In this research, one-dimensional stratiform a novel dual-model system, cold cloud model （1DSC） coupled to Weather Research and Forecast （WRF） model （WRF-1DSC for short）, was employed to investigate the effects ...In this research, one-dimensional stratiform a novel dual-model system, cold cloud model （1DSC） coupled to Weather Research and Forecast （WRF） model （WRF-1DSC for short）, was employed to investigate the effects of cloud seeding by silver iodide （AgI） on rain enhancement. Driven by changing environmental conditions extracted from the WRF model, WRF-1DSC could be used to assess the cloud seeding effects quantitatively. The employment of WRF- 1DSC, in place of a one-dimen- sional two-moment cloud seeding model applied to a three-dimensional mesoscale cloud-resolving model, was found to result in massive reduction of computational resources. Numerical experiments with WRF-1DSC were conducted for a real stratiform precipitation event ob- served on 4-5 July 2004, in Northeast China. A good agreement between the observed and modeled cloud system ensured the ability of WRF-1DSC to simulate the observed precipitation process efficiently. Sensitivity tests were performed with different seeding times, locations, and amounts. Experimental results showed that the optimum seeding effect （defined as the percentage of rain enhancement or rain enhancement rate） could be achieved through proper seeding at locations of maximum cloud water content when the updraft was strong. The optimum seeding effect was found to increase by 5.61% when the cloud was seeded at 5.5 km above ground level around 2300 UTC 4 July 2004, with the maximum AgI mixing ratio （As） equaling 15 ng kg-1. On the other hand, for an overseeded cloud, a significant reduction occurred in the accumulated precipitation （-12.42%） as Xs reached 100 ng kg^-1. This study demonstrates the potential of WRF- 1DSC in determining the optimal AgI seeding strategy in practical operations of precipitation enhancement.展开更多
Seed dispersal by exotic mammals exemplifies mutualistic interactions that can modify the habitat by facilitating the establishment of certain species. We examined the potential for endozoochoric dispersal of exotic p...Seed dispersal by exotic mammals exemplifies mutualistic interactions that can modify the habitat by facilitating the establishment of certain species. We examined the potential for endozoochoric dispersal of exotic plants by Callosciurus erythraeus introduced in the Pampas Region of Argentina. We identified and characterized entire and damaged seeds found in squirrel faeces and evaluated the germination capacity and viability of entire seeds in laboratory assays. We collected 120 samples of squirrel faeces that contained 883 pellets in seasonal surveys conducted between July 2011 and June 2012 at 3 study sites within the main invasion focus of C. erythraeus in Argentina. We found 226 entire seeds in 21% of the samples belonging to 4 species of exotic trees and shrubs. Germination in laboratory assays was recorded for Morus alba and Casuarina sp.; however, germination percentage and rate was higher for seeds obtained from the fruits than for seeds obtained from the faeces. The largest size of entire seeds found in the faeces was 4.2 ~ 4.0 ram, whereas the damaged seeds had at least 1 dimension ≥ 4.7 ram. Our results indi- cated that C. erythraeus can disperse viable seeds of at least 2 species of exotic trees. C. erythraeus predated seeds of other naturalized species in the region. The morphometric description suggested a restriction on the maximum size for the passage of entire seeds through the digestive tract of squirrels, which provides useful information to predict its role as a potential disperser or predator of other species in other invaded communities.展开更多
基金supported by the Knowledge Innovation Program of Chinese Academy of Sciences (Grant No. KZCX2-EW-203)the National Basic Research Program of China (Grant No.2013CB430105)the National Department Public Benefit Research Foundation (Grant No.GYHY201006031)
文摘In this research, one-dimensional stratiform a novel dual-model system, cold cloud model （1DSC） coupled to Weather Research and Forecast （WRF） model （WRF-1DSC for short）, was employed to investigate the effects of cloud seeding by silver iodide （AgI） on rain enhancement. Driven by changing environmental conditions extracted from the WRF model, WRF-1DSC could be used to assess the cloud seeding effects quantitatively. The employment of WRF- 1DSC, in place of a one-dimen- sional two-moment cloud seeding model applied to a three-dimensional mesoscale cloud-resolving model, was found to result in massive reduction of computational resources. Numerical experiments with WRF-1DSC were conducted for a real stratiform precipitation event ob- served on 4-5 July 2004, in Northeast China. A good agreement between the observed and modeled cloud system ensured the ability of WRF-1DSC to simulate the observed precipitation process efficiently. Sensitivity tests were performed with different seeding times, locations, and amounts. Experimental results showed that the optimum seeding effect （defined as the percentage of rain enhancement or rain enhancement rate） could be achieved through proper seeding at locations of maximum cloud water content when the updraft was strong. The optimum seeding effect was found to increase by 5.61% when the cloud was seeded at 5.5 km above ground level around 2300 UTC 4 July 2004, with the maximum AgI mixing ratio （As） equaling 15 ng kg-1. On the other hand, for an overseeded cloud, a significant reduction occurred in the accumulated precipitation （-12.42%） as Xs reached 100 ng kg^-1. This study demonstrates the potential of WRF- 1DSC in determining the optimal AgI seeding strategy in practical operations of precipitation enhancement.
文摘Seed dispersal by exotic mammals exemplifies mutualistic interactions that can modify the habitat by facilitating the establishment of certain species. We examined the potential for endozoochoric dispersal of exotic plants by Callosciurus erythraeus introduced in the Pampas Region of Argentina. We identified and characterized entire and damaged seeds found in squirrel faeces and evaluated the germination capacity and viability of entire seeds in laboratory assays. We collected 120 samples of squirrel faeces that contained 883 pellets in seasonal surveys conducted between July 2011 and June 2012 at 3 study sites within the main invasion focus of C. erythraeus in Argentina. We found 226 entire seeds in 21% of the samples belonging to 4 species of exotic trees and shrubs. Germination in laboratory assays was recorded for Morus alba and Casuarina sp.; however, germination percentage and rate was higher for seeds obtained from the fruits than for seeds obtained from the faeces. The largest size of entire seeds found in the faeces was 4.2 ~ 4.0 ram, whereas the damaged seeds had at least 1 dimension ≥ 4.7 ram. Our results indi- cated that C. erythraeus can disperse viable seeds of at least 2 species of exotic trees. C. erythraeus predated seeds of other naturalized species in the region. The morphometric description suggested a restriction on the maximum size for the passage of entire seeds through the digestive tract of squirrels, which provides useful information to predict its role as a potential disperser or predator of other species in other invaded communities.
