a cold front is a front where cold air places warm air at the surface.
a front where cold air places warm air at the surface?
cold front
a cold front is located at the leading edge of the temperature drop off, which in an isotherm analysis shows up as the leading edge of the isotherm gradient, and it normally lies within a sharp surface trough. cold fronts often bring heavy thunderstorms, rain, and hail. cold fronts can produce sharper changes in weather and move up to twice as quickly as warm fronts, since cold air is denser than warm air and rapidly replaces the warm air preceding the boundary. on weather maps, the surface position of the cold front is marked with the symbol of a blue line of triangle-shaped pips pointing in the direction of travel, and it is placed at the leading edge of the cooler air mass. cold fronts come in association with a low-pressure area. the concept of colder, dense air "wedging" under the less dense warmer air is often used to depict how air is lifted along a frontal boundary. the cold air wedging underneath warmer air creates the strongest winds just above the ground surface, a phenomenon often associated with property-damaging wind gusts. this lift would then form a narrow line of showers and thunderstorms if enough moisture were present. however, this concept isn't an accurate description of the physical processes; upward motion is not produced because of warm air "ramping up" cold, dense air, rather, frontogenetical circulation is behind the upward forcing.
weather front
in general, la niña events are associated with lower temperatures (particularly colder winters) in the pampas. during winter, frosts are more common during la niña events compared to el niño events. this is due to a stronger southerly flow during la niña events caused by a higher concentration of high pressure systems in the south pacific and an increase in cyclonic activity (more low pressure systems) in the south atlantic. this creates conditions that are favourable for bringing cold air from the south, particularly when there is a formation of a high pressure system over patagonia (associated with the passage of a front) that is responsible for bringing cold air from the south. thus, invasions of cold air from the south are more common during la niña events. in contrast, warm spells in the pampas and northern parts of the country are more intense and frequent during el niño events. this is due to stronger westerly winds south of 40s, leading to less frequent incursions of cold air from the south while enhancing winds from the north that bring in warm air. although la niña events lead to colder winters with more frequent incursions of cold air in both the north and central parts of the country, it leads to more frequent and intense warm spells in the last months of the year. in other regions, el niño events lead to more frequent and intense warm spells in northwest argentina (during autumn), northeast argentina (during spring) and central argentina (during summer). cold air anomalies arising from el niño events are observed during spring and are the result of an increase in rainfall that lead to reductions in insolation. for the southern parts of the country, el niño events are associated with more intense and frequent cold spells during the coldest months. in summer, el niño events are associated with warmer summer temperatures in the southern parts of the country.
climate of argentina