP-derived and lidar-measured backscatter was generally best at flight level in homogeneous aerosol fields and at high backscatter values. FSSP data often underestimated low backscatter values especially at the longer wavelengths due to poor counting statistics for larger particles (greater than 0.8 micrometers diameter) that usually dominate aerosol backscatter at these wavelengths. FSSP data also underestimated backscatter at shorter wavelengths when particles smaller than the FSSP lower cutoff diameter (0.35 micrometers) made significant contributions to the total backscatter

Agricultural change and paddock tree loss: implications for an endangered subspecies of red-tailed black-cockatoo

Natural senescence and the intensification of agricultural practices are contributing to the continuing loss of paddock trees from agricultural regions in Australia. This is of particular concern in the southern Wimmera of western Victoria, where much of the endangered Buloke (Allocasuarina luehmannii) Woodland vegetation community is represented only by relict Buloke trees in paddocks, which also constitute critical feeding habitat for the endangered south-eastern subspecies of the Red-tailed Black-Cockatoo (Calyptorhynchus banksii graptogyne). I investigated the rate and correlates of loss of scattered Buloke trees in paddocks by examining aerial photographs taken over a period of 15 years in a region undergoing agricultural intensification. Tree loss over the period was measured using aerial photographs of five localities, covering a total of 7850 ha of agricultural land in the southern Wimmera. The average rate of loss (± 1 SE) was 25.8% ± 6.4% over the 15 years, or 1.7% per annum. The rate of tree loss was higher in areas under cultivation (32.5%) than areas under pasture (20.6%). A disproportionate number of trees was lost from locations where centre pivot irrigation systems were installed. Because of the slow growth rate of Buloke trees, revegetation efforts and offset planting are unlikely to compensate for losses of Red-tailed Black-Cockatoo habitat for approximately 100 years