Assignment 2: chapter 5 precipitation systems in mid-latitude Flashcards
What is capping inversion? What is its effect on convection? What is Convective INhibition (CIN)?
- Capping inversion acts as a lid, which can prevent near-surface parcels from reaching their level of free convection (LFC). This lid can prevent storms from forming, even with high instability aloft.
- In the presence of a capping inversion, some additional mechanism (like heating, moistening and synoptic scale lifting) is required to initiate convection.
- The work needed to lift an air parcel from rest at the surface to the LFC, is called the convective inhibition (CIN).
Estimate the CAPE for a sounding in which the LFC and EL for the reference air parcel are 700 and 250 hPa, respectively, and within the layer between those levels the reference air parcel is, on average, 12 °C warmer than the environmental air at the same level.
How the strength of the vertical wind shear affects the vertical tilt of the updrafts and downdrafts within the convective storm?
- weak shear favors a structure in which the downdraft ultimately isolates the updraft from its supply of low level moisture leading to the storm’s demise
- strong shear favors a tilted structure with a relationship between updraft and downdraft, resulting in more intense, longer lived storms capable of producing hail and strong winds.
What is Bulk Richardson’s Number?
The bulk Richardson’s number is ratio of CAPE to a quantity proportional to the square of the mean vertical shear integrated over height (S2) as an indicator of storm type:
Explain the self-destructive mechanism the single cell storms contain.
The single-cell thunderstorm contains a built in self-destruct mechanism namely, the downdraft circulation. In the absence of vertical wind shear, the precipitation produced in the downdraft destroys the buoyant updrafts that feed it.
Explain how a mesolow forms within the updraft of supercell storms.
The rotation induces the formation of a mesolow within the updraft. The mesolow forms as the rotating air is pulled outward from the center of the updraft by the centrifugal force.
Estimate the magnitude of the upward acceleration at the base of the updraft due to the presence of a dynamically induced pressure perturbation pD that increases from zero at the ground to 1.5 hPa at an altitude of 2 km above the ground. The density of the air is 1 kg m3.
What would be the magnitude of the vertical velocity that would be imparted to the air beneath the updraft in 5 minutes?
Assuming that the flow is in cyclostrophic balance, estimate the pressure deficit óp (relative to the ambient air pressure) in a tornado with a maximum velocity of 75 m s-1. The density of the air is 1.25 kg m-3. Ignore the variation of air density with pressure.
