Why Do Bridges Ice Before Roads? Essay Example

During winter, areas in the polar and temperate regions of the earth experience high precipitation and with the lowering the temperatures to below zero, the liquid solidifies. The axis of the hemisphere being turned away from the sun means that the sun radiations are very far away (Cantrell and Heymsfieldl 796). Without these radiations, the temperature is forced to drop significantly which creates a conducive environment for rainwater to solidify into ice collecting on surfaces such as roads and bridges. The rate, at which this happens, occurs differently depending on the nature of the surface, and this explains why bridges ice before roads do.

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In conditions of normal temperatures, this precipitation in the liquid state has a large number of molecules gliding and colliding against each other. These molecules have weak hydrogen bonds which can be broken easily. The molecules thermal energy is sufficient for them to stay in a liquid state but not enough to be converted into steam (Collings and Hird 28). If the same amount of precipitation is put under very low temperatures causing the water to solidify, the same amount of molecules are retained but in this case, the thermal energy is too little such that they are locked in a solid state and cannot flow (Hoffmann et al. 2128). In this solid arrangement, molecules are farther away from each other which make ice less dense than water although it occupies more space than water.

During winter, a lot of precipitation such as rainwater, fog, and mist reaches the ground but since sun radiations are very low, no evaporation takes place. Air and wind flowing over this precipitation are calm and light such that there is a little stirring of the atmosphere (Hoffmann et al. 2129). A thin layer of really cold temperatures to be formed which then leads to soil and ground temperatures reducing greatly which favors the formation of ice. As rainwater flows down, it encounters layers and layers of subfreezing air which further reduces the temperatures and by the time it hits the ground surface the water is very cold and dry.

The ground is a good conductor of heat which means that there is the low resistance of energy flow through it mainly because the ground retains heat more which slows down the formation of ice on parts exposed to the precipitation (Hoffmann et al. 2131). Roads also are made from materials such as asphalt that are poor conductors of heat hence they reduce the rate at which roads lose heat. Roads, therefore, possess more heat as compared to bridges and other surfaces. Precipitation reaches the road surface first causing it to lose heat (Cantrell and Heymsfield 800). However, as the roads lose heat to the atmosphere, the ground beneath it compensates this through its retained heat. Due to this process ice takes a longer time to accumulate on roads than it does on bridges.

Bridges, on the other hand, are made from materials that are good conductors of heat such as copper and steel with the ability to conduct thermal energy with values over 400 Watts per kilometer (Cantrell and Heymsfieldl 801). Due to their ability to conduct heat efficiently, bridges are able to lose more thermal energy from their tops and exposed sides as compared to the ground. In addition to the materials being good conductors of heat, calm and cold winds circulating over these bridges, further cause them to lose heat (Hoffmann et al. 2133). Roads only lose heat from their surfaces that are exposed to the winds while bridges lose heat from all sides; the top, the bottom, and the sides. As temperatures are dropping on the surfaces, roads have a retainer of heat from the ground while bridges have no way to trap heat causing their temperatures to drop constantly and consistently.

Due to the nature of the bridges and their strategic positioning across structures, air temperature influences the bridge temperatures but it is not the case for road surfaces. If air temperatures fall below zero, bridge temperatures also fall below zero but road temperatures take longer to drop to the air temperatures level. In this regard, precipitation falling from the atmosphere, upon contact with the bridge, it freezes and sticks to the bridge at a faster rate than it do on the roads (Hoffmann et al. 2128). Ice is a poor conductor of heat but a good insulator Due to this nature air bubbles trapped inside its structure cannot circulate freely which reduces heat transfer and the amount of melting that can possibly take place and as more and more precipitation is deposited, the freezing increases.

Conclusion

In conclusion, Bridges ice faster than roads since they are made of materials that are good conductors of heat, therefore, losing more heat to the atmosphere as compared to roads whose materials are poor conductors. The ability to trap heat for roads is better than that of bridges since the ground compensates for any heat lost through its retained heat. Bridges are exposed more to the wind and air circulating from above, below and on the sides. Roads, on the other hand, are only exposed on the surface which enables them to retain heat. Motorists are advised to drive slowly in such areas to prevent accidents.

Works Cited

Cantrell and Heymsfield. "Production of ice in tropospheric clouds: A review." Bulletin of the American Meteorological Society 86.6, 2005: pp. 795-808.

Collings, Peter J., and Michael Hird. Introduction to liquid crystals: chemistry and physics. CRC Press, 2017.

Hoffmann, Fabian, Yign Noh, and Siegfried Raasch. "The route to raindrop formation in a shallow cumulus cloud simulated by a Lagrangian cloud model." Journal of the Atmospheric Sciences, 74, 7, 2017, pp. 2125-2142.