文章来源 | 授权转载自知乎专栏-奥斯陆的气象生活
作者 | 冰心浴血，奥斯陆大学气象研究生
Summary of T-lnP图
We will look at an air parcel containing 1 g of water vapor and 400 g of dry air. The temperature of the air parcel is 5 ℃ , and it is located at 900 hPa. Give a deﬁnition of, and ﬁnd the following quantities
1.Potential Temperature (Θ) – 位温: Potential temperature is the temperature a parcel of air would have it were lifted (expanded) or sunk (compressed) adiabatically to 1000hpa.
Tip: The value of the potential temperature is the temperature of the dry adiabat that runs through the temperature at the pressure level of interest, at 1000hpa.
2.Dewpoint temperature (Td) – 露点: 是在维持空气气压不变的情况下，把空气冷却到相对于纯水面（平面）来说达到饱和时的温度。
3. Wet-bulb Temperature (Tw) – 湿球温度: The minimum temperature at which a parcel of air can obtain by cooling via the process of evaporating water into it at constant pressure. It is the temperature a parcel of air would have if it were cooled to saturation (100% relative humidity) by the evaporation of water into it, with the latent heat being supplied by the parcel.
Tip: To find the wet-bulb temperature follow the moist adiabat through the lifting condensation level and find the temperature of the intersection of this moist adiabat with the original pressure level of interest.
4. Equivalent Temperature (Te) --相当温度: The equivalent temperature is the temperature of a parcel if, via a moist adiabatic process, all moisture was condensed into the parcel. Finding the equivalent temperature is slightly more difficult.
Tip: To find Te, follow the moist adiabat that runs through the lifting condensation level at the pressure level of interest to a pressure level in which the moist adiabat and dry adiabat have similar slopes, then go down the dry adiabat at this point back down to the original pressure level of interest; this temperature is the equivalent temperature. If the dry adiabat continues beyond the boundary of the skew-t in which it cannot be determined, an alternative is to read off the temperature scale that runs diagonally in the middle of the skew-t.
5. Equivalent Potential Temperature (Θe)-- 相当位温: The equivalent potential temperature is similar to the equivalent temperature however after the moisture has been condensed out of the parcel, the parcel is brought down dry adiabatically to 1000hpa.
Tip: The process to find the equivalent potential temperature is the same as the regular equivalent temperature however when the parcel is brought down the dry adiabat it continues past the original pressure level and is brought down to 1000hpa. The temperature at this intersection is the equivalent potential temperature.
6. Saturated Equivalent Potential Temperature (Θes) -- 假相当位温: The temperature at which an unsaturated parcel would have if it were saturated. Saturation equivalent potential temperature (represented as θes) is a special case of equivalent potential temperature (θe) computed by assuming an air parcel is saturated and thus represents the theoretical maximum θe.
Tip: To find the saturated equivalent potential temperature, use a similar process used for determining the equivalent potential temperature however one must follow the moist adiabat through the environmental temperature at the necessary pressure level, unlike using the lifting condensation level for equivalent potential temperature.
7. wet-bulb pseudo temperature (Tsw) – 假湿球温度: Wet-bulb potential temperature, sometimes referred to as pseudo wet-bulb potential temperature, is the temperature that a parcel of air at any level would have if, starting at the wet-bulb temperature, it were brought at the saturated adiabatic lapse rate to the standard pressure of 1000 hpa.（所以你其实可以认为湿球温度和假湿球温度是一个东西，那么找法是一模一样的.并不是说这两个温度没有区别，而是在气象实际应用上，因为这两个差别很小，所以就没有区别。但是在理论定义和公式上还是有很大差别的！）
8. wet-bulb pseudo potential temperature (Θsw) – 假湿球位温: Wet-bulb potential temperature, sometimes referred to as pseudo wet-bulb potential temperature, is the temperature that a parcel of air at any level would have if, starting at the wet-bulb temperature, it were brought at the saturated adiabatic lapse rate to the standard pressure of 1000 hpa.（所以你其实可以认为湿球位温和假湿球位温是一个东西，那么找法是一模一样的。并不是说这两个温度没有区别，而是在气象实际应用上，因为这两个差别很小，所以就没有区别。但是在理论定义和公式上还是有很大差别的！）
Tip: 气块沿干绝热线上升到饱和后再沿 湿绝热线下降到1000hPa处的温度。
1. Lifting Condensation Level (LCL) – 抬升凝结高度: The level at which a parcel of air first becomes saturated when lifted dry adiabatically.
Tip: This level can be found by finding the intersection of the dry adiabat through the temperature at the pressure level of interest, and the mixing ratio through the dewpoint temperature at the pressure level of interest.
2. Convective Condensation Level (CCL) -- 对流凝结高度：The convective condensation level (CCL) represents the height (or pressure) where an air parcel becomes saturated when heated from below and lifted adiabatically due to buoyancy.
Tip: To find the convective condensation level, find the intersection of the mixing ratio through the dewpoint temperature at the pressure level of interest and the temperature sounding.
3. Level of Free Convection (LFC) – 自由对流高度：The level in which a parcel first becomes positively buoyant.
Tip: To find the level of free convection, find the lifting condensation for the level of interest, and find the intersection of the moist adiabat that goes through the LCL, and the temperature curve.
4. Equilibrium Level (EL) – 自由对流高度：The height at which a rising parcel of air is at the same temperature as its environment. The point at which a positively buoyant parcel becomes negatively buoyant, which typically will occur in the upper troposphere.
Tip: To find this level, find the level of free convection, follow the moist adiabat through this level of free convection up until it intersects the temperature sounding again. This point is the equilibrium level.
3. Vapor Pressures
1. Vapor Pressure (e)—水汽压: The amount of atmospheric pressure that is a result of the pressure from water vapor in the atmosphere.
Tip: To find the vapor pressure follow an isotherm (a line parallel to an isotherm) through the dewpoint temperature at the pressure level of interest, up to 622hpa. The value of the mixing ratio at this intersection is the vapor pressure in millibars.
根据给定的露点，在露点??等温线与 622h??等压线的交点处，读出通过该点的等饱和比 湿线的数值，即得到该状态点的实际水汽压值
2. Saturated Vapor Pressure (es) – 饱和水汽压：The amount of atmospheric pressure that is a result of the pressure of water vapor in saturated air.
Tip: This quantity can be found using similar means as the vapor pressure however one must follow a parallel isotherm through the temperature at the pressure level of interest.
根据给定的温度?，找到?等温线与622h??等压线的 交点，读出通过该点的等饱和比湿线的数值，即得 到温度?时的饱和水汽压值。
4. Mixing Ratios
1. Mixing Ratio (r) – 混合比: The mixing ratio is the ratio of the mass of water vapor in the air over the mass of dry air.
Tip: This quantity is found by reading the mixing ratio line that goes through the dewpoint temperature at the pressure level of interest.
2. Saturated Mixing Ratio (rs) – 饱和混合比：A similar mixing ratio as above, however it is the mixing ratio of a saturated parcel of air at a given temperature and pressure.
Tip: It can be found by finding the value of the mixing ratio through the temperature at a pressure level of interest. 根据给定的气压和温度，在图中找到一点A,读出通过A点的等饱和比湿线的数值，即为所求的饱和比湿值??(?)。
本文分享自微信公众号 - 气象学家（Meteorologist2019），作者：冰心浴血
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