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Air Pollution and Its Control
Published in Danny D. Reible, Fundamentals of Environmental Engineering, 2017
Figure 6.5 shows the mean circulation patterns that are observed in the atmosphere. The major feature is the so-called Hadley cell near the equator in both the Northern and Southern Hemispheres that results from the intense solar heating in this region. Heating of the air near the equator decreases its density causing it to rise relative to the cooler air in the more temperate regions. Air moves toward the equator at the surface to fill the void left by this rising air. In addition the air moving aloft moves away from the equator, forced poleward by the continued addition of rising air from the surface. As this air moves poleward it cools, becomes more dense, and falls toward the surface to complete the cycle. This flow directed toward the equator at the surface gives rise to convergence near the equator at what is termed the interhemispheric tropical convergence zone. It is this zone that acts as a barrier to rapid transport between the two hemispheres. Airborne material carried toward the equator at the surface is carried aloft before moving into the other hemisphere. This convergence is not always directly over the equator but moves back and forth as the Hadley cells in each hemisphere strengthen or weaken. During June, July, and August, the sun is directed north of the equator and the northern hemispheric Hadley cell is stronger and causes the zone of convergence to move into the Southern Hemisphere. The opposite occurs during January and February.
Meteorology: Tropical
Published in Yeqiao Wang, Atmosphere and Climate, 2020
The convergence zone in the lower troposphere near the equator is the so-called intertropical convergence zone (ITCZ), otherwise known by sailors as the Doldrums. It is a band of heavy precipitation (Figure 27.2), cyclonic relative vorticity, and relatively low surface pressure in the monthly or seasonal mean map. In a snap shot of an infrared image, the ITCZ is manifested as a zone of transient cloud clusters. In contrast, the subtropics are characterized by relatively high surface pressure and arid climates, where evaporation exceeds precipitation and most of the world's large deserts reside.
Surface water and the atmosphere
Published in Ian Acworth, Investigating Groundwater, 2019
The intertropical convergence zone (ITCZ) is the zone which defines the meteorological equator. It follows the seasonal shift on the sun and extends around the globe in the equatorial latitudes. Air rises from the surface in the ITCZ, often through towering cumulo-nimbus clouds, and flows towards each pole, before beginning to subside again. The ITCZ does not form a continuous belt of storm clouds. The simple circulation is shown in Figure 2.10.
Spatiotemporal climate variability and meteorological drought characterization in Ethiopia
Published in Geomatics, Natural Hazards and Risk, 2022
Jean Moussa Kourouma, Emmanuel Eze, Goitom Kelem, Emnet Negash, Darius Phiri, Royd Vinya, Atkilt Girma, Amanuel Zenebe
The ENSO indicator [(Southern Oscillation Index (SOI), Nino3.4, Pacific Sea surface temperature (SSTs) and Multivariate ENSO Index (MEI)] and the Sub-Tropical Jet (STJ), Red Sea Convergence Zone (RSCZ), Inter-Tropical Convergence Zone (ITCZ), Tropical Easterly Jet (TEJ), and Somalia Jet are the crucial rain-causing weather systems for Ethiopia (NMA, 1996). Previous studies have demonstrated that El Nino-Southern Oscillation (ENSO) has more influence on the amount of rainfall and distribution (Kiem and Verdon-Kidd 2009; Davey et al. 2014; Gleixner et al. 2017; Worku and Sahile 2018), and the variance in annual streamflow (Curry and Zwiers 2018). Babu (1999) found a negative relationship between the pacific SST, belg season, and the SOI. It was observed that during the ENSO years (e.g., 1982/83, 1987/88, 1992/93, 1998/99, and 2000/2001), the belg rains were above-normal, while below-normal rainfall was observed in the belg-producing regions of Ethiopia during La Niña years. The vegetation is dominated by natural gum- and resin-producing tree species such as Boswellia, Commiphora, and Acacia (Gebrehiwot et al. 2003).
Oriented stability and its application in texture control
Published in Philosophical Magazine, 2020
Xi Chen, Yuhui Sha, Songtao Chang, Fang Zhang, Liang Zuo
The contour line maps of oriented stability, , on constant ϕ2 sections under SR are shown in Figure 1. Each section can be divided into four orientation zones according to oriented stability values: fast convergence zone with ≤−1.5, slow convergence zone with −1.5<<0, slow divergence zone with 0<<1.5 and fast divergence zone with 1.5≤. The critical orientation boundaries that distinguish various orientation zones are shown by bold red, black and blue lines. Slow convergence zone and slow divergence zone are the ‘flatland’ with low rotation rate oriented to target orientation. Only if the orientations in slow divergence zone rotate across blue critical boundary into fast divergence zone, they can rapidly deviate from target orientation. Conversely, when the orientations in slow convergence zone evolve across red critical boundary into fast convergence zone, they can rapidly approach to target orientation. Therefore, the oriented stability distribution in Euler space provides a ‘topographic map’ to easily distinguish convergent or divergent orientation zones and clearly characterise how an orientation approaches to or deviates from target orientation.
Modeling emissions for three-dimensional atmospheric chemistry transport models
Published in Journal of the Air & Waste Management Association, 2018
Volker Matthias, Jan A. Arndt, Armin Aulinger, Johannes Bieser, Hugo Denier van der Gon, Richard Kranenburg, Jeroen Kuenen, Daniel Neumann, George Pouliot, Markus Quante
The range of emission estimates on the global scale varies from 1 to 20 Tg (Schumann and Huntrieser 2007; Zhang et al. 2003; Lee et al. 1997). This is mainly because the emission estimate per flash varies. Following IPCC (2001), lightning NOx contributes about 5 Tg N to the global annual emissions, which is about 10%. Because the highest lightning density occurs in the Intertropical Convergence Zone (ITCZ), most emissions are located around the equator.