The European Space Agency Climate Change Initiative Land Cover data (ESA CCI-LC, from 1992 to 2015) is introduced to the National Center for Atmospheric Research Community Earth System Model version 1.2.1 (NCAR CESM1.2.1). In comparison with the original land surface data in the Community Land Model version 4 (ORG), the new data features notable land use and land cover change (LULCC) with increased forests over northeastern Asia and Alaska by decreasing shrublands and grasslands. Overestimated bare land cover over the Tibetan Plateau (TP) and the Rocky Mountains in the ORG are corrected with the replacements by grasslands and shrublands respectively in the new data. The model simulation results show that with the introduction of the ESA CCI-LC, the simulated surface albedo, surface net radiation flux, sensible and latent heat fluxes are relatively improved over the regions where significant LULCC exists, such as northeastern Asia, Alaska, the TP, and Australia. Surface air temperature, precipitation, and atmospheric circulation are improved in boreal winter but degraded in summer. The winter warming over northeastern Asia results from increased longwave downwelling flux and adiabatic heating while the notable winter cooling over Alaska is attributed to strong cold advection followed by reduced longwave downwelling flux. LULCC alters precipitation by influencing water vapor content. In winter, LULCC affects atmospheric circulation via modulating baroclinicity while in summer, it influences land-sea thermal contrast, thus affecting the intensity of East Asian summer monsoon. LULCC also alters the simulated dust burden.
A modified procedure has been proposed for the colorimetric determination of dissolved oxygen in seawater to improve its precision and accuracy. When a pickled sample is acidified, iodine liberated in the iodometric reaction is measured by direct spectrophotometry at 456 nm. Loss of molecular iodine by volatilization is eliminated by transferring the sample to a flow cuvette without contact with air. The method was calibrated for oxygen by spiking known amounts of potassium iodate. Precision was found at better than 0.2% r.s.d. (full scale). Evaluation of accuracy was made by comparison with calculated oxygen solubilities, which shows a relative bias of no more than 0.5% for oxic waters. The analytical throughput was much faster than that of the standard titration procedure. 相似文献
Zooplankton abundance and euphausiid community composition were sampled seasonally (spring, summer, fall) within Monterey Bay, California, between 1997 and 1999. Measurements of sea surface temperature (SST), mixed layer depth, and upwelling indices provided concurrent data on physical oceanographic parameters. Both total zooplankton and krill abundance dramatically declined in the summer of 1997 coincident with a rapid increase in SST and mixed layer depth. Changes in euphausiid community composition occurred in concert with the decline in overall abundance. The relative abundance of the southern neritic Nyctiphanes simplex increased from August to November in 1997, the abundance of cold temperate Euphausia pacifica decreased significantly, and that of the northern neritic Thysanoessa spinifera declined dramatically. The sudden appearance of an adult cohort of N. simplex in July 1997 suggests that rapid poleward flow characteristic of coastally trapped Kelvin waves occurred between June and July of 1997. The persistent presence of warm temperate and subtropical taxa in samples collected between August 1997 and October 1998 indicates that this poleward flow continued in 1998. Zooplankton abundance, euphausiid community composition, and physical oceanographic parameters gradually returned to a more typical upwelling-dominated state in the spring and summer of 1998. E. pacifica and T. spinifera abundances gradually increased during the summer and fall of 1998, while N. simplex abundance abruptly declined in the spring of 1998. However, this recovery was confined to a narrow coastal band as a result of the onshore movement of the oceanic waters of the California Current. This was reflected by higher than normal numbers of the oceanic Nematoscelis difficilis within samples collected during the spring and summer of 1998. By the spring and summer of 1999, both zooplankton and euphausiid abundance had increased to the highest levels recorded during the 3-year study. Both E. pacifica and T. spinifera abundance increased relative to 1998 while N. simplex was completely absent in all samples. These changes reflected the cooler, highly productive environmental conditions associated with the 1998/1999 La Niña. 相似文献
