7 research outputs found
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Precipitation distributions for explicit versus parameterized convection in a large-domain high-resolution tropical case study
Global climate and weather models tend to produce rainfall that is too light and too regular over the tropical ocean. This is likely because of convective parametrizations, but the problem is not well understood. Here, distributions of precipitation rates are analyzed for high-resolution UK Met Office Unified Model simulations of a 10 day case study over a large tropical domain (âŒ20°Sâ20°N and 42°Eâ180°E). Simulations with 12 km grid length and parametrized convection have too many occurrences of light rain and too few of heavier rain when interpolated onto a 1° grid and compared with Tropical Rainfall Measuring Mission (TRMM) data. In fact, this version of the model appears to have a preferred scale of rainfall around 0.4 mm hâ1 (10 mm dayâ1), unlike observations of tropical rainfall. On the other hand, 4 km grid length simulations with explicit convection produce distributions much more similar to TRMM observations. The apparent preferred scale at lighter rain rates seems to be a feature of the convective parametrization rather than the coarse resolution, as demonstrated by results from 12 km simulations with explicit convection and 40 km simulations with parametrized convection. In fact, coarser resolution models with explicit convection tend to have even more heavy rain than observed. Implications for models using convective parametrizations, including interactions of heating and moistening profiles with larger scales, are discussed. One important implication is that the explicit convection 4 km model has temperature and moisture tendencies that favour transitions in the convective regime. Also, the 12 km parametrized convection model produces a more stable temperature profile at its extreme high-precipitation range, which may reduce the chance of very heavy rainfall. Further study is needed to determine whether unrealistic precipitation distributions are due to some fundamental limitation of convective parametrizations or whether parametrizations can be improved, in order to better simulate these distributions
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MetUM-GOML: a near-globally coupled atmosphereâocean-mixed-layer model
Well-resolved airâsea interactions are simulated in a new ocean mixed-layer, coupled configuration of the Met Office Unified Model (MetUM-GOML), comprising the MetUM coupled to the Multi-Column K Profile Parameterization ocean (MC-KPP). This is the first globally coupled system which provides a vertically resolved, high near-surface
resolution ocean at comparable computational cost to running in atmosphere-only mode. As well as being computationally inexpensive, this modelling framework is adaptableâ the independent MC-KPP columns can be applied selectively in space and time â and controllable â by using temperature and salinity corrections the model can be constrained to any ocean state.
The framework provides a powerful research tool for
process-based studies of the impact of airâsea interactions
in the global climate system. MetUM simulations have been
performed which separate the impact of introducing inter-
annual variability in sea surface temperatures (SSTs) from
the impact of having atmosphereâocean feedbacks. The representation of key aspects of tropical and extratropical variability are used to assess the performance of these simulations. Coupling the MetUM to MC-KPP is shown, for example, to reduce tropical precipitation biases, improve the propagation of, and spectral power associated with, the MaddenâJulian Oscillation and produce closer-to-observed patterns of springtime blocking activity over the Euro-Atlantic region
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Modelling suppressed and active convection: Comparisons between three global atmospheric models
Impact of glycerol-3-phosphate dehydrogenase on virulence factor production by Pseudomonas aeruginosa
The digestive morphophysiology of wild, free-living, giraffes
We have measured rumen-complex (rumen, reticulum, omasum, abomasum) and intestine (small and large
combined) mass in 32 wild giraffes of both sexes with body masses ranging from 289 to 1441 kg, and parotid
gland mass, tongue length and mass, masseter and mandible mass in 9 other giraffes ranging in body mass
from 181 to 1396 kg. We have estimated metabolic and energy production rates, feed intake and home range
size. Interspecific analysis of mature ruminants show that components of the digestive system increase linearly
(Mb1) or positively allometric (MbN1)with bodymasswhile variables associatedwith feed intake scalewithmetabolic
rate (Mb.75). Conversely, in giraffes ontogenetic increases in rumen-complex masswere negatively allometric
(Mbb1), and increases in intestine mass, parotid gland mass, masseter mass, and mandible mass were
isometric (Mb1). The relative masseter muscle mass (0.14% of Mb) and the relative parotid mass (0.03% of Mb)
are smaller than in other ruminants. Increases in tongue length scale with head length0.72 andMb.32 and tongue
mass with Mb.69. Absolute mass of the gastrointestinal tract increased throughout growth but its relative mass
declined from 20% to 15% of Mb. Rumen-complex fermentation provides ca 43% of daily energy needs, large intestine
fermentation 24% and 33% by digestion of soluble carbohydrates, proteins, and lipids. Dry matter intake
(kg) was 2.4% of body mass in juveniles and 1.6% in adults. Energy requirements increased from 35 Mj/day to
190 Mj/day. Browse production rate sustains a core home range of 2.2â11.8 km2.Don Craib Trust and the University of Wyoming.http://www.elsevier.com/locate/cbpa2016-09-30hb201