The poultry yard, how to furnish and manage it. A treatise for the amateur poultry raiser and farmer on the management of poultry, and the merits of the different breeds

Burpee, W. Atlee

doi:10.5962/bhl.title.35429

Cited by 5 publications

(15 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The surface feedbacks highlighted in this study could also affect the characteristics of AEWs differently at other latitudes and times of year. For example, one can speculate that differences in surface properties may play a role in determining the contrasting characteristics of AEWs found in the northern and southern Sahel, and indeed over the ocean (Burpee 1974;Duvel 1990).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

The diurnal cycle and African easterly waves: A land surface perspective

Taylor

CLARK

2001

Quarterly Journal of the Royal Meteorological Society

View full text Add to dashboard Cite

S u MM ARYFluxes from the land surface into the atmosphere exhibit strong variability on diurnal and daily time-scales during the Sahelian wet season. The influence of this variability on the atmosphere is examined here using a general circulation model. A land-surface scheme with an improved description of the sparse vegetation which characterizes the Sahel is introduced, and compared with simulations using existing parameters. With smaller evaporation rates, the sparse vegetation results in a warmer and deeper planetary boundary layer (PBL) in better agreement with observations. The diurnal cycle in simulated rainfall is much weaker, due to less frequent triggering of daytime convection. The damping of diurnal variability is accompanied by enhanced daily variability, with a deep moist PBL developing over several days. Above the sparsely vegetated surface, there is also greater African easterly wave (AEW) activity, and more long-lived rain events associated with it.A mechanism is proposed to explain the increased frequency of AEWs above sparser vegetation, based on wave composites in the model. Surface heating of the lower atmosphere is modulated strongly by AEWs. This occurs via a surfacexonvection-radiation feedback. Estimates of the boundary-layer heat budget indicate that variations in surface heating can, to a large extent, account for the low-level temperature signal characteristic of AEWs. By reinforcing the low-level temperature anomalies, the surface may influence the meridional wind signature of the wave above the PBL. Further evidence of the close coupling between the land surface and atmosphere is found by examining the modulation of precipitation by AEWs. Surface heat and moisture fluxes influence the build-up of convective available potential energy ahead of the wave trough. In this way, the properties of the surface can affect the timing and intensity of rainfall associated with, an AEW.

show abstract

Section: Discussionmentioning

confidence: 99%

“…They have periods of 3-5 days, and intensify as they move towards the West African coast (e.g. Burpee 1974;Reed et al 1977;Albignat and Reed 1980;Reed et al 1988).…”

Section: Introductionmentioning

confidence: 99%

The diurnal cycle and African easterly waves: A land surface perspective

Taylor

CLARK

2001

Quarterly Journal of the Royal Meteorological Society

View full text Add to dashboard Cite

show abstract

“…We chose a 10-day average to minimize the effect of synoptic influences associated with African easterly waves (e.g. Carlson 1969;Burpee 1972) and yet still represent meridional seasonal shifts in jet position. We defined the axis of the AEJ in each 10-day period by finding the latitude of the grid point with the minimum zonal wind component at each meridian from 18.0 • W to 30.375 • E. These meridians bound the area for which convective systems were identified.…”

Section: (B) Analysing the African Easterly Jetmentioning

confidence: 99%

“…Cook 1999;Thorncroft and Blackburn 1999) and observational studies (e.g. Burpee 1972;Reed et al 1977;Parker et al 2005). Thorncroft and Blackburn (1999) described the two diabatically forced meridional circulations responsible for its maintenance: one north of the jet, associated with the surface fluxes and dry convection of the Saharan heat-low; the other south of the jet, associated with the deep moist convection in the intertropical convergence zone (ITCZ).…”

Section: Introductionmentioning

confidence: 99%

Intense convective systems in West Africa and their relationship to the African easterly jet

Mohr

Thorncroft

2006

Quart J Royal Meteoro Soc

View full text Add to dashboard Cite

SUMMARYFor May-September 1998, convective systems in West Africa were identified from observations by the Tropical Rainfall Measuring Mission satellite Microwave Imager at 85 GHz. Using re-analysis data, the 10-day average position of the African easterly jet (AEJ) was diagnosed from the 700 hPa zonal winds. The distance from each convective system's centroid to the axis of the AEJ was calculated. Each convective system's minimum brightness temperatures were ranked so that intense convective systems were defined as those in the 10th percentile or lower. The weak (>10th percentile) and intense convective systems were represented statistically as two separate populations, the weak by the skewed Gumbel distribution and the intense by the normal distribution. From May to August, the peak in activity of weak convective systems remained south of 10 • N but shifted east of 10 • E. The peak in activity of the intense convective systems followed the seasonal migration of the AEJ northwards and became increasingly separate from the peak in activity of weak convective systems. The majority of both weak and intense convective systems occurred within 0.50 • of high terrain. The high convective available potential energy, high-shear AEJ environment in the vicinity of high terrain appeared to have the greatest probability of generating intense convective systems in the study area.

show abstract

“…The African easterly jet (AEJ) is a midtropospheric jet located over tropical north Africa during the northern hemisphere summer (e.g. Burpee 1972). It is a key feature of the West African monsoon (WAM), linking large-scale aspects of the WAM to its characteristic weather systems.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the African easterly jet, using aircraft observations from the JET2000 experiment

Parker

Thorncroft

Burton

et al. 2005

Q. J. R. Meteorol. Soc.

140

153

View full text Add to dashboard Cite

SUMMARYAnalyses of the African easterly jet (AEJ) are presented which are based on meridional transects of highresolution dropsonde observations made during JET2000, an aircraft campaign conducted in the last week of August 2000. The observations have confirmed that the AEJ is closely defined by geostrophic balance. The baroclinicity between the extreme northern and southern profiles accurately determines the altitude of the jet core, while the location and morphology of the jet core correspond to a locally-defined geostrophic wind measure. The potential-vorticity (PV) structure has also been found to accord with theoretical expectations, with distinctive positive-and negative-PV anomalies equatorward and poleward of the jet core respectively.The thermodynamic structure of the AEJ environment can be categorized into coherent layers. The monsoon layer is a humid zone connected to the land surface, extending northwards into the Sahel and increasing in depth towards the south. This layer is affected by the land surface on diurnal time-scales, through the growing convective mixed layer and through shallow cumulus clouds. Above the monsoon layer is the Saharan air layer (SAL), which can be identified as a layer of low static-stability and low PV. The SAL is deep where it merges with the Saharan boundary-layer in the north, and becomes thinner toward the south. It has been shown that the boundaries of the SAL can be approximated to good accuracy as adiabatic surfaces, meaning that the SAL comprises air which is adiabatically connected to the land surface via the Saharan boundary-layer. The upper region of the SAL is identified as a layer of high relative-humidity where altocumulus and stratocumulus layers are observed. Finally, the troposphere above the SAL is again almost pseudoadiabatic, with small baroclinicity which determines the closure of the AEJ core aloft. Through inspection of thermodynamic tracers, evidence of convective and lateral transport and exchange between these layers is also presented.

show abstract

The poultry yard, how to furnish and manage it. A treatise for the amateur poultry raiser and farmer on the management of poultry, and the merits of the different breeds

Cited by 5 publications

References 0 publications

The diurnal cycle and African easterly waves: A land surface perspective

The diurnal cycle and African easterly waves: A land surface perspective

Intense convective systems in West Africa and their relationship to the African easterly jet

Analysis of the African easterly jet, using aircraft observations from the JET2000 experiment

Contact Info

Product

Resources

About