Simulating the convective precipitation diurnal cycle in North America's current and future climate
CLIMATE DYNAMICS
Authors: Scaff, Lucia; Prein, Andreas F.; Li, Yanping; Liu, Changhai; Rasmussen, Roy; Ikeda, Kyoko
Abstract
Convection-permitting models (CPM) with at least 4 km horizontal grid spacing enable the cumulus parameterization to be switched off and thus simulate convective processes more realistically than coarse resolution models. This study investigates if a North American scale CPM can reproduce the observed warm season precipitation diurnal cycle on a climate scale. Potential changes in the precipitation diurnal cycle characteristics at the end of the twenty first century are also investigated using the pseudo global warming approach under a high-end anthropogenic emission scenario (RCP8.5). Simulations are performed with the Advanced Research Weather Research and Forecasting (ARW-WRF) model with 4-km horizontal grid spacing. Results from the WRF historical run (2001-2013) are evaluated against hourly precipitation from 2903 weather stations and a gridded hourly precipitation product in the U.S. The magnitude and timing of the diurnal cycle peak are realistically simulated in most of the U.S. and southern Canada. The model also captures the transition from afternoon precipitation peaks eastward of the Rocky Mountains to night peaks in the central U.S., which is related to propagating mesoscale convective systems. However, the historical climate simulation does not capture the observed early morning peaks in the central U.S. and overestimates the magnitude of the diurnal precipitation peak in the southeast region. In the simulation of the future climate, both the precipitation amount of the diurnal cycle and precipitation intensity increase throughout the domain, along with an increase in precipitation frequency in the northern region of the domain in May. These increases indicate a clear intensification of the hydrologic cycle during the warm season with potential impacts on future water resources, agriculture, and flooding.
Protective effects gamma-irradiated Astragalus polysaccharides on intestinal development and mucosal immune function of immunosuppressed broilers
POULTRY SCIENCE
Authors: Li, S.; Wang, X. F.; Ren, L. N.; Li, J. L.; Zhu, X. D.; Xing, T.; Zhang, L.; Gao, F.; Zhou, G. H.
Abstract
This study was aimed to assess the protective effects of gamma-irradiated Astragalus polysaccharides (IAPS) on the development of small intestine and intestinal mucosal immunity of immunosuppressed broilers induced by cyclophosphamide (CPM). A total of 384 one-day-old broiler chicks with similar initial weight were randomly assigned into 6 groups: non-treated group (control), and CPM-treated groups fed either a basal diet or the diets containing 900 mg/kg APS, or 900, 600, 300 mg/kg IAPS, respectively. On days 16, 18, and 20, all broilers except for control group were intramuscularly injected with 0.5 mL CPM (40 mg/kg of BW). Broilers in the control group were intramuscularly injected with 0.5 mL sterilized saline (0.75%, wt/vol). This trial was lasted for 21 d. The results revealed that both APS and IAPS treatment elevated the duodenal IgA-producing cells number and the jejunal mRNA expression of interleukin-2 (IL-2), interleukin-10 (IL-10), and interferon. of CPM-injected broilers (P < 0.05). The decreased jejunal villus height (VH), the ratio of VH to crypt depth (V/C), as well as the intestinal intraepithelial lymphocytes (IELs) and goblet cells number in CPM-injected broilers were elevated by dietary supplementation with 900 mg/kg APS or 900, 600 mg/kg IAPS (P < 0.05). The CPM-induced decrease in jejunum index, the duodenal VH and the jejunal IgA-producing cells number were only improved in the 900 mg/kg IAPS group (P < 0.05). Furthermore, the number of IELs and IgA-producing cells in duodenum, VH, V/C, the number of goblet cells, and mRNA expression of IL-2 and IL-10 in jejunum were higher in the 900 mg/kg IAPS group than those in the 900 mg/kg APS group (P < 0.05). In summary, IAPS possessed stronger immunomodulatory effect than APS at the same supplementation level. Therefore, gamma irradiation can be used as an alternative treatment to enhance the immunomodulatory activity of APS.