Consequently, sustained SSTs and enthalpy flux in the river plume may have helped support warm, moist atmospheric boundary layer conditions (observed via increased equivalent potential temperature
) and may have provided enough atmospheric instability to overcome moderate vertical wind shear and aid in these storms' intensification and RI in this region.
However, calculation of dewpoint, potential temperature, virtual temperature, equivalent potential temperature, virtual potential temperature, and mixing ratio is done in order to improve physical interpretation.
(c) Equivalent potential temperature (station model as in Figure 6).
Defining automated fronts requires quantities (e.g., potential temperature, equivalent potential temperature, wind shifts) and kinematic functions (e.g., gradient, thermal front parameter, and frontogenesis).
Methods range from the relatively simple [e.g., mapping where the surface potential temperature gradient exceeds a fixed magnitude as in Sanders and Hoffman (2002)] to the increasingly complicated [e.g., the method of Hewson and Titley (2010, their Table IA) uses a function of wet-bulb equivalent potential temperature [[theta].sub.w] followed by three different masking functions of [[theta].sub.w] to identify their fronts].
On the other hand, analysts in the United Kingdom and Europe generally favor quantities that incorporate both temperature and humidity: equivalent potential temperature [[theta].sub.e] or wet-bulb potential temperature [[theta].sub.w] (e.g., Hewson 1998; Santurette and Joly 2002; Joly and Santurette 2002).
The Meiyu-Baiurainband can be identified by sharp gradients of specific humidity and equivalent potential temperature  and a horizontal wind shear line .
High equivalent potential temperature controlled this region from surface up to 900 hPa, and the equivalent potential temperature near the surface exceeded 354 K, while a belt of dense, nearly vertically oriented contours of [[theta].sub.e] appeared from 900 hPa to 600 hPa with large vertical gradient of [[theta].sub.e] on both sides of the belt.
Reference  used three criteria to discriminate elevated thunderstorm station reports from surface-based thunderstorm station reports: (1) the observation must lie on the cold side of an analyzed front that shows a clear contrast in temperature, dew point temperature, and wind; (2) the station's wind, temperature, and dew point temperature must be qualitatively similar to the immediately surrounding values; and (3) the surface air on the warm side of the analyzed front must have a higher equivalent potential temperature (0e) than the air on the cold side of the front.
Equivalent potential temperature on the cross-sections shows the background potential instability where de decreases with height over the event region (Figure 10); in all of the composite cross-sections this is found to occur between 850 and 700 hPa.
This quantity is defined as the difference between the dynamic tropopause potential temperature and the 850-hPa equivalent potential temperature. It approximates bulk stability (larger values represent more stable conditions than smaller values), which modulates the degree of interaction between perturbations on the upper and lower boundaries of the free troposphere via the Rossby penetration depth.
An alternative criterion of a maximum 22.5[degrees]C difference between the tropopause-level and 850-hPa equivalent potential temperatures (defined as the coupling index) is proposed for this class of development.